Infaunal biodiversity of converging river estuaries in Mambajao, Camiguin Island in relation to salinity gradients

Infaunal biodiversity of converging river estuaries in Mambajao, Camiguin Island in relation to salinity gradients | 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 Infaunal biodiversity of converging river estuaries in Mambajao, Camiguin Island in relation to salinity gradients Alche Pacudan, Warren Caneos, Reynald Gimena, Dulce Fe Abragan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5367139/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 infauna distribution, species composition, diversity and its correlation with environmental variables were investigated in the two converging river estuaries (Tapon River and Sa’ai River) in Mambajao, Camiguin Island, Philippines. Sample collection using a modified core sampling method, sorting, identification and counting of infauna samples and in-situ measurements of physico-chemical parameters were done. Results showed that Pachychilidae (44.94%), Lumbriculidae (28.09%) and Thiaridae (14.61%) had the highest relative abundance in both rivers which could be due to its wide tolerance of pollution that also resulted to low species diversity (H’) ranging only from 0.267 ± 0.267 to 0.811 ± 0.090. Furthermore, Sa’ai River showed significantly higher temperature compared to Tapon River. Significant differences in salinity, water pH and soil pH were also observed between the two river estuaries. Furthermore, distinct and clear segregation patterns (30% and 50% similarity) between the two river estuaries. Samples from T4R1, T4R2, T3R3 and T1R2 were segregated from T1R1, T2R1 and T3R1 and the rest of the sampling stations. The presence and assemblages of the infauna (e.g. Glyceridae, Pachychilidae, Chironomidae, Neritidae) were strongly influenced by temperature, salinity, water pH and soil pH. Biodiversity Camiguin Island Estuaries Infauna Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Estuaries – semi-enclosed coastal bodies of water where the river meets the sea – are one of the biologically highly productive and dynamic aquatic environments where most intensive exchange of matter and energy between the continents and oceans occurs (Prichard, 1967; Bowmaker, 1968 ; Ahel et al., 1996 ; Day et al., 2012 ). They are also considered as critical transition zones (CTZs) that connect terrestrial, freshwater and marine environments and are often termed as marginal filters (Levin et al., 2001 ; Paturej, 2008 ). They provide valuable ecosystem goods and services to the society and to the majority of the coastal population (Bianchi et al., 1999 ; Cooper et al., 2003 ; Bianchi, 2007 ; McGranahan et al., 2007 ; Kennish and Paerl, 2010). They play a crucial role in ecosystem functioning by facilitating decomposition, nutrient cycling, and nutrient production. Additionally, they serve as key regulators of nutrient, water, particle, and organism exchanges between land, rivers, and the ocean (Levin et al., 2001 ; Newton et al., 2014 ). Estuaries are also characterized by strong salinity gradients (changes in salinity ranging from full strength seawater decreasing to freshwater) (Elliott and McLusky, 2002 ). The salinity range in estuaries serves as a crucial external ecological factor and a defining physiological characteristic of the internal environment for aquatic organisms. This range delineates the suitable living conditions for both freshwater and marine faunas, segregates invertebrate communities based on their osmotic regulation mechanisms, and establishes the distribution boundaries for higher taxa (Telesh and Khlebovich, 2010 ). Studies conducted on estuarine systems has demonstrated that salinity plays a crucial role as an environmental filter, exerting influence over the composition, abundance, and functional characteristics of benthic macroinvertebrates (Martins and Barros, 2022 ). Within tropical estuaries, polychaete communities display functional nestedness along salinity gradients, whereby lower salinity areas harbor subsets of functional traits observed in higher salinity regions (Medeiros et al., 2021 ). Furthermore, fluctuations in salinity within estuarine systems can induce significant alterations in biological processes and biodiversity over time, thereby impacting the stress levels experienced by organisms inhabiting intertidal zones (Sowa et al., 2020 ). These findings underscore the significance of comprehending how salinity gradients influence the distribution patterns of infauna species and their functional roles within estuarine ecosystems. Such understanding provides valuable insights for the development of conservation strategies and the management of these ecosystems (Donatelli et al., 2022 ; Koehler et al., 2022 ). Infauna – animals dwelling in the sediments – are subdivided into different size spectra namely, megafauna, macrofauna, meiofauna and microfauna (Connor et al., 2003 ; Davies et al., 2006 ). These organisms influence water filtration, organic matter recycling, and serve as vital food source to predatory species which are also important to man (Virnstein, 1977 ; Venegas et al., 2017). They also contribute to sediment mixing, modify sediment properties, and impact biogeochemical cycles (Dorgan et al., 2022 ; Mizuno et al., 2022 ). Their activities, like burrowing and building structures, influence sediment structure and geoacoustic properties, affecting sound speed and attenuation (Blackburn and Orth, 2013 ; Ballentine et al., 2017 ). However, increasing human population and destructive interventions create big problems to estuaries and coastal wetlands (Sciberras et al., 2016 ). Therefore, infaunal community studies are increasing and gaining attention of many researchers. It emphasizes careful examination of estuarine habitats and gathering of facts to understand the processes and functions of estuarine community (Schaffner, 1990 ). A need for solid and strong ecological indices to evaluate ecosystem status and condition (Ieno et al., 2006 ; Pinto et al., 2009 ) in which there is need for caution when extrapolating from assumed knowledge of organism traits to how changes in species composition associated with ecological crises may impact ecosystem function (Solan et al., 2008 ). Additionally, several studies presented estuarine habitats in association with infaunal organisms, such as decapod crustaceans (Gore et al., 1981 ), polychaetes, amphipods, clams (Hines and Comtois, 1985 ), anthozoans (Whitlatch and Zajac, 1985 ), oligochaetes (De Deckere et al., 2001 ), hemichordates (Zajac and Whitlatch, 1982 ), copepods (Galván et al., 2008 ). There is a limited number of hierarchical studies that strongly advocate for the inclusion of comparative measures of species turnover, estimates of species pools' size, and information on the spatial distribution of species diversity in relation to habitat patchiness (Kendall et al., 2003 ). Although each index may have a different conceptual basis relying on various assumptions and parameters, they all share a common objective: to provide a valuable tool for assessing the health of a system and aiding in decision-making processes (Pinto et al., 2009 ). The biodiversity within benthic communities holds significant implications for the management of such areas (Fredriksen et al., 2010 ). By studying benthic communities in estuaries, researchers can identify environmental factors that influence the structure of these communities and evaluate their health as an indicator of environmental disturbances, whether natural or anthropogenic in origin (Engle et al., 1994 ). Generally, this study aims to compare the infaunal biodiversity of two converging river estuaries in Mambajao, Camiguin Island, Philippines. Specifically, this study aims to determine the species composition and relative abundance of infauna in all sampling sites; determine the species diversity of infauna between sampling sites; identify and compare the infauna distribution between sampling sites; and identify the correlation between the environmental parameters and the biodiversity within and between the converging river estuaries in Mambajao, Camiguin Island, Philippines. Therefore, the results of the study can be a source of baseline information for future studies on the effects of anthropogenic activities on the biodiversity of infauna and other aquatic organisms in the estuaries. Results of the study can also be used in the preparation and establishment of management plans for the conservation and protection of the estuaries and its resources. Materials and Methods Study area The study was conducted in the two converging river estuaries namely Tapon River and Sa’ai River in Mambajao, Camiguin Island, Philippines (Fig. 1 ). Sa’ai River and Tapon River were assigned with three and four stations, respectively. Tapon River is located near to the private establishments and agricultural farms, subject to anthropogenic activities, such as agricultural pollutants, domestic sewage and industrial effluents. Sa’ai River is situated near the airport and is less disturbed compared to Tapon River. Site survey Initially, the salinity gradient of the river estuaries was measured during the highest high tide using 600 Series Waterproof Portable Meter Kit (Oakton Instruments, Singapore). Following the salinity gradient determination, the furthest distance the salinity can travel was measured also using transect line. The sampling stations were established in 100-m interval from the river bank and ended up to the furthest distance travelled by the seawater. Based on the results of salinity gradients, seawater entering Sa’ai River and Tapon River can reach up to 300 m and 400 m respectively. Finally, seven stations were established: four for Tapon River (T1-T4) and three for Sa’ai River (S1-S3). Field sampling Core sampling method of Bradshaw et al. ( 2003 ) was used with some modifications. A transparent plastic tube with a length of one foot and a diameter of six centimeters was inserted by pushing it into the sediment, about 15 centimeters deep of the cores, to take sediment cores of the riverbed. Three core samples were taken from each sampling station. The infauna samples were then separated from the sediment using 500-µm mesh sieve, placed in the plastic containers, and preserved using ethanol of 95% solution (Virnstein, 1977 ). The samples were brought to the Integrated Fish Laboratory of the College of Fisheries, Mindanao State University – Main Campus, Marawi City for species identification and counting. Furthermore, sediments were put in the plastic ziplock bag and brought to the same laboratory for soil pH analysis. Measurements of physico-chemical parameters In-situ measurements of the physico-chemical parameters, such as water pH, temperature and salinity were measured in each station with three replicates during the highest high tide using 600 Series Waterproof Portable Meter Kit (Oakton Instruments, Singapore). Soil pH analysis The soil pH was determined following the procedures of Jackson ( 1958 ) and Black ( 1965 ) with a soil to water ratio of 1:1. Firstly, 50-g air-dried sediments were weighed using analytical balance (Radwag Wagi Elektroniczne, Poland), placed in a clean plastic container, added with 50-mL distilled water and stirred thoroughly. Then, it was let stand for 1 hour and stirred three times during the hour. Sample suspension was stirred, and pH was immediately determined using a calibrated 600 Series Waterproof Portable Meter Kit (Oakton Instruments, Singapore). Species identification Infauna samples were identified up to the family of the species, but limited to those what was seen by the naked eye following key identification guides of benthic macroinvertebrates (Oscoz et al., 2011 ), mollusks (Ng et al., 2016 ), aquatic annelids, such as oligochaetes and polychaetes (Brinkhurst, 1963; Klemm, 1985 ) and amphipods (White, 2011 ). A compound microscope was used to magnify the images of species for easier identification. Data analyses Abundance and relative abundance were obtained using Microsoft Excel (2016). Relative abundance was measured to determine which species is dominating the zone/area. Venn diagram was also developed using Venny v. 2.1 (Oliveros, 2007–2015) to graphically and clearly show the similarities and differences of the biodiversity within and between sites. Diversity indices such as diversity (H’), species richness (S) and evenness (J’) were analyzed using Paleontological Statistics Software Package (PAST) version 2.17c (Hammer et al., 2001 ). To determine if there are significant differences in the physico-chemical parameters and species diversity among the sampling stations, One-way Analysis of Variance (ANOVA) using SPSS version 21 was done. The infaunal assemblages were analyzed using non-metric multi-dimensional scaling (nMDS) and cluster analysis based on square-root transformed abundance data. Transformed data were subjected to Bray-Curtis similarity measure prior to analysis. One-way Analysis of Similarity Percentages (SIMPER) was also used to determine which species contribute to the clustering and separation of samples. Canonical Correspondence Analysis (CCA) was done to identify the infaunal samples distribution in relation to different environmental parameters. Non-metric multi-dimensional scaling (nMDS), cluster analysis and SIMPER were analyzed using Primer v.7.0 (Clarke and Gorley, 2015 ) while CCA was analyzed using PAST version 2.17c (Hammer et al., 2001 ). Results Species composition and relative abundance A total of 356 individuals belonging to 9 families were found in both river estuaries of Mambajao, Camiguin Island, Philippines. Figure 2 shows the relative abundance of each species present in all sampling stations. Results showed that the dominant species in Sa’ai River belong to family Pachychilidae (Mollusca:Gastropoda) and Thiaridae (Mollusca: Gastropoda) with a relative abundance of 70.07% and 10.95%. Meanwhile, Tapon River was dominated by Lumbriculidae (Annelida: Clitellata) and Pachychilidae dominated the Tapon River with a relative abundance of 43.84% and 29.22%, respectively. Other species found but of less abundance were Neritidae (Mollusca: Gastropoda), Chironomidae (Insecta: Diptera), Nereididae (Annelida: Polychaeta), Phyllodocidae (Annelida: Polychaeta), Leucothoidae (Crustacea: Amphipoda) and Glyceridae (Annelida: Polychaeta). Species distribution Figure 3 shows the common and unique species found in Sa’ai and Tapon River. Between sampling stations of Tapon River (Fig. 3 A), Pachychilidae and Thiaridae were two common families of infauna species in the four sampling stations. Lumbriculidae and Neritidae were also common species but not found in T2 and T4, respectively. Nereididae was the only unique species in Tapon River which was found in T1. Meanwhile, in Sa’ai River (Fig. 3 B), only two common species (Pachychilidae and Neritidae) were found in all stations of Sa’ai River while Chironomidae was the only species found common to S1 and S3 while Thiaridae in S2 and S3. In terms of unique species, Leucothoidae and Phyllodocidae were found only in S2 while Lumbriculidae and Glyceridae were found only in S3. Figure 3 C showed that five families, Chironomidae, Lumbriculidae, Pachychilidae, Neritidae and Thiaridae were common to both rivers. Species belonging to three families, Glyceridae, Leucothoidae and Phyllodocidae, were unique to Sa’ai River while Nereididae was the only unique species found in Tapon River. Infaunal diversity in river estuaries Comparisons of the diversity (H’), species richness (S) and evenness (J’) in the two river estuaries are summarized in Table 1 . In Tapon River, mean H’ ranged from 0.267 ± 0.267 to 0.534 ± 0.299 while in Sa’ai River, mean H’ ranged from 0.363 ± 0.363 to 0.811 ± 0.090. Species richness in Tapon and Sa’ai River ranged from 1.667 ± 0.667 to 2.667 ± 0.882 and 1.667 ± 0.667 to 3.000 ± 1.528, respectively while species evenness ranged from 0.793 ± 0.177 to 0.965 ± 0.035 and 0.391 ± 0.204 to 0.997 ± 0.003, respectively. Table 1 Diversity indices per station of the two converging river estuaries of Mambajao, Camiguin Island, Philippines. Values are mean ± S.E. River Estuaries Stations Shannon-Wiener (H') Species Richness (S) Species Evenness (J’) Tapon River T1 0.267 ± 0.267 1.667 ± 0.667 0.914 ± 0.086 T2 0.277 ± 0.277 1.667 ± 0.667 0.922 ± 0.078 T3 0.534 ± 0.299 2.667 ± 0.882 0.793 ± 0.177 T4 0.329 ± 0.329 1.667 ± 0.667 0.965 ± 0.035 Sa'ai River S1 0.363 ± 0.363 1.667 ± 0.667 0.997 ± 0.003 S2 0.811 ± 0.090 3.000 ± 0.577 0.790 ± 0.088 S3 0.633 ± 0.357 3.000 ± 1.528 0.391 ± 0.204 Physico-chemical parameters The measurements of the four physico-chemical parameters (temperature, salinity, water pH and soil pH) in the four sampling stations of the lake are presented in Fig. 4 . Results revealed Tapon River and Sa’ai River had a mean temperature ranging from 29.05 ± 0.09 ⁰C to 29.06 ± 0.52 ⁰C, 30.40 ± 0.06 ⁰C to 33.30 ± 0.12 ⁰C, respectively. Sa’ai River had significantly higher temperature compared to Tapon River. Significant differences in temperature were also observed among sampling stations of Sa’ai River. In terms of salinity, S1 was significantly higher compared to other sampling stations in Tapon River and Sa’ai River. Tapon River and Sa’ai River had a mean salinity ranging from 0.15 ± 0.01 ppt to 3.48 ± 2.16 ppt, 0.13 ± 0.01 ppt to 7.64 ± 0.14 ppt, respectively. Meanwhile, in terms of water pH, S3 was the only station with significantly higher values compared to other stations. In terms of soil pH, significant differences were observed among sampling stations. T1, T2 and T3 had significantly higher soil pH compared to T4, S1, S2 and S3. However, no significant difference in soil pH was observed between S1 and S3. Infaunal assemblages Figure 5 and Fig. 6 show the nMDS graph and cluster analysis of square-root transformed data of infaunal abundance from Sa’ai River and Tapon River in Mambajao, Camiguin Island, Philippines. Clear segregation patterns (30% and 50% similarity) were observed between sampling stations of two river estuaries. Samples from T4R1, T4R2, T3R3 and T1R2 were segregated from T1R1, T2R1 and T3R1 and the rest of the sampling stations. Furthermore, cluster analysis (Fig. 6 ) revealed that some samples from Tapon River and Sa’ai River had a close relationship. For example, T4R1, T3R3 and T4R2 showed ~ 80% similarity, T4R3 and S3R2 with 80% similarity, T2R3 and S2R1 with ~ 90% similarity, T2R2 and S1R1 with 90% similarity and T3R2, S3R3, T2R3 and S2R1 with 80% similarity. Furthermore, SIMPER analysis revealed that samples from Tapon River and Sa’ai River had 22.40 and 49.61% similarity, respectively. Such similarities in Tapon River were largely contributed by Pachychilidae, Lumbriculidae and Thiaridae with 39.79%,33.48% and 17.33%, respectively while similarity in Sa’ai River was mainly due to Pachychilidae (78.50%) and Neritidae (13.97%). High percentage of dissimilarities was observed between river estuaries. Tapon River and Sa’ai River showed an average dissimilarity of 70.22% and were mainly contributed by Pachychilidae (38.29%), Lumbriculidae (17.37%), Thiaridae (15.67%), Neritidae (14.39%) and Chironomidae (7.87%). Canonical Correspondence Analysis (Fig. 7) showed that the presence and distribution of infauna species, such as Glyceridae, Pachychilidae, Chironomidae, Neritidae, were strongly influenced by the four physico-chemical parameters (e.g. temperature, salinity, water pH and soil pH). Discussion The present study indicated that the relative abundance, diversity and assemblages of infaunal species varied between the different sampling stations of two converging river estuaries of varied salinity levels. These estuaries were mainly dominated by gastropods (family Pachychilidae and Thiaridae) and an annelid species under the family Lumbriculidae. Similar results were observed in the study by Guillena et al. (2022) in the coastal barangays of Roxas, Zamboanga del Norte with Pachychilidae and Thiaridae as the most abundant. Pachychilidae are widely distributed species (Ng et al., 2016 ) and are considered as a conspicuous component of the freshwater and estuarine macroinvertebrates of Southeast Asia (Köhler and Dames, 2009 ). These species were identified to be present in areas exposed to anthropogenic activities such as agricultural pollutants, domestic sewage, industrial effluents and mining waste (Köhler et al., 2012 ; López and Urcuyo, 2012 ). Similarly, the presence of Pachychilid species in the two converging river estuaries was observed in the area even they are exposed to various anthropogenic activities. For example, agricultural activities are taking place in the upper part of the rivers which could contribute agricultural pollutants and sewage that are directly discharged to the river estuaries by the residences, market and other private establishments. However, Köhler et al. ( 2012 ) described family Pachychilidae as extremely restricted ranges, often in specialized habitats, such as river rapids, requiring highly oxygenated unpolluted waters. This might explain why Pachychilids are more abundant in Sa’ai River than Tapon River. Another abundant species in both river estuaries was Lumbriculidae. Usually, this species can be found in freshwater habitats including streams, lakes, wetlands, man-made wells and groundwater. They are commonly found in still or slow-flowing shallow water and are often associated with disturbed habitats, particularly in high nutrient level areas (Frost et al., 2009 ). The study of Frost et al. ( 2009 ) revealed that Lumbriculidae have greater densities when exposed to high nutrients. This might explain why Lumbriculidae was abundant in Tapon River because of nutrient inputs coming from agricultural farms near to it especially during run-off. Lumbriculidae ingest organic detritus and microorganisms, such as bacteria, that are present in the sediments they consume and excrete ( https://keys.lucidcentral.org ). The dominance of this species could be due to abundance of foods in Tapon River as it is surrounded by many trees which can be a source of organic detritus. Microorganisms might also dominate for the decomposition of leaves and other waste materials coming from the households and food establishments. Thiaridae, which are predominantly found in tropical to subtropical regions worldwide, inhabit almost all freshwater and brackishwater bodies, encompassing lotic habitats such as springs, creeks, rivers, and streams, as well as lentic habitats like lakes and ponds (Veeravechsukij et al., 2018 ). Originally, they are widely distributed throughout Southeast Asia and in Australia (Glaubrecht, 2009 ; Glaubrecht, 2011 ). Chironomidae were also found in some sampling stations in both estuaries. Chironomid larvae, being the most prevalent benthic species, can be found in various habitats such as rivers, streams, lakes, ponds, water supplies, and sewage systems. Due to their sediment-dwelling lifestyle, these larvae have limited mobility (Morris and Brooker, 1980 ; Pinder, 1986 ; Hall and Gedhardt, 2002). This could be the reason why Chironomids are present in the two river estuaries. Their presence and abundance could also be linked to the low population of its predators, such as Nereididae which was observed by Rönn et al. ( 1988 ) in their study on gut content analysis of Nereididae. Additionally, Chironomidae consume detritus and typically forage on aquatic substrates (Hall and Gedhardt, 2002). During sampling, there were a lot of organic materials, such as leaves, twigs, branches obtained together with the sediment samples. These organic materials were at the stage of decomposition which could attract many organisms that can be consumed as food by Chironomids. Lencioni et al. ( 2012 ) also mentioned that anthropogenic activities could affect the distribution of Chironomidae which resulted to low species abundance and richness. Moreover, the results revealed that Chironomidae were influenced by soil and water pH. On the contrary, results of the studies by March ( 2015 ), Oku et al. (2015) and Sharif et al. ( 2017 ) showed that Chironomidae exhibited no affinity to soil and water pH. In terms of species diversity, both river estuaries had relatively lower species diversity which could be linked to the anthropogenic pressures in the area and only those pollution-tolerant species were commonly present as observed also by Lencioni et al. ( 2012 ). Similarly, the study of Connor et al. ( 2003 ) in Ireland wherein species richness was greatly influenced by temperature. Furthermore, a study by Kunitzer et al. (1992) described that one of the factors structuring species distributions and assemblages seem to be influenced by high temperature. Similar results were observed by Moller (1986) wherein Nereidid sp. was not affected by high temperature due to its ability to migrate. In the study of Ndhlovu et al. ( 2024 ), they found that estuaries receiving wastewater effluent discharges exhibited a higher abundance of macroinvertebrates that can thrive in environments with high levels of organic pollution. The salinity gradient of the two river estuaries had large differences from the mouth to the upper part of the rivers. Such salinity variations in river estuaries were due to the freshwater inputs coming from rivers and springs and tidal influence. Results of CCA showed that most of the species were influenced by salinity. Some species prefer to thrive in a low-saline or freshwater environments such as Pachychilidae (e.g. Sulcospira , Tylomelania, Brotia ) and Thiaridae (e.g. Melanoides ) (Köhler et al., 2012 ; Ng et al., 2016 ); Lumbriculidae ( https://keys.lucidcentral.org ) and a few species of Chironomidae (Hall and Gedhardt, 2002). Alongi and Christoffersen (1990) mentioned that low-salinity zones are generally characterized by low diversity both among and within functional groups. Another factor that significantly influences the presence and composition of infauna in estuaries is the pH. Several studies have demonstrated that alterations in pH can result in shifts in the makeup of infaunal communities (Hossain and Marshall, 2014 ; Weinmann et al., 2021 ). For instance, exposure to acidified seawater has been found to cause significant changes in community structure and reduced diversity of macrofaunal and nematode assemblages. Notably, sandy sediments tend to be more affected by these changes compared to muddy sediments (Bone et al., 2022 ). Furthermore, in tropical estuarine systems, the structuring of benthic infaunal communities is influenced by a steep gradient in salinity and pH, highlighting the impact of pH variations on these ecosystems (Hansen et al., 2019 ). These findings underscore the vulnerability of infaunal communities to pH fluctuations in estuarine environments, emphasizing the necessity for further research to comprehend and mitigate the potential consequences of ocean acidification on these crucial ecosystems. Conclusion A study on the infauna distribution, species composition, diversity and its correlation with environmental variables was conducted in the two converging river estuaries of Mambajao, Camiguin Island, Philippines. Using a modified core sampling method, samples were collected and were immediately sorted, identified and counted. In-situ measurements of physico-chemical parameters (e.g. salinity, water pH and temperature) and analysis of soil pH were done using 600 Series Waterproof Portable Meter Kit. Results showed that Pachychilidae (44.94%), Lumbriculidae (28.09%) and Thiaridae (14.61%) had the highest relative abundance in both rivers which could be due to its wide tolerance of pollution that also resulted to low species diversity (H’) ranging only from 0.267 ± 0.267 to 0.811 ± 0.090. Furthermore, Sa’ai River showed significantly higher temperature compared to Tapon River. Significant differences in salinity, water pH and soil pH were also observed between the two river estuaries. Clear segregation patterns (30% and 50% similarity) were observed between sampling stations of two river estuaries. Samples from T4R1, T4R2, T3R3 and T1R2 were segregated from T1R1, T2R1 and T3R1 and the rest of the sampling stations. Similar results were also observed in the cluster analysis and SIMPER. The assemblages of the infauna (e.g. Glyceridae, Pachychilidae, Chironomidae, Neritidae) were strongly influenced by temperature, salinity, water pH and soil pH. Declarations Author Contribution A.P. and W.C. conceptualized the study, conducted the experiments, performed the analyses, and drafted the manuscript. The manuscript was reviewed and edited by A.P., W.C., R.G. and D.F.A. Acknowledgement We would like to extend our deepest gratitude to the Provincial Government of Camiguin headed by Gov. Xavier Jesus D. Romualdo, Cong. Jurdin Jesus M. Romualdo, Mayor Yñigo Jesus D. Romualdo and Mrs. Fe A. Belara for their permission and moral support; Mr. Archie A. Along and Mr. Jan Mark S. Viter for the data analysis; Mr. Ralph V. Namayan and Mr. John Mark S. Morales for making the location map of the study and; College of Fisheries and Aquatic Sciences, Mindanao State University – Marawi for allowing us to use the Multi-Parameter Instrument and the Integrated Laboratory and administrative support. References Ahel M, Barlow RG, Mantoura RFC (1996) Effect of salinity gradients on the distribution of phytoplankton pigments in a stratified estuary. Mar Ecol Prog Ser 143:289–295. https://doi.org/10.3354/meps143289 Alongi DM, Christoffersen P (1992) Benthic infauna and organism-sediment relations in a shallow, tropical coastal area: Influence of outwelled mangrove detritus and physical disturbance. Mar Ecol Progress Ser Oldendorf 81(3):229–245. https:///www.doi.org/10.3354/meps081229 Ballentine WM, Dorgan KM, Lee KM, Ballard MS, McNeese AR, Wilson PS, Venegas GR (2017) Effects of marine infauna on the acoustic properties of sediment. J Acoust Soc Am 142(4Supplement):2693–2693. https://doi.org/10.1121/1.5014824 Bianchi TS (2007) Biogeochemistry of estuaries. Oxford University Press. https://doi.org/10.1093/oso/9780195160826.001.0001 Bianchi TS, Pennock JR, Twilley RR (eds) (1999) Biogeochemistry of Gulf of Mexico estuaries. Wiley Black CA (1965) Methods of soil analysis. Part II. Agronomy series No. 9. Amer. Soc. Agron., Inc., Wisconsin, USA Blackburn NJ, Orth RJ (2013) Seed burial in eelgrass Zostera marina: the role of infauna. Mar Ecol Prog Ser 474:135–145. https://dx.doi.org/doi:10.25773/v5-t6b8-6808 Bone JR, Stafford R, Hall AE, Boyd I, George N, Herbert RJ (2022) Estuarine infauna within incidentally retained sediment in artificial rockpools. Front Mar Sci 8:780720. https://doi.org/10.3389/fmars.2021.780720 Bowmaker AP (1968) The use of the word estuary in a freshwater context. Newsl Limnol Soc Sthn Afr 11:1–22 Bradshaw C, Collins P, Brand AR (2003) To what extent does upright sessile epifauna affect benthic biodiversity and community composition? Mar Biol 143(4):783–791. https://doi.org/10.1007/s00227-003-1115-7 Clarke KR, Gorley RN (2015) Getting started with PRIMER v7. PRIMER-e: plymouth, plymouth marine laboratory , 20 (1) Connor DW, Allen JH, Golding N, Howell KL, Lieberknecht LM, Northen KO, Reker JB (2003) The national marine habitat classification for Britain and Ireland. Joint Nature Conservation Committee, Peterborough Cooper J, Jayiya T, Van Niekerk L, De Wit M, Leaner J, Moshe D (2003) An assessment of the economic values of different uses of estuaries in South Africa. CSIR Report No. ENVSC 139. Davies AJ, Narayanaswamy BE, Hughes DJ, Roberts JM (2006) An Introduction to the benthic ecology of the Rockall-Hatton area (SEA 7). A Report for the DTI by the Scottish Association for Marine Science. Dunstaffnage Marine Laboratory, Oban Day JW, Kemp WM, Yáñez-Arancibia A, Crump BC (2012) Estuarine Ecology. Wiley. https://doi.org/10.1002/9781118412787 De Deckere EMGT, Tolhurst TJ, De Brouwer JFC, Estuarine (2001) Coastal Shelf Sci, 53(5):665–669. https://doi.org/10.1006/ecss.2001.0811 Donatelli C, Duran-Matute M, Gräwe U, Gerkema T (2022) Statistical detection of spatio-temporal patterns in the salinity field within an inter-tidal basin. Estuaries Coasts 45(8):2345–2361. https://doi.org/10.1007/s12237-022-01089-3 Dorgan KM, Frey MR, Clemo WC, Venegas GR, Lee KM, Ballard M, Wilson PS (2022) Impacts of infauna on sediment heterogeneity and acoustic propagation. J Acoust Soc Am 152(4):A102–A102. https://doi.org/10.1121/10.0015685 Elliott M, McLusky DS (2002) The need for definitions in understanding estuaries. Estuar Coast Shelf Sci 55(6):815–827. https://doi.org/10.1006/ecss.2002.1031 Engle VD, Summers JK, Gaston GR (1994) A benthic index of environmental condition of Gulf of Mexico estuaries. Estuaries 17(2):372–384. https://doi.org/10.2307/1352670 Fredriksen S, De Backer A, Boström C, Christie H (2010) Infauna from Zostera marina L. meadows in Norway. Differences in vegetated and unvegetated areas. Mar Biol Res 6(2):189–200. https://doi.org/10.1080/17451000903042461 Frost JW, Schleicher T, Craft C (2009) Effects of nitrogen and phosphorus additions on primary production and invertebrate densities in a Georgia (USA) tidal freshwater marsh. Wetlands 29(1):196–203. https://doi.org/10.1672/07-79.1 Galván K, Fleeger JW, Fry B (2008) Stable isotope addition reveals dietary importance of phytoplankton and microphytobenthos to saltmarsh infauna. Mar Ecol Prog Ser 359:37–49. https://doi.org/10.3354/meps07321 Glaubrecht M (2009) On Darwinian Mysteries or molluscs as models in evolutionary biology: from local speciation to global radiation. Am Malacological Bull 27(1/2):3–23. https://doi.org/10.4003/006.027.0202 Glaubrecht M (2011) Towards solving Darwin's mystery: speciation and radiation in lacustrine and riverine freshwater gastropods. Am Malacological Bull 29(1/2):187–216. https://doi.org/10.4003/006.029.0211 Gore RH, Gallaher EE, Scotto LE, Wilson KA (1981) Studies on decapod crustacea from the Indian River Region of Florida: XI. Community composition, structure, biomass and species-areal relationships of seagrass and drift algae-associated macrocrustaceans. Estuar Coast Shelf Sci 12(4):485–508. https://doi.org/10.1016/S0302-3524(81)80007-2 Guillena MD (2022) Macroinvertebrates as bio-indicator of water quality in Estuaries. J Biodivers Environ Sci (JBES) 21(1):146–151 Hall RD, Gerhardt RR (2002) Flies (Diptera). Medical and Veterinary Entomology, 127–145 Hammer O, Harper DAT, Ryan PD (2001) PAST: Paleontological Statistics software package for education and data analysis. Palaeontologia Electronica 4(1):9 Hansen BW, Andersen CM, Hansen PJ, Nielsen TG, Vismann B, Tiselius P (2019) In situ and experimental evidence for effects of elevated pH on protistan and metazoan grazers. J Plankton Res 41(3):257–271. https://doi.org/10.1093/plankt/fbz020 Hines AH, Comtois KL (1985) Vertical distribution of infauna in sediments of a subestuary of central Chesapeake Bay. Estuaries 8(3):296–304. https://doi.org/10.2307/1351490 Hossain MB, Marshall DJ (2014) Benthic infaunal community structuring in an acidified tropical estuarine system. Aquat Biosyst 10:1–12. https://doi.org/10.1186/2046-9063-10-11 Ieno EN, Solan M, Batty P, Pierce GJ (2006) How biodiversity affects ecosystem functioning: roles of infaunal species richness, identity and density in the marine benthos. Mar Ecol Prog Ser 311:263–271. https://doi.org/10.3354/meps311263 Jackson ML (1958) Soil Chemical Analysis. Englewood Cliffs. NT Prentice Hall Inc, p 498 Kendall MA, Widdicombe S, Weslawski JM (2003) A multi-scale study of the biodiversity of the benthic infauna of the high-latitude Kongsfjord. Svalbard Polar Biology 26(6):383–388. https://doi.org/10.1007/s00300-003-0496-x Kennish MJ, Paerl HW (eds) 2010. Coastal lagoons: critical habitats of environmental change. CRC press. https://doi.org/10.1201/EBK1420088304 Key to Australian freshwater and terrestrial invertebrates. (n.d.). Retrieved from https://keys.lucidcentral.org/ Klemm DJ (1985) A guide to the freshwater Annelida (Polychaeta, Naidid and tubificid Oligochaeta, and Hirudinea) of North America. https://doi.org/10.2307/1467872 . Kendall Hunt Publishing Company Köhler F, Dames C (2009) Phylogeny and systematics of the Pachychilidae of mainland South-East Asia–novel insights from morphology and mitochondrial DNA (Mollusca, Caenogastropoda, Cerithioidea). Zool J Linn Soc 157(4):679–699. https://doi.org/10.1111/j.1096-3642.2009.00541.x Köhler F, Seddon M, Bogan AE, Van Tu D, Sri-aroon P, Allen D (2012) Chapter 4. The status and distribution of freshwater molluscs of the Indo-Burma region. IUCN 66–89 Koehler B, Erlandsson M, Karlsson M, Bergström L (2022) Species richness and functional attributes of fish assemblages across a large-scale salinity gradient in shallow coastal areas. Biogeosciences 19(8):2295–2312. https://doi.org/10.5194/bg-19-2295-2022 Künitzer A, Basford D, Craeymeersch JA, Dewarumez JM, Dörjes J, Duineveld GCA, Eleftheriou A, Heip C, Herman P, Kingston P, Niermann U (1992) The benthic infauna of the North Sea: species distribution and assemblages. ICES J Mar Sci 49(2):127–143. https://doi.org/10.1093/icesjms/49.2.127 Lencioni V, Marziali L, Rossaro B (2012) Chironomids as bioindicators of environmental quality in mountain springs. Freshw Sci 31(2):525–541. https://doi.org/10.1899/11-038.1 Levin LA, Boesch DF, Covich A, Dahm C, Erséus C, Ewel KC, Kneib RT, Moldenke A, Palmer MA, Snelgrove P, Strayer D (2001) The function of marine critical transition zones and the importance of sediment biodiversity. Ecosystems 4(5):430–451. https://doi.org/10.1007/s10021-001-0021-4 López SJA, Urcuyo J (2012) First report of Faunus ater (Pachychilidae: Gastropod) on the American Continent: A mature empty specimen from Masachapa, Nicaragua, Central America. UNED Res J 4(2):187–189 March C (2015) Biodiversity of benthic invertebrate communities in the Mobile-Tensaw Delta region of Alabama (Doctoral dissertation, California State University, Northridge) Martins AD, Barros F (2022) Ecological functions of polychaetes along estuarine gradients. Front Mar Sci 9:780318. https://doi.org/10.3389/fmars.2022.780318 McGranahan G, Balk D, Anderson B (2007) The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones. Environ urbanization 19(1):17–37. https://doi.org/10.1177/0956247807076960 Medeiros CR, Paiva FF, Ligeiro R, Molozzi J, Melo AS (2021) Saline gradient drives functional nestedness of polychaete communities in tropical estuaries. Estuar Coast Shelf Sci 251:107185. https://doi.org/10.1016/j.ecss.2021.107185 Mizuno K, Nomaki H, Chen C, Seike K (2022) Deep-sea infauna with calcified exoskeletons imaged in situ using a new 3D acoustic coring system (A-core-2000). Sci Rep 12(1):12101. https://doi.org/10.1038/s41598-022-16356-3 Möller P (1986) Physical factors and biological interactions regulating infauna in shallow boreal areas. Mar Ecol Prog Ser 30:33–47. https://doi.org/10.3354/meps030033 Morris DL, Brooker MP (1980) An assessment of the importance of the Chironomidae (Diptera) in biological surveillance. Chironomidae Pergamon 195–202. https://doi.org/10.1016/B978-0-08-025889-8.50033-7 Ndhlovu A, Adams JB, Lemley DA, Nhleko J, Rishworth GM (2024) Benthic macrofauna communities reflect eutrophic condition in a low-inflow estuary. Reg Stud Mar Sci 70:103351. https://doi.org/10.1016/j.rsma.2023.103351 Newton A, Icely J, Cristina S, Brito A, Cardoso AC, Colijn F, Zaldívar JM (2014) An overview of ecological status, vulnerability and future perspectives of European large shallow, semi-enclosed coastal systems, lagoons and transitional waters. Estuarine, Coastal and Shelf Science, 140, 95–122. https://doi.org/10.1016/j.ecss.2013.05.023 Ng TH, Tan SK, Wong WH, Meier R, Chan SY, Tan HH, Yeo DC (2016) Molluscs for sale: assessment of freshwater gastropods and bivalves in the ornamental pet trade. PLoS ONE 11(8). https://doi.org/10.1371/journal.pone.0161130 Oku EE, Andem AB, Arong BG, Odjadjare E (2014) Effect of water quality on the distribution of aquatic entomofauna of Great Kwa River, Southern Nigeria. Am J Eng Res (AJER) 3(4):265–270 Oliveros JC (2007–2015) Venny. An interactive tool for comparing lists with Venn's diagrams. http://bioinfogp.cnb.csic.es/tools/venny/index.html Oscoz J, Galicia D, Miranda R (2011) Why, Where and How: An Identification Guide of Macroinvertebrates. In: Oscoz J, Galicia D, Miranda R (eds) Identification Guide of Freshwater Macroinvertebrates of Spain. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-1554-7_1 Paturej E (2008) Estuaries-types, role and impact on human life. Baltic Coastal Zone. Journal of Ecology and Protection of the Coastline, (12) Pinder LCV (1986) Biology of freshwater Chironomidae. Ann Rev Entomol 31(1):1–23. https://doi.org/10.1146/annurev.en.31.010186.000245 Pinto R, Patrício J, Baeta A, Fath BD, Neto JM, Marques JC (2009) Review and evaluation of estuarine biotic indices to assess benthic condition. Ecol Ind 9(1):1–25. https://doi.org/10.1016/j.ecolind.2008.01.005 Pritchard DW (1967) What is an estuary: physical viewpoint. American Association for the Advancement of Science Rönn C, Bonsdorff E, Nelson WG (1988) Predation as a mechanism of interference within infauna in shallow brackish water soft bottoms; experiments with an infauna predator, Nereis diversicolor O.F. Müller. Journal of Experimental Marine Biology and Ecology, 116(2):143–157. https://doi.org/10.1016/0022-0981(88)90052-4 Schaffner LC (1990) Small-scale organism distributions and patterns of species diversity: evidence for positive interactions in an estuarine benthic community. Mar Ecol Prog Ser 61:107–117. https://doi.org/10.3354/meps061107 Sciberras M, Parker R, Powell C, Robertson C, Kröger S, Bolam S, Geert Hiddink J (2016) Impacts of bottom fishing on the sediment infaunal community and biogeochemistry of cohesive and non-cohesive sediments. Limnol Oceanogr 61(6):2076–2089. https://doi.org/10.1002/lno.10354 Sharif ASM, Islam S, Islam M (2017) Occurrence and distribution of macrobenthos in relation to physico-chemical parameters in the lower Meghna River estuary, Bangladesh. Int J Mar Sci 7(12):102–113 Solan M, Batty P, Bulling MT, Godbold JA (2008) How biodiversity affects ecosystem processes: implications for ecological revolutions and benthic ecosystem function. Aquat Biology 2(3):289–301. https://doi.org/10.3354/ab00058 Sowa A, Krodkiewska M, Halabowski D (2020) How does mining salinisation gradient affect the structure and functioning of macroinvertebrate communities? Water Air Soil Pollut 231(9):453. https://doi.org/10.1007/s11270-020-04823-4 Telesh IV, Khlebovich VV (2010) Principal processes within the estuarine salinity gradient: a review. Mar Pollut Bull 61(4–6):149–155. https://doi.org/10.1016/j.marpolbul.2010.02.008 Veeravechsukij N, Krailas D, Namchote S, Wiggering B, Neiber MT, Glaubrecht M (2018) Molecular phylogeography and reproductive biology of the freshwater snail Tarebia granifera in Thailand and Timor (Cerithioidea, Thiaridae): morphological disparity versus genetic diversity. Zoosystematics Evol 94(2):461–493. https://doi.org/10.3897/zse.94.28981 Virnstein RW (1977) The importance of predation by crabs and fishes on benthic infauna. Chesapeake Bay Ecol 58(6):1199–1217. https://doi.org/10.2307/1935076 Weinmann AE, Goldstein ST, Triantaphyllou MV, Langer MR (2021) Community responses of intertidal foraminifera to pH variations: a culture experiment with propagules. Aquat Ecol 55(1):309–325. https://doi.org/10.1007/s10452-021-09833-w White KN (2011) A taxonomic review of the Leucothoidae (Crustacea: Amphipoda). Zootaxa 3078(1):1–113. https://doi.org/10.11646/zootaxa.3078.1.1 Whitlatch RB, Zajac RN (1985) Biotic interactions among estuarine infaunal opportunistic species. Mar Ecol Prog Ser 21(3):299–311. https://doi.org/10.3354/meps021299 Zajac RN, Whitlatch RB (1982) Responses of estuarine infauna to disturbance. I. Spatial and temporal variation of initial recolonization. Mar Ecol Prog Ser 10(1):1–14. https://doi.org/10.3354/meps010001 Additional Declarations No competing interests reported. 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-5367139","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":373405220,"identity":"d74e9923-dd26-4b73-9d8b-2da55b8007d7","order_by":0,"name":"Alche Pacudan","email":"","orcid":"","institution":"Mindanao State University – Main Campus","correspondingAuthor":false,"prefix":"","firstName":"Alche","middleName":"","lastName":"Pacudan","suffix":""},{"id":373405221,"identity":"377b52e0-37fc-4696-aadb-65eaab264a77","order_by":1,"name":"Warren Caneos","email":"data:image/png;base64,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","orcid":"","institution":"Mindanao State University – Main Campus","correspondingAuthor":true,"prefix":"","firstName":"Warren","middleName":"","lastName":"Caneos","suffix":""},{"id":373405222,"identity":"25a04db2-5559-47ac-83a1-2e44a0628a99","order_by":2,"name":"Reynald Gimena","email":"","orcid":"","institution":"Mindanao State University – Main Campus","correspondingAuthor":false,"prefix":"","firstName":"Reynald","middleName":"","lastName":"Gimena","suffix":""},{"id":373405223,"identity":"45b0df4a-0c93-4abc-96ce-7b0eb1f15831","order_by":3,"name":"Dulce Fe Abragan","email":"","orcid":"","institution":"Mindanao State University – Main Campus","correspondingAuthor":false,"prefix":"","firstName":"Dulce","middleName":"Fe","lastName":"Abragan","suffix":""}],"badges":[],"createdAt":"2024-10-31 11:23:41","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5367139/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5367139/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":68676229,"identity":"b9f04fed-ba23-4598-a38f-6538f1037fcf","added_by":"auto","created_at":"2024-11-11 02:32:38","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":329915,"visible":true,"origin":"","legend":"\u003cp\u003eLocation map of the two converging river estuaries, Sa’ai River (S1-S3) and Tapon River (T1-T4), in Mambajao, Camiguin Island, Philippines.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5367139/v1/bc07869aa6056295c392451e.jpg"},{"id":68676000,"identity":"42ad20e7-f875-49d8-bf73-af2582b48940","added_by":"auto","created_at":"2024-11-11 02:24:38","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":109043,"visible":true,"origin":"","legend":"\u003cp\u003eRelative abundance of the different infauna species present in the two converging river estuaries of Mambajao, Camiguin Island, Philippines.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5367139/v1/fad792daf413d8dd304d1c79.jpg"},{"id":68675994,"identity":"b4a74892-ce58-4486-aa46-ae10ab83d834","added_by":"auto","created_at":"2024-11-11 02:24:37","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":207677,"visible":true,"origin":"","legend":"\u003cp\u003eCommon and unique species found in the four sampling stations (T1, T2, T3, T4) of Tapon River (A), three sampling stations (S1, S2, S3) of Sa’ai River (B) and both rivers (C).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5367139/v1/d78e1dd9d5a99da893f8994e.png"},{"id":68675998,"identity":"d7d19630-0956-4e51-946b-4dbb43913133","added_by":"auto","created_at":"2024-11-11 02:24:38","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":108328,"visible":true,"origin":"","legend":"\u003cp\u003ePhysico-chemical parameters, temperature (A), salinity (B), water pH (C) and soil pH (D), measured in the different sampling stations. Values are mean ± S.E. Different letters (A-D) indicate a significant difference (\u003cem\u003ep\u003c/em\u003e≤0.05) between the physico-chemical parameters and sampling stations of the two river estuaries.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5367139/v1/c6eb80c526b2dad2bd49104f.png"},{"id":68676228,"identity":"af7ee6c0-9c3f-48b2-bf37-7ebd245d8ef1","added_by":"auto","created_at":"2024-11-11 02:32:38","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":29260,"visible":true,"origin":"","legend":"\u003cp\u003eNon-metric Multidimensional scaling (nMDS) of square-root transformed data of infaunal abundance data showing the similarities of the samples from Sa’ai and Tapon River in Mambajao, Camiguin Island, Philippines.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5367139/v1/f84a48d0c5da229d70a61a1e.jpg"},{"id":68675996,"identity":"feaad41a-847e-4f77-9185-ebb65737a5f8","added_by":"auto","created_at":"2024-11-11 02:24:38","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":35325,"visible":true,"origin":"","legend":"\u003cp\u003eCluster analysis based on Bray-Curtis similarity resemblance of square-root transformed abundance data showing the similarities of the samples from Sa’ai and Tapon River in Mambajao, Camiguin Island, Philippines.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5367139/v1/e6585b3677d34fb5c32fbbec.jpg"},{"id":68675999,"identity":"86edff75-ab29-4649-b983-56cd4370a47a","added_by":"auto","created_at":"2024-11-11 02:24:38","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":136237,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5367139/v1/b241621854fb85ea8f9870fe.png"},{"id":68677480,"identity":"34cb4dad-637c-4ae6-a88d-657c0fab2ba0","added_by":"auto","created_at":"2024-11-11 02:48:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1368716,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5367139/v1/28b5508d-f817-4203-a3d7-b51a2f2f7a18.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Infaunal biodiversity of converging river estuaries in Mambajao, Camiguin Island in relation to salinity gradients","fulltext":[{"header":"Introduction","content":"\u003cp\u003eEstuaries \u0026ndash; semi-enclosed coastal bodies of water where the river meets the sea \u0026ndash; are one of the biologically highly productive and dynamic aquatic environments where most intensive exchange of matter and energy between the continents and oceans occurs (Prichard, 1967; Bowmaker, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1968\u003c/span\u003e; Ahel et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Day et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). They are also considered as critical transition zones (CTZs) that connect terrestrial, freshwater and marine environments and are often termed as marginal filters (Levin et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Paturej, \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). They provide valuable ecosystem goods and services to the society and to the majority of the coastal population (Bianchi et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Cooper et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Bianchi, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; McGranahan et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Kennish and Paerl, 2010). They play a crucial role in ecosystem functioning by facilitating decomposition, nutrient cycling, and nutrient production. Additionally, they serve as key regulators of nutrient, water, particle, and organism exchanges between land, rivers, and the ocean (Levin et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Newton et al., \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEstuaries are also characterized by strong salinity gradients (changes in salinity ranging\u003c/p\u003e \u003cp\u003efrom full strength seawater decreasing to freshwater) (Elliott and McLusky, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). The salinity range in estuaries serves as a crucial external ecological factor and a defining physiological characteristic of the internal environment for aquatic organisms. This range delineates the suitable living conditions for both freshwater and marine faunas, segregates invertebrate communities based on their osmotic regulation mechanisms, and establishes the distribution boundaries for higher taxa (Telesh and Khlebovich, \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Studies conducted on estuarine systems has demonstrated that salinity plays a crucial role as an environmental filter, exerting influence over the composition, abundance, and functional characteristics of benthic macroinvertebrates (Martins and Barros, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Within tropical estuaries, polychaete communities display functional nestedness along salinity gradients, whereby lower salinity areas harbor subsets of functional traits observed in higher salinity regions (Medeiros et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Furthermore, fluctuations in salinity within estuarine systems can induce significant alterations in biological processes and biodiversity over time, thereby impacting the stress levels experienced by organisms inhabiting intertidal zones (Sowa et al., \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These findings underscore the significance of comprehending how salinity gradients influence the distribution patterns of infauna species and their functional roles within estuarine ecosystems. Such understanding provides valuable insights for the development of conservation strategies and the management of these ecosystems (Donatelli et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Koehler et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eInfauna \u0026ndash; animals dwelling in the sediments \u0026ndash; are subdivided into different size spectra namely, megafauna, macrofauna, meiofauna and microfauna (Connor et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Davies et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). These organisms influence water filtration, organic matter recycling, and serve as vital food source to predatory species which are also important to man (Virnstein, \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e1977\u003c/span\u003e; Venegas et al., 2017). They also contribute to sediment mixing, modify sediment properties, and impact biogeochemical cycles (Dorgan et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Mizuno et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Their activities, like burrowing and building structures, influence sediment structure and geoacoustic properties, affecting sound speed and attenuation (Blackburn and Orth, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Ballentine et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eHowever, increasing human population and destructive interventions create big problems to estuaries and coastal wetlands (Sciberras et al., \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Therefore, infaunal community studies are increasing and gaining attention of many researchers. It emphasizes careful examination of estuarine habitats and gathering of facts to understand the processes and functions of estuarine community (Schaffner, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). A need for solid and strong ecological indices to evaluate ecosystem status and condition (Ieno et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Pinto et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) in which there is need for caution when extrapolating from assumed knowledge of organism traits to how changes in species composition associated with ecological crises may impact ecosystem function (Solan et al., \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Additionally, several studies presented estuarine habitats in association with infaunal organisms, such as decapod crustaceans (Gore et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1981\u003c/span\u003e), polychaetes, amphipods, clams (Hines and Comtois, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1985\u003c/span\u003e), anthozoans (Whitlatch and Zajac, \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e1985\u003c/span\u003e), oligochaetes (De Deckere et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2001\u003c/span\u003e), hemichordates (Zajac and Whitlatch, \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e1982\u003c/span\u003e), copepods (Galv\u0026aacute;n et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThere is a limited number of hierarchical studies that strongly advocate for the inclusion of comparative measures of species turnover, estimates of species pools' size, and information on the spatial distribution of species diversity in relation to habitat patchiness (Kendall et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). Although each index may have a different conceptual basis relying on various assumptions and parameters, they all share a common objective: to provide a valuable tool for assessing the health of a system and aiding in decision-making processes (Pinto et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). The biodiversity within benthic communities holds significant implications for the management of such areas (Fredriksen et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). By studying benthic communities in estuaries, researchers can identify environmental factors that influence the structure of these communities and evaluate their health as an indicator of environmental disturbances, whether natural or anthropogenic in origin (Engle et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1994\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eGenerally, this study aims to compare the infaunal biodiversity of two converging river estuaries in Mambajao, Camiguin Island, Philippines. Specifically, this study aims to determine the species composition and relative abundance of infauna in all sampling sites; determine the species diversity of infauna between sampling sites; identify and compare the infauna distribution between sampling sites; and identify the correlation between the environmental parameters and the biodiversity within and between the converging river estuaries in Mambajao, Camiguin Island, Philippines.\u003c/p\u003e \u003cp\u003eTherefore, the results of the study can be a source of baseline information for future studies on the effects of anthropogenic activities on the biodiversity of infauna and other aquatic organisms in the estuaries. Results of the study can also be used in the preparation and establishment of management plans for the conservation and protection of the estuaries and its resources.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy area\u003c/h2\u003e \u003cp\u003eThe study was conducted in the two converging river estuaries namely Tapon River and Sa\u0026rsquo;ai River in Mambajao, Camiguin Island, Philippines (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Sa\u0026rsquo;ai River and Tapon River were assigned with three and four stations, respectively. Tapon River is located near to the private establishments and agricultural farms, subject to anthropogenic activities, such as agricultural pollutants, domestic sewage and industrial effluents. Sa\u0026rsquo;ai River is situated near the airport and is less disturbed compared to Tapon River.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSite survey\u003c/h3\u003e\n\u003cp\u003eInitially, the salinity gradient of the river estuaries was measured during the highest high tide using 600 Series Waterproof Portable Meter Kit (Oakton Instruments, Singapore). Following the salinity gradient determination, the furthest distance the salinity can travel was measured also using transect line. The sampling stations were established in 100-m interval from the river bank and ended up to the furthest distance travelled by the seawater. Based on the results of salinity gradients, seawater entering Sa\u0026rsquo;ai River and Tapon River can reach up to 300 m and 400 m respectively. Finally, seven stations were established: four for Tapon River (T1-T4) and three for Sa\u0026rsquo;ai River (S1-S3).\u003c/p\u003e\n\u003ch3\u003eField sampling\u003c/h3\u003e\n\u003cp\u003eCore sampling method of Bradshaw et al. (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) was used with some modifications. A transparent plastic tube with a length of one foot and a diameter of six centimeters was inserted by pushing it into the sediment, about 15 centimeters deep of the cores, to take sediment cores of the riverbed. Three core samples were taken from each sampling station.\u003c/p\u003e \u003cp\u003eThe infauna samples were then separated from the sediment using 500-\u0026micro;m mesh sieve, placed in the plastic containers, and preserved using ethanol of 95% solution (Virnstein, \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e1977\u003c/span\u003e). The samples were brought to the Integrated Fish Laboratory of the College of Fisheries, Mindanao State University \u0026ndash; Main Campus, Marawi City for species identification and counting. Furthermore, sediments were put in the plastic ziplock bag and brought to the same laboratory for soil pH analysis.\u003c/p\u003e\n\u003ch3\u003eMeasurements of physico-chemical parameters\u003c/h3\u003e\n\u003cp\u003eIn-situ measurements of the physico-chemical parameters, such as water pH, temperature and salinity were measured in each station with three replicates during the highest high tide using 600 Series Waterproof Portable Meter Kit (Oakton Instruments, Singapore).\u003c/p\u003e\n\u003ch3\u003eSoil pH analysis\u003c/h3\u003e\n\u003cp\u003eThe soil pH was determined following the procedures of Jackson (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1958\u003c/span\u003e) and Black (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1965\u003c/span\u003e) with a soil to water ratio of 1:1. Firstly, 50-g air-dried sediments were weighed using analytical balance (Radwag Wagi Elektroniczne, Poland), placed in a clean plastic container, added with 50-mL distilled water and stirred thoroughly. Then, it was let stand for 1 hour and stirred three times during the hour. Sample suspension was stirred, and pH was immediately determined using a calibrated 600 Series Waterproof Portable Meter Kit (Oakton Instruments, Singapore).\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eSpecies identification\u003c/h2\u003e \u003cp\u003eInfauna samples were identified up to the family of the species, but limited to those what was seen by the naked eye following key identification guides of benthic macroinvertebrates (Oscoz et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), mollusks (Ng et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), aquatic annelids, such as oligochaetes and polychaetes (Brinkhurst, 1963; Klemm, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1985\u003c/span\u003e) and amphipods (White, \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). A compound microscope was used to magnify the images of species for easier identification.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eData analyses\u003c/h3\u003e\n\u003cp\u003eAbundance and relative abundance were obtained using Microsoft Excel (2016). Relative abundance was measured to determine which species is dominating the zone/area. Venn diagram was also developed using Venny v. 2.1 (Oliveros, 2007\u0026ndash;2015) to graphically and clearly show the similarities and differences of the biodiversity within and between sites. Diversity indices such as diversity (H\u0026rsquo;), species richness (S) and evenness (J\u0026rsquo;) were analyzed using Paleontological Statistics Software Package (PAST) version 2.17c (Hammer et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). To determine if there are significant differences in the physico-chemical parameters and species diversity among the sampling stations, One-way Analysis of Variance (ANOVA) using SPSS version 21 was done.\u003c/p\u003e \u003cp\u003eThe infaunal assemblages were analyzed using non-metric multi-dimensional scaling (nMDS) and cluster analysis based on square-root transformed abundance data. Transformed data were subjected to Bray-Curtis similarity measure prior to analysis. One-way Analysis of Similarity Percentages (SIMPER) was also used to determine which species contribute to the clustering and separation of samples. Canonical Correspondence Analysis (CCA) was done to identify the infaunal samples distribution in relation to different environmental parameters. Non-metric multi-dimensional scaling (nMDS), cluster analysis and SIMPER were analyzed using Primer v.7.0 (Clarke and Gorley, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) while CCA was analyzed using PAST version 2.17c (Hammer et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2001\u003c/span\u003e).\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eSpecies composition and relative abundance\u003c/h2\u003e \u003cp\u003eA total of 356 individuals belonging to 9 families were found in both river estuaries of Mambajao, Camiguin Island, Philippines. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the relative abundance of each species present in all sampling stations. Results showed that the dominant species in Sa\u0026rsquo;ai River belong to family Pachychilidae (Mollusca:Gastropoda) and Thiaridae (Mollusca: Gastropoda) with a relative abundance of 70.07% and 10.95%. Meanwhile, Tapon River was dominated by Lumbriculidae (Annelida: Clitellata) and Pachychilidae dominated the Tapon River with a relative abundance of 43.84% and 29.22%, respectively. Other species found but of less abundance were Neritidae (Mollusca: Gastropoda), Chironomidae (Insecta: Diptera), Nereididae (Annelida: Polychaeta), Phyllodocidae (Annelida: Polychaeta), Leucothoidae (Crustacea: Amphipoda) and Glyceridae (Annelida: Polychaeta).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eSpecies distribution\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the common and unique species found in Sa\u0026rsquo;ai and Tapon River. Between sampling stations of Tapon River (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA), Pachychilidae and Thiaridae were two common families of infauna species in the four sampling stations. Lumbriculidae and Neritidae were also common species but not found in T2 and T4, respectively. Nereididae was the only unique species in Tapon River which was found in T1. Meanwhile, in Sa\u0026rsquo;ai River (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB), only two common species (Pachychilidae and Neritidae) were found in all stations of Sa\u0026rsquo;ai River while Chironomidae was the only species found common to S1 and S3 while Thiaridae in S2 and S3. In terms of unique species, Leucothoidae and Phyllodocidae were found only in S2 while Lumbriculidae and Glyceridae were found only in S3.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC showed that five families, Chironomidae, Lumbriculidae, Pachychilidae, Neritidae and Thiaridae were common to both rivers. Species belonging to three families, Glyceridae, Leucothoidae and Phyllodocidae, were unique to Sa\u0026rsquo;ai River while Nereididae was the only unique species found in Tapon River.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eInfaunal diversity in river estuaries\u003c/h2\u003e \u003cp\u003eComparisons of the diversity (H\u0026rsquo;), species richness (S) and evenness (J\u0026rsquo;) in the two river estuaries are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. In Tapon River, mean H\u0026rsquo; ranged from 0.267\u0026thinsp;\u0026plusmn;\u0026thinsp;0.267 to 0.534\u0026thinsp;\u0026plusmn;\u0026thinsp;0.299 while in Sa\u0026rsquo;ai River, mean H\u0026rsquo; ranged from 0.363\u0026thinsp;\u0026plusmn;\u0026thinsp;0.363 to 0.811\u0026thinsp;\u0026plusmn;\u0026thinsp;0.090. Species richness in Tapon and Sa\u0026rsquo;ai River ranged from 1.667\u0026thinsp;\u0026plusmn;\u0026thinsp;0.667 to 2.667\u0026thinsp;\u0026plusmn;\u0026thinsp;0.882 and 1.667\u0026thinsp;\u0026plusmn;\u0026thinsp;0.667 to 3.000\u0026thinsp;\u0026plusmn;\u0026thinsp;1.528, respectively while species evenness ranged from 0.793\u0026thinsp;\u0026plusmn;\u0026thinsp;0.177 to 0.965\u0026thinsp;\u0026plusmn;\u0026thinsp;0.035 and 0.391\u0026thinsp;\u0026plusmn;\u0026thinsp;0.204 to 0.997\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003, respectively.\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\u003eDiversity indices per station of the two converging river estuaries of Mambajao, Camiguin Island, Philippines. Values are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;S.E.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRiver Estuaries\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStations\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eShannon-Wiener (H')\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSpecies Richness (S)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSpecies Evenness (J\u0026rsquo;)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eTapon River\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eT1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.267\u0026thinsp;\u0026plusmn;\u0026thinsp;0.267\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.667\u0026thinsp;\u0026plusmn;\u0026thinsp;0.667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.914\u0026thinsp;\u0026plusmn;\u0026thinsp;0.086\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eT2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.277\u0026thinsp;\u0026plusmn;\u0026thinsp;0.277\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.667\u0026thinsp;\u0026plusmn;\u0026thinsp;0.667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.922\u0026thinsp;\u0026plusmn;\u0026thinsp;0.078\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eT3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.534\u0026thinsp;\u0026plusmn;\u0026thinsp;0.299\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e2.667\u0026thinsp;\u0026plusmn;\u0026thinsp;0.882\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.793\u0026thinsp;\u0026plusmn;\u0026thinsp;0.177\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eT4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.329\u0026thinsp;\u0026plusmn;\u0026thinsp;0.329\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.667\u0026thinsp;\u0026plusmn;\u0026thinsp;0.667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.965\u0026thinsp;\u0026plusmn;\u0026thinsp;0.035\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eSa'ai River\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.363\u0026thinsp;\u0026plusmn;\u0026thinsp;0.363\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.667\u0026thinsp;\u0026plusmn;\u0026thinsp;0.667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.997\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.811\u0026thinsp;\u0026plusmn;\u0026thinsp;0.090\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e3.000\u0026thinsp;\u0026plusmn;\u0026thinsp;0.577\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.790\u0026thinsp;\u0026plusmn;\u0026thinsp;0.088\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.633\u0026thinsp;\u0026plusmn;\u0026thinsp;0.357\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e3.000\u0026thinsp;\u0026plusmn;\u0026thinsp;1.528\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e0.391\u0026thinsp;\u0026plusmn;\u0026thinsp;0.204\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003ePhysico-chemical parameters\u003c/h2\u003e \u003cp\u003eThe measurements of the four physico-chemical parameters (temperature, salinity, water pH and soil pH) in the four sampling stations of the lake are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. Results revealed Tapon River and Sa\u0026rsquo;ai River had a mean temperature ranging from 29.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09 ⁰C to 29.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52 ⁰C, 30.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 ⁰C to 33.30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 ⁰C, respectively. Sa\u0026rsquo;ai River had significantly higher temperature compared to Tapon River. Significant differences in temperature were also observed among sampling stations of Sa\u0026rsquo;ai River. In terms of salinity, S1 was significantly higher compared to other sampling stations in Tapon River and Sa\u0026rsquo;ai River. Tapon River and Sa\u0026rsquo;ai River had a mean salinity ranging from 0.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 ppt to 3.48\u0026thinsp;\u0026plusmn;\u0026thinsp;2.16 ppt, 0.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 ppt to 7.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14 ppt, respectively.\u003c/p\u003e \u003cp\u003eMeanwhile, in terms of water pH, S3 was the only station with significantly higher values compared to other stations. In terms of soil pH, significant differences were observed among sampling stations. T1, T2 and T3 had significantly higher soil pH compared to T4, S1, S2 and S3. However, no significant difference in soil pH was observed between S1 and S3.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eInfaunal assemblages\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e show the nMDS graph and cluster analysis of square-root transformed data of infaunal abundance from Sa\u0026rsquo;ai River and Tapon River in Mambajao, Camiguin Island, Philippines. Clear segregation patterns (30% and 50% similarity) were observed between sampling stations of two river estuaries. Samples from T4R1, T4R2, T3R3 and T1R2 were segregated from T1R1, T2R1 and T3R1 and the rest of the sampling stations.\u003c/p\u003e \u003cp\u003eFurthermore, cluster analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) revealed that some samples from Tapon River and Sa\u0026rsquo;ai River had a close relationship. For example, T4R1, T3R3 and T4R2 showed\u0026thinsp;~\u0026thinsp;80% similarity, T4R3 and S3R2 with 80% similarity, T2R3 and S2R1 with ~\u0026thinsp;90% similarity, T2R2 and S1R1 with 90% similarity and T3R2, S3R3, T2R3 and S2R1 with 80% similarity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFurthermore, SIMPER analysis revealed that samples from Tapon River and Sa\u0026rsquo;ai River had 22.40 and 49.61% similarity, respectively. Such similarities in Tapon River were largely contributed by Pachychilidae, Lumbriculidae and Thiaridae with 39.79%,33.48% and 17.33%, respectively while similarity in Sa\u0026rsquo;ai River was mainly due to Pachychilidae (78.50%) and Neritidae (13.97%).\u003c/p\u003e \u003cp\u003eHigh percentage of dissimilarities was observed between river estuaries. Tapon River and Sa\u0026rsquo;ai River showed an average dissimilarity of 70.22% and were mainly contributed by Pachychilidae (38.29%), Lumbriculidae (17.37%), Thiaridae (15.67%), Neritidae (14.39%) and Chironomidae (7.87%).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCanonical Correspondence Analysis (Fig.\u0026nbsp;7) showed that the presence and distribution of infauna species, such as Glyceridae, Pachychilidae, Chironomidae, Neritidae, were strongly influenced by the four physico-chemical parameters (e.g. temperature, salinity, water pH and soil pH).\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study indicated that the relative abundance, diversity and assemblages of infaunal species varied between the different sampling stations of two converging river estuaries of varied salinity levels. These estuaries were mainly dominated by gastropods (family Pachychilidae and Thiaridae) and an annelid species under the family Lumbriculidae. Similar results were observed in the study by Guillena et al. (2022) in the coastal barangays of Roxas, Zamboanga del Norte with Pachychilidae and Thiaridae as the most abundant.\u003c/p\u003e \u003cp\u003ePachychilidae are widely distributed species (Ng et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) and are considered as a conspicuous component of the freshwater and estuarine macroinvertebrates of Southeast Asia (K\u0026ouml;hler and Dames, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). These species were identified to be present in areas exposed to anthropogenic activities such as agricultural pollutants, domestic sewage, industrial effluents and mining waste (K\u0026ouml;hler et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; L\u0026oacute;pez and Urcuyo, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Similarly, the presence of Pachychilid species in the two converging river estuaries was observed in the area even they are exposed to various anthropogenic activities. For example, agricultural activities are taking place in the upper part of the rivers which could contribute agricultural pollutants and sewage that are directly discharged to the river estuaries by the residences, market and other private establishments. However, K\u0026ouml;hler et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) described family Pachychilidae as extremely restricted ranges, often in specialized habitats, such as river rapids, requiring highly oxygenated unpolluted waters. This might explain why Pachychilids are more abundant in Sa\u0026rsquo;ai River than Tapon River.\u003c/p\u003e \u003cp\u003eAnother abundant species in both river estuaries was Lumbriculidae. Usually, this species can be found in freshwater habitats including streams, lakes, wetlands, man-made wells and groundwater. They are commonly found in still or slow-flowing shallow water and are often associated with disturbed habitats, particularly in high nutrient level areas (Frost et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). The study of Frost et al. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) revealed that Lumbriculidae have greater densities when exposed to high nutrients. This might explain why Lumbriculidae was abundant in Tapon River because of nutrient inputs coming from agricultural farms near to it especially during run-off. Lumbriculidae ingest organic detritus and microorganisms, such as bacteria, that are present in the sediments they consume and excrete (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://keys.lucidcentral.org\u003c/span\u003e\u003cspan address=\"https://keys.lucidcentral.org\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). The dominance of this species could be due to abundance of foods in Tapon River as it is surrounded by many trees which can be a source of organic detritus. Microorganisms might also dominate for the decomposition of leaves and other waste materials coming from the households and food establishments.\u003c/p\u003e \u003cp\u003eThiaridae, which are predominantly found in tropical to subtropical regions worldwide, inhabit almost all freshwater and brackishwater bodies, encompassing lotic habitats such as springs, creeks, rivers, and streams, as well as lentic habitats like lakes and ponds (Veeravechsukij et al., \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Originally, they are widely distributed throughout Southeast Asia and in Australia (Glaubrecht, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Glaubrecht, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eChironomidae were also found in some sampling stations in both estuaries. Chironomid larvae, being the most prevalent benthic species, can be found in various habitats such as rivers, streams, lakes, ponds, water supplies, and sewage systems. Due to their sediment-dwelling lifestyle, these larvae have limited mobility (Morris and Brooker, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e1980\u003c/span\u003e; Pinder, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Hall and Gedhardt, 2002). This could be the reason why Chironomids are present in the two river estuaries. Their presence and abundance could also be linked to the low population of its predators, such as Nereididae which was observed by R\u0026ouml;nn et al. (\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e1988\u003c/span\u003e) in their study on gut content analysis of Nereididae. Additionally, Chironomidae consume detritus and typically forage on aquatic substrates (Hall and Gedhardt, 2002). During sampling, there were a lot of organic materials, such as leaves, twigs, branches obtained together with the sediment samples. These organic materials were at the stage of decomposition which could attract many organisms that can be consumed as food by Chironomids. Lencioni et al. (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) also mentioned that anthropogenic activities could affect the distribution of Chironomidae which resulted to low species abundance and richness. Moreover, the results revealed that \u003cem\u003eChironomidae\u003c/em\u003e were influenced by soil and water pH. On the contrary, results of the studies by March (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), Oku et al. (2015) and Sharif et al. (\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) showed that \u003cem\u003eChironomidae\u003c/em\u003e exhibited no affinity to soil and water pH.\u003c/p\u003e \u003cp\u003eIn terms of species diversity, both river estuaries had relatively lower species diversity which could be linked to the anthropogenic pressures in the area and only those pollution-tolerant species were commonly present as observed also by Lencioni et al. (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Similarly, the study of Connor et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) in Ireland wherein species richness was greatly influenced by temperature. Furthermore, a study by Kunitzer et al. (1992) described that one of the factors structuring species distributions and assemblages seem to be influenced by high temperature. Similar results were observed by Moller (1986) wherein Nereidid sp. was not affected by high temperature due to its ability to migrate. In the study of Ndhlovu et al. (\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), they found that estuaries receiving wastewater effluent discharges exhibited a higher abundance of macroinvertebrates that can thrive in environments with high levels of organic pollution.\u003c/p\u003e \u003cp\u003eThe salinity gradient of the two river estuaries had large differences from the mouth to the upper part of the rivers. Such salinity variations in river estuaries were due to the freshwater inputs coming from rivers and springs and tidal influence. Results of CCA showed that most of the species were influenced by salinity. Some species prefer to thrive in a low-saline or freshwater environments such as Pachychilidae (e.g. \u003cem\u003eSulcospira\u003c/em\u003e, \u003cem\u003eTylomelania, Brotia\u003c/em\u003e) and Thiaridae (e.g. \u003cem\u003eMelanoides\u003c/em\u003e) (K\u0026ouml;hler et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Ng et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2016\u003c/span\u003e); Lumbriculidae (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://keys.lucidcentral.org\u003c/span\u003e\u003cspan address=\"https://keys.lucidcentral.org\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e) and a few species of Chironomidae (Hall and Gedhardt, 2002). Alongi and Christoffersen (1990) mentioned that low-salinity zones are generally characterized by low diversity both among and within functional groups.\u003c/p\u003e \u003cp\u003eAnother factor that significantly influences the presence and composition of infauna in estuaries is the pH. Several studies have demonstrated that alterations in pH can result in shifts in the makeup of infaunal communities (Hossain and Marshall, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Weinmann et al., \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). For instance, exposure to acidified seawater has been found to cause significant changes in community structure and reduced diversity of macrofaunal and nematode assemblages. Notably, sandy sediments tend to be more affected by these changes compared to muddy sediments (Bone et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Furthermore, in tropical estuarine systems, the structuring of benthic infaunal communities is influenced by a steep gradient in salinity and pH, highlighting the impact of pH variations on these ecosystems (Hansen et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). These findings underscore the vulnerability of infaunal communities to pH fluctuations in estuarine environments, emphasizing the necessity for further research to comprehend and mitigate the potential consequences of ocean acidification on these crucial ecosystems.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eA study on the infauna distribution, species composition, diversity and its correlation with environmental variables was conducted in the two converging river estuaries of Mambajao, Camiguin Island, Philippines. Using a modified core sampling method, samples were collected and were immediately sorted, identified and counted. \u003cem\u003eIn-situ\u003c/em\u003e measurements of physico-chemical parameters (e.g. salinity, water pH and temperature) and analysis of soil pH were done using 600 Series Waterproof Portable Meter Kit. Results showed that Pachychilidae (44.94%), Lumbriculidae (28.09%) and Thiaridae (14.61%) had the highest relative abundance in both rivers which could be due to its wide tolerance of pollution that also resulted to low species diversity (H\u0026rsquo;) ranging only from 0.267\u0026thinsp;\u0026plusmn;\u0026thinsp;0.267 to 0.811\u0026thinsp;\u0026plusmn;\u0026thinsp;0.090. Furthermore, Sa\u0026rsquo;ai River showed significantly higher temperature compared to Tapon River. Significant differences in salinity, water pH and soil pH were also observed between the two river estuaries.\u003c/p\u003e \u003cp\u003eClear segregation patterns (30% and 50% similarity) were observed between sampling stations of two river estuaries. Samples from T4R1, T4R2, T3R3 and T1R2 were segregated from T1R1, T2R1 and T3R1 and the rest of the sampling stations. Similar results were also observed in the cluster analysis and SIMPER.\u003c/p\u003e \u003cp\u003eThe assemblages of the infauna (e.g. Glyceridae, Pachychilidae, Chironomidae, Neritidae) were strongly influenced by temperature, salinity, water pH and soil pH.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eA.P. and W.C. conceptualized the study, conducted the experiments, performed the analyses, and drafted the manuscript. The manuscript was reviewed and edited by A.P., W.C., R.G. and D.F.A.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe would like to extend our deepest gratitude to the Provincial Government of Camiguin headed by Gov. Xavier Jesus D. Romualdo, Cong. Jurdin Jesus M. Romualdo, Mayor Y\u0026ntilde;igo Jesus D. Romualdo and Mrs. Fe A. Belara for their permission and moral support; Mr. Archie A. Along and Mr. Jan Mark S. Viter for the data analysis; Mr. Ralph V. Namayan and Mr. John Mark S. Morales for making the location map of the study and; College of Fisheries and Aquatic Sciences, Mindanao State University \u0026ndash; Marawi for allowing us to use the Multi-Parameter Instrument and the Integrated Laboratory and administrative support.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAhel M, Barlow RG, Mantoura RFC (1996) Effect of salinity gradients on the distribution of phytoplankton pigments in a stratified estuary. Mar Ecol Prog Ser 143:289\u0026ndash;295. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3354/meps143289\u003c/span\u003e\u003cspan address=\"10.3354/meps143289\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlongi DM, Christoffersen P (1992) Benthic infauna and organism-sediment relations in a shallow, tropical coastal area: Influence of outwelled mangrove detritus and physical disturbance. Mar Ecol Progress Ser Oldendorf 81(3):229\u0026ndash;245. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps:///www.doi.org/10.3354/meps081229\u003c/span\u003e\u003cspan address=\"https:///www.10.3354/meps081229\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBallentine WM, Dorgan KM, Lee KM, Ballard MS, McNeese AR, Wilson PS, Venegas GR (2017) Effects of marine infauna on the acoustic properties of sediment. J Acoust Soc Am 142(4Supplement):2693\u0026ndash;2693. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1121/1.5014824\u003c/span\u003e\u003cspan address=\"10.1121/1.5014824\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBianchi TS (2007) Biogeochemistry of estuaries. Oxford University Press. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/oso/9780195160826.001.0001\u003c/span\u003e\u003cspan address=\"10.1093/oso/9780195160826.001.0001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBianchi TS, Pennock JR, Twilley RR (eds) (1999) Biogeochemistry of Gulf of Mexico estuaries. Wiley\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBlack CA (1965) Methods of soil analysis. Part II. Agronomy series No. 9. Amer. Soc. Agron., Inc., Wisconsin, USA\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBlackburn NJ, Orth RJ (2013) Seed burial in eelgrass Zostera marina: the role of infauna. Mar Ecol Prog Ser 474:135\u0026ndash;145. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://dx.doi.org/doi:10.25773/v5-t6b8-6808\u003c/span\u003e\u003cspan address=\"doi:10.25773/v5-t6b8-6808\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBone JR, Stafford R, Hall AE, Boyd I, George N, Herbert RJ (2022) Estuarine infauna within incidentally retained sediment in artificial rockpools. Front Mar Sci 8:780720. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3389/fmars.2021.780720\u003c/span\u003e\u003cspan address=\"10.3389/fmars.2021.780720\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBowmaker AP (1968) The use of the word estuary in a freshwater context. Newsl Limnol Soc Sthn Afr 11:1\u0026ndash;22\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBradshaw C, Collins P, Brand AR (2003) To what extent does upright sessile epifauna affect benthic biodiversity and community composition? Mar Biol 143(4):783\u0026ndash;791. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00227-003-1115-7\u003c/span\u003e\u003cspan address=\"10.1007/s00227-003-1115-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eClarke KR, Gorley RN (2015) Getting started with PRIMER v7. \u003cem\u003ePRIMER-e: plymouth, plymouth marine laboratory\u003c/em\u003e, \u003cem\u003e20\u003c/em\u003e(1)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eConnor DW, Allen JH, Golding N, Howell KL, Lieberknecht LM, Northen KO, Reker JB (2003) The national marine habitat classification for Britain and Ireland. Joint Nature Conservation Committee, Peterborough\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCooper J, Jayiya T, Van Niekerk L, De Wit M, Leaner J, Moshe D (2003) An assessment of the economic values of different uses of estuaries in South Africa. CSIR Report No. ENVSC 139.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDavies AJ, Narayanaswamy BE, Hughes DJ, Roberts JM (2006) An Introduction to the benthic ecology of the Rockall-Hatton area (SEA 7). A Report for the DTI by the Scottish Association for Marine Science. Dunstaffnage Marine Laboratory, Oban\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDay JW, Kemp WM, Y\u0026aacute;\u0026ntilde;ez-Arancibia A, Crump BC (2012) Estuarine Ecology. Wiley. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/9781118412787\u003c/span\u003e\u003cspan address=\"10.1002/9781118412787\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDe Deckere EMGT, Tolhurst TJ, De Brouwer JFC, Estuarine (2001) Coastal Shelf Sci, 53(5):665\u0026ndash;669. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1006/ecss.2001.0811\u003c/span\u003e\u003cspan address=\"10.1006/ecss.2001.0811\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDonatelli C, Duran-Matute M, Gr\u0026auml;we U, Gerkema T (2022) Statistical detection of spatio-temporal patterns in the salinity field within an inter-tidal basin. Estuaries Coasts 45(8):2345\u0026ndash;2361. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s12237-022-01089-3\u003c/span\u003e\u003cspan address=\"10.1007/s12237-022-01089-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDorgan KM, Frey MR, Clemo WC, Venegas GR, Lee KM, Ballard M, Wilson PS (2022) Impacts of infauna on sediment heterogeneity and acoustic propagation. J Acoust Soc Am 152(4):A102\u0026ndash;A102. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1121/10.0015685\u003c/span\u003e\u003cspan address=\"10.1121/10.0015685\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eElliott M, McLusky DS (2002) The need for definitions in understanding estuaries. Estuar Coast Shelf Sci 55(6):815\u0026ndash;827. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1006/ecss.2002.1031\u003c/span\u003e\u003cspan address=\"10.1006/ecss.2002.1031\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEngle VD, Summers JK, Gaston GR (1994) A benthic index of environmental condition of Gulf of Mexico estuaries. Estuaries 17(2):372\u0026ndash;384. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2307/1352670\u003c/span\u003e\u003cspan address=\"10.2307/1352670\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFredriksen S, De Backer A, Bostr\u0026ouml;m C, Christie H (2010) Infauna from \u003cem\u003eZostera marina\u003c/em\u003e L. meadows in Norway. Differences in vegetated and unvegetated areas. Mar Biol Res 6(2):189\u0026ndash;200. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/17451000903042461\u003c/span\u003e\u003cspan address=\"10.1080/17451000903042461\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFrost JW, Schleicher T, Craft C (2009) Effects of nitrogen and phosphorus additions on primary production and invertebrate densities in a Georgia (USA) tidal freshwater marsh. Wetlands 29(1):196\u0026ndash;203. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1672/07-79.1\u003c/span\u003e\u003cspan address=\"10.1672/07-79.1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGalv\u0026aacute;n K, Fleeger JW, Fry B (2008) Stable isotope addition reveals dietary importance of phytoplankton and microphytobenthos to saltmarsh infauna. Mar Ecol Prog Ser 359:37\u0026ndash;49. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3354/meps07321\u003c/span\u003e\u003cspan address=\"10.3354/meps07321\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGlaubrecht M (2009) On Darwinian Mysteries or molluscs as models in evolutionary biology: from local speciation to global radiation. Am Malacological Bull 27(1/2):3\u0026ndash;23. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.4003/006.027.0202\u003c/span\u003e\u003cspan address=\"10.4003/006.027.0202\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGlaubrecht M (2011) Towards solving Darwin's mystery: speciation and radiation in lacustrine and riverine freshwater gastropods. Am Malacological Bull 29(1/2):187\u0026ndash;216. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.4003/006.029.0211\u003c/span\u003e\u003cspan address=\"10.4003/006.029.0211\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGore RH, Gallaher EE, Scotto LE, Wilson KA (1981) Studies on decapod crustacea from the Indian River Region of Florida: XI. Community composition, structure, biomass and species-areal relationships of seagrass and drift algae-associated macrocrustaceans. Estuar Coast Shelf Sci 12(4):485\u0026ndash;508. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S0302-3524(81)80007-2\u003c/span\u003e\u003cspan address=\"10.1016/S0302-3524(81)80007-2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuillena MD (2022) Macroinvertebrates as bio-indicator of water quality in Estuaries. J Biodivers Environ Sci (JBES) 21(1):146\u0026ndash;151\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHall RD, Gerhardt RR (2002) Flies (Diptera). Medical and Veterinary Entomology, 127\u0026ndash;145\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHammer O, Harper DAT, Ryan PD (2001) PAST: Paleontological Statistics software package for education and data analysis. Palaeontologia Electronica 4(1):9\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHansen BW, Andersen CM, Hansen PJ, Nielsen TG, Vismann B, Tiselius P (2019) In situ and experimental evidence for effects of elevated pH on protistan and metazoan grazers. J Plankton Res 41(3):257\u0026ndash;271. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/plankt/fbz020\u003c/span\u003e\u003cspan address=\"10.1093/plankt/fbz020\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHines AH, Comtois KL (1985) Vertical distribution of infauna in sediments of a subestuary of central Chesapeake Bay. Estuaries 8(3):296\u0026ndash;304. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2307/1351490\u003c/span\u003e\u003cspan address=\"10.2307/1351490\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHossain MB, Marshall DJ (2014) Benthic infaunal community structuring in an acidified tropical estuarine system. Aquat Biosyst 10:1\u0026ndash;12. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1186/2046-9063-10-11\u003c/span\u003e\u003cspan address=\"10.1186/2046-9063-10-11\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIeno EN, Solan M, Batty P, Pierce GJ (2006) How biodiversity affects ecosystem functioning: roles of infaunal species richness, identity and density in the marine benthos. Mar Ecol Prog Ser 311:263\u0026ndash;271. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3354/meps311263\u003c/span\u003e\u003cspan address=\"10.3354/meps311263\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJackson ML (1958) Soil Chemical Analysis. Englewood Cliffs. NT Prentice Hall Inc, p 498\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKendall MA, Widdicombe S, Weslawski JM (2003) A multi-scale study of the biodiversity of the benthic infauna of the high-latitude Kongsfjord. Svalbard Polar Biology 26(6):383\u0026ndash;388. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00300-003-0496-x\u003c/span\u003e\u003cspan address=\"10.1007/s00300-003-0496-x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKennish MJ, Paerl HW (eds) 2010. Coastal lagoons: critical habitats of environmental change. CRC press. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1201/EBK1420088304\u003c/span\u003e\u003cspan address=\"10.1201/EBK1420088304\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKey to Australian freshwater and terrestrial invertebrates. (n.d.). Retrieved from \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://keys.lucidcentral.org/\u003c/span\u003e\u003cspan address=\"https://keys.lucidcentral.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKlemm DJ (1985) A guide to the freshwater Annelida (Polychaeta, Naidid and tubificid Oligochaeta, and Hirudinea) of North America. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2307/1467872\u003c/span\u003e\u003cspan address=\"10.2307/1467872\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. Kendall Hunt Publishing Company\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eK\u0026ouml;hler F, Dames C (2009) Phylogeny and systematics of the Pachychilidae of mainland South-East Asia\u0026ndash;novel insights from morphology and mitochondrial DNA (Mollusca, Caenogastropoda, Cerithioidea). Zool J Linn Soc 157(4):679\u0026ndash;699. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/j.1096-3642.2009.00541.x\u003c/span\u003e\u003cspan address=\"10.1111/j.1096-3642.2009.00541.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eK\u0026ouml;hler F, Seddon M, Bogan AE, Van Tu D, Sri-aroon P, Allen D (2012) Chapter 4. The status and distribution of freshwater molluscs of the Indo-Burma region. IUCN 66\u0026ndash;89\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKoehler B, Erlandsson M, Karlsson M, Bergstr\u0026ouml;m L (2022) Species richness and functional attributes of fish assemblages across a large-scale salinity gradient in shallow coastal areas. Biogeosciences 19(8):2295\u0026ndash;2312. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5194/bg-19-2295-2022\u003c/span\u003e\u003cspan address=\"10.5194/bg-19-2295-2022\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eK\u0026uuml;nitzer A, Basford D, Craeymeersch JA, Dewarumez JM, D\u0026ouml;rjes J, Duineveld GCA, Eleftheriou A, Heip C, Herman P, Kingston P, Niermann U (1992) The benthic infauna of the North Sea: species distribution and assemblages. ICES J Mar Sci 49(2):127\u0026ndash;143. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/icesjms/49.2.127\u003c/span\u003e\u003cspan address=\"10.1093/icesjms/49.2.127\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLencioni V, Marziali L, Rossaro B (2012) Chironomids as bioindicators of environmental quality in mountain springs. Freshw Sci 31(2):525\u0026ndash;541. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1899/11-038.1\u003c/span\u003e\u003cspan address=\"10.1899/11-038.1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLevin LA, Boesch DF, Covich A, Dahm C, Ers\u0026eacute;us C, Ewel KC, Kneib RT, Moldenke A, Palmer MA, Snelgrove P, Strayer D (2001) The function of marine critical transition zones and the importance of sediment biodiversity. Ecosystems 4(5):430\u0026ndash;451. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10021-001-0021-4\u003c/span\u003e\u003cspan address=\"10.1007/s10021-001-0021-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eL\u0026oacute;pez SJA, Urcuyo J (2012) First report of \u003cem\u003eFaunus ater\u003c/em\u003e (Pachychilidae: Gastropod) on the American Continent: A mature empty specimen from Masachapa, Nicaragua, Central America. UNED Res J 4(2):187\u0026ndash;189\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMarch C (2015) Biodiversity of benthic invertebrate communities in the Mobile-Tensaw Delta region of Alabama (Doctoral dissertation, California State University, Northridge)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMartins AD, Barros F (2022) Ecological functions of polychaetes along estuarine gradients. Front Mar Sci 9:780318. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3389/fmars.2022.780318\u003c/span\u003e\u003cspan address=\"10.3389/fmars.2022.780318\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMcGranahan G, Balk D, Anderson B (2007) The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones. Environ urbanization 19(1):17\u0026ndash;37. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1177/0956247807076960\u003c/span\u003e\u003cspan address=\"10.1177/0956247807076960\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMedeiros CR, Paiva FF, Ligeiro R, Molozzi J, Melo AS (2021) Saline gradient drives functional nestedness of polychaete communities in tropical estuaries. Estuar Coast Shelf Sci 251:107185. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ecss.2021.107185\u003c/span\u003e\u003cspan address=\"10.1016/j.ecss.2021.107185\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMizuno K, Nomaki H, Chen C, Seike K (2022) Deep-sea infauna with calcified exoskeletons imaged in situ using a new 3D acoustic coring system (A-core-2000). Sci Rep 12(1):12101. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41598-022-16356-3\u003c/span\u003e\u003cspan address=\"10.1038/s41598-022-16356-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM\u0026ouml;ller P (1986) Physical factors and biological interactions regulating infauna in shallow boreal areas. Mar Ecol Prog Ser 30:33\u0026ndash;47. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3354/meps030033\u003c/span\u003e\u003cspan address=\"10.3354/meps030033\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMorris DL, Brooker MP (1980) An assessment of the importance of the Chironomidae (Diptera) in biological surveillance. Chironomidae Pergamon 195\u0026ndash;202. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/B978-0-08-025889-8.50033-7\u003c/span\u003e\u003cspan address=\"10.1016/B978-0-08-025889-8.50033-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNdhlovu A, Adams JB, Lemley DA, Nhleko J, Rishworth GM (2024) Benthic macrofauna communities reflect eutrophic condition in a low-inflow estuary. Reg Stud Mar Sci 70:103351. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.rsma.2023.103351\u003c/span\u003e\u003cspan address=\"10.1016/j.rsma.2023.103351\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNewton A, Icely J, Cristina S, Brito A, Cardoso AC, Colijn F, Zald\u0026iacute;var JM (2014) An overview of ecological status, vulnerability and future perspectives of European large shallow, semi-enclosed coastal systems, lagoons and transitional waters. Estuarine, Coastal and Shelf Science, 140, 95\u0026ndash;122. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ecss.2013.05.023\u003c/span\u003e\u003cspan address=\"10.1016/j.ecss.2013.05.023\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNg TH, Tan SK, Wong WH, Meier R, Chan SY, Tan HH, Yeo DC (2016) Molluscs for sale: assessment of freshwater gastropods and bivalves in the ornamental pet trade. PLoS ONE 11(8). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1371/journal.pone.0161130\u003c/span\u003e\u003cspan address=\"10.1371/journal.pone.0161130\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOku EE, Andem AB, Arong BG, Odjadjare E (2014) Effect of water quality on the distribution of aquatic entomofauna of Great Kwa River, Southern Nigeria. Am J Eng Res (AJER) 3(4):265\u0026ndash;270\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOliveros JC (2007\u0026ndash;2015) Venny. An interactive tool for comparing lists with Venn's diagrams. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://bioinfogp.cnb.csic.es/tools/venny/index.html\u003c/span\u003e\u003cspan address=\"http://bioinfogp.cnb.csic.es/tools/venny/index.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOscoz J, Galicia D, Miranda R (2011) Why, Where and How: An Identification Guide of Macroinvertebrates. In: Oscoz J, Galicia D, Miranda R (eds) Identification Guide of Freshwater Macroinvertebrates of Spain. Springer, Dordrecht. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/978-94-007-1554-7_1\u003c/span\u003e\u003cspan address=\"10.1007/978-94-007-1554-7_1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePaturej E (2008) Estuaries-types, role and impact on human life. Baltic Coastal Zone. Journal of Ecology and Protection of the Coastline, (12)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePinder LCV (1986) Biology of freshwater Chironomidae. Ann Rev Entomol 31(1):1\u0026ndash;23. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1146/annurev.en.31.010186.000245\u003c/span\u003e\u003cspan address=\"10.1146/annurev.en.31.010186.000245\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePinto R, Patr\u0026iacute;cio J, Baeta A, Fath BD, Neto JM, Marques JC (2009) Review and evaluation of estuarine biotic indices to assess benthic condition. Ecol Ind 9(1):1\u0026ndash;25. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ecolind.2008.01.005\u003c/span\u003e\u003cspan address=\"10.1016/j.ecolind.2008.01.005\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePritchard DW (1967) What is an estuary: physical viewpoint. American Association for the Advancement of Science\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eR\u0026ouml;nn C, Bonsdorff E, Nelson WG (1988) Predation as a mechanism of interference within infauna in shallow brackish water soft bottoms; experiments with an infauna predator, \u003cem\u003eNereis diversicolor\u003c/em\u003e O.F. M\u0026uuml;ller. Journal of Experimental Marine Biology and Ecology, 116(2):143\u0026ndash;157. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/0022-0981(88)90052-4\u003c/span\u003e\u003cspan address=\"10.1016/0022-0981(88)90052-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchaffner LC (1990) Small-scale organism distributions and patterns of species diversity: evidence for positive interactions in an estuarine benthic community. Mar Ecol Prog Ser 61:107\u0026ndash;117. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3354/meps061107\u003c/span\u003e\u003cspan address=\"10.3354/meps061107\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSciberras M, Parker R, Powell C, Robertson C, Kr\u0026ouml;ger S, Bolam S, Geert Hiddink J (2016) Impacts of bottom fishing on the sediment infaunal community and biogeochemistry of cohesive and non-cohesive sediments. Limnol Oceanogr 61(6):2076\u0026ndash;2089. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/lno.10354\u003c/span\u003e\u003cspan address=\"10.1002/lno.10354\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSharif ASM, Islam S, Islam M (2017) Occurrence and distribution of macrobenthos in relation to physico-chemical parameters in the lower Meghna River estuary, Bangladesh. Int J Mar Sci 7(12):102\u0026ndash;113\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSolan M, Batty P, Bulling MT, Godbold JA (2008) How biodiversity affects ecosystem processes: implications for ecological revolutions and benthic ecosystem function. Aquat Biology 2(3):289\u0026ndash;301. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3354/ab00058\u003c/span\u003e\u003cspan address=\"10.3354/ab00058\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSowa A, Krodkiewska M, Halabowski D (2020) How does mining salinisation gradient affect the structure and functioning of macroinvertebrate communities? Water Air Soil Pollut 231(9):453. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11270-020-04823-4\u003c/span\u003e\u003cspan address=\"10.1007/s11270-020-04823-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTelesh IV, Khlebovich VV (2010) Principal processes within the estuarine salinity gradient: a review. Mar Pollut Bull 61(4\u0026ndash;6):149\u0026ndash;155. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.marpolbul.2010.02.008\u003c/span\u003e\u003cspan address=\"10.1016/j.marpolbul.2010.02.008\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVeeravechsukij N, Krailas D, Namchote S, Wiggering B, Neiber MT, Glaubrecht M (2018) Molecular phylogeography and reproductive biology of the freshwater snail Tarebia granifera in Thailand and Timor (Cerithioidea, Thiaridae): morphological disparity versus genetic diversity. Zoosystematics Evol 94(2):461\u0026ndash;493. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3897/zse.94.28981\u003c/span\u003e\u003cspan address=\"10.3897/zse.94.28981\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVirnstein RW (1977) The importance of predation by crabs and fishes on benthic infauna. Chesapeake Bay Ecol 58(6):1199\u0026ndash;1217. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2307/1935076\u003c/span\u003e\u003cspan address=\"10.2307/1935076\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeinmann AE, Goldstein ST, Triantaphyllou MV, Langer MR (2021) Community responses of intertidal foraminifera to pH variations: a culture experiment with propagules. Aquat Ecol 55(1):309\u0026ndash;325. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10452-021-09833-w\u003c/span\u003e\u003cspan address=\"10.1007/s10452-021-09833-w\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWhite KN (2011) A taxonomic review of the Leucothoidae (Crustacea: Amphipoda). Zootaxa 3078(1):1\u0026ndash;113. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.11646/zootaxa.3078.1.1\u003c/span\u003e\u003cspan address=\"10.11646/zootaxa.3078.1.1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWhitlatch RB, Zajac RN (1985) Biotic interactions among estuarine infaunal opportunistic species. Mar Ecol Prog Ser 21(3):299\u0026ndash;311. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3354/meps021299\u003c/span\u003e\u003cspan address=\"10.3354/meps021299\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZajac RN, Whitlatch RB (1982) Responses of estuarine infauna to disturbance. I. Spatial and temporal variation of initial recolonization. Mar Ecol Prog Ser 10(1):1\u0026ndash;14. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3354/meps010001\u003c/span\u003e\u003cspan address=\"10.3354/meps010001\" 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":true,"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":"Biodiversity, Camiguin Island, Estuaries, Infauna","lastPublishedDoi":"10.21203/rs.3.rs-5367139/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5367139/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe infauna distribution, species composition, diversity and its correlation with environmental variables were investigated in the two converging river estuaries (Tapon River and Sa\u0026rsquo;ai River) in Mambajao, Camiguin Island, Philippines. Sample collection using a modified core sampling method, sorting, identification and counting of infauna samples and \u003cem\u003ein-situ\u003c/em\u003e measurements of physico-chemical parameters were done. Results showed that Pachychilidae (44.94%), Lumbriculidae (28.09%) and Thiaridae (14.61%) had the highest relative abundance in both rivers which could be due to its wide tolerance of pollution that also resulted to low species diversity (H\u0026rsquo;) ranging only from 0.267\u0026thinsp;\u0026plusmn;\u0026thinsp;0.267 to 0.811\u0026thinsp;\u0026plusmn;\u0026thinsp;0.090. Furthermore, Sa\u0026rsquo;ai River showed significantly higher temperature compared to Tapon River. Significant differences in salinity, water pH and soil pH were also observed between the two river estuaries. Furthermore, distinct and clear segregation patterns (30% and 50% similarity) between the two river estuaries. Samples from T4R1, T4R2, T3R3 and T1R2 were segregated from T1R1, T2R1 and T3R1 and the rest of the sampling stations. The presence and assemblages of the infauna (e.g. Glyceridae, Pachychilidae, Chironomidae, Neritidae) were strongly influenced by temperature, salinity, water pH and soil pH.\u003c/p\u003e","manuscriptTitle":"Infaunal biodiversity of converging river estuaries in Mambajao, Camiguin Island in relation to salinity gradients","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-11 02:24:33","doi":"10.21203/rs.3.rs-5367139/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":"3f09a6c4-051b-4413-a73c-0a15aead183c","owner":[],"postedDate":"November 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-11-11T02:24:35+00:00","versionOfRecord":[],"versionCreatedAt":"2024-11-11 02:24:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5367139","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5367139","identity":"rs-5367139","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}