Marine Trophic Architecture and Hidden Ecological Connections in the Strait of Magellan: Keystone Species and Ecosystem Resilience

Marine Trophic Architecture and Hidden Ecological Connections in the Strait of Magellan: Keystone Species and Ecosystem Resilience | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL Oikos This is a preprint and has not been peer reviewed. Data may be preliminary. 27 May 2025 V1 Latest version Share on Marine Trophic Architecture and Hidden Ecological Connections in the Strait of Magellan: Keystone Species and Ecosystem Resilience Authors : Claudia Andrade 0000-0003-0804-6348 [email protected] , Taryn Sepúlveda 0009-0006-6369-0792 , Cristóbal Rivera , Cristian Aldea 0000-0002-4473-6509 , and Tomás Marina 0000-0002-9203-7411 Authors Info & Affiliations https://doi.org/10.22541/au.174836891.12332650/v1 Published Oikos Version of record Peer review timeline 689 views 243 downloads Contents Abstract Introduction Materials and Methods Food web dataset Food web analysis Results Species properties Discussion Conclusion Supplementary Material Supplementary Material References Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Understanding the intricate ecological implications of species coexistence through trophic network analysis is crucial for biodiversity studies and for deciphering the environmental drivers of ecosystem dynamics. This study examines, in detail, the complexity, structure, and potential responses of the Strait of Magellan’s trophic network to both environmental and anthropogenic disturbances. Based on an extensive dataset of prey-predator interactions, we characterized the network’s topology and its theoretical resilience using a complex network methodology, analyzing the system at both the network-wide (holistic) and species-specific (reductionist) levels. Our analysis of 140 trophic species and 438 interactions reveals a network with low connectivity (0.022) and an asymmetrical distribution of links, where a few species disproportionately perform most interactions. The network exhibits a ”small-world” architecture, with high clustering and short path lengths, suggesting a rapid propagation of local disturbances. A significant proportion (over 50%) of species are omnivorous, a trait likely contributing to ecosystem stability amidst fluctuating prey availability. Key taxa – polychaetes, Fuegian sprat ( Sprattus fuegensis ) “sardina”, squat lobster ( Grimothea gregaria ) “langostino”, and Patagonian blenny ( Eleginops maclovinus ) “róbalo” – emerge as central conduits for matter and energy flow, effectively linking benthic and pelagic primary productivity to higher trophic levels and significantly underpinning ecosystem function. While the network shows potential robustness to general fluctuations, its concentrated interaction structure makes it vulnerable to the loss or migration of these pivotal species. These findings highlight the importance of understanding trophic relationships to inform effective conservation and ecosystem management strategies in this sensitive Sub-Antarctic marine region. This study provides a foundational understanding of the Strait of Magellan’s marine trophic architecture. Introduction The Strait of Magellan, one of the most significant channels in the Magellanic Province (Spalding et al. 2007), serves as a crucial connection between the Pacific and Atlantic Oceans. Its unique high-energy dynamics, influenced by water masses from the Pacific, Atlantic, and Southern Oceans (Panella et al. 1991), along with its geological features shaped during the last glaciation (Antezana 1999), make it a region of substantial economic, geopolitical, and ecological importance (e.g., Ramírez 2005, Ríos et al. 2013, Onetto 2020). For decades, the Strait of Magellan has supported southern Chile’s small-scale fisheries, i.e., artisanal and susbsitence providing essential resources for the local community (Torres and Ruz 2011). However, these small-scale fisheries are at risk of falling into overexploitation, as most of them lack formal control measures or regulatory safeguards, and concerns are growing over the expansion of unregulated fisheries in the Strait (e.g., Sanchez et al. 2011, Almonacid et al. 2018). In addition to fisheries, oil and gas exploration and extraction have played a key role in regional and national economic growth since the early 20th century (Thomas 1949), and the Strait’s global strategic importance as a maritime trade route has led to extensive shipping traffic. However, the expansion of these economic activities has introduced significant environmental risks, including pollution, habitat degradation, and disruptions in ecological dynamics. Industrial development and maritime operations contribute to nutrient enrichment, marine litter, and hydrocarbon contamination, with potential cascading effects on marine ecosystems (Butnariu 2022). Furthermore, the historical presence of harmful algal blooms (HABs) has also affected fishery resources since the early 1970s, further complicating the environmental challenges in the region (Guzmán and Campodónico 1975, Guzmán et al. 2002). Preliminary studies by Andrade et al. (2016) suggest that nitrogen enrichment from localized anthropogenic pressures may drive shifts in the trophic structure at the base of the benthic food web, and recently, Salinas et al. (2024) reported significant marine litter accumulation along the coast, further underscoring the need to address human impacts on these vulnerable ecosystems. Reviewing historical events, such as the B/T Metula oil spill of 1974, serves as a stark reminder of the long-lasting consequences of carrying out industrial activities in ecologically sensitive areas, with oil pollution severely affecting marine habitats, including benthic communities (Straughan 1977). At the time of the spill, no baseline studies of the affected marine ecosystem existed, which made it difficult to properly assess the area’s biodiversity and natural fluctuations, as well as the long-term effects of contamination (Guzmán 1976). In addition to this, there are emerging concerns over the potential impacts of future hydrogen energy developments on the Strait’s ecologically and economically valuable habitats (Cruz 2024). Expanding industrial activities may introduce additional stressors to an already dynamic marine environment, where human-induced changes have historically influenced ecosystem structure and function. Global studies suggest that the resilience of marine species and ecosystems to anthropogenic pressures may be more limited than previously thought (Malakoff 1997, Hughes et al. 2005, Rombouts et al. 2013). Although the effects of human activities on marine systems are well-documented, accurately quantifying these impacts remains a significant challenge (Vitousek et al. 1997). Food webs provide a powerful framework to analyze ecosystem structure and functioning, linking predator-prey interactions and energy transfer across trophic levels (Dunne 2006). In high-latitude marine environments like the Strait of Magellan, characterized by strong environmental variability and unique ecological dynamics, food web studies are particularly valuable. These studies help assess ecosystem resilience and stability in response to natural and anthropogenic disturbances, offering critical insights into trophic organization, energy flow, and ecosystem vulnerability (Mestre et al. 2022). Establishing this knowledge base is essential for designing management strategies that balance economic development, biodiversity conservation, and the sustainable use of ecosystem services. The limited understanding of invertebrate taxonomy and the scarcity of quantitative biodiversity assessments, as highlighted by Ríos et al. (2003) and Ríos (2007), continue to hinder the recognition of biodiversity value in these ecosystems. To date, even localized biodiversity assessments remain incomplete, as most studies have been isolated and case-specific (e.g., Ríos and Mutschke 1999, Cari et al. 2024). This underscores the urgent need for comprehensive ecological modeling to improve our understanding of species interactions in the Strait of Magellan ecosystem. Developing a more integrated framework is crucial for interpreting population and community dynamics, as well as providing actionable insights for management and conservation. Recent research has begun to address these gaps, providing quantitative assessments of ecosystem structure and predator-prey dynamics. Haro et al. (2025) constructed the first Ecopath model for the Strait of Magellan, focusing on the ecological role of marine mammals and their influence on food web dynamics. Their findings highlight that killer whales ( Orcinus orca ) can exert top-down control on large predators, such as sea lions and seabirds, indirectly increasing the biomass of commercially valuable fish like the Patagonian blenny fish ( Eleginops maclovinus ). Similarly, humpback whales ( Megaptera novaeangliae ) play a significant role by preying on Fuegian sprats ( Sprattus fuegensi s) and squat lobsters ( Grimothea gregaria ), underscoring their influence in energy transfer between pelagic and benthic compartments. While biomass-based models provide valuable insights into the trophic impact of top predators (Pauly et al. 2000), a broader ecological perspective is necessary to fully comprehend the structure and function of the Strait of Magellan ecosystem. Beyond the role of apex predators, understanding the diversity of whole trophic compartments is key to evaluating the resilience and stability of the food web (Barnes et al. 2018, Thompson et al. 2020). The Strait supports a diverse and productive benthic and pelagic community, shaped by distinct spatial gradients. Along the coastline, intertidal and subtidal zones are dominated by mussels ( Aulacomya atra , Mytilus chilensis ) and limpets ( Nacella magellanica ), while extensive kelp forests ( Macrocystis pyrifera ) provide essential habitats and feeding grounds for a wide range of marine organisms, including invertebrates, fish, and mammals. These forests enhance biodiversity and trophic complexity, playing a key role in structuring benthic communities (e.g., Ríos et al. 2003, Ríos et al. 2007, Thatje and Brown, 2009). At the infaunal level, polychaetes dominate benthic communities, comprising up to 60% of the benthic biomass, followed by mollusks, which account for 9-10% (Ríos & Gerdes 1997, Cattaneo-Vietti et al. 1999, Montiel et al. 2011). The Strait harbors an impressive array of marine species, with at least 166 species of polychaetes (Montiel et al. 2011), 412 species of mollusks (Aldea et al. 2020), and 225 species of crustaceans (Malacostraca) (Lancelloti and Vásquez, 2000). Among these taxa, several species have been identified as endemic, particularly within polychaetes (e.g., Moreno et al. 2006), though further research is needed to clarify endemism across other groups. The structural complexity of benthic habitats plays a critical role in ecosystem functioning (Carvalho et al. 2017, Soukup et al. 2022). Three-dimensional structures, such as bivalve matrices, provide essential microhabitats for a variety of organisms, supporting high biodiversity and crucial ecosystem processes (Försterra et al. 2017). These habitats enhance nutrient recycling through deposit feeders and detritivores, while grazers and scavengers regulate organic matter and algal growth (Valdivia et al. 2019, Haro et al. 2022). The benthic assemblages in the Strait of Magellan do not form sharply distinct communities but rather a continuum shaped by substrate type, depth, and current velocity, as highlighted by Gutt et al. (1999). Variations in trophic structure and energy flow further emphasize the complexity of this ecosystem. For instance, intertidal communities in the Strait are relatively well studied, with simple food webs composed by three trophic levels, dominated by grazing gastropods, filter-feeding bivalves, and their predators (Guzmán and Ríos 1986), but little is known about the subtidal food webs. Stable isotope analyses in shallow coastal benthic communities from Punta Santa Ana and Bahía Laredo have revealed a high proportion of omnivorous species, leading to a less compartmentalized trophic structure (Andrade et al. 2016). This configuration suggests a trophic continuum, where δ 15 N values gradually increase among consumers rather than forming discrete trophic levels (Gillies et al. 2012). Additionally, benthic food webs in the Strait rely on a diverse array of organic matter sources, including macroalgae and sediment-derived inputs, contributing to the isotopic niche diversity of consumers and reflecting dynamic trophic interactions. To further elucidate the functional relationships within the Strait’s food web, topological network analyses have proven instrumental in marine ecosystem studies, particularly in high-latitude regions (Marina et al. 2018a, Rodríguez et al. 2022, Marina et al. 2024). These approaches allow for a more detailed examination of trophic interactions, revealing species connectivity, network stability, and key ecological roles (Belgrano et al. 2005). By mapping predator-prey relationships, network analyses offer insights into energy flow, species dependencies, and potential vulnerabilities within the food web (Dunne et al. 2002a, de Santana et al. 2013, Marina et al. 2018b, Rossi et al. 2019, Marina et al. 2024). This research addresses the pressing need to understand and model the complex dynamics of the Strait of Magellan’s ecosystem, given its high biodiversity and the diverse ecosystem services it provides. The Strait supports recreational activities due to its unique natural features, including the presence of marine mammals, as well as established marine routes of international importance, and invaluable cultural heritage, making it a region of rich ecological and socio-economic value (Vergara et al. 2021). By analyzing its trophic network and topology, this study aims to establish a baseline or roadmap of ecological interactions, contributing essential knowledge for the sustainable management and conservation of this strategic marine region. Materials and Methods Study Area The Strait of Magellan, one of the few natural waterways connecting the Pacific and Atlantic Oceans (Aldea and Rosenfeld 2011), extends approximately 570 km in length, with widths varying between 4 and 37 km and depths ranging from 30 to 1,100 meters (Lutz et al. 2016). Its complex geomorphology, semidiurnal tidal regime, and low salinity, influenced by precipitation and freshwater inputs, create highly heterogeneous environmental conditions (Brun et al. 2020; Aravena-Yáñez et al. 2025). The Strait is a multi-structured system with strong spatial heterogeneity in geomorphology, hydrodynamics, and trophic conditions. As described by Cattaneo-Vietti et al. (1999), ecological processes within the system are shaped by pelagic-benthic coupling, driven by variations in primary productivity, the presence of both high- and low-quality particulate organic matter, and intense resuspension processes. These dynamics highlight the complex interplay between physical and biological factors that define the ecological significance of the Strait. Within the Paso Ancho basin, the central micro-basin and the widest section of the Strait, high phytoplankton standing stocks (Iriarte et al. 2001) and significant primary production (Magazzú et al. 1996) have been reported, supporting a zooplankton community dominated by copepods, particularly during spring phytoplankton blooms (Hamamé and Antezana 1999). Under favorable conditions, suspension-feeding species such as mussels and limpets thrive, contributing to the region’s high benthic secondary production (Cattaneo-Vietti et al. 1999, Ríos and Mutschke 1999). Benthic secondary production in the Magellan Region is relatively high, predominantly driven by mollusks, polychaetes, and arthropods, which play a key role in benthic energy flow and nutrient cycling in the region (Brey and Gerdes 1999). Figure 1. The Strait of Magellan, an important Sub-Antarctic waterway in South America, is the geographical area investigated in this study. The map illustrates the three distinct micro-basins within the Strait: the eastern micro-basin (represented by blue squares), the central micro-basin (represented by blue lines), and the western micro-basin (represented by blue circles). Food web dataset We conducted a long-term review of prey-predator relationships, analyzing 50 years of data (1975–2025) compiled from 98 sources, including scientific articles, gray literature and direct field observations across the Magellanic region. The dataset was constructed using standardized sampling protocols, field observations, experimental studies, direct observations, personal communications, and analytical approaches. A detailed dataset was created, comprising the scientific and common names of both predators and prey, and bibliographic references from journal articles, books, technical reports, theses, and local studies. To compile the dataset, systematic searches were conducted in academic databases (Web of Science, Scopus, Google Scholar, SciELO) and national/international repositories (Biblioteca Digital Aike, https://bibliotecadigital.umag.cl/; https://repositorio.uchile.cl/; https://repositorio.unab.cl/; https://repositorio.uc.cl/; http://opac.pucv.cl/; https://bibliotecadigital.exactas.uba.ar/; https://aquadocs.org/; https://figshare.utas.edu.au/; https://www.globalbioticinteractions.org/; https://epic.awi.de/) using keywords such as ”predator-prey interactions,” ”trophic dynamics,” ”Magellanic region,” ”Magellan region,” ”Strait of Magellan,” ”Magellan Strait,” ”feeding behavior,” ”diet”, ”diet composition” and ”food”. Boolean operators (e.g., AND, OR) were applied to refine results, and inclusion criteria focused on studies that reported specific prey-predator interactions, trophic relationships, or feeding behaviors in marine ecosystems. Articles were screened for relevance, and only studies meeting these criteria were incorporated into the dataset. The keyword search was conducted in both Spanish and English to ensure a comprehensive collection of relevant studies and sources, broadening the dataset to include local, regional and international literature. The trophic interactions included in this analysis represent studies conducted across the western, central, and eastern micro-basins of the Strait, as identified in previous oceanographic and ecological assessments (Valdenegro and Silva 2003). This integrative approach allows for a spatially comprehensive representation of species interactions, accounting for biogeographic and environmental variability along the longitudinal axis of the Strait. The list of interactions that comprise the food web of the Strait of Magellan is in Supplementary Material (Table S1). Food web analysis We analyzed the food web of the Strait of Magellan by means of widely-used network properties describing the complexity and structure in food web studies (e.g., Dunne et al. 2002a, Landi et al. 2018, Marina et al. 2024). The properties that we used were: connectance, degree distribution, generality, vulnerability, omnivory, modularity and small-world pattern (Table 1). These properties were selected to better understand how the food web may respond to ongoing disturbances in the Strait, including marine pollution, industrial development, and the still emerging invasion of salmonids resulting from escapes from salmon farms (e.g., Correa and Gross 2008, da Silva et al. 2023, Giesecke et al. 2024, Salinas et al. 2024), an issue understudied at the ecosystem level in the Strait of Magellan. Table 1 provides a definition and ecological interpretation for each of the mentioned network-level properties. We also performed analyses at the node level (Delmas et al. 2019), with the aim of characterizing species’ roles. The properties that we used were: trophic level, degree, closeness, betweenness and topological role (Table 1). Topological roles describe the tendency of food webs to organize into non-random, modular structures, where modules consist of species that interact more frequently with each other than with species outside the module (Guimerà and Nunes Amaral 2005). This structure suggests that both prey and predator groups have stronger interactions within their respective modules compared to those with species from other modules. Depending on their interaction patterns within and across modules, species assume various topological roles. Specifically, we classified each species into one of four roles: ‘module hub,’ characterized by a high number of interactions concentrated within its own module; ‘module specialist,’ having relatively few interactions mainly within its module; ‘module connector,’ with limited interactions primarily occurring between modules; and ‘network connector,’ exhibiting high connectivity both within and across modules (Guimerà and Nunes Amaral 2005, Rodriguez et al. 2022). See Table 1 for definition and ecological meaning of the other node-level properties. Based on selected node-level properties, we created the Keystone Species Index (hereafter KSI). This index considers the so-called centrality indices: degree, closeness and betweenness. To do this, we ranked each species according to each of the centrality indices: the higher the degree, closeness and betweenness, the higher the species rank. Then we averaged these three rankings to obtain the KSI for each species. When two or more species had the same KSI value, they shared the same position in the ranking. Moreover, we considered the trophic level and topological role to complement the results of the KSI and comprehend the species’ role. All analyses were performed using the R software (version 4.4.1, Posit Team 2024), particularly packages igraph (version 2.1.2, Csárdi et al. 2025), NetIndices (version 1.4.4.1, Kones et al. 2009), and multiweb (version 0.6.9, Saravia 2025). The source code and data are available at https://anonymous.4open.science/r/StraitMagellan-FoodWeb-4638/. Table 1. Food web properties at the network and node (species) level, analyzed in this study. For each property a definition and ecological interpretation is provided. Property Symbol Definition and ecological meaning Reference Network level Number of species S Total number of trophic species (nodes) in a food web. May (1973), Tilman (1996) Number of interactions L Total number of prey-predator or trophic interactions (links) in a food web. It represents the number of pathways along which energy flows in an ecosystem. Dunne et al. (2002a) Connectance C Proportion of established trophic interactions among species (L) relative to all possible ones (S 2 ). It represents a fundamental measure of food web complexity. Estimator of food web robustness to perturbations. May (1973), Dunne et al. (2002a), Montoya et al. (2006) Degree distribution DD Frequency of trophic species with k or more interactions in a food web. Estimator of food web vulnerability to random failures and intentional attacks (species extinction). Albert and Barabási (2002) Generality Gen Frequency of predators with g or more prey in a food web. It represents the number of prey of a predator and its diet breadth. Estimator of generalist/specialist predators in a food web. Schoener (1989) Vulnerability Vul Frequency of prey with v or more predators in a food web. It represents the number of predators of a prey. Estimator of most/least demanded prey in a food web. Schoener (1989) Omnivory Omn Proportion of predators that feed on prey at different trophic levels. Estimator of trophic flexibility of an ecosystem with implications on food web stability depending on the interaction strength distribution. McCann and Hastings (1997) Modularity Mod Intensity of connectivity (interactions) of subgroups of species, called modules, compared to species from other modules. Modular organization is positively associated with stability and enhances the persistence of a food web. Stouffer and Bascompte (2011) Small-world pattern SW Compared to random networks, this network exhibits a relatively short average path length (short distance between nodes) and a high clustering coefficient (strong tendency to form tightly interconnected compartments). The implications of this structural pattern in food webs are crucial for understanding evolutionary trajectories and assessing vulnerability to disturbances. Watts and Strogatz (1998), Montoya and Solé (2002) Node level Trophic level TL Position of a species relative to the primary source of energy in a food web (basal species). It represents the number of interactions separating an organism from the base of production, and indicates basal, intermediate and top species. Lindeman (1942), Thompson et al. (2007) Degree Deg Total number of interactions of a species, considering in- (number of predators) and out-interactions (number of prey). Species with a high degree are the most connected, so their influence on the robustness of the network is high. Delmas et al. (2019) Closeness Clo Number of steps (interactions) required to reach every other species from a given species. Estimator of how efficiently perturbations on a species are likely to influence the food web. Freeman (1978), Delmas et al. (2019) Betweenness Btw Frequency of a species in the shortest path between a pair of species. It measures the influence of species loss in fragmentation processes and the potential dispersion of disturbances. Freeman (1978), Delmas et al. (2019) Topological role TR Role of a species according to the proportion of interactions within and across modules. Four roles are defined: network connector, module connector, module hub and module specialist. Network and module connectors maintain the connectivity of the food web. Guimerà and Nunes Amaral (2005), Kortsch et al. (2015) Results Food web properties The food web of the Strait of Magellan (Figure 2) is composed of 139 trophic species (S), where 3 are non-living nodes (sediment, detritus and phytodetritus). The network complexity of the food web includes a total of 435 (L) interactions, a density of interactions (L/S) of 3.13 and a connectance value (L/S 2 ) of 0.022. More than half of the species (56.12%) occupy intermediate trophic positions, meaning they are involved in interactions as both prey and predators. Intermediate-level species outnumber top (33.09%) and basal species (10.79%). Additionally, omnivory accounts for 50.36% of the total species in the food web. The mean trophic level of the network is 2.77, and the maximum trophic level is 5.57 (killer whale or Orcinus orca ). Moreover, path length and clustering coefficient were calculated: 1.88 and 0.09, respectively. The food web presents a small-world pattern (Table S3). The degree distribution of the food web fits an exponential model, meaning that the majority of the species have a few interactions and only a few species have many interactions (Figure 3A, Table S4). Figure 2. Graph of the food web of the Strait of Magellan. Circles represent trophic species and arrows represent prey-predator interactions, where the direction depicts the flow of energy in the ecosystem. Vertical position and color gradient indicate trophic level (max. trophic level = 5.57). Species properties The variation in species degree or total number of interactions show that the three nodes with the highest degree were Phytoplankton, Detritus, and the Patagonian blenny, with 28, 24 and 23 interactions, respectively. Generality and vulnerability were asymmetric (Figures 3B, C). Most predators have few prey species (3.51 preys per predator on average). Vulnerability is much more skewed than the degree distribution for the entire network. There are only a few species or a small number of highly demanded prey (4.68 predators per prey on average). When interactions were aggregated by group (Figure 3B), most were concentrated in a limited number of species. The species with the highest number of interactions, comprising groups of more than two species, were the Patagonian blenny and the Fuegian sprat (Teleostei); the limpets Nacella deaurata and N. magellanica (Gastropoda); the southern king crab Lithodes santolla and the false king crab Paralomis granulosa (Decapoda); Otaria byronia (Mammalia), and Mytilus sp. (Bivalvia). Overall, the distribution of interactions among species exhibits a clear asymmetry across different levels of organization, gathered by groups, and by prey and predator. Figure 3. Distribution of predator-prey interactions in the food web of the Strait of Magellan. A) Cumulative. Best fit model is exponential. B) By group. Groups are vertically ordered by increasing trophic level (following coloration of Figure 2); groups with fewer than 3 species were not plotted (e.g., Foraminifera, Ostracoda). All groups and the species that comprise them are shown in Table S2. C) Generality or distribution of prey among predators. D) Vulnerability or distribution of predators among prey. Fitting details for cumulative distribution are provided in Supplementary Material (Table S4). The role of species within the network varies according to their trophic position. In terms of degree (Figure 4A), the most connected species were those at basal trophic levels (e.g., Phytoplankton and Detritus) (see circle size). When considering closeness centrality (Figure 4B), species at intermediate trophic levels (TL = 2.5 - 3.5) (e.g., Patagonian blenny, Copepoda and Polychaeta) emerged as the most influential, showing a positive correlation with degree. Similarly, betweenness centrality (Figure 4C) indicated that species such as Polychaeta, Patagonian blenny and Fuegian sprat occupied these intermediate trophic levels. Figure 4. A) Degree; B) Closeness; and C) Betweenness for the species of the food web of the Strait of Magellan. Circle diameter is relative to the importance of the corresponding property (i.e., in A) the bigger the circle, the higher the species degree). Circles represent trophic species and arrows represent prey-predator interactions, where the direction depicts the flow of energy in the ecosystem. Vertical position and color indicate trophic level. Refer to the Supplementary Material (Table S2) for node-level properties of species. According to the Keystone Species Index (Table 2), the top 10 most influential species in the Strait of Magellan’s food web include the Patagonian blenny, polychaetes, benthic decapods, copepods, the limpet Nacella deaurata , the Fuegian sprat, amphipods, the southern king crab, the rockcod ( Patagonotothen tessellata ), foraminifera, and ostracods. Table 2. Keystone Species Index (KSI) for the Magellan Strait food web. The KSI scores for different species indicated the ecological importance of each species. The rank accounts for the total number of interactions (degree), the species’ role as a bridge between other species (betweenness), and its proximity to all other species within the network (closeness). Trophic Species/Taxa KSI Rank Eleginops maclovinus 2.33 1 Polychaeta 2.67 2 Benthic Decapoda 4.33 3 Copepoda 5.67 4 Nacella deaurata 6.33 5 Sprattus fuegensis 7.67 6 Amphipoda 10.00 7 Lithodes santolla 11.00 8 Patagonotothen tessellata 13.00 9 Foraminifera 13.00 9 Ostracoda 13.33 10 When analyzing the topological role of the 139 trophic species within the food web, we identified 120 species as module specialists (i.e., species with few links primarily within their own module), 15 as module connectors (i.e., species with few links mainly between modules), 2 as module hubs (i.e., species with a high number of links mostly within their module), and 2 as network connectors (i.e., species with high connectivity both within and between modules) (Figure 5). Key species identified by the KSI were also recognized as module connectors, including teleost fishes such as the notothenioids Patagonian blenny, rockcod, and Patagonotothen sima (KSI ranking = 25) , as well as the squat lobster (KSI ranking = 28). Other module connectors span diverse taxonomic groups, including Ostracoda, Polychaeta, Cephalopoda, Copepoda, Gastropoda, Bryozoa, and Ophiuroidea. Additionally, lower-trophic level species, such as phytodetritus and benthic diatoms, played a similar role as module connectors. Moreover, detritus and phytoplankton, fundamental benthic and pelagic resources respectively, emerged as network connectors. Finally, brown macroalgae and benthic decapods functioned as the module hubs within the Strait’s food web. Figure 5. Topological role for the species of the food web of the Strait of Magellan. Four roles, according to ‘within module degree’ and ‘among module connectance’ parameters, are possible: network connector (“hubcon”), module connector (“modcon”), module hub (“modhub”), and module specialist (“modspe”). Each colored dot represents a trophic species and its topological role. Labelled dots correspond to network connectors and module connectors. Refer to the Supplementary Material (Table S2) for the topological role of each species. Discussion Food web properties Understanding how food web structure shapes ecosystem functioning is fundamental to predicting responses to disturbances (e.g., Dunne 2006, Montoya et al. 2006, Martins et al. 2024). In this study, we examined key trophic attributes of the food web in the Strait of Magellan to explore patterns of complexity, structure, and potential vulnerability to stressors. Our findings contribute to ongoing efforts to understand how the network of trophic interactions reflects and potentially mediates ecosystem responses, particularly in high-latitude marine systems (Rodriguez et al. 2022, Marina et al. 2024). Our results reveal a relatively low connectance for the food web of the Strait of Magellan (C = 0.02). In comparison to other Sub-Antarctic complex food webs (Scotia Sea, Beagle Channel, Burdwood Bank and Yaganes) (López-López et al. 2022, Rodriguez et al. 2022, Marina et al. 2024, Scian et al. 2025), such a connectance falls within the lower limit considering the recorded range in adjacent marine ecosystems (0.01 - 0.05). Interestingly, the Beagle Channel, an adjacent coastal ecosystem, shows the highest connectance of such a range (C = 0.05) (Rodriguez et al. 2022), suggesting that local ecological drivers may significantly influence food web structure (Saravia et al. 2022), even within geographically close regions. The level of connectance in food webs is a key determinant of ecosystem stability, influencing properties such as robustness (Dunne et al. 2002a). Low-connectance networks (< 0.05) are very sensitive to the loss of highly connected nodes, often exhibiting reduced stability, lower resistance to invasions, and greater susceptibility to secondary extinctions (Estrada 2007, López-López et al. 2022, Dunne et al. 2002a). In fact, the removal of one-quarter or less of their species can lead to the collapse of the least connected networks (Dunne et al. 2002b). Conversely, empirical evidence suggests that highly connected ecological networks are more resilient to external disturbances, including species invasions (Smith-Ramesh et al. 2017) and local extinctions (Dunne et al. 2002b, Montoya and Solé 2003), underscoring the role of connectance in buffering ecosystems against biodiversity loss. Overall, the connectance exhibited by the food web of the Strait of Magellan suggests limited functional redundancy and increased susceptibility to perturbations, particularly in the event of the loss of highly connected keystone species (Jordán et al. 2024). This low level of connectance may result from a combination of functional specialization, environmental constraints, and other structural features, as suggested by research in other high-latitude marine ecosystems, where high specialization and modularity may reflect limited trophic niche overlap (e.g., Link 2002, Kortsch et al. 2019, Mestre et al. 2022). In particular, habitat heterogeneity and microhabitat segregation—consistent with the spatial patchiness previously described for the Strait of Magellan (e.g., Arntz 1999, Gutt et al. 1999, Ríos 2007)—may reduce the number of realized trophic interactions, even when omnivory is present. Interestingly, this finding contrasts with previous work by Andrade et al. (2016), which suggested the presence of a trophic continuum in the region’s benthic food web, based on stable isotope analyses. The trophic continuum structure is characterized by blurred boundaries between trophic levels, where omnivory and niche overlap allow energy to flow more flexibly across the web. The discrepancy may reflect the broader scope of the present study—including both benthic and pelagic compartments—as well as methodological differences, given that the current study relies on empirical trophic data rather than isotopic integration. Moreover, previous research on functional diversity in the Magellan Region—specifically in Parry Bay, Almirantazgo Sound, a proglacial fjord influenced by glacial meltwater—showed high functional redundancy among benthic taxa, likely shaped by strong environmental filtering (Sepúlveda et al. 2024). In contrast, the more stable and heterogeneous conditions of the Strait of Magellan could support a broader array of functional traits, potentially enabling more flexible trophic interactions. Although the present study reports low connectance, the presence of omnivory and trophic niche overlap in some compartments may reflect a partial trophic continuum, as previously suggested for benthic communities in the region (Andrade et al. 2016). Further research is needed to better understand how environmental heterogeneity, species traits, and methodological approaches shape the trophic architecture—that is, the structural and functional organization of species interactions and energy flow—in Sub-Antarctic marine food webs, and how this architecture relates to ecosystem stability. The food web of the Strait of Magellan, along with those of Sub-Antarctic and Antarctic areas, such as Burdwood Bank, Yaganes and Potter Cove (Rodriguez et al. 2022, Marina et al. 2024, Scian et al. 2025), exhibits an exponential degree distribution with asymmetric generality (prey per predator) and vulnerability (predator per prey). This pattern, common in complex marine food webs, indicates that these networks are vulnerable to the loss of highly-connected species, potentially leading to secondary extinctions and the fragmentation of the network (Albert et al. 2000, Dunne et al. 2002b). While networks with exponential degree distributions are typically prone to collapse, studies on systems like Potter Cove (Antarctica) have shown resilience to species loss without complete collapse (Cordone et al. 2018, 2020). Disturbances to generalist species are more likely to trigger cascading extinctions, while disturbances to specialist species have less severe effects on network stability (McCann and Hastings 1997, Rodriguez et al. 2022). Overall, the exponential degree distribution of these food webs highlights their susceptibility to the loss of key species but also suggests some resilience against disturbances. Furthermore, the food web of the Strait displays a high degree of clustering and short path lengths between species, features that are characteristic of a small-world architecture (Watts and Strogatz 1998, Montoya and Solé 2002). These properties are commonly associated with complex food webs that combine high species richness and taxonomic resolution, and may support the presence of multiple, redundant energy pathways (Eskuche-Keith et al. 2023). In particular, this architecture facilitates the rapid spread of perturbations, such as biodiversity loss, marine contamination, or overfishing, throughout the network (Delmas et al. 2019). However, the high clustering observed in this food web suggests the formation of tightly connected subnetworks, which can localize disturbances and prevent their widespread impact (Kortsch et al. 2019, Heer et al. 2020). This balance between connectivity and compartmentalization enhances the adaptive capacity of the ecosystem, allowing for a more efficient response to environmental fluctuations (Montoya and Solé 2002, Gilarranz et al. 2017, Stouffer & Bascompte 2011). These findings highlight the dual role of small-world topology in marine ecosystems, where its resilience-enhancing properties must be considered alongside its potential vulnerabilities in the face of stressors. A notable feature of the Strait of Magellan food web is the high proportion of species occupying intermediate trophic levels, functioning both as predators and prey. This structural trait plays a critical role in maintaining energy flow and ensuring connectivity among different components of the network (e.g., Link 2002, Scian et al. 2025). Additionally, the prevalence of omnivory—exceeding 50%—may serve as a stabilizing mechanism, promoting trophic redundancy and dietary flexibility (Fagan 1997, Borrvall et al. 2000, Neutel et al. 2002). The high proportion of omnivory observed in the Strait of Magellan’s food web suggests that the network might be more resilient to variations in prey abundance and could support greater persistence (Stouffer & Bascompte 2010). However, the overall effect of omnivory on stability depends on the strength of species interactions, thus, further analysis of these interaction dynamics is needed (Gellner and McCann 2012). The dominance of species with intermediate trophic positions and omnivory reflects a broader ecological configuration that has not only been previously reported for the Strait of Magellan (Andrade et al. 2016), but has also been observed in other high-latitude marine ecosystems (Rodriguez et al. 2022, Marina et al. 2024, Scian et al. 2025). This pattern appears to be a common feature in Sub-Antarctic systems, where local resource diversity and environmental variability promote generalist trophic strategies. Taken together, our findings suggest that the Magellan Strait food web exhibits a combination of traits associated with both robustness and vulnerability. Intermediate consumers and widespread omnivory may enhance the system’s capacity to buffer against certain disturbances. However, the asymmetric distribution of interactions and the dependence on a few highly-connected species could constrain the system’s ability to absorb more severe or prolonged stressors. Species’ role in the Magellan Strait food web Classical ecological theory suggests that keystone species play a fundamental role in structuring ecosystems and shaping food web dynamics by regulating species abundance and driving critical ecological processes (Paine 1969, Piraino et al. 2002). However, the definition of keystone species remains debated, as there is no universally accepted criterion for their identification, especially in complex and variable systems (e.g., Cottee-Jones and Whittaker 2012, Fulton and Sainsbury 2024, Jordán et al. 2024). The few biomass-based modeling approaches applied in the Strait of Magellan, such as that of Haro et al. (2025), have identified apex predators as keystone species, reflecting a traditional view that emphasizes top-down control in ecosystem analysis. In contrast, our analysis incorporates species from multiple trophic levels, meaning from primary producers and detritus to top predators, enabling a more inclusive perspective in which mid-trophic level species can also play important roles by acting as trophic intermediaries, linking multiple species and, lastly, contributing to overall food web stability (Jordán 2009, Scian et al. 2025). In this sense, our network analysis has identified several key species that might contribute to the maintenance of the trophic structure in the ecosystem of the Strait of Magellan. Among them, the Patagonian blenny emerged as the most significant keystone species (i.e., top 10 KSI and module connector). It inhabits shallow coastal areas and estuaries, and feeds on diverse benthic organisms (Guzmán and Campodónico 1973, Licandeo et al. 2006, Rumbold et al. 2024). This suggests that this benthic-demersal fish plays an essential role in energy transfer, linking benthic and pelagic components of the food web. Its high trophic connectivity suggests that the Patagonian blenny acts as a central element in the ecosystem, influencing both its predators and prey. The ecological importance highlighted in this study contrasts with the species’ population decline in recent decades, likely driven by overfishing, predation by introduced salmonids, and biological traits such as hermaphroditism, which increases vulnerability to size-selective fishing (Guzmán and Campodónico 1973, Pequeño and Olivera 2005, Rumbold et al. 2024). As an essential connector for the food web, the blenny’s decline could trigger cascading effects, impacting top predators like Chilean and Peale’s dolphins (Brickle et al. 2005, Martin and Bastida 2008), and the benthic communities it helps regulate through opportunistic feeding (Licandeo et al. 2006). Despite being historically lightly fished (~151 tons/year; Guzmán and Campodónico 1973), the blenny’s fishery remains unregulated. No stock assessments have been conducted to guide the sustainable management of its population. Polychaetes were identified as the second keystone trophic species in our analysis (i.e., top 10 KSI and module connector). Their identification as module connectors highlights their importance in maintaining food web structure. Their high diversity and broad distribution, from intertidal to deep-sea habitats, make them essential in both the soft and hard-bottom communities of the Magellan region, where they represent ~20% of the benthic fauna (Montiel 2005). Despite their ecological relevance, polychaetes may be increasingly vulnerable to climate change-related stressors such as rising temperatures, oxygen depletion, and changes in sediment dynamics (e.g., Riedel et al. 2012, Herrera-Perez and Méndez 2019). These environmental changes can particularly affect polychaetes due to their diverse feeding strategies, including suspension and deposit feeding (Fauchald and Jumars 1979), which are tightly linked to water column properties and sediment quality. Alterations in particulate organic matter availability, turbidity, and sedimentation rates could impair their feeding efficiency, survival, and overall functional roles in benthic ecosystems. Moreover, shifts in primary production may reduce the quantity and quality of organic matter reaching the benthos, potentially compromising food availability for detritivorous- and suspension-feeding species (Ríos and Mutschke 1999, Ríos et al. 2003, Hüne and Rivera 2010, Andrade et al. 2022). Polychaetes function as primary or secondary consumers (Bergamino et al. 2011, Jumars et al. 2015), and are preyed upon by notothenioid fishes, southern king crab, and squat lobster (Hüne and Rivera 2010, Karas et al. 2007, Andrade et al. 2022), which suggests an important role in supporting ecosystem productivity and resilience (Brey and Gerdes 1999). Our results also present the squat lobster as the third keystone species in the Strait of Magellan (i.e., top 10 KSI and module connector). This observation aligns with previous experimental and field-based studies highlighting its importance in Sub-Antarctic food webs (Romero et al. 2004, 2006). With an omnivorous diet—small crustaceans, macroalgae, polychaetes, and organic matter—and vertical mobility, the squat lobster connects benthic and pelagic realms (Vinuesa and Varisco 2007, Haro et al. 2016, 2022). Dynamic trophic model simulations have shown that the squat lobster is preyed upon by at least 12 functional groups and supports the biomass of red cod, whales, and penguins in the central Magellan Strait (Haro et al. 2022). Our analyses suggest that this species is an important one at mid-trophic levels, facilitating energy transfer across the food web. Similar patterns have been reported in the Beagle Channel, Tierra del Fuego’s Atlantic coast, and Burdwood Bank, where this species performs a wasp-waist control (Riccialdelli et al. 2020). Notably, previous studies in the Strait of Magellan have reported densities ranging from 3 to 27 individuals per square meter (Retamal and Gorny 2001), reinforcing the ecological relevance of the species in terms of biomass and its potential influence on trophic interactions. Given the increasing commercial interest in squat lobster due to its nutritional value (Varisco et al. 2020), concerns have emerged regarding the potential ecosystem-wide effects of growing extractions. A fishery targeting this species could reduce its biomass and impact predators like red cod, hake, whales, penguins, seabirds, and sea lions (Haro et al. 2022). Therefore, monitoring programs and impact assessments are essential to maintaining ecosystem balance. Copepods also constitute a keystone pelagic trophic species in the Strait of Magellan revealed by our analysis (i.e., top 10 KSI and module connector). Their dominance is evidenced by their status as the most abundant zooplankton taxa in the central microbasin (Guglielmo et al. 2011), where they act as a vital link between primary production and higher trophic levels. Dense copepod aggregations in semi-enclosed areas create predictable foraging grounds for larval fish, including ecologically significant species such as Patagonotothen tessellata (Salas-Berrios et al. 2013). Furthermore, their diel vertical migrations enhance pelagic-benthic coupling by facilitating the downward transport of organic matter through grazing and fecal pellet export (Guglielmo et al. 2011). These combined roles—as trophic intermediaries, larval fish prey, and habitat couplers—highlight their central role in this Sub-Antarctic ecosystem. Other top-ranked species identified in our analysis offer valuable insights into the trophic complexity of the ecosystem, each representing distinct functional roles and interaction pathways within the food web. The limpet Nacella deaurata , an omnivorous grazer found on rocky shores, feeds on algae and small invertebrates (Andrade and Brey 2014, Rosenfeld et al. 2018). It plays a dual role in the food web—as both consumer and prey—being targeted by predators such as the starfish Cosmasterias lurida and the flightless steamer duck Tachyeres pteneres (Castilla 1985). Historically, this limpet has also been part of human diets (Morello et al. 2012), highlighting its cultural and ecological significance. The Fuegian sprat is one of the most abundant fish species in the region (Diez et al. 2018, Friedlander et al. 2018), functioning as a key energy conduit between lower and upper trophic levels. It supports a broad range of predators—including penguins, seabirds, humpback whales, sea lions, and hakes—interacting with at least 10 functional groups (Haro et al. 2022). Recognized as a wasp-waist species in the Southwest Atlantic (Riccialdelli et al. 2020), its ecological role is critical; the potential consequences of its decline underscore the importance of integrating functional traits into conservation efforts. Despite its significance, there is a notable lack of current data on its population trends or fisheries in the Magellan region, emphasizing the need for targeted monitoring and stock assessments to guide sustainable management. The southern king crab is a key mid-trophic species with an omnivorous diet that connects primary producers to higher trophic levels. It interacts closely with Macrocystis pyrifera kelp forests, which serve not only as critical habitat but also as nursery grounds during the crab’s early life stages (Cárdenas et al. 2007). M. pyrifera also represents a significant source of organic carbon and a relevant dietary resource for the southern king crab , contributing to its nutrition and, therefore, making these habitats ecologically important in the Magellan region (Andrade et al. 2022). Beyond its ecological role, L. santolla holds economic significance, though it remains vulnerable to overfishing and habitat degradation (Lovrich 1997, Vinuesa et al. 2013). Finally, the rockcod—also identified as module connector and within the top 10 KSI in our analyses—is the most abundant notothenioid fish in southern Chilean Patagonia (Hüne and Vega 2016). Notothenioids are fundamental components of Sub-Antarctic food webs, with diverse trophic strategies (Eastman 1993, Reyes and Hüne 2012). In the Magellan region, the rockcod functions both as a predator of benthic and planktonic organisms, and as prey for top-level consumers including marine birds and mammals (Viddi and Lescrauwaet 2005, Hüne and Vega 2016, Pütz et al. 2021), underscoring its pivotal ecological role. It is important to highlight that our analysis identified several species and groups that, in addition to ranking among the top 10 in the KSI, also function as module connectors—that is, species with few but ecologically meaningful links between modules—in the food web of the Strait of Magellan. These include the Patagonian blenny—the top-ranked keystone species in the Strait—along with polychaetes, copepods, the rockcod, and ostracods. Collectively, these taxa represent a variety of habitats and ecological functions, ranging from lower to mid-trophic levels. Their localized but critical roles emphasize the importance of capturing different topological dimensions when evaluating species’ contributions to ecosystem structure. Such topological roles offer a robust framework for identifying key functional players and prioritizing species for targeted conservation and management actions. In addition to these localized roles, our analysis also revealed detritus as the most significant network connector—a distinct topological role defined by numerous links that span across modules. This underscores the central integrative function of detritus in connecting disparate trophic groups and enhancing overall food web cohesion. The prominence of detritus likely reflects the importance of benthic–pelagic coupling in the Magellan Strait (e.g., Cattaneo-Vietti et al. 1999) and may buffer the system against perturbations. This hypothesis warrants further investigation, particularly by exploring the role of sediment-associated detritus in the diets of benthic consumers. When compared with empirical evidence from a stable isotope-based study in the region (Andrade et al. 2016), which identified macroalgae and sediments as key basal carbon sources supporting multiple consumer compartments, our findings provide a complementary structural perspective. Stable isotope analyses reveal the assimilated sources of energy flow (Andrade et al. 2016), while the network-based approach identifies the organizational role of species—such as detritus—in maintaining system connectivity across trophic levels, including top predators. Together, these lines of evidence suggest that prevailing hydrodynamic conditions may facilitate detrital pathways via macroalgal decomposition, reinforcing the ecological centrality of detritus in supporting the resilience and integrity of the Strait of Magellan food web. Overall, our analysis of species’ topological roles in the Strait of Magellan food web reveals a structure dominated by module connectors and specialists, with only two species—both basal sources—functioning as network connectors (i.e., species with numerous links spanning across modules). While highly connected species are generally expected to exert a stronger influence on ecosystem dynamics (Wootton and Stouffer 2016), the marked asymmetry in interaction distribution observed in this network suggests that a limited subset of species plays a disproportionately critical role in sustaining overall cohesion. These findings underscore the importance of identifying and protecting structurally pivotal species and compartments that underpin the resilience and integrity of the broader ecosystem. The potential loss or decline of such key nodes could significantly disrupt energy transfer efficiency and compromise network stability (Jordán 2009, Lai et al. 2012, Gilarranz et al. 2017), particularly in a system already characterized by low connectance (Dunne et al. 2002a). Inference on ecosystem response to stressors This study contributes to ongoing efforts reinforcing the notion that species should not be viewed as isolated elements, but rather as integral components within complex and dynamic trophic systems. Our analysis highlights how ecosystem resilience is supported by food web complexity and structure features and the presence of species acting as structural connectors across multiple trophic levels, both of which contribute to food web cohesion and stability. Within this framework, the identification of keystone and wasp-waist species further underscores the importance of functional roles. In the Strait of Magellan, native notothenioid fishes such as the Patagonian blenny and the rockcod exemplify these roles by bridging energy pathways across different trophic compartments. Their central positions in the web may enhance energy flow and contribute to the overall resilience of the system—provided that these structural features remain intact in the face of increasing anthropogenic stressors. One of the most immediate and potentially disruptive threats to ecosystem resilience in the Strait of Magellan is the southward expansion of aquaculture and the potential establishment of non-native salmonids in Patagonian zones (Buschmann et al. 2023, Soto et al. 2023). Similar patterns have already been observed in southern Chile’s freshwater systems, where introduced salmonids have significantly altered native food web structures through competition, predation, and habitat displacement (Soto et al. 2006, Elgueta et al. 2013, Arismendi et al. 2014, Ortiz-Sandoval et al. 2017). In those ecosystems, native fishes such as Galaxias maculatus , Aplochiton zebra , and A. taeniatus have shown marked population declines in areas of high salmonid density, often accompanied by shifts in diet, habitat use, and trophic position (Arismendi et al. 2014). These alterations not only affect individual species but can also disrupt energy flow across trophic levels and compromise the structural integrity of the food web. If a similar invasion occurs in the Strait of Magellan, keystone species like the Patagonian blenny and the rockcod could face strong ecological pressures that reshape their behavior, dietary patterns, and ecological roles—ultimately disrupting the structure and functioning of the food web. Although no scientific studies have yet documented direct interactions between salmonids and native notothenioid fishes such as the Patagonian blenny in marine or estuarine habitats, anecdotal observations shared by artisanal fishers in the region suggest that such interactions may be occurring (Andrade pers. comm.). These unverified accounts point to the presence of salmonids in nearshore areas where the Patagonian blenny is commonly found, raising concerns about potential trophic overlap, competition, or predation. Such pressures may compromise the role of native fishes as trophic connectors—representing a significant threat to native biodiversity and the long-term stability of Sub-Antarctic marine ecosystems. Beyond biological invasions, environmental disturbances such as climate change and pollution can alter the quantity and quality of particulate organic matter in the water column (e.g., Canuel et al. 2012, Deininger and Frigstad 2019). These changes influence food availability for benthic organisms and affect the dynamics and structure of food webs (Campanyà-Llovet et al. 2017). For instance, in Laredo Bay (central micro-basin of the Strait), nitrogen loading has already been reported in basal sources of the food web (Andrade et al. 2016), and recent analyses suggest potential anthropogenic impacts in the same area (Author et al., anonymized for review). Nevertheless, further research is needed to understand the ecological consequences of sustained nutrient inputs in coastal zones from intensive industrial activity taking place in the Strait of Magellan. Microplastic pollution is also increasingly being detected in key species in Patagonian fjords, posing additional threats to food web functioning. In central Chile, Patagonian blenny specimens have shown up to 30% microplastic ingestion (Pozo et al. 2019). Recent findings have reported microplastic particles (PET, acrylic, polypropylene, nylon) in the limpet Nacella deaurata , squat lobsters, and southern king crabs in southern Patagonia (Andrade et al. 2025). These contaminants may alter trophic transfer and reduce the nutritional value of prey. Future research should quantify the dietary roles of these species for mid- and top-level consumers, as declines in their populations could weaken food web dynamics and stability. Such disruptions may trigger cascading effects, increasing the risk of secondary extinctions (Olmo-Gilabert et al. 2024) and ultimately compromising ecosystem resilience (Eskuche-Keith et al. 2023). Another emerging physical stressor is the alteration of salinity due to brine discharge from the future expansion of desalination plants in the Magellan Strait. This potential is amplified by the growing global interest in green hydrogen production, for which the Magallanes region, with its abundant renewable energy resources (Vicuña et al. 2022), is considered a strategic location. Desalination will likely be a key supporting industry, providing the necessary water for electrolysis (Vicuña et al. 2022). However, despite this significant potential, the ecological consequences of brine discharge from desalination plants associated with hydrogen production in the unique environment of the Magellan Strait remain largely unstudied, with official environmental impact assessments currently absent. Our analysis revealed a small-world pattern in the Strait of Magellan’s food web, which suggests that even localized salinity fluctuations resulting from brine discharge could rapidly propagate through the system, potentially leading to significant shifts in food web composition and structure. Existing research on the sensitivity of Patagonian fjord ecosystems to salinity changes indicates that alterations in trophic groups and species composition occur, coupled with changes in trophic structure that negatively affect benthic communities (i.e., species turnover, Cari et al. 2020) and fish larvae (i.e, growth and feeding, Landaeta et al. 2012), further underscoring the potential for ecological disruption. Therefore, there is an urgent need for specific research focused on the impacts of desalination brine in the Strait of Magellan as these industries set foot in the area, to ensure the sustainable and responsible development of both green hydrogen and its supporting infrastructure in this ecologically important region. Lastly, the intensification of artisanal fishing, which remains largely unregulated, or the opening of new fisheries targeting key species, pose significant challenges to the stability and functionality of southern marine ecosystems. According to our results, the Patagonian blenny plays a key trophic role, either as mid-level consumers or as essential prey for fish, seabirds, and marine mammals. The intensive removal of this fish could trigger cascading trophic effects, altering food web structure and compromising ecosystem resilience. In fragile ecosystems with low seasonal productivity, the extraction of trophically central species—such as forage fish or mid-level predators—can reduce food web cohesion and increase vulnerability to additional disturbances (Paine 1966, Jackson et al. 2001, Estes et al. 2011).The loss of redundancy in energy pathways may limit the system’s ability to sustain essential ecological functions when certain species experience abrupt changes in abundance or disappear entirely, thereby increasing vulnerability by concentrating key functions in a few specialized species whose loss could result in the disappearance of unique ecosystem properties (Biggs et al. 2020, Sepúlveda et al. 2024). In this context, ecosystem stability—defined as the capacity to maintain structure and function in the face of disturbances—may be compromised. As documented in other empirical food web studies, lower connectivity and limited redundancy are associated with greater magnitudes of change following extreme fluctuations in the densities of one or more species (e.g., Dunne et al. 2002b, Marina et al. 2018a, Marina et al. 2018b, Mérillet et al. 2022). Consequently, opening new fisheries without a thorough understanding of ecological interactions could increase the risk of trophic imbalances, ultimately compromising ecosystem resilience and recovery capacity. Caveats and future perspectives The food web analyzed in this study integrates information from research conducted in the western, central, and eastern micro-basins of the Strait of Magellan, a spatial variability previously described in oceanographic assessments (Antezana 1999). Despite this heterogeneity, we constructed a unified food web for the entire Strait, supported by the strong longitudinal oceanographic connectivity from the southwestern Pacific to the Atlantic, highlighting its function as a bio-oceanic corridor (Brun et al. 2020), according to the information available that we were able to compile for this study. The region exhibits significant spatial variability along its longitudinal axis, shaping the distribution of the previously mentioned functional groups (Andrade et al. 2016; Hüne et al. 2018). Seasonal fluctuations may further influence environmental conditions and biological communities, with documented shifts in certain taxa such as zooplankton community composition along the Strait (e.g., Guglielmo et al. 2011, Zagami et al. 2011), although such patterns remain poorly studied in other groups, particularly benthic organisms. These variations likely impact the transfer of energy and matter within the food web. Comparable patterns have been documented in the nearby Beagle Channel, where differences in water chemistry and nutrient availability influence plankton community dynamics and energy transfer between micro-basins (e.g., Giesecke et al. 2021, Bruno et al. 2023, Latorre et al. 2023). Acknowledging these complexities, we constructed a food web representing year-round dynamics in the Strait of Magellan ecosystem. Given that this is the first study of its kind in the area, future work should incorporate key environmental factors such as depth, current flow, and nutrient availability, as demonstrated in recent studies on food web structure (Cordone et al. 2020). Quantitative data, such as species abundance and biomass, were not included in this analysis due to inconsistencies in taxonomic resolution, despite their availability for certain taxa (e.g., Mutschke and Thatje 1999, Gorny and Retamales 2001, Montiel et al. 2011). For instance, kelp forests—known to be highly abundant in the Strait of Magellan and to provide critical ecological functions such as shelter, nursery grounds, and energy sources for a variety of marine organisms (Cárdenas et al. 2007, Ríos et al. 2007, Andrade et al. 2016)—were not explicitly emphasized in terms of their topological roles within the food web. This omission is partly due to the limited availability of updated dietary data, particularly from stomach content analyses, which may lead to an underestimation of the role of macroalgae as a basal energy source in Sub-Antarctic ecosystems such as the Strait. This concern is especially relevant given the high number of macroalgal species recorded in the region by Ramírez (2010) and Marambio et al. (2016) and the atypical latitudinal gradient in their richness, which, contrary to general global patterns, increases toward the poles (Santelices and Marquet 1998). Therefore, future research should also prioritize the acquisition of quantitative data on prey frequency and occurrence in the diets of marine fauna in the Strait of Magellan, in order to improve estimates of interaction strength and better understand energy flow within this ecosystem. To further advance understanding of the ecosystem’s structure and function, we suggest future research should: (1) assess spatial variability across the Strait’s micro-basins, as it may influence food web organization (Kortsch et al. 2019, Cordone et al. 2020); (2) incorporate species traits, such as body size and mass, which play a critical role in predator-prey dynamics (Brose et al. 2019); (3) evaluate the impacts of human-induced stressors as disturbances within the food web (e.g., Correa and Gross 2007, da Silva et al. 2023, Giesecke et al. 2024, Salinas et al. 2024); (4) estimate predator-prey interaction strength depicting ecosystem’s energy flow by accounting for species traits, habitat structure, and population density (Nilsson and McCann 2016, Gauzens et al. 2019), and (5) assess secondary production, which is key to understanding energy availability for higher trophic levels and the capacity of the ecosystem to support consumers over time (Dolbeth et al. 2012). Previous studies in the region have addressed secondary production at the population and community levels for marine invertebrates (e.g., Brey and Gerdes 1999, Andrade et al. 2009), providing a valuable foundation for broader ecosystem-scale evaluations. Such information is essential to improve energy flow models and to assess the ecosystem’s functional capacity and resilience under increasing anthropogenic pressures. Conclusion The application of an ecological network analysis enabled the identification of species that are crucial for maintaining ecosystem structure in the Magellan Strait. As the understanding of trophic ecology in Sub-Antarctic waters advances, it is essential to integrate these methodological tools into fisheries management policies and marine protected area planning, to ensure a holistic and ecosystem-based approach to conservation—one that explicitly considers the preservation of keystone species and their functional roles within the food web (Christensen et al. 1996). However, current management plans and the designation of protected species often tend to focus on charismatic or commercially important species, potentially overlooking the critical functional roles of less conspicuous organisms within the food web (Boero 2021). Management areas and protected species designations should move beyond a focus solely on charismatic megafauna or target species, and instead more comprehensively consider the underlying ecological structure and functioning of the ecosystem, including the preservation of species that play key roles in maintaining food web stability and resilience (Worm et al. 2006, Long et al. 2015, Shchipanov and Kalinin 2024). Topological approaches offer valuable insights into the complexity and structure of food webs and their capacity to respond to environmental and anthropogenic stressors (e.g., Estrada, 2007, Kortsch et al. 2015, Marina et al. 2024, Scian et al. 2025). By incorporating such an approach, this study contributes to a deeper understanding, at the ecosystem level, of species’ role within these “hidden connections”, therefore providing critical information for long-term conservation efforts and resource management in the Magellan Strait, a sensitive Sub-Antarctic marine region. As mentioned in section 4.3, given the growing pressures from climate change and expanding industrial activities in southern Patagonia, including unregulated fisheries, future research should prioritize assessing the resilience of these trophic networks under disturbance scenarios. It should also support the development of adaptive, network-informed management strategies. To effectively address these challenges and to fully realize the potential of the newly defined ecosystemic approach in Chilean law (Ministry of Environment, Resolution 1597 EXENTA 27 March 2025, Law N° 21.600), a paradigm shift is urgently needed. We must move away from traditional species-based management towards approaches that integrate both the structural and functional properties of ecological networks and the roles of individual species. Supplementary Material Table S1. List of trophic interactions of the food web of the Strait of Magellan. Table S2. List of trophic species and node-level properties of the food web of the Strait of Magellan. Table S3. Parameters of the small-world pattern. Table S4. Fit of the cumulative degree distribution of the food web of the Strait of Magellan. Supplementary Material File (oik-11711-file008.docx) Download 10.77 KB References 1. Acevedo, J. and Urbán, J. 2021. Estimates of Fuegian sprat consumption by humpback whales in the Magellan Strait feeding area as predicted by a bioenergetic model. - Mar. Ecol. Prog. Ser. 657: 223–239. Albert, R. and Barabási, A.-L. 2002. Statistical mechanics of complex networks. - Rev. Mod. Phys. 74: 47–97. Aldea, C. and Rosenfeld, S. 2011. Macromoluscos intermareales de sustratos rocosos de la playa Buque Quemado, Estrecho de Magallanes, sur de Chile. - Rev. Biol. Mar. Oceanogr. 46: 115–124. Aldea, C., Novoa, L., Alcaino, S. and Rosenfeld, S. 2020. 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Collection Oikos Keywords biodiversity food web pelagic and benthic communities species’ role sub-antarctic Authors Affiliations Claudia Andrade 0000-0003-0804-6348 [email protected] Universidad de Magallanes Instituto de la Patagonia View all articles by this author Taryn Sepúlveda 0009-0006-6369-0792 Universidad de Magallanes Instituto de la Patagonia View all articles by this author Cristóbal Rivera Universidad de Magallanes Instituto de la Patagonia View all articles by this author Cristian Aldea 0000-0002-4473-6509 Universidad de Magallanes Instituto de la Patagonia View all articles by this author Tomás Marina 0000-0002-9203-7411 Centro Austral de Investigaciones Cientificas View all articles by this author Metrics & Citations Metrics Article Usage 689 views 243 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Claudia Andrade, Taryn Sepúlveda, Cristóbal Rivera, et al. 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