Bioaccumulation of Arsenic and Zinc by Chironomid larvae in Lacustrine Environments: Exploring this Community as Indicator of Trace Element Dynamics in Patagonian Food Webs

Bioaccumulation of Arsenic and Zinc by Chironomid larvae in Lacustrine Environments: Exploring this Community as Indicator of Trace Element Dynamics in Patagonian Food Webs | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Bioaccumulation of Arsenic and Zinc by Chironomid larvae in Lacustrine Environments: Exploring this Community as Indicator of Trace Element Dynamics in Patagonian Food Webs Natalia Williams, Andrea Rizzo, Romina Juncos, Diego Añón Suárez, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7376220/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The chironomid community is a key component of lacustrine systems, considering their larvae as a doorway for trace elements from benthic substrates to higher trophic levels. In Lake Moreno Oeste, a northern Patagonian lake (Argentina), arsenic (As), a non-essential and toxic metalloid, and zinc (Zn), an essential metal, were measured in several substrates and their associated chironomid larvae to evaluate their dynamics by understanding their distribution, and bioaccumulation and excretion patterns in this community. The highest As concentrations ([As]) were observed in sediment from littoral vegetated areas and deep zones, while the highest [Zn] were recorded in Myriophyllum sp. leaves. Larval feeding strategies influenced bioaccumulation patterns: collectors accumulated higher [As] (suggesting that the main As pathway is through the sediment ingestion), and predators and shredders recorded higher [Zn] (associated with its environmental availability and specific larval requirements). In purged material, both elements reached their maximum excretion factors in biological substrates ( Myriophyllum sp. and submerged riparian leaves); however, [As] exceeded values in both substrates and larvae, while [Zn] surpassed values in substrates but remained lower than in larvae. Our findings explore chironomid larvae as vectors of trace elements from benthic substrates to upper trophic levels, highlighting their potential as metal bioindicators. Heavy metal bioaccumulation Benthic larvae Functional feeding habits Lacustrine substrates Lake Moreno Oeste Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction In aquatic ecosystems, natural trace element concentrations are mainly associated with weathering and leaching processes in the watershed and their subsequent environmental distribution. Anthropogenic activities can increase the input of heavy metals into the catchment area through the transport of pollutants via atmospheric deposition and/or direct discharges [ 1 , 2 ]. These elements are mostly deposited in bottom sediments by hydrological and geochemical processes, turning them into a reservoir of pollutants. Then, through physical and chemical reactions, contaminants can be remobilized from sediments and return to the water column, causing long-term pollution [ 3 , 4 ]. Sediment composition has a significant influence on metal accumulation, as a positive relationship has been observed between element concentrations and the proportion of finer substrate fractions (silt and clay) and organic matter content [ 5 ]. Hence, variable metal concentrations may be recorded within a lacustrine watershed associated by several factors, such as sediment granulometric composition, pH, depth, temperature, substrate type, presence of macrophytes, among other variables [ 6 ]. Although heavy metals are primarily deposited in lacustrine bottom sediments [ 7 – 9 ], they can be also bioaccumulated by aquatic organisms, becoming toxic when they exceed certain thresholds [ 10 ]. Organisms living closely associated with benthic substrates are most exposed to metals bound in sediments [ 11 ]. Whether essential (e.g., copper, iron, zinc) or non-essential (e.g., arsenic, cadmium, mercury, lead), these elements can cause negative effects on biota, as organisms can ingest and accumulate all trace elements [ 12 ]. Due to their persistence, high toxicity, and potential to bioaccumulate, essential and non-essential elements are considered contaminants in aquatic environments [ 13 ], so it is key to understand their trophic transference in aquatic food webs [ 14 ]. We evaluated two contrasting trace elements: arsenic (As), a non-essential metal, and zinc (Zn), an essential one. Arsenic, a highly toxic metalloid naturally present in the environment, is distributed in soil, aquatic systems, air, and even in living organisms [ 15 ]. In aquatic ecosystems, As can be present in various chemical forms, including most toxic inorganic species (e.g., arsenite and arsenate) and organic forms (e.g., methylated species, arsenolipids, and arsenosugars) [ 16 , 17 ]. On the other hand, Zn is present in organisms acting as a fundamental component of several proteins and considered essential for normal physiological functions [ 18 , 19 ]. Since Zn is indispensable for many metabolic processes, individual organisms control its bioaccumulation, and it is considered toxic when it exceeds certain concentrations. This has led to the evaluation of sediment quality to predict adverse effects on sediment-dwelling organisms in freshwater systems [ 20 ]. Bioaccumulation and trophic transference of As and Zn have been initially studied in different Patagonian lakes (Argentina). For instance, a previous work revealed higher As concentrations [As] in Diplodon chilensis mussels from lakes Nahuel Huapi and Moreno (47 and 38 µg g-1 dry weight, respectively) in zones with population settlements [ 21 ]. Based on a trophodynamic study, a biodilution pattern was observed in the food web from Lake Moreno [ 22 ]. On the other hand, in Lake Nahuel Huapi, several fish species varied their [As] according to their feeding habits, with higher values recorded in benthivores, like the creole perch ( Percichthys trucha ), compared to those feeding on pelagic prey, such as rainbow trout ( Oncorhynchus mykiss ) and brown trout ( Salmo trutta ) [ 23 ]. In the case of Zn, although the literature is scarce and based on only a fraction of the food web, in natural freshwater systems a general biomagnification pattern has been observed [ 24 ]. However, along the trophic chain from Lake Nahuel Huapi, it was presented the first research reporting Zn biodilution [ 25 ]. Therefore, element bioaccumulation and transference through the food web is complex, and may be associated not only with chemical properties, but also with multiple environmental factors, such as exposure route or species-specific physiological attributes [ 26 ]. Chironomidae (Insecta: Diptera) is the most widely distributed, numerous, species-rich, and ecologically diverse family of aquatic insects in freshwater systems, with its larvae considered a principal component of benthic invertebrate communities [ 27 , 28 ]. In southern Patagonian lakes, chironomid larvae constitute an important part of the diet of the small puyen ( Galaxias maculatus ) [ 29 ], and this small fish is a main prey for larger fish, such as the exotic brown and rainbow trout, and the native creole perch [ 30 ]. Based on its ontogenetic habitat shift, the small puyen changes from pelagic larvae to littoral-benthic juvenile and adult, playing an important role in coupling both compartments, and could transfer contaminants between benthic deposits and pelagic environment. Moreover, since chironomid larvae are good accumulators of metals, able to tolerate low oxygen levels [ 31 , 32 ], and due to their initial trophic position, they are considered the entry point for heavy metals and other trace elements to upper levels of lacustrine food webs. Consequently, it is possible that chironomid larvae could be used as indicators of bioavailability by analyzing their element bioaccumulation and regulation, as well as their potential to transfer contaminants to higher trophic levels. Although several previous studies have analyzed metal bioaccumulation in macroinvertebrate communities, including chironomid larvae [ 33 – 36 ], there is still a lack of research contrasting the distribution and bioaccumulation dynamics of essential and non-essential elements under natural environmental conditions within the same lacustrine system. To address this point, chironomid larvae were selected as study organisms due to their abundance, wide spatial distribution, and strong association with several benthic substrates that could be important element reservoirs. While their larvae often burrow into surficial sediments and feed on particulate organic matter [ 37 ], some species show a clear preference for a particular substrate, others are versatile, occupying a wide variety of habitat patches [ 27 , 38 ]. Besides their widespread spatial distribution, chironomid larvae exhibit a varied diversity of functional feeding strategies. Therefore, studying this insect community may provide insights into general patterns of metal assimilation and transport along the trophic chain by evaluating their initial uptake from benthic substrates and successive transference to upper levels. This makes this aquatic insect group a suitable community to explore environmental dynamics of essential and non-essential elements in freshwater ecosystems. In this context, the main objective of the present study is to examine the natural environmental distribution of two contrasting trace elements within the same lacustrine system, and their bioaccumulation and excretion patterns in chironomid larvae. This research explores the role of chironomid larvae as an indicator community of the initial uptake of an essential trace element (Zn) and a non-essential one (As) from benthic lacustrine substrates, and their potential transference to upper trophic levels in Lake Moreno Oeste (northern Patagonia). For this purpose, larval bioaccumulation was studied in relation to the spatiotemporal taxa distribution, their respective feeding strategies, and associated substrate type. Material and methods Study site Lake Moreno Oeste (MO) (41°03′33″ S; 71°32′24″ W; 758 m asl; 5.22 km 2 ; 90 m max. depth) is located in Nahuel Huapi National Park (NHNP) (northern Patagonia, Argentina). It is the western branch of Lake Moreno and is connected to Lake Moreno Este (5.42 km 2 , 106 m max. depth) via a narrow channel [ 39 ] (Fig. 1 a). Lake MO is a warm monomictic system that exhibits stratification from late spring to early autumn, an extensive euphotic zone (Secchi disk ~ 20 m), dissolved organic carbon around 0.8 mg L − 1 , chlorophyll a level of 1 µg L − 1 , total nitrogen of 140 µg L − 1 , and total phosphorus of 4 µg L − 1 [ 40 ]. The lacustrine shoreline has peninsulas, bays, and inundated regions occupied by native forests Nothofagus dombeyi (“coihue”) and Astrocedrus chilensis (“cordilleran cypress”) [ 41 ]. In the littoral zone, dense aquatic vegetation includes both submerged macrophytes, such as Myriophyllum quitense and Nitella sp., and the emergent Schoenoplectus californicus . The macroinvertebrate community of the Lake Moreno system is dominated by insect larvae (Diptera, Trichoptera, Odonata, Ephemeroptera, and Plecoptera), mollusks, annelids, amphipods, and benthic crustaceans ( Aegla spp. and Samastacus spirinifrons (Philippi)) [ 42 ]. The fish community includes both exotic rainbow, brown, and brook trout ( Salvelinus fontinalis ) and native species (creole perch, big puyen ( Galaxias platei ), and small puyen) [ 30 ]. Sample collection Chironomid larvae are distributed across the littoral, sublittoral, and deep zones of Lake MO, occupying numerous substrate types such as submerged riparian leaves from the surrounding forest, submerged macrophytes, and bed sediments from both vegetated and non-vegetated zones at different depths. Therefore, to include all habitat patches inhabited by chironomid larvae, different substrate types were sampled from littoral to deep zones. The selected lacustrine bays were Llao Llao (LL) and Guardaparques (GP) (Fig. 1 b) and the sampling period extended from April 2014 (austral autumn) to February 2015 (austral summer). In sublittoral (6 m depth) and deep (20, 40, and 90 m depth) zones, bottom sediment was collected with an Ekman dredge (225 cm3) (Fig. 1 b). In the littoral zone from LL bay, sediment was taken from areas dominated by submerged macrophytes using an Ekman dredge, and from areas occupied by emergent species using a short plastic corer. Moreover, samples of Myriophyllum sp. leaves were manually collected. In the littoral zone from GP bay, sampling areas (531 cm 2 ) within patches covered with submerged riparian leaves and stones were delimited, where decomposing leaves were manually retrieved and sediment below stones was collected using a short plastic corer. All samples were stored in plastic bags. Six replicates of each substrate type were collected at each sampling season. At the laboratory, chironomid larvae were separated from each substrate sample and identified under a binocular glass until subfamily or tribe level [ 43 ]. To determine [As] and [Zn] in chironomid larvae from each substrate, individuals of the same group were pooled until reaching a mass of at least 0.5 mg. When weight was limited, samples were obtained with mixed individuals; and when chironomid mass was sufficient, replicate samples were prepared to evaluate variability (Table 1 ). After extracting chironomid larvae, biological ( Myriophyllum sp. and riparian leaves) and sedimentary samples were conserved for elemental analysis (see “Analytical procedures” section). Table 1 Chironomid samples analyzed for arsenic (As) and zinc (Zn) contents in Lake Moreno Oeste. The sampling station, substrate, dominant chironomid taxa, and feeding habit are indicated (PRED = predator, CG = collector-gatherer, CF = collector-filterer, SH = shredder). Analytical uncertainties are indicated after ±. Sampling season Substrate Dominant taxa Feeding habit Biological fraction (%) [As] concentration (µg g − 1 DW) [Zn] concentration (µg g − 1 DW) Austral Autumn Sed. S. californicus sp. Myriophyllum sp. leaves Sed. Myriophyllum sp. Sed. Nitella sp. Bed. Sed. 6 m. depth Bed. Sed. 20 m. depth Cryptochironomus sp. Cryptochironomus sp. Parachironomus sp. Parapsectrocladius sp. Djalmabatista sp. Parapsectrocladius sp. Polypedilum sp.1 Djalmabatista sp. Riethia sp. ( 3 a ) Cryptochironomus sp. Cryptochironomus sp. PRED PRED PRED CG PRED CG SH PRED CF PRED PRED 55.56 81.78 97.59 100 98.69 92.2 81.54 92.96 62.81 ± 0.53 100 49 2.2 ± 1.9 - 0.39 ± 0.22 0.31 ± 0.1 0.93 ± 0.21 - - 0.95 ± 0.84 3.3 ± 0.36 0.361 ± 0.097 7.6 ± 2.2 - 482 ± 49 264 ± 24 227 ± 24 208 ± 20 420 ± 190 870 ± 190 1390 ± 540 215.2 ± 119.9 345 ± 46 - Austral Winter Myriophyllum sp. leaves Sed. Myriophyllum sp. Sed. Nitella sp. Bed. Sed. 6 m. depth Bed. Sed. 20 m. depth Parapsectrocladius sp. and Apedilum sp. Djalmabatista sp. Riethia sp. Riethia sp. ( 5 a ) Polypedilum sp.2 CGCG PRED CF CF PRED 93.77 82.46 46.57 72.17 ± 4.38 75.68 2 ± 1 2.03 ± 0.55 5.4 ± 2.17 2.07 ± 0.19 - 781 ± 32 472 ± 61 - 147 ± 5.72 273 ± 25 Austral Spring Myriophyllum sp. leaves Sed. Myriophyllum sp. Sed. Nitella sp. Bed. Sed. 6 m. depth Bed. Sed. 20 m. depth Tanytarsini members Macropelopia sp. Polypedilum sp.1 Djalmabatista sp. Dicrotendipes sp. and Riethia sp. ( 2 a ) Cryptochironomus sp. CG PRED SH PRED CGCF PRED 98.87 98.31 21.48 66.79 62.22 ± 5 43.58 0.82 ± 0.41 0.82 ± 0.5 - - - - 180 ± 23 152 ± 10 - 749 ± 91 299 ± 119 - Austral Summer Littoral riparian leaves Sed. under stones Sed. S. californicus sp. Myriophyllum sp. leaves Sed. Myriophyllum sp. Sed. Nitella sp. Bed. Sed. 6 m. depth Bed. Sed. 20 m. depth Ablabesmyia sp. Tanytarsini members and Riethia sp. Djalmabatista sp. Tanytarsini members and Riethia sp. Apedilum sp. and Parachironomus sp. Riethia sp. Chironomus sp. and Riethia sp. ( 3 a ) Djalmabatista sp. Dicrotendipes sp. Macropelopia sp. PRED CGCF PRED CGCF CGPRED CF CGCF PRED CG PRED 99.37 100 11.88 79.36 97.74 20.33 43.55 ± 5.19 38.45 51.30 100 0.32 ± 0.11 5.09 ± 0.48 - 3.24 ± 0.63 0.33 ± 0.15 - 11.64 ± 3.54 - - 0.49 ± 0.2 164 ± 10 238 ± 20 - 458 ± 48 460 ± 56 - 267 ± 15.14 - 430 ± 37 528 ± 52 a When replicates were analyzed, they are in parenthesis. Biological fractions, elemental concentrations, and error values reported are replicates average * Concentrations corrected by geological particulate contamination – element concentration was not recorded To compare [As] and [Zn] in chironomid larvae with different feeding habits (collector-gatherers and predators), one-way ANOVAs were performed in PRIMER Version 5.2.9 [ 44 ] and results were considered statistically significant with p values < 0.05. Chironomid’s purge In aquatic organisms, particularly species that feed on detritus or sediment, gut content can represent an important proportion of the total contaminant body burden [ 45 ]. Direct gut clearing has been suggested in previous bioaccumulation studies to reduce possible errors from indirect estimation methods [ 46 – 48 ]. Therefore, chironomid larvae were kept in beakers with ASTM (American Society for Testing and Materials) type 1 water for 48–72 h until their gut contents were emptied [ 48 , 49 ]. Then, samples for metal analyses were prepared with cleaned and purged chironomids, and when gut contents (named purged material) obtained were significant (> 0.5 mg), they were also preserved to evaluate As and Zn larval excretion. Analytical procedures Biological samples (chironomid larvae and purged material) were stored in SUPRASIL quartz ampoules for analysis, freeze-dried to constant weight, and sealed. Bulk sedimentary samples were freeze-dried, sieved with a 63-µm mesh, and between 3–65 mg of this fraction were placed in plastic vials for elemental analysis. Only the < 63 µm fraction was analyzed, because chironomids mostly ingest small particles and metals are mainly associated with this finer fraction [ 5 ]. Biological and sedimentary samples were analyzed by irradiation in the RA-6 nuclear reactor (Centro Atómico Bariloche, Argentina), and metal concentrations were determined by Instrumental Neutron Activation Analysis (INNA). Ampoules and plastic vials were irradiated for 20 and 6 h, respectively. Two gamma-ray spectra were recorded at different decay times after irradiation, using an intrinsic High-Purity Germanium (HPGe) detector and a 4096-channel analyzer. Using the absolute parametric method, [As] and [Zn] were determined and reported on a dry weight (DW) basis, with analytical uncertainties indicated after “±”. Geological material contamination Biological samples may be contaminated with inorganic geological particles, producing errors in analytical determinations, even when chironomid larvae have been cleaned and purged. So, possible geological contributions were subtracted to correct the elemental concentrations in biota samples and obtain accurate estimations. Inorganic geological particles in larvae and purge samples were estimated by determining lithophile elements, such as samarium (Sm), a rare earth element that can be used as a geochemical tracer. The INAA technique allows the simultaneous determination of up to 35 elements, including Sm, which shows the highest sensitivity to geological contamination in biological samples. Therefore, it was used to estimate contamination by geological particles and achieve elemental corrections. After the subtraction of the geological content, the remaining material corresponds to the biological fraction: $$\:{\text{F}}_{\text{b}}\:=\:1\:-\:\frac{{\text{C}}_{\text{L},\text{V}}}{{\text{C}}_{\text{L},\text{G}}}$$ F b = Biological fraction of the sample, determined by subtraction of the geological fraction evaluated by the determination of lithophile element (Sm) CL, V = Concentration of the lithophile element (Sm) in the biota sample CL, G = Concentration of the lithophile element (Sm) in geological material present in the biota sample The INAA technique has detection limits that depend on the irradiation conditions and sample composition, which can be significantly variable among different biota samples. The corrections in elemental determinations are possible when a lithophile element is present in biological samples. The detection limit for Sm was low enough to affirm that contamination by geological material was below analytical uncertainty. Moreover, to apply this correction, it is necessary to determine elemental concentrations in geological material present in biota samples in order to estimate the biological fraction and implement the corresponding measurement adjustment. All biological samples presented here include this geological correction. Biota samples with corrections higher than 50% were excluded due to their high uncertainties, and samples with biological fractions below 50% were not considered for correction as inorganic material was considered predominant. Elemental bioaccumulation and excretion factors To evaluate the long-term metal bioaccumulation in aquatic organisms, the determination of bioaccumulation factors (BAFs) is a commonly used method [ 50 ]. In the present study, As and Zn BAFs were calculated along a year to compare the assimilation of both elements in chironomid larvae according to their associated substrate. The formula used to estimate As and Zn BAFs is the ratio between the metal concentration in the chironomid larvae and the corresponding substrate: $$\:\text{BAF}=\frac{{\left[\text{element}\right]}_{ch}}{{\left[\text{element}\right]}_{s}}$$ [element] ch = [element] in chironomid larvae [element] s = [element] in associated substrate Additionally, to estimate As and Zn excretion by chironomid larvae, the ratio between the elemental concentration in purged material and purged larvae, named excretion factor (EF), was also calculated as follows: $$\:\text{EF}=\frac{{\left[\text{element}\right]}_{pu}}{{\left[\text{element}\right]}_{ch}}$$ [element) pu = [element] in purged material obtained of chironomid larvae [element] ch = [element] in chironomid larvae Finally, to evaluate the potential origin of the purged material from its associated substrate, the ratio between the elemental concentration in the purge and in its corresponding substrate was also calculated ([element] pu /[element] s ) [ 51 ]. This metric shows whether the excreted material results directly from the ingestion and elimination of sediment-associated elements. This allows us to visualize the errors introduced when the element concentration in sediment is considered equivalent to that in the gut content, instead of measuring the purged material when possible. Results We first report [As] and [Zn] measured in substrates from Lake MO to evaluate their natural lacustrine distribution; and then, to assess their bioaccumulation and excretion patterns in chironomids, [As] and [Zn] in the corresponding larvae and purged material are presented. Although chironomid larvae were observed in most substrates, in some cases they were only found in summer, such as submerged riparian leaves and sediment from the stoned area. Larvae were absent in sediment at 40 and 90 m depths during the entire sampling period; so, element concentrations at these deeper zones were excluded from the analysis. Elements in substrates The [As] recorded in sedimentary substrates ranged from 2.92 to 13.7 µg g − 1 DW. The highest [As] were observed in littoral vegetated zones dominated by submerged macrophytes Nitella sp. (12.06 ± 1.65 µg g − 1 DW) and Myriophyllum sp. (11.13 ± 0.86 µg g − 1 DW); followed by sediment from sublittoral (6 m depth; 10.52 ± 0.62 µg g − 1 DW) and deeper (20 m depth; 10.48 ± 1.18 µg g − 1 DW) zones. The remaining samples, corresponding to vegetated zones dominated by emergent S. californicus and stoned areas, showed lower [As] (6.14 ± 1.26 and 4.67 ± 2.87 µg g − 1 DW, respectively). Biological samples ( Myriophyllum sp. and submerged riparian leaves) exhibited the lowest mean [As] (0.92 ± 0.35 and 0.74 ± 0.43 µg g − 1 DW, respectively); and recorded their maximum values in summer (1.42 and 1.09 µg g − 1 DW, respectively) (Fig. 2a; Supporting information). For the case of Zn, Myriophyllum sp. leaves showed the highest concentrations, with an average of 188.82 ± 60.84 µg g − 1 DW, and reaching a maximum value of 266 µg g − 1 DW in autumn. Among sedimentary substrates, slightly higher [Zn] were observed in sublittoral (166.4 ± 25.89 µg g − 1 DW) and deeper (165.7 ± 9.35 µg g − 1 DW) zones. Sedimentary littoral substrates from vegetated and stoned areas showed lower [Zn], averaging 122 ± 12.54 µg g − 1 DW. The lowest [Zn] were observed in submerged riparian leaves, with an average of 22.64 ± 10.16 µg g − 1 DW, and a maximum value (33.29 µg g − 1 DW) in winter (Fig. 2b; Supporting Information). Arsenic and zinc bioaccumulation in chironomid larvae In general, [As] in chironomid larvae were lower than their corresponding substrate (maintainig a BAF < 1), with some exceptions associated with particular larval feeding strategies. Analysis of [As] in larvae and As BAFs revealed a significantly higher bioaccumulation in collectors compared to predators (ANOVA, p < 0.05). For instance, larvae inhabiting sediment from vegetated zones dominated by Myriophyllum sp. showed the highest [As] during summer (11.64 µg g − 1 DW; BAF = 1.12) compared to other seasons. During summer, chironomid larvae were represented by collector feeders ( Chironomus sp. and Riethia sp.) in contrast to the other seasons, when were dominated by predators ( Djalmabatista sp. and Macropelopia sp.) (average [As] 1.26 ± 0.67 µg g − 1 DW) (Fig. 3 a; b). Similarly, in Myriophyllum sp. leaves, although chironomid larvae showed a lower annual average [As] compared to this substrate (Fig. 2a), this seasonal study revealed that when the chironomid community was dominated by collector taxa, their [As] were higher than when predators also composed the sample. For example, collector-gatherers ( Parapsectrocladius sp., Apedilum sp., and Tanytarsyni members) were dominant during winter and spring, observing larval [As] (2 and 0.82 µg g − 1 DW, respectively) higher than those recorded in the macrophyte leaves (recording BAFs of 2.44 and 1.3, respectively). But during the other seasons, when chironomid assemblages were also composed of predators ( Parachironomus sp.), [As] decreased (averaging 0.34 ± 0.014 µg g-1 DW) (Fig. 3 a; b). In other substrates, while chironomid collector larvae exhibited higher [As] than predators, their values always remained below [As] in the corresponding substrates (maintaining BAF < 1). For example, in sediment from vegetated areas dominated by S. californicus and Nitella sp., and from sublittoral zones, when the chironomid community was dominated by collector-filterers ( Riethia sp.), their [As] (mean value = 3.78 ± 1.23 µg g − 1 DW) were higher than in predators ( Cryptochironomus sp. and Djalmabatista sp.) (1.2 ± 0.9 µg g − 1 DW) (Fig. 3 a; b). Chironomid larvae exhibited elevated [Zn], even exceeding values observed in their corresponding substrates and purged material (Fig. 2b; Fig. 3 c; d). In contrast to As, [Zn] and Zn BAFs showed lower values in collectors than in predators and shredders (ANOVA, p < 0.05). The highest [Zn] were recorded in larvae from littoral sediment occupied by Nitella sp., represented by predators ( Djalmabatista sp.) (averaging 1069 ± 453 µg g − 1 DW; BAF = 8.7 ± 3). In submerged riparian leaves, the highest Zn BAF (17.47) was recorded in predators ( Ablabesmyia sp.) (164 µg g − 1 DW). In littoral sediment dominated by Myriophyllum sp., the highest [Zn] was observed in shredders ( Polypedilum sp.) (870 µg g − 1 DW; BAF = 7.02) compared to collectors ( Parapsectrocladius sp., Chironomus sp., and Riethia sp.) (averaging 318 ± 89 µg g − 1 DW; BAF = 2.47 ± 0.79) and predators ( Djalmabatista sp. and Macropelopia sp.) (277 ± 171 µg g − 1 DW; BAF = 2.25 ± 1.33) (Fig. 3 c; d). Arsenic and zinc excretion in chironomid larvae Eleven samples of purged material were recovered for metal analysis. In general, [As] in chironomid purges showed higher values (between 8.53 and 12.8 µg g − 1 DW) than the corresponding larvae and substrates. The highest [As] were recorded in purges obtained from larvae inhabiting areas dominated by Myriophyllum sp. (12.25 ± 0.78 µg g − 1 DW) (Fig. 2a; Supporting Information). Although all chironomid larvae excreted more As than they bioaccumulated (resulting in EF > 1), the highest EF were exhibited by those inhabiting biological substrates, both submerged riparian leaves (8.53 µg g − 1 DW; EF = 25) and Myriophyllum sp. leaves (10.2 µg g − 1 DW; EF = 20.4) (Fig. 4 a). While [As] observed in purges was generally higher than the corresponding substrates, this difference was more pronounced in littoral areas (with maximum values in biological substrates) and progressively decreased with depth. In fact, at 6 and 20 m depth, during some sampling seasons [As] in purges were even lower than the sediment (Fig. 4 b). It is important to emphasize that for most substrates, a sufficient mass of purged material was obtained only for one sampling season; and in most cases, purges from all corresponding larvae were pooled to reach an adequate weight. However, in sediment at 6 m depth, where purge material was collected during three sampling seasons, similar [As] and EFs (10.9 ± 1.77 µg g − 1 DW and 2.2 ± 0.5, respectively) were observed (Fig. 4 a). Zinc concentrations measured in chironomid purges were higher than the corresponding substrate, but in general lower than the associated larvae (Fig. 2b; Supporting Information). The highest [Zn] were recorded in purged material from larvae inhabiting both Myriophyllum sp. leaves and sediment occupied by this macrophyte (averaging 418 ± 221.7 µg g − 1 DW) (Fig. 2b). Zinc EFs exhibited variable values between substrates, some showed increased levels and others remained below 1. The highest EFs (with values > 1) were observed in submerged riparian leaves, Myriophyllum sp. leaves and sediment dominated by this macrophyte (autumn), and at 6 m depth (during the colder season) (Fig. 4 c). Additionally, [Zn] in purged material was, in general, similar to that recorded in the corresponding substrate, except in submerged riparian leaves and littoral sediment occupied by Myriophyllum sp., where [Zn] in purges notably exceeded values in substrates (Fig. 4 d). Discussion This study examined the natural lacustrine distribution of two contrasting trace elements in Lake MO and compared their bioaccumulation and excretion in chironomid larvae, considering their associated substrate type and functional feeding strategies. Here, we first analyze and assess the elemental concentration in several lacustrine substrates; and then, bioaccumulation and excretion factors in chironomids are presented and discuss. Arsenic, a potentially toxic element, was primarily associated with sediment, which acts as its main reservoir and makes it largely unavailable to organisms. Zinc, an essential and crucial element for normal metabolic functions, was abundant on submerged macrophyte leaves, being more readily available to organisms. Differences in As and Zn patterns were recorded among substrates, chironomid larvae, and purged material, reflecting particular biogeochemical dynamics between both elements. In general, the highest [As] were observed in the purged material, followed by sedimentary substrates > chironomid larvae > biological substrates ( Myriophyllum sp. and submerged riparian leaves). In contrast, the highest [Zn] were recorded in chironomid larvae, followed by purged material > Myriophyllum sp. leaves > sedimentary substrates > submerged riparian leaves (Fig. 2). The main differences between these elements in relation to their lacustrine distribution and biological aspects associated with their bioaccumulation and excretion in chironomid larvae, are presented in Table 2 . Lastly, our findings are compared with previous Patagonian studies, highlighting the chironomid community as an indicator of metal bioavailability and a potential vector from benthic substrates to upper trophic levels in lacustrine food webs. Table 2 Main differences in the dynamics of environmental distribution, and bioaccumulation and excretion in chironomid larvae between Arsenic (As) and Zinc (Zn) in Lago Moreno Oeste Substrate with higher larval excretion Biological substrates (Submerged riparian leaves and Myriophyllum sp.) Biological substrates, and sediment from Myriophyllum sp. area and sublittoral zone (mostly during colder seasons) Accumulation pattern order Purged material > sediment > chironomid larvae > biological substrates Chironomid larvae > purged material > Myriophyllum sp. leaves > sediment > submerged riparian leaves Larval Feeding habits with greater bioaccumulation Collector-gatherers ( CG ) Collector-filterers ( CF ) Predators ( PRED ) Shredders ( SH ) Substrate with higher larval bioaccumulation Myriophyllum sp. area (sediment and leaves) Submerged riparian leaves and littoral vegetated sediment ( Myriophyllum sp. and Nitella sp.) Main reservoir in the lacustrine environment Sediment , mainly from littoral areas dominated by submerged vegetation ( Nitella sp. and Myriophyllum sp.) and deeper zones (6 and 20 m depth) Myriophyllum sp. leaves (followed by sublittoral and deeper sediment) Arsenic (As) Zinc (Zn) Arsenic and zinc in lacustrine substrates Arsenic concentrations recorded in sediments from Lake MO were lower than the local geochemical background levels established for Lake Moreno (LGB2 = 24.5 µg g − 1 ) and, in most cases, they were also below than those defined for Lake Nahuel Huapi (LGB1 = 12.75 µg g − 1 ), except in littoral sediment dominated by Nitella sp., where [As] exceeded 13 µg g − 1 . Moreover, [As] in sedimentary substrates from Lake MO are comparable to those reported for surface sediments in eleven other Patagonian lakes, with values generally around LGB1, with one exception above 200 µg g − 1 recorded in the deep zone of Lake Gutiérrez associated with redox gradients. In the case of Zn, all values recorded in sediments from Lake MO were above LGB1 (96.7 µg g − 1 ), and some samples from sublittoral and deep zones exceeded LGB2 (172.5 µg g − 1 ). In general, [Zn] were similar to those in other lakes from the region, most of which are close to 121 µg g − 1 , except for the deep zones of some lakes reaching up to 400 µg g − 1 [ 52 ]. In this context, our results indicate that [As] and [Zn] observed in Lake MO are similar to those from surface sediments in other Patagonian lakes and geochemical baselines across the region. The highest [As] were recorded in littoral sediment occupied by submerged macrophytes ( Myriophyllum sp. and Nitella sp.), followed by sediment from sublittoral and deep zones; and the lowest [As] were observed in biological substrates ( Myriophyllum sp. and submerged riparian leaves). In contrast, the highest [Zn] were recorded in Myriophyllum sp. leaves, while sedimentary substrates showed relatively constant [Zn], with a slight tendency to increase in deeper zones (Fig. 2; Table 2 ; Supporting Information). Lacustrine sediments have been recognized by reduce pollution in surrounding water by their high capacity to adsorb heavy metals [ 53 – 55 ]. In Lake MO, elevated [As], and to a lesser extent [Zn], were observed in sublittoral and deeper zones, which is consistent with the tendency of metals to be deposited in bottom sediments. Lacustrine systems without continuous input of soluble forms, tend to deposit these elements at their deepest parts [ 56 , 57 ]. A previous study identified a general trend to increasing [As] from the deepest areas of Patagonian lakes, where deposition processes prevail over suspension, noting a positive correlation between [As] and lake depth [ 52 ]. This may be also associated with smaller particle sizes composing sediment from deeper zones; and since heavy metals are strongly adsorbed on particle surfaces, profundal sediments, due to their higher surface/volume ratio, tend to exhibit elevated metal concentrations [ 58 – 60 ]. Moreover, As tends to bind to iron, manganese, and the residual fraction, making it less available in comparison with Zn, which is mainly present in the easily mobilizable fraction [ 61 ]. Elevated [As] in littoral sediment occupied by submerged vegetation are associated with the capability of macrophytes to adsorb metals through their fibrous root systems, which have a large contact area [ 62 , 63 ]. Particularly, [As] are usually higher in the root systems because the root endodermis limits its translocation to the leaves [ 64 ]. Then, metals can be lost and return to the adjacent sediment through leaching or other biogeochemical mechanisms, like root exudation processes, which may acidify the rhizosphere, also causing the release of heavy metals to soil particles, often increasing their availability and toxicity [ 62 , 65 ]. Hence, although heavy metals are primarily stored in sediments from deeper zones, littoral vegetated sediments may also act as important lacustrine reservoirs for trace elements, including As [ 57 ]. Myriophyllum sp. leaves recorded the highest [Zn], mainly during autumn and winter. Previous studies have shown that aquatic macrophytes are highly capable of accumulating substantial amounts of elements in their tissues, mostly those essential for organisms, such as Zn and copper (Cu), which are considered key elements required for growth and maintenance mechanisms [ 63 ]. In accordance with our results, a study on several heavy metals (mercury, cadmium, lead, nickel, chromium, Cu, and Zn) in various submerged macrophytes species, reported that Zn was the most accumulated element [ 66 ]. Some characteristics of submerged plants, such as their morphology and a much thinner cuticle, could facilitate uptake of heavy metals [ 65 ], explaining the elevated [Zn] in their leaves. The lowest [As] and [Zn] in Lake MO were observed in submerged riparian leaves. Foliar metal uptake is associated with their environmental availability, and may occur either by deposition on the leaf surface or by penetrate the cuticle and being translocated to internal plant tissues [ 67 – 69 ]. A previous study conducted in several Patagonian lakes emphasized the role of riparian vegetation in the cycling and storage of trace elements [ 70 ]. Those authors observed that native and exotic terrestrial plants ( Lomatia hirsute, Luma apiculata, Maytenus boaria, Nothofagus antarctica , and Nothofagus dombeyi ) exhibited lower heavy metal concentrations in decomposing leaves, including As (0.05–0.15 µg g − 1 ) and Zn (15–30 µg g − 1 ) compared to fresh leaves (As = 0.22 µg g − 1 ; Zn = 25–60 µg g − 1 ). These lower values could be related to element dynamics during litter decomposition, which is influenced by litter quality, the decomposer community, and environmental factors such as temperature, pH, and nutrient availability [ 71 ]. Similarly, the low [As] and [Zn] reported in submerged riparian leaves from Lake MO may also be attributed to element liberation during decomposition, resulting in the release of these elements into the surrounding lacustrine environment. Arsenic bioaccumulation and excretion in chironomid larvae Arsenic concentrations observed in chironomid larvae followed the variations in their respective substrates, but with consistently lower values. Some exceptions were recorded in larvae inhabiting Myriophyllum sp. and sediment from the area occupied by this macrophyte, supporting the idea that even at low metal concentrations, chironomids are capable of accumulating significant amounts of metals, demostrating their role as sentitive indicators [ 32 ]. In Lake MO, variations in [As] were associated with specific larval feeding strategies, for example, in sediment from the Myriophyllum sp. area, higher larval [As] during summer was observed in collector organisms, but during other seasons, chironomids were mainly predators and recorded lower [As]. Collector-gatherer taxa, such as Chironomus riparius , are more adapted to accumulate contaminants because they exhibit a high tolerance to sediment-bound toxicants [ 72 ]. This higher susceptibility to heavy metals contamination is associated with the fact that collector chironomids mainly feed on detritus, remaining in close contact with the bottom sediment [ 38 , 73 ], and, as we observed in Lake MO, it often contains elevated [As]. Therefore, these organisms are susceptible to element bioaccumulation due to their strong contact with the major reservoir of contaminants in lacustrine systems [ 74 , 36 , 75 ]. Low As bioaccumulation in predator larvae may be mostly associated with their reduced direct exposure to sediment-bound contaminants, avoiding the ingestion of sediment and limiting the assimilation of heavy metals [ 76 ]. These findings could be also indicative of a As biodilution pattern among different functional feeding groups of chironomids, as was also observed for silver (Ag) [ 77 ]. On the other hand, it is important to highlight the elevated [As] found in chironomid predators collected at 20 m depth, which may be partially attributed to exoskeletal contamination by inorganic particles. As was reported previously, the external surfaces of specimens may be littered with As-bearing particles trapped by setae, despite repeated rinsing prior to analysis [ 78 ]. In our results, this may have occurred in organisms at 20 m depth, because this sediment, composed of finer particles, is more likely to adhere to the exoskeleton, possibly leading to an overestimation of As in their tissues. Elevated [As] were observed in chironomid purged material, which exceeded values recorded in both larvae and their corresponding substrates (Fig. 2a). This indicates that the purging process is efficiently acting as a detoxification mechanism, temporarily storing As before its excretion. The most elevated EF values recorded in purges from larvae inhabiting biological substrates evidence the influence of the substrate type and larval feeding strategies on metal excretion rate. These larvae primarily feed on biofilm associated with biological surfaces, mainly composed of fungal and bacterial microorganisms [ 79 – 81 ], which are capable to accumulate elevated metal concentrations through adsorption. Therefore, biofilm act as an important sink for trace metals and play a crucial role in their transference into the food chain, including As. Consequently, as chironomid larvae consume large quantities of biofilms enriched in As (3.8–23 µg g − 1 ) [ 82 ], they regulate their high metal loads by excreting elevated [As] through their purges. This finding highlights the role of this insect community not only as bioindicators of contamination, but also as potential regulators of metal cycling in aquatic systems. Zinc bioaccumulation and excretion in chironomid larvae Zinc concentrations in chironomid larvae from Lake MO generally exceeded values recorded in their respective substrates, indicating an accumulation of this element in their tissues. Understanding the source of Zn, its availability, and its bioaccumulation are fundamental for evaluating trophic transference and environmental distribution. Highest [Zn] and BAFs were observed in larvae from littoral zone, principally in sediment from areas occupied by submerged species ( Myriophullum sp. and Nitella sp.) and biological substrates. In this case, higher Zn uptake was associated with predators ( Djalmabatista sp., Ablabesmyia sp., and Cryptochironomus sp.) and shedders ( Polypedilum sp.) (Fig. 3 c; d). Although the relative importance of diet and food uptake pathways is context-dependent, in predators, elevated Zn assimilation may be linked to their diet, as their prey could exhibit higher concentrations of biologically required trace elements, mainly in the order Zn > Fe > Mn, during grazing [ 83 ]. Shredder chironomids base their diet on periphytic algae and coarse particulate organic matter while grazing on biological substrates such as submerged vegetation, algae, wood, or detrital debris [ 84 , 85 ]. As was previously mentioned, epilithic periphyton (biofilm) serves as a major sink for metals (often accumulating higher concentrations than sediments), explaining the elevated metal bioaccumulation in shredders feeding on biological substrates and adjacent sediment. Therefore, a key factor associated with increased Zn observed in these larvae is their direct interaction with biofilm-associated microbes with heavy metals [ 86 ], facilitating the assimilation of essential elements. Additionally, the deposition of fine particulate organic matter on periphyton can further enhance metal uptake in organisms feeding on biofilm, increasing their total metal burden [ 36 ]. In purged material, [Zn] in general surpassed values in their corresponding substrates, but remained lower than those in their associated larvae (Fig. 2b), suggesting an effective regulatory mechanism for this essential element. In accordance, it was also noted that high EF values were observed in some purges from substrates where BAFs were also elevated, such as sediment under Myriophyllum sp. and submerged riparian leaves (Fig. 3 d; 4 c). Our findings suggest that the gut content may serve as a significant Zn reservoir, allowing larvae to temporarily sequester metal excess to maintain a constant [Zn], regardless of the adjacent sediment, showing their ability to regulate essential elements, including Zn [ 87 ]. In substrates with purged material available during several sampling seasons, a trend of increased amounts of Zn during colder months was observed (Fig. 4 c). This pattern could be partially explained by an increased Zn release from biological substrates during cold sampling seasons, and therefore, a higher environmental availability for organisms. Moreover, at low temperatures, decreased physiological activity produces a reduction in metal uptake in chironomid larvae [ 88 ]. As a result, under high external availability but lower metabolic demand, as occurs during colder seasons, Zn tends to be more excreted by chironomid larvae, explaining the elevated concentrations in purged material. Why measure purged material instead of using estimation methods? Previous studies have affirmed that chironomid gut sediments can contribute between 2 and 65% of the total body burden, introducing a considerable bias in elemental determinations when whole larvae are analyzed to assess tissue metal assimilation [ 45 , 51 ]; so, accurate estimation of metal content in the gut is critical [ 48 ]. In this context, some works affirmed that when it is not possible to purge organisms or remove their guts, it may be considered valid to apply a formula to estimate the concentration in the guts and subtract it from the total body burden [ 45 ]. However, an important premise of this formula is the assumption that the surrounding sediment element concentrations exactly reflect what the organisms have in their guts as ingested food, which assumes homogeneity in sediment composition and does not include feeding selection [ 48 ]. Our findings in this study evidenced that, while the ratio between [As] and [Zn] in purges and the associated sediment often approached one (confirming their equivalence), this was not consistent (Fig. 4 b; d). In lacustrine ecosystems, trace element are not homogeneously distributed within the lake, since they may be differentially associated with particles according to sediment granulometric composition, organic matter content, presence of aquatic vegetation, among other variables. The sedimentary phase is considered relevant in the transference of elements to organisms [ 89 ], where the finer fraction has a greater metal adsorbing capacity, mainly due to a higher surface/volume ratio [ 58 , 59 , 60 ]. As was observed in chironomid larvae, since they mostly exhibit selective feeding behavior, ingesting specific sediment particle sizes or different food types, their purged material showed variable [As] and [Zn] according to its content. This information reinforces the advantage of using a direct method to remove and separately measure the purge, to achieve accurate metal determinations instead of applying an estimation formulae. This suggestion had already been introduced by previous studies, which observed that indirect calculation methods to estimate metal content using a specific formula may not be as reliable as purging organisms and directly measuring the eliminated content [ 46 , 48 ]. Insights into trace elements dynamics trough midge communities In Lake MO, As bioaccumulation in chironomid larvae was similar to that reported for Ag, another non-essential element considered one of the most toxic metal ions in aquatic ecosystems. In both cases, the main element transference occurred from the littoral zone, principally from Myriophyllum sp. leaves and sediment from vegetated areas [ 77 ]. These comparable results suggest that non-essential elements may be stored in specific zones of lacustrine systems, which can act as hot spots of bioaccumulation for aquatic organisms. These results support the role of the chironomid larvae community as an important pathway for element transference from benthic lacustrine substrates to upper levels in Patagonian food webs. Our findings in chironomid larvae are consistent with results observed for the fish community in Lake Nahuel Huapi, where the main As transference to the aquatic biota occurs principally through organisms closely associated with sediment, exhibiting significantly higher concentrations than pelagic species. For example, the benthivorous creole perch recorded elevated [As] in muscle and liver compared with the piscivorous species rainbow and brown trout, which mostly prey on bentho-pelagic species [ 90 , 23 ]. This indicates As transference based on diet, as was also reported by other studies worldwide, indicating that bottom-feeding fishes accumulate more As than pelagic predatory species [ 91 – 93 ]. Our results in chironomid larvae support this transference pattern, as that collector feeders, which directly ingest fine particulate organic matter from sediment, showed significantly higher [As] than predators, revealing that even within macroinvertebrate communities, species associated with benthic substrates exhibit higher As bioaccumulation. Moreover, arsenic bioaccumulation in chironomids from Lake MO align with a global decrease in As assimilation across trophic levels in Patagonian food webs [ 82 , 22 ], suggesting that biodilution occurs not only across different trophic levels, but also among different chironomid functional groups. Based on our findings, chironomid larvae can mobilize contaminants associated with sediments, such as inorganic As, which can constitute up to 98% of total As in chironomid larvae [ 57 ], being considered critical vectors from benthic reservoirs to higher trophic levels. Unlike As, Zn is an essential trace element for many metabolic processes and regulated according to individual physiological requirements. Zinc trophodynamics in freshwater ecosystems remain poorly studied compared to other trace elements. While Zn biomagnification has been observed in several previous studies in aquatic systems, laboratory experiments, and marine food webs [ 24 , 94 , 95 ], a decreasing trend with increasing trophic level was reported in Lake Nahuel Huapi [ 25 ], evidencing a biodilution pattern along the food web in this system. This phenomenon has been observed separately in both pelagic and benthic compartments, suggesting that Zn transference is not only driven by trophic accumulation, but also influenced by local environmental availability and biological regulation. Our findings evidence that Zn bioaccumulation in chironomid larvae is also related to their specific feeding strategies, with shredders and predators recording higher [Zn] compared with collector feeders. These results contrast with Zn biodilution pattern observed in Lake Nahuel Huapi (a system with considerably larger dimensions than Lake MO), supporting that this environment provides adequate Zn levels to cover basic physiological requirements. This suggests that Zn biomagnification or biodilution depends on the local characteristics of each aquatic system, with a trend toward increased [Zn] in environments where this essential element is deficient or present less than optimal levels. Moreover, as we observed in chironomid larvae, aquatic organisms can effectively regulate their Zn levels, even under extreme environmental events, such as the Puyehue-Cordón Caulle volcanic eruption 2011, which introduced significant Zn inputs via pyroclastic material [ 96 ]. This research present information about the natural distribution of essential and non-essential trace elements in lacustrine environments, and their dynamics of bioaccumulation and excretion in aquatic organisms. Arsenic and Zn exhibited contrasting patterns in chironomid larvae, influenced by the spatiotemporal distribution of taxa and their specific feeding strategies. While As was mainly transfer from bottom sediments and reflected a biodilution trend, Zn showed bioaccumulation patterns driven by its environmental availability and particular larvae requirements. Conclusion Different lacustrine distribution patterns of arsenic (As) and zinc (Zn) were observed in substrates from Lake MO, recording values similar to established background levels for surficial sediments in other Patagonian lacustrine environments (between 12.75–24.5 and 96.7–172.5 µg g − 1 DW for As and Zn, respectively). The highest [As] were observed in sedimentary substrates, principally in littoral vegetated areas dominated by submerged macrophytes ( Myriophyllum sp. and Nitella sp) and deeper zones (6 and 20 m depth), reaching the maximum (13 µg g − 1 DW) in sediment occupied by Nitella sp. The highest [Zn] were recorded in Myriophyllum sp. leaves, peaking at 266 µg g − 1 DW. Regarding bioaccumulation and excretion dynamics in chironomid larvae, our results also reflect contrasting elemental responses. While the main transference of both As and Zn from benthic substrates to chironomid larvae occurred in the littoral zone (mainly from biological substrates ( Myriophyllum sp. and submerged riparian leaves) and sediment dominated by submerged macrophytes), particular feeding strategies influenced element bioaccumulation. Arsenic bioaccumulation was notably higher in collectors, indicating sediment ingestion as a major pathway for this non-essential element uptake. In contrast, predators and shredders exhibited higher [Zn], probably associated with this essential element availability in the lacustrine system and particular individual requirements. In relation to chironomid excretion, the highest [As] and [Zn] in purged material were recorded in biological substrates and littoral vegetated sediment, although [As] in purges exceeded values in both substrates and larvae, while [Zn] surpassed values in substrates but remained lower than those in larvae. In Patagonian lakes, chironomid larvae constitute a key component in the diet of small puyen. This native species is a crucial prey for larger fishes, including the introduced brown and rainbow trout, as well as the native creole perch. Our results are consistent with previous studies that observed greater As bioaccumulation in organisms closely associated with sediment, while Zn appears to be influenced by multiple environmental factors, such as exposure route, elemental availability, or individual physiological attributes. The bioaccumulation of As and Zn in chironomid larvae suggests that they may act as an entry point for heavy metals and other trace elements from benthic substrates, particularly from littoral vegetated areas, to upper trophic levels in Patagonian lacustrine food webs. This study highlights the importance of including a wide variety of lacustrine substrates, sampling seasons, and taxa with different functional feeding habits to better represent environmental variability, improve the analysis of metal bioaccumulation in aquatic organisms, and evaluate their potential transference from benthic reservoirs to the food web. Our results also help to elucidate the main drivers of distribution, bioaccumulation, and excretion of essential and non-essential elements in lacustrine systems. Declarations Ethical Approval This is not applicable. Consent to Participate All authors have reviewed and gave their consent to participate in the article. Consent to Publish All authors read and approved the final version to publish the article. Competing Interests The authors declare no competing interests to declare that are relevant to the content of this article. Table II. Seasonally measured arsenic [As] and zinc [Zn] concentrations in chironomid purged material from Lake Moreno Oeste. Chironomid sample composition, feeding habits, and biological fraction are also presented. Analytical uncertainties are indicated after ±. Funding This work was partially supported by the projects PICT 2005–33838 and PICT 2006 − 1051 of the Agencia Nacional de Promoción Científica y Tecnológica (Argentina), Fundación Balseiro (2010/2011), and by the International Atomic Agency, project TCA-ARG/7/006. Author Contribution NW: Investigation & conceptualization, material preparation, data collection, sample processing, data analysis, writing-original draft, writing-review & editing. AR: Investigation & conceptualization, material preparation, data collection, sample processing, writing-review & editing. RJ: Data analysis, figure design, review & editing. DAS: Material preparation, data collection, sample processing, review & editing. 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J S Am Earth Sci 49:1–14. https://doi.org//10.1016/j.jsames.2013.10.006 Additional Declarations No competing interests reported. Supplementary Files TableISupplementarymaterial.doc TableIISupplementarymaterial.doc Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7376220","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":500952291,"identity":"51ffd4c2-dd68-4446-9d6d-80acd8c5479d","order_by":0,"name":"Natalia Williams","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAElEQVRIiWNgGAWjYNACAwsZNhD9ocIGSDI2HsCvnBmkRYIHpIVxxpk0ENVAhBYGCR4wk7flMFgMrxZz9vPHpHkKJHj42E8nf5zZcN5ubfthoC01NtG4tFj2JLNJ84AcxpO7TeLjjtvJ284kArUcS8ttwKHF4ABQSw7YL7nbGGeeuZ1sdgCohbHhMG4t5x9DtfC/3fyZt+1cstn5hwS03IDZIpG7QZq37YCd2Q1Cttx4bGz9B6zl7TbJGWeSE8xuAG1JwOeX84kPb874YyMn35+7+cOHCjt7s/PpDx98qLHBqQUIWCSQeYlglQm4lYMA8wdknj1+xaNgFIyCUTASAQDjWmATjPtrnQAAAABJRU5ErkJggg==","orcid":"","institution":"Centro Atómico Bariloche, Comisión Nacional de Energía Atómica","correspondingAuthor":true,"prefix":"","firstName":"Natalia","middleName":"","lastName":"Williams","suffix":""},{"id":500952292,"identity":"b6633c89-d02f-4837-822d-36bc161e5d43","order_by":1,"name":"Andrea Rizzo","email":"","orcid":"","institution":"Centro Atómico Bariloche, Comisión Nacional de Energía Atómica","correspondingAuthor":false,"prefix":"","firstName":"Andrea","middleName":"","lastName":"Rizzo","suffix":""},{"id":500952294,"identity":"fd12af7b-f79f-4119-9a69-871496745355","order_by":2,"name":"Romina Juncos","email":"","orcid":"","institution":"Centro Atómico Bariloche, Comisión Nacional de Energía Atómica","correspondingAuthor":false,"prefix":"","firstName":"Romina","middleName":"","lastName":"Juncos","suffix":""},{"id":500952296,"identity":"0b9fbde0-f7f9-46e6-93d4-6023d8fae91d","order_by":3,"name":"Diego Añón Suárez","email":"","orcid":"","institution":"Universidad Nacional del Comahue, Centro Regional Universitario Bariloche (CRUB)","correspondingAuthor":false,"prefix":"","firstName":"Diego","middleName":"Añón","lastName":"Suárez","suffix":""},{"id":500952298,"identity":"7dc5996c-e52a-4ae0-9ea0-d0517621699f","order_by":4,"name":"María Angélica Arribére","email":"","orcid":"","institution":"Centro Atómico Bariloche, Comisión Nacional de Energía Atómica","correspondingAuthor":false,"prefix":"","firstName":"María","middleName":"Angélica","lastName":"Arribére","suffix":""},{"id":500952300,"identity":"2e70daaa-9908-4b90-857f-8dbfe7c4b181","order_by":5,"name":"Sergio Ribeiro Guevara","email":"","orcid":"","institution":"Centro Atómico Bariloche, Comisión Nacional de Energía Atómica","correspondingAuthor":false,"prefix":"","firstName":"Sergio","middleName":"Ribeiro","lastName":"Guevara","suffix":""}],"badges":[],"createdAt":"2025-08-14 18:08:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7376220/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7376220/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89671215,"identity":"0882a359-80da-4b48-a3b7-587b9641aa8a","added_by":"auto","created_at":"2025-08-22 12:55:42","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":772907,"visible":true,"origin":"","legend":"\u003cp\u003ea) Representative image of Lake Moreno Oeste (MO). The connection with Lake Moreno Este is also shown; b) Study area indicating sampling sites at Lake MO. GP (Guardaparque) and LL (Llao-Llao) indicate sampled bays for littoral substrate, and red points 6, 20, 40, and 90 indicate sampled depths in sublittoral and deeper zones.\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-7376220/v1/2801074d2c85b716911ec77c.png"},{"id":89671220,"identity":"ac0a366a-a29c-4911-942e-f6f404a500e5","added_by":"auto","created_at":"2025-08-22 12:55:42","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":268226,"visible":true,"origin":"","legend":"\u003cp\u003eAverage annual concentracions (μg g\u003csup\u003e-1\u003c/sup\u003e DW) of a) Arsenic ([As[), and b) Zinc ([Zn]) measured in sedimentary (brown) and biological (green) substrates, chironomid larvae (red), and purged material (gray) from Lake Moreno Oeste. Asterisks (*) represent outlier values.\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-7376220/v1/6827b7aad3f7a047bf2d77fb.png"},{"id":89671216,"identity":"958c05f3-3722-4640-ac8e-01f49330b1a8","added_by":"auto","created_at":"2025-08-22 12:55:42","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":75497,"visible":true,"origin":"","legend":"\u003cp\u003ea) Arsenic [As] and b) Zinc [Zn] concentration in analyzed substrates and chironomid larvae from Lake Moreno Oeste. Green (biological) and brown (sedimentary) squares indicate substrates, and red circles represent larvae. Sampling season and functional feeding groups are also showed; c) Arsenic (As), and d) Zinc (Zn) bioaccumulation factor (BAF) values in chironomid larvae from Lake Moreno Oeste. Functional feeding groups of chironomids composing the sample and corresponding sampling seasons are also indicated (Su = summer; A = autumn; W = Winter; Sp = Spring). Bars with two colors represented samples containing larvae from mixed functional feeding groups.\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-7376220/v1/14cc83e404b738f26ea1ce69.png"},{"id":89671524,"identity":"d1cd8ed3-22c1-4166-9269-f1ba7664edb9","added_by":"auto","created_at":"2025-08-22 13:03:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":59725,"visible":true,"origin":"","legend":"\u003cp\u003ea) Arsenic (As) and; b) Zinc (Zn) excretion factor (EF) values calculated based on purges obtained from chironomid larvae; c) As ([As]) and Zn ([Zn]) concentrations in purged material relative to their associated substrates. Colors indicate the functional feeding groups of the corresponding larvae. Sampling seasons are also indicated (Su = Summer; A = Autumn; W = Winter; Sp = Spring). Bars with two or three colors represented samples containing mixed purged material from several functional feeding groups.\u003c/p\u003e","description":"","filename":"Fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-7376220/v1/bc5b46d17f56645b9bc82c9f.png"},{"id":90734893,"identity":"03e1b44f-f3f4-4d2c-b43b-1c77f10bb857","added_by":"auto","created_at":"2025-09-06 19:46:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2706576,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7376220/v1/2f1ae387-469b-43ca-a971-1a6cc0f8dce0.pdf"},{"id":89671526,"identity":"8dd09789-0ed9-4a54-9c96-637ade08a71c","added_by":"auto","created_at":"2025-08-22 13:03:42","extension":"doc","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":45568,"visible":true,"origin":"","legend":"","description":"","filename":"TableISupplementarymaterial.doc","url":"https://assets-eu.researchsquare.com/files/rs-7376220/v1/b545a7d904e7d53e57477656.doc"},{"id":89671525,"identity":"f74cc5d1-58ff-4545-a4d5-2e3cdb5e58b8","added_by":"auto","created_at":"2025-08-22 13:03:42","extension":"doc","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":43008,"visible":true,"origin":"","legend":"","description":"","filename":"TableIISupplementarymaterial.doc","url":"https://assets-eu.researchsquare.com/files/rs-7376220/v1/3b0e95862a84a3d8eb0c1567.doc"}],"financialInterests":"No competing interests reported.","formattedTitle":"Bioaccumulation of Arsenic and Zinc by Chironomid larvae in Lacustrine Environments: Exploring this Community as Indicator of Trace Element Dynamics in Patagonian Food Webs","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIn aquatic ecosystems, natural trace element concentrations are mainly associated with weathering and leaching processes in the watershed and their subsequent environmental distribution. Anthropogenic activities can increase the input of heavy metals into the catchment area through the transport of pollutants via atmospheric deposition and/or direct discharges [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. These elements are mostly deposited in bottom sediments by hydrological and geochemical processes, turning them into a reservoir of pollutants. Then, through physical and chemical reactions, contaminants can be remobilized from sediments and return to the water column, causing long-term pollution [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Sediment composition has a significant influence on metal accumulation, as a positive relationship has been observed between element concentrations and the proportion of finer substrate fractions (silt and clay) and organic matter content [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Hence, variable metal concentrations may be recorded within a lacustrine watershed associated by several factors, such as sediment granulometric composition, pH, depth, temperature, substrate type, presence of macrophytes, among other variables [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAlthough heavy metals are primarily deposited in lacustrine bottom sediments [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], they can be also bioaccumulated by aquatic organisms, becoming toxic when they exceed certain thresholds [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Organisms living closely associated with benthic substrates are most exposed to metals bound in sediments [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Whether essential (e.g., copper, iron, zinc) or non-essential (e.g., arsenic, cadmium, mercury, lead), these elements can cause negative effects on biota, as organisms can ingest and accumulate all trace elements [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Due to their persistence, high toxicity, and potential to bioaccumulate, essential and non-essential elements are considered contaminants in aquatic environments [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], so it is key to understand their trophic transference in aquatic food webs [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eWe evaluated two contrasting trace elements: arsenic (As), a non-essential metal, and zinc (Zn), an essential one. Arsenic, a highly toxic metalloid naturally present in the environment, is distributed in soil, aquatic systems, air, and even in living organisms [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In aquatic ecosystems, As can be present in various chemical forms, including most toxic inorganic species (e.g., arsenite and arsenate) and organic forms (e.g., methylated species, arsenolipids, and arsenosugars) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. On the other hand, Zn is present in organisms acting as a fundamental component of several proteins and considered essential for normal physiological functions [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Since Zn is indispensable for many metabolic processes, individual organisms control its bioaccumulation, and it is considered toxic when it exceeds certain concentrations. This has led to the evaluation of sediment quality to predict adverse effects on sediment-dwelling organisms in freshwater systems [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eBioaccumulation and trophic transference of As and Zn have been initially studied in different Patagonian lakes (Argentina). For instance, a previous work revealed higher As concentrations [As] in \u003cem\u003eDiplodon chilensis\u003c/em\u003e mussels from lakes Nahuel Huapi and Moreno (47 and 38 \u0026micro;g g-1 dry weight, respectively) in zones with population settlements [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Based on a trophodynamic study, a biodilution pattern was observed in the food web from Lake Moreno [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. On the other hand, in Lake Nahuel Huapi, several fish species varied their [As] according to their feeding habits, with higher values recorded in benthivores, like the creole perch (\u003cem\u003ePercichthys trucha\u003c/em\u003e), compared to those feeding on pelagic prey, such as rainbow trout (\u003cem\u003eOncorhynchus mykiss\u003c/em\u003e) and brown trout (\u003cem\u003eSalmo trutta\u003c/em\u003e) [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In the case of Zn, although the literature is scarce and based on only a fraction of the food web, in natural freshwater systems a general biomagnification pattern has been observed [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. However, along the trophic chain from Lake Nahuel Huapi, it was presented the first research reporting Zn biodilution [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Therefore, element bioaccumulation and transference through the food web is complex, and may be associated not only with chemical properties, but also with multiple environmental factors, such as exposure route or species-specific physiological attributes [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eChironomidae (Insecta: Diptera) is the most widely distributed, numerous, species-rich, and ecologically diverse family of aquatic insects in freshwater systems, with its larvae considered a principal component of benthic invertebrate communities [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. In southern Patagonian lakes, chironomid larvae constitute an important part of the diet of the small puyen (\u003cem\u003eGalaxias maculatus\u003c/em\u003e) [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], and this small fish is a main prey for larger fish, such as the exotic brown and rainbow trout, and the native creole perch [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Based on its ontogenetic habitat shift, the small puyen changes from pelagic larvae to littoral-benthic juvenile and adult, playing an important role in coupling both compartments, and could transfer contaminants between benthic deposits and pelagic environment. Moreover, since chironomid larvae are good accumulators of metals, able to tolerate low oxygen levels [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], and due to their initial trophic position, they are considered the entry point for heavy metals and other trace elements to upper levels of lacustrine food webs. Consequently, it is possible that chironomid larvae could be used as indicators of bioavailability by analyzing their element bioaccumulation and regulation, as well as their potential to transfer contaminants to higher trophic levels.\u003c/p\u003e\u003cp\u003eAlthough several previous studies have analyzed metal bioaccumulation in macroinvertebrate communities, including chironomid larvae [\u003cspan additionalcitationids=\"CR34 CR35\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], there is still a lack of research contrasting the distribution and bioaccumulation dynamics of essential and non-essential elements under natural environmental conditions within the same lacustrine system. To address this point, chironomid larvae were selected as study organisms due to their abundance, wide spatial distribution, and strong association with several benthic substrates that could be important element reservoirs. While their larvae often burrow into surficial sediments and feed on particulate organic matter [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], some species show a clear preference for a particular substrate, others are versatile, occupying a wide variety of habitat patches [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Besides their widespread spatial distribution, chironomid larvae exhibit a varied diversity of functional feeding strategies. Therefore, studying this insect community may provide insights into general patterns of metal assimilation and transport along the trophic chain by evaluating their initial uptake from benthic substrates and successive transference to upper levels. This makes this aquatic insect group a suitable community to explore environmental dynamics of essential and non-essential elements in freshwater ecosystems.\u003c/p\u003e\u003cp\u003eIn this context, the main objective of the present study is to examine the natural environmental distribution of two contrasting trace elements within the same lacustrine system, and their bioaccumulation and excretion patterns in chironomid larvae. This research explores the role of chironomid larvae as an indicator community of the initial uptake of an essential trace element (Zn) and a non-essential one (As) from benthic lacustrine substrates, and their potential transference to upper trophic levels in Lake Moreno Oeste (northern Patagonia). For this purpose, larval bioaccumulation was studied in relation to the spatiotemporal taxa distribution, their respective feeding strategies, and associated substrate type.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy site\u003c/h2\u003e\u003cp\u003eLake Moreno Oeste (MO) (41\u0026deg;03\u0026prime;33\u0026Prime; S; 71\u0026deg;32\u0026prime;24\u0026Prime; W; 758 m asl; 5.22 km\u003csup\u003e2\u003c/sup\u003e; 90 m max. depth) is located in Nahuel Huapi National Park (NHNP) (northern Patagonia, Argentina). It is the western branch of Lake Moreno and is connected to Lake Moreno Este (5.42 km\u003csup\u003e2\u003c/sup\u003e, 106 m max. depth) via a narrow channel [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Lake MO is a warm monomictic system that exhibits stratification from late spring to early autumn, an extensive euphotic zone (Secchi disk\u0026thinsp;~\u0026thinsp;20 m), dissolved organic carbon around 0.8 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, chlorophyll \u003cem\u003ea\u003c/em\u003e level of 1 \u0026micro;g L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, total nitrogen of 140 \u0026micro;g L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and total phosphorus of 4 \u0026micro;g L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. The lacustrine shoreline has peninsulas, bays, and inundated regions occupied by native forests \u003cem\u003eNothofagus dombeyi\u003c/em\u003e (\u0026ldquo;coihue\u0026rdquo;) and \u003cem\u003eAstrocedrus chilensis\u003c/em\u003e (\u0026ldquo;cordilleran cypress\u0026rdquo;) [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the littoral zone, dense aquatic vegetation includes both submerged macrophytes, such as \u003cem\u003eMyriophyllum quitense\u003c/em\u003e and \u003cem\u003eNitella\u003c/em\u003e sp., and the emergent \u003cem\u003eSchoenoplectus californicus\u003c/em\u003e. The macroinvertebrate community of the Lake Moreno system is dominated by insect larvae (Diptera, Trichoptera, Odonata, Ephemeroptera, and Plecoptera), mollusks, annelids, amphipods, and benthic crustaceans (\u003cem\u003eAegla\u003c/em\u003e spp. and \u003cem\u003eSamastacus spirinifrons\u003c/em\u003e (Philippi)) [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The fish community includes both exotic rainbow, brown, and brook trout (\u003cem\u003eSalvelinus fontinalis\u003c/em\u003e) and native species (creole perch, big puyen (\u003cem\u003eGalaxias platei\u003c/em\u003e), and small puyen) [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eSample collection\u003c/h3\u003e\n\u003cp\u003eChironomid larvae are distributed across the littoral, sublittoral, and deep zones of Lake MO, occupying numerous substrate types such as submerged riparian leaves from the surrounding forest, submerged macrophytes, and bed sediments from both vegetated and non-vegetated zones at different depths. Therefore, to include all habitat patches inhabited by chironomid larvae, different substrate types were sampled from littoral to deep zones. The selected lacustrine bays were Llao Llao (LL) and Guardaparques (GP) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) and the sampling period extended from April 2014 (austral autumn) to February 2015 (austral summer).\u003c/p\u003e\u003cp\u003eIn sublittoral (6 m depth) and deep (20, 40, and 90 m depth) zones, bottom sediment was collected with an Ekman dredge (225 cm3) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). In the littoral zone from LL bay, sediment was taken from areas dominated by submerged macrophytes using an Ekman dredge, and from areas occupied by emergent species using a short plastic corer. Moreover, samples of \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves were manually collected. In the littoral zone from GP bay, sampling areas (531 cm\u003csup\u003e2\u003c/sup\u003e) within patches covered with submerged riparian leaves and stones were delimited, where decomposing leaves were manually retrieved and sediment below stones was collected using a short plastic corer. All samples were stored in plastic bags. Six replicates of each substrate type were collected at each sampling season.\u003c/p\u003e\u003cp\u003eAt the laboratory, chironomid larvae were separated from each substrate sample and identified under a binocular glass until subfamily or tribe level [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. To determine [As] and [Zn] in chironomid larvae from each substrate, individuals of the same group were pooled until reaching a mass of at least 0.5 mg. When weight was limited, samples were obtained with mixed individuals; and when chironomid mass was sufficient, replicate samples were prepared to evaluate variability (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). After extracting chironomid larvae, biological (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and riparian leaves) and sedimentary samples were conserved for elemental analysis (see \u0026ldquo;Analytical procedures\u0026rdquo; section).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eChironomid samples analyzed for arsenic (As) and zinc (Zn) contents in Lake Moreno Oeste. The sampling station, substrate, dominant chironomid taxa, and feeding habit are indicated (PRED\u0026thinsp;=\u0026thinsp;predator, CG\u0026thinsp;=\u0026thinsp;collector-gatherer, CF\u0026thinsp;=\u0026thinsp;collector-filterer, SH\u0026thinsp;=\u0026thinsp;shredder). Analytical uncertainties are indicated after \u0026plusmn;.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSampling season\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSubstrate\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDominant taxa\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eFeeding habit\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eBiological fraction (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e[As] concentration (\u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e[Zn] concentration\u003c/p\u003e\u003cp\u003e(\u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAustral Autumn\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSed. \u003cem\u003eS. californicus\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eMyriophyllum\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eNitella\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eBed. Sed. 6 m. depth\u003c/p\u003e\u003cp\u003eBed. Sed. 20 m. depth\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eCryptochironomus\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eCryptochironomus\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eParachironomus\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eParapsectrocladius\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eDjalmabatista\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eParapsectrocladius\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003ePolypedilum\u003c/em\u003e sp.1\u003c/p\u003e\u003cp\u003e\u003cem\u003eDjalmabatista\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eRiethia\u003c/em\u003e sp. (\u003cb\u003e3\u003c/b\u003e \u003csup\u003ea\u003c/sup\u003e)\u003c/p\u003e\u003cp\u003e\u003cem\u003eCryptochironomus\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eCryptochironomus\u003c/em\u003e sp.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eCG\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eCG\u003c/p\u003e\u003cp\u003eSH\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eCF\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e55.56\u003c/p\u003e\u003cp\u003e81.78\u003c/p\u003e\u003cp\u003e97.59\u003c/p\u003e\u003cp\u003e100\u003c/p\u003e\u003cp\u003e98.69\u003c/p\u003e\u003cp\u003e92.2\u003c/p\u003e\u003cp\u003e81.54\u003c/p\u003e\u003cp\u003e92.96\u003c/p\u003e\u003cp\u003e62.81\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003c/p\u003e\u003cp\u003e100\u003c/p\u003e\u003cp\u003e49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e0.39\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003c/p\u003e\u003cp\u003e0.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\u003cp\u003e0.93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e \u003cp\u003e0.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84\u003c/p\u003e\u003cp\u003e3.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36\u003c/p\u003e\u003cp\u003e0.361\u0026thinsp;\u0026plusmn;\u0026thinsp;0.097\u003c/p\u003e\u003cp\u003e7.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e482\u0026thinsp;\u0026plusmn;\u0026thinsp;49\u003c/p\u003e\u003cp\u003e264\u0026thinsp;\u0026plusmn;\u0026thinsp;24\u003c/p\u003e\u003cp\u003e227\u0026thinsp;\u0026plusmn;\u0026thinsp;24\u003c/p\u003e\u003cp\u003e208\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u003c/p\u003e\u003cp\u003e420\u0026thinsp;\u0026plusmn;\u0026thinsp;190\u003c/p\u003e\u003cp\u003e870\u0026thinsp;\u0026plusmn;\u0026thinsp;190\u003c/p\u003e\u003cp\u003e1390\u0026thinsp;\u0026plusmn;\u0026thinsp;540\u003c/p\u003e\u003cp\u003e215.2\u0026thinsp;\u0026plusmn;\u0026thinsp;119.9\u003c/p\u003e\u003cp\u003e345\u0026thinsp;\u0026plusmn;\u0026thinsp;46\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAustral Winter\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eMyriophyllum\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eNitella\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eBed. Sed. 6 m. depth\u003c/p\u003e\u003cp\u003eBed. Sed. 20 m. depth\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eParapsectrocladius\u003c/em\u003e sp. and \u003cem\u003eApedilum\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eDjalmabatista\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eRiethia\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eRiethia\u003c/em\u003e sp. (\u003cb\u003e5\u003c/b\u003e \u003csup\u003ea\u003c/sup\u003e)\u003c/p\u003e\u003cp\u003e\u003cem\u003ePolypedilum\u003c/em\u003e sp.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCGCG\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eCF\u003c/p\u003e\u003cp\u003eCF\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e93.77\u003c/p\u003e\u003cp\u003e82.46\u003c/p\u003e\u003cp\u003e46.57\u003c/p\u003e\u003cp\u003e72.17\u0026thinsp;\u0026plusmn;\u0026thinsp;4.38\u003c/p\u003e\u003cp\u003e75.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u003c/p\u003e\u003cp\u003e2.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.55\u003c/p\u003e\u003cp\u003e5.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2.17\u003c/p\u003e\u003cp\u003e2.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e781\u0026thinsp;\u0026plusmn;\u0026thinsp;32\u003c/p\u003e\u003cp\u003e472\u0026thinsp;\u0026plusmn;\u0026thinsp;61\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e147\u0026thinsp;\u0026plusmn;\u0026thinsp;5.72\u003c/p\u003e\u003cp\u003e273\u0026thinsp;\u0026plusmn;\u0026thinsp;25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAustral Spring\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eMyriophyllum\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eNitella\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eBed. Sed. 6 m. depth\u003c/p\u003e\u003cp\u003eBed. Sed. 20 m. depth\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTanytarsini members\u003c/p\u003e\u003cp\u003e\u003cem\u003eMacropelopia\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003ePolypedilum\u003c/em\u003e sp.1\u003c/p\u003e\u003cp\u003e\u003cem\u003eDjalmabatista\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eDicrotendipes\u003c/em\u003e sp. and \u003cem\u003eRiethia\u003c/em\u003e sp. (\u003cb\u003e2\u003c/b\u003e \u003csup\u003ea\u003c/sup\u003e)\u003c/p\u003e\u003cp\u003e\u003cem\u003eCryptochironomus\u003c/em\u003e sp.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCG\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eSH\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eCGCF\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e98.87\u003c/p\u003e\u003cp\u003e98.31\u003c/p\u003e\u003cp\u003e21.48\u003c/p\u003e\u003cp\u003e66.79\u003c/p\u003e\u003cp\u003e62.22\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e\u003cp\u003e43.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.82\u0026thinsp;\u0026plusmn;\u0026thinsp;0.41\u003c/p\u003e\u003cp\u003e0.82\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e \u003cp\u003e-\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e180\u0026thinsp;\u0026plusmn;\u0026thinsp;23\u003c/p\u003e\u003cp\u003e152\u0026thinsp;\u0026plusmn;\u0026thinsp;10\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e749\u0026thinsp;\u0026plusmn;\u0026thinsp;91\u003c/p\u003e\u003cp\u003e299\u0026thinsp;\u0026plusmn;\u0026thinsp;119\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAustral Summer\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLittoral riparian leaves\u003c/p\u003e\u003cp\u003eSed. under stones\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eS. californicus\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eMyriophyllum\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eSed. \u003cem\u003eNitella\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eBed. Sed. 6 m. depth\u003c/p\u003e\u003cp\u003eBed. Sed. 20 m. depth\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eAblabesmyia\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eTanytarsini members and \u003cem\u003eRiethia\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eDjalmabatista\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003eTanytarsini members and \u003cem\u003eRiethia\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eApedilum\u003c/em\u003e sp. and \u003cem\u003eParachironomus\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eRiethia\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eChironomus\u003c/em\u003e sp. and \u003cem\u003eRiethia\u003c/em\u003e sp. (\u003cb\u003e3\u003c/b\u003e\u003csup\u003ea\u003c/sup\u003e)\u003c/p\u003e\u003cp\u003e\u003cem\u003eDjalmabatista\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eDicrotendipes\u003c/em\u003e sp.\u003c/p\u003e\u003cp\u003e\u003cem\u003eMacropelopia\u003c/em\u003e sp.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eCGCF\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eCGCF\u003c/p\u003e\u003cp\u003eCGPRED\u003c/p\u003e\u003cp\u003eCF\u003c/p\u003e\u003cp\u003eCGCF\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003cp\u003eCG\u003c/p\u003e\u003cp\u003ePRED\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e99.37\u003c/p\u003e\u003cp\u003e100\u003c/p\u003e\u003cp\u003e11.88\u003c/p\u003e\u003cp\u003e79.36\u003c/p\u003e\u003cp\u003e97.74\u003c/p\u003e\u003cp\u003e20.33\u003c/p\u003e\u003cp\u003e43.55\u0026thinsp;\u0026plusmn;\u0026thinsp;5.19\u003c/p\u003e\u003cp\u003e38.45\u003c/p\u003e\u003cp\u003e51.30\u003c/p\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\u003cp\u003e5.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e3.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.63\u003c/p\u003e\u003cp\u003e0.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e \u003cp\u003e11.64\u0026thinsp;\u0026plusmn;\u0026thinsp;3.54\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e0.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e164\u0026thinsp;\u0026plusmn;\u0026thinsp;10\u003c/p\u003e\u003cp\u003e238\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e458\u0026thinsp;\u0026plusmn;\u0026thinsp;48\u003c/p\u003e\u003cp\u003e460\u0026thinsp;\u0026plusmn;\u0026thinsp;56\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e267\u0026thinsp;\u0026plusmn;\u0026thinsp;15.14\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e430\u0026thinsp;\u0026plusmn;\u0026thinsp;37\u003c/p\u003e\u003cp\u003e528\u0026thinsp;\u0026plusmn;\u0026thinsp;52\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003ea\u003c/sup\u003e When replicates were analyzed, they are in parenthesis. Biological fractions, elemental concentrations, and error values reported are replicates average\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e* Concentrations corrected by geological particulate contamination\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u0026ndash; element concentration was not recorded\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTo compare [As] and [Zn] in chironomid larvae with different feeding habits (collector-gatherers and predators), one-way ANOVAs were performed in PRIMER Version 5.2.9 [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e] and results were considered statistically significant with p values\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\n\u003ch3\u003eChironomid’s purge\u003c/h3\u003e\n\u003cp\u003eIn aquatic organisms, particularly species that feed on detritus or sediment, gut content can represent an important proportion of the total contaminant body burden [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Direct gut clearing has been suggested in previous bioaccumulation studies to reduce possible errors from indirect estimation methods [\u003cspan additionalcitationids=\"CR47\" citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. Therefore, chironomid larvae were kept in beakers with ASTM (American Society for Testing and Materials) type 1 water for 48\u0026ndash;72 h until their gut contents were emptied [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Then, samples for metal analyses were prepared with cleaned and purged chironomids, and when gut contents (named purged material) obtained were significant (\u0026gt;\u0026thinsp;0.5 mg), they were also preserved to evaluate As and Zn larval excretion.\u003c/p\u003e\n\u003ch3\u003eAnalytical procedures\u003c/h3\u003e\n\u003cp\u003eBiological samples (chironomid larvae and purged material) were stored in SUPRASIL quartz ampoules for analysis, freeze-dried to constant weight, and sealed. Bulk sedimentary samples were freeze-dried, sieved with a 63-\u0026micro;m mesh, and between 3\u0026ndash;65 mg of this fraction were placed in plastic vials for elemental analysis. Only the \u0026lt;\u0026thinsp;63 \u0026micro;m fraction was analyzed, because chironomids mostly ingest small particles and metals are mainly associated with this finer fraction [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eBiological and sedimentary samples were analyzed by irradiation in the RA-6 nuclear reactor (Centro At\u0026oacute;mico Bariloche, Argentina), and metal concentrations were determined by Instrumental Neutron Activation Analysis (INNA). Ampoules and plastic vials were irradiated for 20 and 6 h, respectively. Two gamma-ray spectra were recorded at different decay times after irradiation, using an intrinsic High-Purity Germanium (HPGe) detector and a 4096-channel analyzer. Using the absolute parametric method, [As] and [Zn] were determined and reported on a dry weight (DW) basis, with analytical uncertainties indicated after \u0026ldquo;\u0026plusmn;\u0026rdquo;.\u003c/p\u003e\n\u003ch3\u003eGeological material contamination\u003c/h3\u003e\n\u003cp\u003eBiological samples may be contaminated with inorganic geological particles, producing errors in analytical determinations, even when chironomid larvae have been cleaned and purged. So, possible geological contributions were subtracted to correct the elemental concentrations in biota samples and obtain accurate estimations. Inorganic geological particles in larvae and purge samples were estimated by determining lithophile elements, such as samarium (Sm), a rare earth element that can be used as a geochemical tracer. The INAA technique allows the simultaneous determination of up to 35 elements, including Sm, which shows the highest sensitivity to geological contamination in biological samples. Therefore, it was used to estimate contamination by geological particles and achieve elemental corrections. After the subtraction of the geological content, the remaining material corresponds to the biological fraction:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{\\text{F}}_{\\text{b}}\\:=\\:1\\:-\\:\\frac{{\\text{C}}_{\\text{L},\\text{V}}}{{\\text{C}}_{\\text{L},\\text{G}}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eF\u003csub\u003eb\u003c/sub\u003e = Biological fraction of the sample, determined by subtraction of the geological fraction evaluated by the determination of lithophile element (Sm)\u003c/p\u003e\u003cp\u003eCL, V\u0026thinsp;=\u0026thinsp;Concentration of the lithophile element (Sm) in the biota sample\u003c/p\u003e\u003cp\u003eCL, G\u0026thinsp;=\u0026thinsp;Concentration of the lithophile element (Sm) in geological material present in the biota sample\u003c/p\u003e\u003cp\u003eThe INAA technique has detection limits that depend on the irradiation conditions and sample composition, which can be significantly variable among different biota samples. The corrections in elemental determinations are possible when a lithophile element is present in biological samples. The detection limit for Sm was low enough to affirm that contamination by geological material was below analytical uncertainty. Moreover, to apply this correction, it is necessary to determine elemental concentrations in geological material present in biota samples in order to estimate the biological fraction and implement the corresponding measurement adjustment. All biological samples presented here include this geological correction. Biota samples with corrections higher than 50% were excluded due to their high uncertainties, and samples with biological fractions below 50% were not considered for correction as inorganic material was considered predominant.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eElemental bioaccumulation and excretion factors\u003c/h2\u003e\u003cp\u003eTo evaluate the long-term metal bioaccumulation in aquatic organisms, the determination of bioaccumulation factors (BAFs) is a commonly used method [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. In the present study, As and Zn BAFs were calculated along a year to compare the assimilation of both elements in chironomid larvae according to their associated substrate. The formula used to estimate As and Zn BAFs is the ratio between the metal concentration in the chironomid larvae and the corresponding substrate:\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:\\text{BAF}=\\frac{{\\left[\\text{element}\\right]}_{ch}}{{\\left[\\text{element}\\right]}_{s}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e[element]\u003csub\u003e\u003cem\u003ech\u003c/em\u003e\u003c/sub\u003e = [element] in chironomid larvae\u003c/p\u003e\u003cp\u003e[element]\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e = [element] in associated substrate\u003c/p\u003e\u003cp\u003eAdditionally, to estimate As and Zn excretion by chironomid larvae, the ratio between the elemental concentration in purged material and purged larvae, named excretion factor (EF), was also calculated as follows:\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\:\\text{EF}=\\frac{{\\left[\\text{element}\\right]}_{pu}}{{\\left[\\text{element}\\right]}_{ch}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e[element)\u003csub\u003e\u003cem\u003epu\u003c/em\u003e\u003c/sub\u003e = [element] in purged material obtained of chironomid larvae\u003c/p\u003e\u003cp\u003e[element]\u003csub\u003e\u003cem\u003ech\u003c/em\u003e\u003c/sub\u003e = [element] in chironomid larvae\u003c/p\u003e\u003cp\u003eFinally, to evaluate the potential origin of the purged material from its associated substrate, the ratio between the elemental concentration in the purge and in its corresponding substrate was also calculated ([element]\u003csub\u003e\u003cem\u003epu\u003c/em\u003e\u003c/sub\u003e/[element]\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e) [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. This metric shows whether the excreted material results directly from the ingestion and elimination of sediment-associated elements. This allows us to visualize the errors introduced when the element concentration in sediment is considered equivalent to that in the gut content, instead of measuring the purged material when possible.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eWe first report [As] and [Zn] measured in substrates from Lake MO to evaluate their natural lacustrine distribution; and then, to assess their bioaccumulation and excretion patterns in chironomids, [As] and [Zn] in the corresponding larvae and purged material are presented. Although chironomid larvae were observed in most substrates, in some cases they were only found in summer, such as submerged riparian leaves and sediment from the stoned area. Larvae were absent in sediment at 40 and 90 m depths during the entire sampling period; so, element concentrations at these deeper zones were excluded from the analysis.\u003c/p\u003e\n\u003ch3\u003eElements in substrates\u003c/h3\u003e\n\u003cp\u003eThe [As] recorded in sedimentary substrates ranged from 2.92 to 13.7 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW. The highest [As] were observed in littoral vegetated zones dominated by submerged macrophytes \u003cem\u003eNitella\u003c/em\u003e sp. (12.06\u0026thinsp;\u0026plusmn;\u0026thinsp;1.65 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) and \u003cem\u003eMyriophyllum\u003c/em\u003e sp. (11.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.86 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW); followed by sediment from sublittoral (6 m depth; 10.52\u0026thinsp;\u0026plusmn;\u0026thinsp;0.62 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) and deeper (20 m depth; 10.48\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) zones. The remaining samples, corresponding to vegetated zones dominated by emergent \u003cem\u003eS. californicus\u003c/em\u003e and stoned areas, showed lower [As] (6.14\u0026thinsp;\u0026plusmn;\u0026thinsp;1.26 and 4.67\u0026thinsp;\u0026plusmn;\u0026thinsp;2.87 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW, respectively). Biological samples (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and submerged riparian leaves) exhibited the lowest mean [As] (0.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35 and 0.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.43 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW, respectively); and recorded their maximum values in summer (1.42 and 1.09 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW, respectively) (Fig.\u0026nbsp;2a; Supporting information).\u003c/p\u003e\u003cp\u003eFor the case of Zn, \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves showed the highest concentrations, with an average of 188.82\u0026thinsp;\u0026plusmn;\u0026thinsp;60.84 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW, and reaching a maximum value of 266 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW in autumn. Among sedimentary substrates, slightly higher [Zn] were observed in sublittoral (166.4\u0026thinsp;\u0026plusmn;\u0026thinsp;25.89 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) and deeper (165.7\u0026thinsp;\u0026plusmn;\u0026thinsp;9.35 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) zones. Sedimentary littoral substrates from vegetated and stoned areas showed lower [Zn], averaging 122\u0026thinsp;\u0026plusmn;\u0026thinsp;12.54 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW. The lowest [Zn] were observed in submerged riparian leaves, with an average of 22.64\u0026thinsp;\u0026plusmn;\u0026thinsp;10.16 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW, and a maximum value (33.29 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) in winter (Fig.\u0026nbsp;2b; Supporting Information).\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eArsenic and zinc bioaccumulation in chironomid larvae\u003c/h2\u003e\u003cp\u003eIn general, [As] in chironomid larvae were lower than their corresponding substrate (maintainig a BAF\u0026thinsp;\u0026lt;\u0026thinsp;1), with some exceptions associated with particular larval feeding strategies. Analysis of [As] in larvae and As BAFs revealed a significantly higher bioaccumulation in collectors compared to predators (ANOVA, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). For instance, larvae inhabiting sediment from vegetated zones dominated by \u003cem\u003eMyriophyllum\u003c/em\u003e sp. showed the highest [As] during summer (11.64 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW; BAF\u0026thinsp;=\u0026thinsp;1.12) compared to other seasons. During summer, chironomid larvae were represented by collector feeders (\u003cem\u003eChironomus\u003c/em\u003e sp. and \u003cem\u003eRiethia\u003c/em\u003e sp.) in contrast to the other seasons, when were dominated by predators (\u003cem\u003eDjalmabatista\u003c/em\u003e sp. and \u003cem\u003eMacropelopia\u003c/em\u003e sp.) (average [As] 1.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.67 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ea; b). Similarly, in \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves, although chironomid larvae showed a lower annual average [As] compared to this substrate (Fig.\u0026nbsp;2a), this seasonal study revealed that when the chironomid community was dominated by collector taxa, their [As] were higher than when predators also composed the sample. For example, collector-gatherers (\u003cem\u003eParapsectrocladius\u003c/em\u003e sp., \u003cem\u003eApedilum\u003c/em\u003e sp., and Tanytarsyni members) were dominant during winter and spring, observing larval [As] (2 and 0.82 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW, respectively) higher than those recorded in the macrophyte leaves (recording BAFs of 2.44 and 1.3, respectively). But during the other seasons, when chironomid assemblages were also composed of predators (\u003cem\u003eParachironomus\u003c/em\u003e sp.), [As] decreased (averaging 0.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.014 \u0026micro;g g-1 DW) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ea; b).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn other substrates, while chironomid collector larvae exhibited higher [As] than predators, their values always remained below [As] in the corresponding substrates (maintaining BAF\u0026thinsp;\u0026lt;\u0026thinsp;1). For example, in sediment from vegetated areas dominated by \u003cem\u003eS. californicus\u003c/em\u003e and \u003cem\u003eNitella\u003c/em\u003e sp., and from sublittoral zones, when the chironomid community was dominated by collector-filterers (\u003cem\u003eRiethia\u003c/em\u003e sp.), their [As] (mean value\u0026thinsp;=\u0026thinsp;3.78\u0026thinsp;\u0026plusmn;\u0026thinsp;1.23 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) were higher than in predators (\u003cem\u003eCryptochironomus\u003c/em\u003e sp. and \u003cem\u003eDjalmabatista\u003c/em\u003e sp.) (1.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.9 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ea; b).\u003c/p\u003e\u003cp\u003eChironomid larvae exhibited elevated [Zn], even exceeding values observed in their corresponding substrates and purged material (Fig.\u0026nbsp;2b; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ec; d). In contrast to As, [Zn] and Zn BAFs showed lower values in collectors than in predators and shredders (ANOVA, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The highest [Zn] were recorded in larvae from littoral sediment occupied by \u003cem\u003eNitella\u003c/em\u003e sp., represented by predators (\u003cem\u003eDjalmabatista\u003c/em\u003e sp.) (averaging 1069\u0026thinsp;\u0026plusmn;\u0026thinsp;453 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW; BAF\u0026thinsp;=\u0026thinsp;8.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3). In submerged riparian leaves, the highest Zn BAF (17.47) was recorded in predators (\u003cem\u003eAblabesmyia\u003c/em\u003e sp.) (164 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW). In littoral sediment dominated by \u003cem\u003eMyriophyllum\u003c/em\u003e sp., the highest [Zn] was observed in shredders (\u003cem\u003ePolypedilum\u003c/em\u003e sp.) (870 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW; BAF\u0026thinsp;=\u0026thinsp;7.02) compared to collectors (\u003cem\u003eParapsectrocladius\u003c/em\u003e sp., \u003cem\u003eChironomus\u003c/em\u003e sp., and \u003cem\u003eRiethia\u003c/em\u003e sp.) (averaging 318\u0026thinsp;\u0026plusmn;\u0026thinsp;89 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW; BAF\u0026thinsp;=\u0026thinsp;2.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.79) and predators (\u003cem\u003eDjalmabatista\u003c/em\u003e sp. and \u003cem\u003eMacropelopia\u003c/em\u003e sp.) (277\u0026thinsp;\u0026plusmn;\u0026thinsp;171 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW; BAF\u0026thinsp;=\u0026thinsp;2.25\u0026thinsp;\u0026plusmn;\u0026thinsp;1.33) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ec; d).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eArsenic and zinc excretion in chironomid larvae\u003c/h2\u003e\u003cp\u003eEleven samples of purged material were recovered for metal analysis. In general, [As] in chironomid purges showed higher values (between 8.53 and 12.8 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) than the corresponding larvae and substrates. The highest [As] were recorded in purges obtained from larvae inhabiting areas dominated by \u003cem\u003eMyriophyllum\u003c/em\u003e sp. (12.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.78 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) (Fig.\u0026nbsp;2a; Supporting Information). Although all chironomid larvae excreted more As than they bioaccumulated (resulting in EF\u0026thinsp;\u0026gt;\u0026thinsp;1), the highest EF were exhibited by those inhabiting biological substrates, both submerged riparian leaves (8.53 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW; EF\u0026thinsp;=\u0026thinsp;25) and \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves (10.2 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW; EF\u0026thinsp;=\u0026thinsp;20.4) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). While [As] observed in purges was generally higher than the corresponding substrates, this difference was more pronounced in littoral areas (with maximum values in biological substrates) and progressively decreased with depth. In fact, at 6 and 20 m depth, during some sampling seasons [As] in purges were even lower than the sediment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003eb).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIt is important to emphasize that for most substrates, a sufficient mass of purged material was obtained only for one sampling season; and in most cases, purges from all corresponding larvae were pooled to reach an adequate weight. However, in sediment at 6 m depth, where purge material was collected during three sampling seasons, similar [As] and EFs (10.9\u0026thinsp;\u0026plusmn;\u0026thinsp;1.77 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW and 2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5, respectively) were observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ea).\u003c/p\u003e\u003cp\u003eZinc concentrations measured in chironomid purges were higher than the corresponding substrate, but in general lower than the associated larvae (Fig.\u0026nbsp;2b; Supporting Information). The highest [Zn] were recorded in purged material from larvae inhabiting both \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves and sediment occupied by this macrophyte (averaging 418\u0026thinsp;\u0026plusmn;\u0026thinsp;221.7 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) (Fig.\u0026nbsp;2b). Zinc EFs exhibited variable values between substrates, some showed increased levels and others remained below 1. The highest EFs (with values\u0026thinsp;\u0026gt;\u0026thinsp;1) were observed in submerged riparian leaves, \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves and sediment dominated by this macrophyte (autumn), and at 6 m depth (during the colder season) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). Additionally, [Zn] in purged material was, in general, similar to that recorded in the corresponding substrate, except in submerged riparian leaves and littoral sediment occupied by \u003cem\u003eMyriophyllum\u003c/em\u003e sp., where [Zn] in purges notably exceeded values in substrates (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ed).\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study examined the natural lacustrine distribution of two contrasting trace elements in Lake MO and compared their bioaccumulation and excretion in chironomid larvae, considering their associated substrate type and functional feeding strategies. Here, we first analyze and assess the elemental concentration in several lacustrine substrates; and then, bioaccumulation and excretion factors in chironomids are presented and discuss.\u003c/p\u003e\u003cp\u003eArsenic, a potentially toxic element, was primarily associated with sediment, which acts as its main reservoir and makes it largely unavailable to organisms. Zinc, an essential and crucial element for normal metabolic functions, was abundant on submerged macrophyte leaves, being more readily available to organisms. Differences in As and Zn patterns were recorded among substrates, chironomid larvae, and purged material, reflecting particular biogeochemical dynamics between both elements. In general, the highest [As] were observed in the purged material, followed by sedimentary substrates\u0026thinsp;\u0026gt;\u0026thinsp;chironomid larvae\u0026thinsp;\u0026gt;\u0026thinsp;biological substrates (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and submerged riparian leaves). In contrast, the highest [Zn] were recorded in chironomid larvae, followed by purged material\u0026thinsp;\u0026gt;\u0026thinsp;\u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves\u0026thinsp;\u0026gt;\u0026thinsp;sedimentary substrates\u0026thinsp;\u0026gt;\u0026thinsp;submerged riparian leaves (Fig.\u0026nbsp;2). The main differences between these elements in relation to their lacustrine distribution and biological aspects associated with their bioaccumulation and excretion in chironomid larvae, are presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Lastly, our findings are compared with previous Patagonian studies, highlighting the chironomid community as an indicator of metal bioavailability and a potential vector from benthic substrates to upper trophic levels in lacustrine food webs.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMain differences in the dynamics of environmental distribution, and bioaccumulation and excretion in chironomid larvae between Arsenic (As) and Zinc (Zn) in Lago Moreno Oeste\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSubstrate with higher larval excretion\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBiological substrates\u003c/p\u003e\u003cp\u003e(Submerged riparian leaves and \u003cem\u003eMyriophyllum\u003c/em\u003e sp.)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eBiological substrates, and sediment from \u003cem\u003eMyriophyllum\u003c/em\u003e sp. area and sublittoral zone (mostly during colder seasons)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAccumulation \u003cb\u003epattern order\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003ePurged material\u003c/b\u003e\u0026thinsp;\u0026gt;\u0026thinsp;sediment\u0026thinsp;\u0026gt;\u0026thinsp;chironomid larvae\u0026thinsp;\u0026gt;\u0026thinsp;biological substrates\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eChironomid larvae\u003c/b\u003e\u0026thinsp;\u0026gt;\u0026thinsp;purged material\u0026thinsp;\u0026gt;\u0026thinsp;\u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves\u0026thinsp;\u0026gt;\u0026thinsp;sediment\u0026thinsp;\u0026gt;\u0026thinsp;submerged riparian leaves\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLarval \u003cb\u003eFeeding\u003c/b\u003e habits with greater \u003cb\u003ebioaccumulation\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCollector-gatherers (\u003cb\u003eCG\u003c/b\u003e)\u003c/p\u003e\u003cp\u003eCollector-filterers (\u003cb\u003eCF\u003c/b\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePredators (\u003cb\u003ePRED\u003c/b\u003e)\u003c/p\u003e\u003cp\u003eShredders (\u003cb\u003eSH\u003c/b\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSubstrate\u003c/b\u003e with higher larval \u003cb\u003ebioaccumulation\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eMyriophyllum\u003c/b\u003e \u003cb\u003esp. area\u003c/b\u003e (sediment and leaves)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eSubmerged riparian leaves\u003c/b\u003e and \u003cb\u003elittoral vegetated sediment\u003c/b\u003e (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and \u003cem\u003eNitella\u003c/em\u003e sp.)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMain reservoir\u003c/b\u003e in the lacustrine environment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eSediment\u003c/b\u003e,\u003c/p\u003e\u003cp\u003emainly from littoral areas dominated by submerged vegetation (\u003cem\u003eNitella\u003c/em\u003e sp. and \u003cem\u003eMyriophyllum\u003c/em\u003e sp.) and deeper zones (6 and 20 m depth)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eMyriophyllum\u003c/b\u003e \u003cb\u003esp.\u003c/b\u003e leaves\u003c/p\u003e\u003cp\u003e(followed by sublittoral and deeper sediment)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eArsenic\u003c/b\u003e (As)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eZinc\u003c/b\u003e (Zn)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003eArsenic and zinc in lacustrine substrates\u003c/h2\u003e\u003cp\u003eArsenic concentrations recorded in sediments from Lake MO were lower than the local geochemical background levels established for Lake Moreno (LGB2\u0026thinsp;=\u0026thinsp;24.5 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and, in most cases, they were also below than those defined for Lake Nahuel Huapi (LGB1\u0026thinsp;=\u0026thinsp;12.75 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), except in littoral sediment dominated by \u003cem\u003eNitella\u003c/em\u003e sp., where [As] exceeded 13 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Moreover, [As] in sedimentary substrates from Lake MO are comparable to those reported for surface sediments in eleven other Patagonian lakes, with values generally around LGB1, with one exception above 200 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e recorded in the deep zone of Lake Guti\u0026eacute;rrez associated with redox gradients. In the case of Zn, all values recorded in sediments from Lake MO were above LGB1 (96.7 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and some samples from sublittoral and deep zones exceeded LGB2 (172.5 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). In general, [Zn] were similar to those in other lakes from the region, most of which are close to 121 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, except for the deep zones of some lakes reaching up to 400 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. In this context, our results indicate that [As] and [Zn] observed in Lake MO are similar to those from surface sediments in other Patagonian lakes and geochemical baselines across the region. The highest [As] were recorded in littoral sediment occupied by submerged macrophytes (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and \u003cem\u003eNitella\u003c/em\u003e sp.), followed by sediment from sublittoral and deep zones; and the lowest [As] were observed in biological substrates (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and submerged riparian leaves). In contrast, the highest [Zn] were recorded in \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves, while sedimentary substrates showed relatively constant [Zn], with a slight tendency to increase in deeper zones (Fig.\u0026nbsp;2; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e; Supporting Information).\u003c/p\u003e\u003cp\u003eLacustrine sediments have been recognized by reduce pollution in surrounding water by their high capacity to adsorb heavy metals [\u003cspan additionalcitationids=\"CR54\" citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. In Lake MO, elevated [As], and to a lesser extent [Zn], were observed in sublittoral and deeper zones, which is consistent with the tendency of metals to be deposited in bottom sediments. Lacustrine systems without continuous input of soluble forms, tend to deposit these elements at their deepest parts [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e]. A previous study identified a general trend to increasing [As] from the deepest areas of Patagonian lakes, where deposition processes prevail over suspension, noting a positive correlation between [As] and lake depth [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. This may be also associated with smaller particle sizes composing sediment from deeper zones; and since heavy metals are strongly adsorbed on particle surfaces, profundal sediments, due to their higher surface/volume ratio, tend to exhibit elevated metal concentrations [\u003cspan additionalcitationids=\"CR59\" citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. Moreover, As tends to bind to iron, manganese, and the residual fraction, making it less available in comparison with Zn, which is mainly present in the easily mobilizable fraction [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eElevated [As] in littoral sediment occupied by submerged vegetation are associated with the capability of macrophytes to adsorb metals through their fibrous root systems, which have a large contact area [\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e, \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e]. Particularly, [As] are usually higher in the root systems because the root endodermis limits its translocation to the leaves [\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e]. Then, metals can be lost and return to the adjacent sediment through leaching or other biogeochemical mechanisms, like root exudation processes, which may acidify the rhizosphere, also causing the release of heavy metals to soil particles, often increasing their availability and toxicity [\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e, \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e]. Hence, although heavy metals are primarily stored in sediments from deeper zones, littoral vegetated sediments may also act as important lacustrine reservoirs for trace elements, including As [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves recorded the highest [Zn], mainly during autumn and winter. Previous studies have shown that aquatic macrophytes are highly capable of accumulating substantial amounts of elements in their tissues, mostly those essential for organisms, such as Zn and copper (Cu), which are considered key elements required for growth and maintenance mechanisms [\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e]. In accordance with our results, a study on several heavy metals (mercury, cadmium, lead, nickel, chromium, Cu, and Zn) in various submerged macrophytes species, reported that Zn was the most accumulated element [\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e]. Some characteristics of submerged plants, such as their morphology and a much thinner cuticle, could facilitate uptake of heavy metals [\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e], explaining the elevated [Zn] in their leaves.\u003c/p\u003e\u003cp\u003eThe lowest [As] and [Zn] in Lake MO were observed in submerged riparian leaves. Foliar metal uptake is associated with their environmental availability, and may occur either by deposition on the leaf surface or by penetrate the cuticle and being translocated to internal plant tissues [\u003cspan additionalcitationids=\"CR68\" citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e]. A previous study conducted in several Patagonian lakes emphasized the role of riparian vegetation in the cycling and storage of trace elements [\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e]. Those authors observed that native and exotic terrestrial plants (\u003cem\u003eLomatia hirsute, Luma apiculata, Maytenus boaria, Nothofagus antarctica\u003c/em\u003e, and \u003cem\u003eNothofagus dombeyi\u003c/em\u003e) exhibited lower heavy metal concentrations in decomposing leaves, including As (0.05\u0026ndash;0.15 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and Zn (15\u0026ndash;30 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) compared to fresh leaves (As =\u0026thinsp;0.22 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Zn\u0026thinsp;=\u0026thinsp;25\u0026ndash;60 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). These lower values could be related to element dynamics during litter decomposition, which is influenced by litter quality, the decomposer community, and environmental factors such as temperature, pH, and nutrient availability [\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e]. Similarly, the low [As] and [Zn] reported in submerged riparian leaves from Lake MO may also be attributed to element liberation during decomposition, resulting in the release of these elements into the surrounding lacustrine environment.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003eArsenic bioaccumulation and excretion in chironomid larvae\u003c/h2\u003e\u003cp\u003eArsenic concentrations observed in chironomid larvae followed the variations in their respective substrates, but with consistently lower values. Some exceptions were recorded in larvae inhabiting \u003cem\u003eMyriophyllum\u003c/em\u003e sp. and sediment from the area occupied by this macrophyte, supporting the idea that even at low metal concentrations, chironomids are capable of accumulating significant amounts of metals, demostrating their role as sentitive indicators [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. In Lake MO, variations in [As] were associated with specific larval feeding strategies, for example, in sediment from the \u003cem\u003eMyriophyllum\u003c/em\u003e sp. area, higher larval [As] during summer was observed in collector organisms, but during other seasons, chironomids were mainly predators and recorded lower [As]. Collector-gatherer taxa, such as \u003cem\u003eChironomus riparius\u003c/em\u003e, are more adapted to accumulate contaminants because they exhibit a high tolerance to sediment-bound toxicants [\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e]. This higher susceptibility to heavy metals contamination is associated with the fact that collector chironomids mainly feed on detritus, remaining in close contact with the bottom sediment [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e], and, as we observed in Lake MO, it often contains elevated [As]. Therefore, these organisms are susceptible to element bioaccumulation due to their strong contact with the major reservoir of contaminants in lacustrine systems [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eLow As bioaccumulation in predator larvae may be mostly associated with their reduced direct exposure to sediment-bound contaminants, avoiding the ingestion of sediment and limiting the assimilation of heavy metals [\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e]. These findings could be also indicative of a As biodilution pattern among different functional feeding groups of chironomids, as was also observed for silver (Ag) [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e]. On the other hand, it is important to highlight the elevated [As] found in chironomid predators collected at 20 m depth, which may be partially attributed to exoskeletal contamination by inorganic particles. As was reported previously, the external surfaces of specimens may be littered with As-bearing particles trapped by setae, despite repeated rinsing prior to analysis [\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e]. In our results, this may have occurred in organisms at 20 m depth, because this sediment, composed of finer particles, is more likely to adhere to the exoskeleton, possibly leading to an overestimation of As in their tissues.\u003c/p\u003e\u003cp\u003eElevated [As] were observed in chironomid purged material, which exceeded values recorded in both larvae and their corresponding substrates (Fig.\u0026nbsp;2a). This indicates that the purging process is efficiently acting as a detoxification mechanism, temporarily storing As before its excretion. The most elevated EF values recorded in purges from larvae inhabiting biological substrates evidence the influence of the substrate type and larval feeding strategies on metal excretion rate. These larvae primarily feed on biofilm associated with biological surfaces, mainly composed of fungal and bacterial microorganisms [\u003cspan additionalcitationids=\"CR80\" citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e81\u003c/span\u003e], which are capable to accumulate elevated metal concentrations through adsorption. Therefore, biofilm act as an important sink for trace metals and play a crucial role in their transference into the food chain, including As. Consequently, as chironomid larvae consume large quantities of biofilms enriched in As (3.8\u0026ndash;23 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) [\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e], they regulate their high metal loads by excreting elevated [As] through their purges. This finding highlights the role of this insect community not only as bioindicators of contamination, but also as potential regulators of metal cycling in aquatic systems.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003eZinc bioaccumulation and excretion in chironomid larvae\u003c/h2\u003e\u003cp\u003eZinc concentrations in chironomid larvae from Lake MO generally exceeded values recorded in their respective substrates, indicating an accumulation of this element in their tissues. Understanding the source of Zn, its availability, and its bioaccumulation are fundamental for evaluating trophic transference and environmental distribution. Highest [Zn] and BAFs were observed in larvae from littoral zone, principally in sediment from areas occupied by submerged species (\u003cem\u003eMyriophullum\u003c/em\u003e sp. and \u003cem\u003eNitella\u003c/em\u003e sp.) and biological substrates. In this case, higher Zn uptake was associated with predators (\u003cem\u003eDjalmabatista\u003c/em\u003e sp., \u003cem\u003eAblabesmyia\u003c/em\u003e sp., and \u003cem\u003eCryptochironomus\u003c/em\u003e sp.) and shedders (\u003cem\u003ePolypedilum\u003c/em\u003e sp.) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ec; d).\u003c/p\u003e\u003cp\u003eAlthough the relative importance of diet and food uptake pathways is context-dependent, in predators, elevated Zn assimilation may be linked to their diet, as their prey could exhibit higher concentrations of biologically required trace elements, mainly in the order Zn\u0026thinsp;\u0026gt;\u0026thinsp;Fe\u0026thinsp;\u0026gt;\u0026thinsp;Mn, during grazing [\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e]. Shredder chironomids base their diet on periphytic algae and coarse particulate organic matter while grazing on biological substrates such as submerged vegetation, algae, wood, or detrital debris [\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e, \u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e85\u003c/span\u003e]. As was previously mentioned, epilithic periphyton (biofilm) serves as a major sink for metals (often accumulating higher concentrations than sediments), explaining the elevated metal bioaccumulation in shredders feeding on biological substrates and adjacent sediment. Therefore, a key factor associated with increased Zn observed in these larvae is their direct interaction with biofilm-associated microbes with heavy metals [\u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e86\u003c/span\u003e], facilitating the assimilation of essential elements. Additionally, the deposition of fine particulate organic matter on periphyton can further enhance metal uptake in organisms feeding on biofilm, increasing their total metal burden [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn purged material, [Zn] in general surpassed values in their corresponding substrates, but remained lower than those in their associated larvae (Fig.\u0026nbsp;2b), suggesting an effective regulatory mechanism for this essential element. In accordance, it was also noted that high EF values were observed in some purges from substrates where BAFs were also elevated, such as sediment under \u003cem\u003eMyriophyllum\u003c/em\u003e sp. and submerged riparian leaves (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003ed; \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). Our findings suggest that the gut content may serve as a significant Zn reservoir, allowing larvae to temporarily sequester metal excess to maintain a constant [Zn], regardless of the adjacent sediment, showing their ability to regulate essential elements, including Zn [\u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e87\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn substrates with purged material available during several sampling seasons, a trend of increased amounts of Zn during colder months was observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). This pattern could be partially explained by an increased Zn release from biological substrates during cold sampling seasons, and therefore, a higher environmental availability for organisms. Moreover, at low temperatures, decreased physiological activity produces a reduction in metal uptake in chironomid larvae [\u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e88\u003c/span\u003e]. As a result, under high external availability but lower metabolic demand, as occurs during colder seasons, Zn tends to be more excreted by chironomid larvae, explaining the elevated concentrations in purged material.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003eWhy measure purged material instead of using estimation methods?\u003c/h2\u003e\u003cp\u003ePrevious studies have affirmed that chironomid gut sediments can contribute between 2 and 65% of the total body burden, introducing a considerable bias in elemental determinations when whole larvae are analyzed to assess tissue metal assimilation [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]; so, accurate estimation of metal content in the gut is critical [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. In this context, some works affirmed that when it is not possible to purge organisms or remove their guts, it may be considered valid to apply a formula to estimate the concentration in the guts and subtract it from the total body burden [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. However, an important premise of this formula is the assumption that the surrounding sediment element concentrations exactly reflect what the organisms have in their guts as ingested food, which assumes homogeneity in sediment composition and does not include feeding selection [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. Our findings in this study evidenced that, while the ratio between [As] and [Zn] in purges and the associated sediment often approached one (confirming their equivalence), this was not consistent (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003eb; d). In lacustrine ecosystems, trace element are not homogeneously distributed within the lake, since they may be differentially associated with particles according to sediment granulometric composition, organic matter content, presence of aquatic vegetation, among other variables. The sedimentary phase is considered relevant in the transference of elements to organisms [\u003cspan citationid=\"CR89\" class=\"CitationRef\"\u003e89\u003c/span\u003e], where the finer fraction has a greater metal adsorbing capacity, mainly due to a higher surface/volume ratio [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. As was observed in chironomid larvae, since they mostly exhibit selective feeding behavior, ingesting specific sediment particle sizes or different food types, their purged material showed variable [As] and [Zn] according to its content. This information reinforces the advantage of using a direct method to remove and separately measure the purge, to achieve accurate metal determinations instead of applying an estimation formulae. This suggestion had already been introduced by previous studies, which observed that indirect calculation methods to estimate metal content using a specific formula may not be as reliable as purging organisms and directly measuring the eliminated content [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003eInsights into trace elements dynamics trough midge communities\u003c/h2\u003e\u003cp\u003eIn Lake MO, As bioaccumulation in chironomid larvae was similar to that reported for Ag, another non-essential element considered one of the most toxic metal ions in aquatic ecosystems. In both cases, the main element transference occurred from the littoral zone, principally from \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves and sediment from vegetated areas [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e]. These comparable results suggest that non-essential elements may be stored in specific zones of lacustrine systems, which can act as hot spots of bioaccumulation for aquatic organisms. These results support the role of the chironomid larvae community as an important pathway for element transference from benthic lacustrine substrates to upper levels in Patagonian food webs.\u003c/p\u003e\u003cp\u003eOur findings in chironomid larvae are consistent with results observed for the fish community in Lake Nahuel Huapi, where the main As transference to the aquatic biota occurs principally through organisms closely associated with sediment, exhibiting significantly higher concentrations than pelagic species. For example, the benthivorous creole perch recorded elevated [As] in muscle and liver compared with the piscivorous species rainbow and brown trout, which mostly prey on bentho-pelagic species [\u003cspan citationid=\"CR90\" class=\"CitationRef\"\u003e90\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. This indicates As transference based on diet, as was also reported by other studies worldwide, indicating that bottom-feeding fishes accumulate more As than pelagic predatory species [\u003cspan additionalcitationids=\"CR92\" citationid=\"CR91\" class=\"CitationRef\"\u003e91\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e93\u003c/span\u003e]. Our results in chironomid larvae support this transference pattern, as that collector feeders, which directly ingest fine particulate organic matter from sediment, showed significantly higher [As] than predators, revealing that even within macroinvertebrate communities, species associated with benthic substrates exhibit higher As bioaccumulation. Moreover, arsenic bioaccumulation in chironomids from Lake MO align with a global decrease in As assimilation across trophic levels in Patagonian food webs [\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], suggesting that biodilution occurs not only across different trophic levels, but also among different chironomid functional groups. Based on our findings, chironomid larvae can mobilize contaminants associated with sediments, such as inorganic As, which can constitute up to 98% of total As in chironomid larvae [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e], being considered critical vectors from benthic reservoirs to higher trophic levels.\u003c/p\u003e\u003cp\u003eUnlike As, Zn is an essential trace element for many metabolic processes and regulated according to individual physiological requirements. Zinc trophodynamics in freshwater ecosystems remain poorly studied compared to other trace elements. While Zn biomagnification has been observed in several previous studies in aquatic systems, laboratory experiments, and marine food webs [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR94\" class=\"CitationRef\"\u003e94\u003c/span\u003e, \u003cspan citationid=\"CR95\" class=\"CitationRef\"\u003e95\u003c/span\u003e], a decreasing trend with increasing trophic level was reported in Lake Nahuel Huapi [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], evidencing a biodilution pattern along the food web in this system. This phenomenon has been observed separately in both pelagic and benthic compartments, suggesting that Zn transference is not only driven by trophic accumulation, but also influenced by local environmental availability and biological regulation. Our findings evidence that Zn bioaccumulation in chironomid larvae is also related to their specific feeding strategies, with shredders and predators recording higher [Zn] compared with collector feeders. These results contrast with Zn biodilution pattern observed in Lake Nahuel Huapi (a system with considerably larger dimensions than Lake MO), supporting that this environment provides adequate Zn levels to cover basic physiological requirements. This suggests that Zn biomagnification or biodilution depends on the local characteristics of each aquatic system, with a trend toward increased [Zn] in environments where this essential element is deficient or present less than optimal levels. Moreover, as we observed in chironomid larvae, aquatic organisms can effectively regulate their Zn levels, even under extreme environmental events, such as the Puyehue-Cord\u0026oacute;n Caulle volcanic eruption 2011, which introduced significant Zn inputs via pyroclastic material [\u003cspan citationid=\"CR96\" class=\"CitationRef\"\u003e96\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis research present information about the natural distribution of essential and non-essential trace elements in lacustrine environments, and their dynamics of bioaccumulation and excretion in aquatic organisms. Arsenic and Zn exhibited contrasting patterns in chironomid larvae, influenced by the spatiotemporal distribution of taxa and their specific feeding strategies. While As was mainly transfer from bottom sediments and reflected a biodilution trend, Zn showed bioaccumulation patterns driven by its environmental availability and particular larvae requirements.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eDifferent lacustrine distribution patterns of arsenic (As) and zinc (Zn) were observed in substrates from Lake MO, recording values similar to established background levels for surficial sediments in other Patagonian lacustrine environments (between 12.75\u0026ndash;24.5 and 96.7\u0026ndash;172.5 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW for As and Zn, respectively). The highest [As] were observed in sedimentary substrates, principally in littoral vegetated areas dominated by submerged macrophytes (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and \u003cem\u003eNitella\u003c/em\u003e sp) and deeper zones (6 and 20 m depth), reaching the maximum (13 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW) in sediment occupied by \u003cem\u003eNitella\u003c/em\u003e sp. The highest [Zn] were recorded in \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves, peaking at 266 \u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e DW. Regarding bioaccumulation and excretion dynamics in chironomid larvae, our results also reflect contrasting elemental responses. While the main transference of both As and Zn from benthic substrates to chironomid larvae occurred in the littoral zone (mainly from biological substrates (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and submerged riparian leaves) and sediment dominated by submerged macrophytes), particular feeding strategies influenced element bioaccumulation. Arsenic bioaccumulation was notably higher in collectors, indicating sediment ingestion as a major pathway for this non-essential element uptake. In contrast, predators and shredders exhibited higher [Zn], probably associated with this essential element availability in the lacustrine system and particular individual requirements. In relation to chironomid excretion, the highest [As] and [Zn] in purged material were recorded in biological substrates and littoral vegetated sediment, although [As] in purges exceeded values in both substrates and larvae, while [Zn] surpassed values in substrates but remained lower than those in larvae.\u003c/p\u003e\u003cp\u003eIn Patagonian lakes, chironomid larvae constitute a key component in the diet of small puyen. This native species is a crucial prey for larger fishes, including the introduced brown and rainbow trout, as well as the native creole perch. Our results are consistent with previous studies that observed greater As bioaccumulation in organisms closely associated with sediment, while Zn appears to be influenced by multiple environmental factors, such as exposure route, elemental availability, or individual physiological attributes. The bioaccumulation of As and Zn in chironomid larvae suggests that they may act as an entry point for heavy metals and other trace elements from benthic substrates, particularly from littoral vegetated areas, to upper trophic levels in Patagonian lacustrine food webs.\u003c/p\u003e\u003cp\u003eThis study highlights the importance of including a wide variety of lacustrine substrates, sampling seasons, and taxa with different functional feeding habits to better represent environmental variability, improve the analysis of metal bioaccumulation in aquatic organisms, and evaluate their potential transference from benthic reservoirs to the food web. Our results also help to elucidate the main drivers of distribution, bioaccumulation, and excretion of essential and non-essential elements in lacustrine systems.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eEthical Approval\u003c/h2\u003e\u003cp\u003eThis is not applicable.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConsent to Participate\u003c/strong\u003e\u003cp\u003eAll authors have reviewed and gave their consent to participate in the article.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConsent to Publish\u003c/strong\u003e\u003cp\u003eAll authors read and approved the final version to publish the article.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003cp\u003eThe authors declare no competing interests to declare that are relevant to the content of this article.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eTable II.\u003c/h2\u003e\u003cp\u003eSeasonally measured arsenic [As] and zinc [Zn] concentrations in chironomid purged material from Lake Moreno Oeste. Chironomid sample composition, feeding habits, and biological fraction are also presented. Analytical uncertainties are indicated after \u0026plusmn;.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThis work was partially supported by the projects PICT 2005\u0026ndash;33838 and PICT 2006\u0026thinsp;\u0026minus;\u0026thinsp;1051 of the Agencia Nacional de Promoci\u0026oacute;n Cient\u0026iacute;fica y Tecnol\u0026oacute;gica (Argentina), Fundaci\u0026oacute;n Balseiro (2010/2011), and by the International Atomic Agency, project TCA-ARG/7/006.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eNW: Investigation \u0026amp; conceptualization, material preparation, data collection, sample processing, data analysis, writing-original draft, writing-review \u0026amp; editing. AR: Investigation \u0026amp; conceptualization, material preparation, data collection, sample processing, writing-review \u0026amp; editing. RJ: Data analysis, figure design, review \u0026amp; editing. DAS: Material preparation, data collection, sample processing, review \u0026amp; editing. MAA: Determination of trace element concentrations. SRG: Conceptualization \u0026amp; development, determination of trace element concentrations.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors wish to express their gratitude to the reactor RA-6 operation staff for their colaboration and assistance in sample analysis.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets obtained and analyzed during the development of this study are included as electronic supplementary material. Any additional data that may be relevant or missing can be made available by the corresponding author upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eTarvainen T, Lahermo P, Mannio J (1997) Sources of trace metals in streams and headwater lakes in Finland. Water Air Soil Pollut 94:1\u0026ndash;32. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/BF02407090\u003c/span\u003e\u003cspan address=\"10.1007/BF02407090\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSheikh JA, Jeelani G, Gavali RS, Shah RA (2014) Weathering and anthropogenic influences on the water and sediment chemistry of Wular Lake, Kashmir Himalaya. 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J S Am Earth Sci 49:1\u0026ndash;14. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org//10.1016/j.jsames.2013.10.006\u003c/span\u003e\u003cspan address=\"/10.1016/j.jsames.2013.10.006\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Heavy metal bioaccumulation, Benthic larvae, Functional feeding habits, Lacustrine substrates, Lake Moreno Oeste","lastPublishedDoi":"10.21203/rs.3.rs-7376220/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7376220/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe chironomid community is a key component of lacustrine systems, considering their larvae as a doorway for trace elements from benthic substrates to higher trophic levels. In Lake Moreno Oeste, a northern Patagonian lake (Argentina), arsenic (As), a non-essential and toxic metalloid, and zinc (Zn), an essential metal, were measured in several substrates and their associated chironomid larvae to evaluate their dynamics by understanding their distribution, and bioaccumulation and excretion patterns in this community. The highest As concentrations ([As]) were observed in sediment from littoral vegetated areas and deep zones, while the highest [Zn] were recorded in \u003cem\u003eMyriophyllum\u003c/em\u003e sp. leaves. Larval feeding strategies influenced bioaccumulation patterns: collectors accumulated higher [As] (suggesting that the main As pathway is through the sediment ingestion), and predators and shredders recorded higher [Zn] (associated with its environmental availability and specific larval requirements). In purged material, both elements reached their maximum excretion factors in biological substrates (\u003cem\u003eMyriophyllum\u003c/em\u003e sp. and submerged riparian leaves); however, [As] exceeded values in both substrates and larvae, while [Zn] surpassed values in substrates but remained lower than in larvae. Our findings explore chironomid larvae as vectors of trace elements from benthic substrates to upper trophic levels, highlighting their potential as metal bioindicators.\u003c/p\u003e","manuscriptTitle":"Bioaccumulation of Arsenic and Zinc by Chironomid larvae in Lacustrine Environments: Exploring this Community as Indicator of Trace Element Dynamics in Patagonian Food Webs","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-22 12:55:38","doi":"10.21203/rs.3.rs-7376220/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"bd7a421d-d211-4f9d-95d0-906ca9d917ca","owner":[],"postedDate":"August 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-13T17:38:25+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-22 12:55:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7376220","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7376220","identity":"rs-7376220","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}