Freshwater Ecosystems Research Articles

Mining tailings alter insects: revealing fluctuating asymmetry in the caddisfly Smicridea coronata.

The Samarco/Vale/BHP mine tailing dam breach that took place in Minas Gerais, southeastern Brazil, in 2015, deposited high concentrations of metals and metalloids in the Rio Doce basin, severely impacting freshwater and riverine forest ecosystems. To assess developmental instability of caddisflies in response to the environmental impacts of the dam breach, we investigated the fluctuating asymmetry (FA) in the species Smicridea (Rhyacophylax) coronata (Trichoptera: Hydropsychidae). FA was assessed at individual and populational scales using geometric morphometric methods in the cephalic capsule and mandibles of larvae and also on the forewings of adults, both collected under the impacted condition, and under the least disturbed condition. The levels of FA increased in response to stressors on the forewings at the populational scale, and on the mandibles, at individual scale. These morphological variations in the larval and adult stages may lead to detrimental effects and result in high mortality rates as well as lower adult fitness. Trichoptera forewings are revealed as suitable traits for assessing FA, holding potential for applications in biomonitoring programs. Directional asymmetry levels were higher than FA levels for all traits, and this correlation could be explained by a transition from fluctuating to directional asymmetry in the presence of heightened disturbance. Our results validate the relationship between the impacts from the dam breach and increased developmental instability in this species with likely cascade effects on the insect community.

Human-Made 1,000 Hectare Archipelago “Marker Wadden” Has Positive Impact on Regional and Flyway Populations of Waterbirds of Dynamic Freshwater Ecosystems

Human-Made 1,000 Hectare Archipelago “Marker Wadden” Has Positive Impact on Regional and Flyway Populations of Waterbirds of Dynamic Freshwater Ecosystems

Multiple‐stressor effects on leaf litter decomposition in freshwater ecosystems: A meta‐analysis

Abstract Recent years have witnessed a surge in research on the effects of multiple stressors in freshwater ecosystems. While studies have increased, the synthesis of their findings into a broader understanding of ecosystem‐level effects remains an ongoing endeavour. Leaf litter decomposition, a frequently investigated and pivotal ecosystem function in freshwaters, is sensitive to changes in abiotic conditions and biotic communities, and therefore susceptible to multiple‐stressor effects. Here, we synthesize findings from 27 manipulative experimental studies encompassing 61 responses of litter decomposition to paired stressors such as warming, nutrient enrichment and emerging pollutants in freshwater ecosystems. We calculated the individual and overall interaction effect sizes resulting from two stressors occurring simultaneously. Furthermore, we analysed the effect of moderator variables in the size and direction of interaction effect sizes using a meta‐analytical approach. Although the vote‐counting method showed additive interactions to dominate individual observations (91.8%), weighted random‐effects meta‐analysis revealed an overall antagonistic interaction between stressors (i.e. the cumulative effect of paired stressors on litter decomposition was less than the sum of their single effects). Our results emphasized the influence of experimental characteristics such as macroinvertebrate involvement, habitat type (lentic vs. lotic) and litter quality (assumed from plant mycorrhizal association) in shaping the responses of litter decomposition to multiple stressors. Our meta‐analysis highlights the need to incorporate local ecological complexities in manipulative experiments to improve predictions of multiple‐stressor effects on biodiversity and ecosystem functions. The present study underscores the importance of considering biotic interactions and adopting the metacommunity framework in conservation and restoration actions to support the management of freshwater ecosystems in an era of rapid global change. Read the free Plain Language Summary for this article on the Journal blog.

Development and validation of a TaqMan-based qPCR assay for reliable detection of invasive sailfin catfishes (Pterygoplichthys spp.) through measurements of environmental DNA

Sailfin catfishes (Pterygoplichthys spp.) are a group of fishes introduced to several freshwater habitats across the globe. Sailfin catfishes are a hard-armoured fish with no economic importance as a food species. These catfishes have been reported to be affecting the growth of several economically valuable species that are native to different freshwater ecosystems. In this manuscript, we developed a TaqMan-based assay targeting the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene, to specifically detect the presence of catfishes by environmental DNA (eDNA) measurements. The developed assay was screened against 16 species of fish and mussel that co-occur in the habitats along with sailfin catfishes, and the qPCR reaction did not have any non-target amplifications. The assay was further validated under laboratory conditions by measuring eDNA from tanks having different biomass of catfishes (1 and 0.5 g L−1), and the copy number of the amplified product was directly proportional to the biomass maintained in the tanks. Overall, the study provides a robust molecular tool based on eDNA measurements to facilitate detection of invasive sailfin catfishes and, in turn, contributes towards the management of the invaded habitats.

Simultaneous methane mitigation and nitrogen removal by denitrifying anaerobic methane oxidation in lake sediments

Methane (CH4) is a potent greenhouse gas, with lake ecosystems significantly contributing to its global emissions. Denitrifying anaerobic methane oxidation (DAMO) process, mediated by NC10 bacteria and ANME-2d archaea, links global carbon and nitrogen cycles. However, their potential roles in mitigating methane emissions and removing nitrogen from lake ecosystems remain unclear. This study explored the spatial variations in activities of nitrite- and nitrate-DAMO and their functional microbes in Changdanghu Lake sediments (Jiangsu Province, China). The results showed that although the average abundance of ANME-2d archaea (5.0 × 106 copies g−1) was significantly higher than that of NC10 bacteria (2.1 × 106 copies g−1), the average potential rates of nitrite-DAMO (4.59 nmol 13CO2 g−1 d−1) and nitrate-DAMO (5.01 nmol 13CO2 g−1 d−1) showed no significant difference across all sampling sites. It is estimated that nitrite- and nitrate-DAMO consumed approximately 6.46 and 7.05 mg CH4 m−2 d−1, respectively, which accordingly achieved 15.07–24.95 mg m−2 d−1 nitrogen removal from the studied lake sediments. Statistical analyses found that nitrite- and nitrate-DAMO activities were both significantly related to sediment nitrate contents and ANME-2d archaeal abundance. In addition, NC10 bacterial and ANME-2d archaeal community compositions showed significant correlations with sediment organic carbon content and water depth. Overall, this study underscores the dual roles of nitrite- and nitrate-DAMO processes in CH4 mitigation and nitrogen elimination and their key environmental impact factors (sediment organic carbon and inorganic nitrogen contents, and water depth) in shallow lake, enhancing the understanding of carbon and nitrogen cycles in freshwater aquatic ecosystems.

Substantial unrealised global biodiversity of continental microcrustaceans

Abstract Freshwater ecosystems provide essential services for human well-being, with their conservation success reliant on the precise quantification of biodiversity. Diplostraca (= Cladocera) and Copepoda are diverse groups of microcrustaceans in aquatic ecosystems, important for a multitude of these services. We examined biodiversity trends of these groups, utilizing a comprehensive dataset, approximately 2341 studies, spanning from the early 19th Century to the present day, aiming at predicting the total number of microcrustacean species that will have been described by 2100. Descriptions increased until the 1900s, surged, and then declined after 1975. The predictive models indicate that by the year 2100, an additional 16–68% of cladoceran species and 37–126% of copepod species are likely to be identified, representing a significant portion of currently unrealised biodiversity. Eighteen prolific authors contributed to a quarter of these descriptions, with the rest spread among numerous authorities. Based on our extrapolation, the total number of microcrustacean species could potentially exceed 6114 by 2050 and 9046 by 2100, notwithstanding extinctions. These findings, which point to a significant amount of unrealised biodiversity, underscore the need to refine biodiversity estimates beyond conventional expert opinion. Such accuracy is crucial for addressing the underappreciated scale of the current biodiversity crisis.

How low is too low? Partnering with stakeholders and managers to define ecologically based low‐flow thresholds in a perennial temperate river

AbstractManaging aquatic ecosystems for people and nature can be improved by collaboration among scientists, managers, decision‐makers, and other stakeholders. Many collaborative and interdisciplinary approaches have been developed to address the management of freshwater ecosystems; however, there are still barriers to overcome. We worked as part of a regional stakeholder group comprising municipal water utility operators, conservation organizations, academic partners, and other stakeholders to understand the effects of low‐flow and drought on ecological functions of the upper Flint River, Georgia (USA), a free‐flowing river important for municipal water supply, recreation, and native biota. We used published literature and locally targeted studies to identify quantitative flow targets that could be used to inform water management and drought planning. Drawing from principles of Translational Ecology, we relied on an iterative process to develop information needs for the group and maintained communication and engagement throughout data collection, analysis, and synthesis. We identified three quantitative flow benchmarks to evaluate the ecological impacts of drought in the river. The results were valuable to both the water utilities represented in the working group and State regional water planning, which is used to guide water management strategies and permitting for the basin. We identified principles that were important for the successful engagement in the working group and helped to overcome the challenge of working across sectors and without direct authority guiding the implementation of our work. Interdisciplinary work and creative solutions are crucial to plan for and adapt to greater pressure on our water resources.

Enzyme-treated microalgal co-product diets for rainbow trout aquaculture: Supporting fish growth, phosphorus digestibility, and reducing phosphorus waste emission

Aquaculture is one of the fastest-growing food sectors, producing almost 50% of fish for human consumption worldwide. However, relying on fish meal and oil for aquaculture diets is not sustainable economically or environmentally. Aquaculture feeds also contain terrestrial plant ingredients with indigestible forms of phosphorus (P), of which 70%–80% can be released into aquatic environments. This P influx contributes to eutrophication of freshwater ecosystems that can lead to anoxic conditions. This study explores a more sustainable diet for salmonids, an important and valuable seafood. Our aim was to test ingredients with highly digestible forms of P in nutritionally balanced portions to support fish growth and reduce P loading. We determined the digestibility of three feeds containing raw, extruded, and enzymatically processed microalgal co-product of Nannochloropsis oculata compared to a conventional diet. We also quantified how much P was retained and excreted. We detected highest growth in trout fed enzymatically processed co-product feed, though it was not statistically different (p = 0.846) from growth of fish fed the reference or other co-product diets. The enzyme-treated, microalgal co-product ingredient and diet had comparable values for P digestibility and solid P excretion to the reference diet, but the lowest average solid P excretion of all test diets. Trout fed the enzyme-treated diet had the highest P retention, while the reference diet had the lowest (p = 0.0429). Trout fed the enzyme-treated diet had the lowest (p = 0.0174) and negative dissolved P excretion, while those fed the reference diet had the highest. Results showed that enzyme-treated N. oculata co-product maintains digestibility, increases P retention, and reduces dissolved P excretion compared to the reference diet in rainbow trout. These findings encourage follow-up research to design and test growth performance of diets containing enzyme-treated microalgal co-product as sustainable trout aquafeed.

Response of Functional Traits of Aquatic Plants to Water Depth Changes under Short-Term Eutrophic Clear-Water Conditions: A Mesocosm Study

Aquatic plants play a key role in the structuring and functioning of shallow lake ecosystems. However, eutrophication often triggers shifts in plant communities and species diversity, especially in the early stages when the water is still clear. Additionally, water depth is an important factor regulating aquatic plant communities. We conducted a 50-day mesocosm study to investigate how water depth (50 cm and 100 cm) affected the functional traits (vertical expansion versus horizontal colonisation) of 20 aquatic plants under eutrophic clear-water conditions. Among the selected species, the submerged plants Hydrocotyle vulgaris and Limnophila indica exhibited higher plant height or biomass in deeper water, while the emergent plants Myriophyllum aquaticum showed the opposite trend. Additionally, Ludwigia peploides subsp. stipulacea exhibited better vertical growth than the remaining species, and the submerged species Vallisneria denseserrulata had better horizontal colonisation. There was a positive correlation between plant height and rhizome length, indicating the absence of a trade-off between vertical growth and horizontal expansion. Our findings suggest an overall resilience of aquatic plants to varying water depths within our study range and highlight the importance of analysing functional traits when selecting appropriate species in freshwater ecosystem restoration, particularly in the face of climate change-induced water depth fluctuations.

Unveiling nature’s beat: analyzing the acoustics of an aquatic bug in relation to urban sounds

AbstractAnthropophony is a prominent component of soundscapes worldwide and is known to impact biota. While responses to anthropophony in terrestrial and marine animals have been relatively well-studied, there is still a lack of knowledge regarding freshwater animals. In fact, freshwater taxa are among the possibly most threatened groups, and unveiling the reasons for their threat is crucial. We investigated the effect of low-frequency sounds -usually associated with anthropophony- on the stridulation of Krizousacorixa femorata, a common water bug in Mexico City. Using aerial recordings, we estimated the Normalized Difference Soundscape Index (NDSI), which is the most commonly used index to measure anthropophony, to characterize soundscapes in six city sites throughout the year. Additionally, from underwater recordings in the same sites, we obtained the peak frequency (Pf) of the stridulations, as it is the frequency with the highest energy and, therefore, the one that can travel the farthest and can be identified even in the presence of overlapping sounds. Finally, we evaluated the relationships between soundscapes and Pf through a mixed linear model. There was a negative correlation between NDSI and Pf, indicating higher-pitched stridulations at sites with dominant anthropophony. While we cannot rule out other factors contributing to stridulation variation, we remain uncertain about how low-frequency sounds impact freshwater ecosystems and the intricate relationship between soundscapes and aquatic life in urban settings.

Spatiotemporal variation in methylmercury and related water quality variables in a temperate river under highly dynamic hydrologic conditions

The understanding of the essential environmental factors affecting the spatiotemporal variation in methylmercury (MeHg) in river water is limited to date, despite its importance for predicting the effect of ongoing climate change on MeHg accumulation in freshwater ecosystems. This study aimed to explore the variation in MeHg concentration and related environmental factors in the downstream zone of the Yeongsan River under highly dynamic hydrologic conditions by using water quality and hydrologic data collected from 1997 to 2022, and Hg and MeHg data collected from 2017 to 2022. The mean concentration of unfiltered MeHg was 35.7 ± 13.7 pg L−1 (n = 24) in summer and 26.7 ± 7.43 pg L−1 (n = 24) in fall. Dissolved oxygen (DO), conductivity, nitrate, and dissolved organic carbon (DOC) were determined to be the most influential variables in terms of MeHg variation based on the partial least squares regression model, and their effects on the MeHg concentration were negative, except for DOC. Heatmaps representing the similarity distances between temporal trends of hydrologic and water quality variables were constructed to determine fundamental factors related to the time-based variations in DO, conductivity, nitrate, and DOC using a dynamic time warping algorithm. The heatmap cluster analysis showed that the temporal trends of these variables were closely related to rainfall variation rather than irradiance or water temperature. Overall, biogeochemical factors directly related to in situ methylation rate of Hg(II)—rather than transport of Hg(II) and MeHg from external sources—mainly control the spatiotemporal variation of MeHg in the downstream zone of the Yeongsan River.

Diversity of Dematiaceous Freshwater Hyphomycetes from Dang Forest of Gujrat, India

Hyphomycetes paly significant role in freshwater ecosystem. Dang district is located in the south eastern part Gujarat state of western India. Dang has an area of 1,764 km². Present paper deals with 6 species of submerged freshwater hyphomycetes belonging to 5 genera viz. Aquapteridospora bambusinum Bao, Dictyosporella aquatica Abdel Aziz, Pseudoberkleasmium chiangmaiense Lu and Hyde, Sporidesmium nujiangense Bao, Su, Hyde and Luo, Vamsapriya aquatica Bao, Su, Hyde and Luo and Vamsapriya indica Gawas and Bhat. The survey was conducted in winter season of 2019.

Alien emergent aquatic plants develop better ciprofloxacin tolerance and metabolic capacity than one native submerged species

Antibiotic pollution and biological invasion pose significant risks to freshwater biodiversity and ecosystem health. However, few studies have compared the ecological adaptability and ciprofloxacin (CIPR) degradation potential between alien and native macrophytes. We examined growth, physiological response, and CIPR accumulation, translocation and metabolic abilities of two alien plants (Eichhornia crassipes and Myriophyllum aquaticum) and one native submerged species (Vallisneria natans) exposed to CIPR at 0, 1 and 10 mg/L. We found that E. crassipes and M. aquaticum's growth were unaffected by CIPR while V. natans was significantly hindered under the 10 mg/L treatment. CIPR significantly decreased the maximal quantum yield of PSII, actual quantum yield of PSII and relative electron transfer rate in E. crassipes and V. natans but didn't impact these photosynthetic characteristics in M. aquaticum. All the plants can accumulate, translocate and metabolize CIPR. M. aquaticum and E. crassipes in the 10 mg/L treatment group showed greater CIPR accumulation potential than V. natans indicated by higher CIPR contents in their roots. The oxidative cleavage of the piperazine ring acts as a key pathway for these aquatic plants to metabolize CIPR and the metabolites mainly distributed in plant roots. M. aquaticum and E. crassipes showed a higher production of CIPR metabolites compared to V. natans, with M. aquaticum exhibiting the strongest CIPR metabolic ability, as indicated by the most extensive structural breakdown of CIPR and the largest number of potential metabolic pathways. Taken together, alien species outperformed the native species in ecological adaptability, CIPR accumulation and metabolic capacity. These findings may shed light on the successful invasion mechanisms of alien aquatic species under antibiotic pressure and highlight the potential ecological impacts of alien species, particularly M. aquaticum. Additionally, the interaction of antibiotic contamination and invasion might further challenge the native submerged macrophytes and pose greater risks to freshwater ecosystems.

Informing the Exposure Landscape: The Fate of Microplastics in a Large Pelagic In-Lake Mesocosm Experiment.

Understanding microplastic exposure and effects is critical to understanding risk. Here, we used large, in-lake closed-bottom mesocosms to investigate exposure and effects on pelagic freshwater ecosystems. This article provides details about the experimental design and results on the transport of microplastics and exposure to pelagic organisms. Our experiment included three polymers of microplastics (PE, PS, and PET) ranging in density and size. Nominal concentrations ranged from 0 to 29,240 microplastics per liter on a log scale. Mesocosms enclosed natural microbial, phytoplankton, and zooplankton communities and yellow perch (Perca flavescens). We quantified and characterized microplastics in the water column and in components of the food web (biofilm on the walls, zooplankton, and fish). The microplastics in the water stratified vertically according to size and density. After 10 weeks, about 1% of the microplastics added were in the water column, 0.4% attached to biofilm on the walls, 0.01% within zooplankton, and 0.0001% in fish. Visual observations suggest the remaining >98% were in a surface slick and on the bottom. Our study suggests organisms that feed at the surface and in the benthos are likely most at risk, and demonstrates the value of measuring exposure and transport to inform experimental designs and achieve target concentrations in different matrices within toxicity tests.

Ecology and life cycle of the filter-feeding Amphipsyche meridiana Ulmer 1902 (Trichoptera: Hydropsychidae) in an irrigation canal, central Thailand

The life cycle and larval diet of Amphipsyche meridiana Ulmer 1902 were investigated in a natural freshwater habitat at Kasetsart University's Kamphaeng Saen Campus in Nakhon Pathom Province, Thailand. Larvae were collected monthly from December 2021 to November 2022. Most species of Hydropsychidae have five larval instars. The first to fifth larval instars were found in the stream throughout the year. Head capsule widths of the first to fifth instar larvae were 0.1–0.3, 0.4–0.6, 0.7–0.9, 1.0–1.2, and 1.3–1.6 millimeters, respectively. The highest number of larvae was found in July 2022. Adult emergence occurred throughout the year, with the highest number occurring in April 2022. A. meridiana's life cycle was characterized as multivoltine, with year-round recruitment. The Canonical Correspondence Analysis (CCA) was used to determine how conditions in the environment influenced larval abundance. The factors influencing the amounts of larvae are water depth, water temperature, pH, dissolved oxygen, ammonia-nitrogen, and sulfate. The larvae of this species are omnivorous filterers. The main food types found in the gut were blue-green algae and green algae, comprising 34.11% and 33.07% of its ingestion. In addition, the digestive tract was abundant with diatoms, rotifers, and insect fragments, accounting for 32.82% of the diet.

The potential of acoustic monitoring of aquatic insects for freshwater assessment.

Aquatic insects are a major indicator used to assess ecological condition in freshwater environments. However, current methods to collect and identify aquatic insects require advanced taxonomic expertise and rely on invasive techniques that lack spatio-temporal replication. Passive acoustic monitoring (PAM) is emerging as a non-invasive complementary sampling method allowing broad spatio-temporal and taxonomic coverage. The application of PAM in freshwater ecosystems has already proved useful, revealing unexpected acoustic diversity produced by fishes, amphibians, submerged aquatic plants, and aquatic insects. However, the identity of species producing sounds remains largely unknown. Among them, aquatic insects appear to be the major contributor to freshwater soundscapes. Here, we estimate the potential number of soniferous aquatic insects worldwide using data from the Global Biodiversity Information Facility. We found that four aquatic insect orders produce sounds totalling over 7000 species. This number is probably underestimated owing to poor knowledge of aquatic insects bioacoustics. We then assess the value of sound producing aquatic insects to evaluate ecological condition and find that they might be useful despite having similar responses in pristine and degraded environments in some cases. Both expert and automated identifications will be necessary to build international reference libraries and to conduct acoustic bioassessment in freshwaters. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Geophysics as a hypothesis‐testing tool for critical zone hydrogeology

AbstractGeophysical methods have long been used in earth and environmental science for the characterization of subsurface properties. While imaging the subsurface opens the “black box” of subsurface heterogeneity, we argue here that these tools can be used in a more powerful way than characterization, which is to develop and test hypotheses. Critical zone science has opened new questions and hypotheses in the hydrologic sciences holistically around controls on water fluxes between surface, biological, and underground compartments. While groundwater flows can be monitored in boreholes, water fluxes from the atmosphere to the aquifer through the soil and the root system are more complex to study than boreholes can inform upon. Here, we focus on the successful application of various geophysical tools to explore hypotheses in critical zone hydrogeology and highlight areas where future contributions could be made. Specifically, we look at questions around subsurface structural controls on flow, the dimensionality and partitioning of those flows in the subsurface, plant water uptake, and how geophysics may be used to constrain reactive transport. We also outline areas of future research that may push the boundaries of how geophysical methods are used to quantify critical zone complexity.This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Science of Water > Hydrological Processes Water and Life > Methods

Ecological implications and drivers of emerging contaminants in Dongting Lake of Yangtze River Basin, China: A multi-substance risk analysis

Emerging contaminants (ECs) are increasingly recognized as a global threat to biodiversity and ecosystem health. However, the cumulative risks posed by ECs to aquatic organisms and ecosystems, as well as the influence of anthropogenic activities and natural factors on these risks, remain poorly understood. This study assessed the mixed risks of ECs in Dongting Lake, a Ramsar Convention-classified Typically Changing Wetland, to elucidate the major EC classes, key risk drivers, and magnitude of anthropogenic and natural impacts. Results revealed that ECs pose non-negligible acute (30% probability) and chronic (70% probability) mixed risks to aquatic organisms in the freshwater lake ecosystem, with imidacloprid identified as the primary pollutant stressor. Redundancy analysis (RDA) and structural equation modeling (SEM) indicated that cropland and precipitation were major drivers of EC contamination levels and ecological risk. Cropland was positively associated with EC concentrations, while precipitation exhibited a dilution effect. These findings provide critical insights into the ecological risk status and key risk drivers in a typical freshwater lake ecosystem, offering data-driven support for the control and management of ECs in China.

Land-use effects on leaf-litter breakdown in streams in a tropical lowland catchment

The expansion of oil palm and cattle grazing in the tropics continues to alter numerous ecosystem functions. The generated land-use change is potentially impacting stream leaf-litter breakdown, a fundamental process for freshwater ecosystems. To assess the effect of land-use change, we studied breakdown rates of forest (Pachira aquatica, Pouroma aspera, Sloanea ampla, and Hippocratea volubilis) and oil palm (Elaeis guineensis) leaves after a 26-day immersion in streams surrounded by rainforests, grazing lands, or oil palm plantations with and without riparian buffers. In addition, we assessed breakdown drivers by deploying litter bags (248) of two mesh sizes (15 mm and 0.5 mm) allowing or restricting macroinvertebrates’ access (134 coarse-mesh bags and 114 fine-mesh bags). Forest leaf breakdown by microbes (fine-mesh) was lower by 55% in the plantations compared to forests; while microbial oil palm-leaf breakdown was lower by 32% in the unbuffered plantations compared to forests (p < 0.05). Total litter breakdown was lower (p > 0.05) in the plantations but not when these preserved riparian buffers. Litter breakdown was driven primarily by microbes in all land uses except in the buffered plantations, possibly due to increased shredder biomass. These results suggest that oil palm agriculture may decrease microbial stream leaf-litter breakdown, especially in streams with no riparian buffers.

Bioaccumulation and health risk assessment of trace elements in Tilapia (Oreochromis mossambicus) from selected inland water bodies.

The presence of toxic trace elements (TEs) has resulted in a worldwide deterioration in freshwater ecosystem quality. This study aimed to analyze the distribution of TEs, including chromium (Cr), nickel (Ni), arsenic (As), mercury (Hg), cadmium (Cd), and lead (Pb), in water, sediment, and organs of Tilapia (Oreochromis mossambicus) collected from selected inland water bodies in Tamil Nadu, India. The water samples exhibited a range of concentrations for TEs: Cr varied from 0.014 to 5.193µg/L, Ni ranged from 0.283 to 11.133µg/L, As ranged from 0.503 to 1.519µg/L, Cd from 0.001 to 0.616µg/L, and Pb ranged from non-detectable (ND) to 6.103µg/L. The concentrations of TEs in sediment were found to vary within the following ranges: 5.259 to 32.621mg/kg for Cr, 1.932 to 30.487mg/kg for Ni, 0.129 to 0.563mg/kg for As, 0.003 to 0.011mg/kg for Cd, ND to 0.003mg/kg for Hg, and 0.404 to 1.575mg/kg for Pb. The study found that the accumulation pattern of TE in fishes across all selected areas was liver > bone > gill > muscle. The organs had TE concentrations of Cr (ND-0.769mg/kg), Ni (ND-1.053mg/kg), As (0.002-0.080mg/kg), Pb (ND-0.411mg/kg), and Hg (ND-0.067mg/kg), which was below the maximum residual limit prescribed by EC and FSSAI. The bioconcentration factor (BCF) of TEs exhibited a greater magnitude in comparison with the biota-sediment accumulation factor due to the higher concentration of TEs in fish and lower level in water. The assessment of both carcinogenic and non-carcinogenic risks suggests that the consumption of Tilapia from the study region does not pose any significant risks.