Freshwater Systems Research Articles

Salt pollution reduces turbidity, dissolved organic matter, and cyanobacteria in experimental vernal pool communities

Anthropogenic activities such as the over-application of road deicers are causing an increase in the concentration of salts in historically fresh waters. Experimental and field investigations demonstrate that freshwater salinization disrupts ecosystem functions and services, causing the death of freshwater organisms and changes to nutrient conditions. Wetland habitats are one system negatively affected by salt pollution, including ephemeral wetlands (vernal pools) that fill with salt-polluted water after snowmelt. In urbanized areas, the degradation of these ecosystems could result in irreversible ecological damage including reduced water quality and a reduction in biodiversity. To investigate the effects of freshwater salinization on vernal pool communities, we exposed soils from vernal pools to water containing no salt (control), or four concentrations of three salts standardized by chloride concentration (50 mg Cl− L−1, 100 mg Cl− L−1, 200 mg Cl− L−1, and 400 mg Cl− L−1; magnesium chloride, calcium chloride, and sodium chloride). The results of this experiment suggest that emerging zooplankton communities in vernal pools are sensitive to low concentrations of salt pollution, and that alternative salts such as magnesium chloride and calcium chloride are more toxic than sodium chloride. We did not find positive or negative changes in the abundance of eukaryotic phytoplankton but did find negative effects of salt on cyanobacteria abundance, possibly due to corresponding reductions in turbidity which might be needed as a fixation site for cyanobacteria to form heterocysts. Finally, we found that salt pollution likely caused flocculation of Dissolved Organic Matter (DOM), resulting in reduced concentrations of DOM which could alter the buffering capacity of freshwater systems, light attenuation, and the populations of planktonic heterotrophs.

Assessment and accumulation of microplastics in the Indian riverine systems: Risk assessment and implications of translocation across the water-to-fish continuum.

Microplastic (MP) pollution has engulfed global aquatic systems, and the concerns about microplastic translocation and bioaccumulation in fish and other aquatic organisms are now an unpleasant truth. In the past few years, MP pollution in freshwater systems, particularly rivers and subsequently in freshwater organisms, especially in fish, has caught the attention of researchers. Rivers provide livelihood to approximately 40 % of the global population through food and potable water. Hence, assessment of emerging contaminants like microplastics in rivers and the associated fauna is crucial. This study assessed microplastics (MPs) in fish, sediment and freshwater samples across the third largest riverine system of peninsular India, the Mahanadi River. The number concentrations of MPs measured in water, sediment and fish ranged from 337.5±54.4-1333.3±557.2 MPs/m3, 14.7±3.7-69.3±10.1 MPs/kg. Dry weight and 0.4-3.2 MPs/Fish, respectively. Surprisingly, MPs were found in every second fish sample, with a higher MP number in the gut than in the gills. Black and blue coloured filaments with <0.5 mm size were the dominant MPs with polypropylene and polyethylene polymers in abundance. The Polymer Hazard Index (PHI) and the Potential Ecological Risk Index (PERI) studies revealed that the majority of the sampling sites fell in Risk category V (dangerous category). An irregular trend in the MP concentration was observed downstream of the river, though relatively elevated MP concentrations in water and fish samples were observed downstream of the river. t-Distributed Stochastic Neighbour Embedding (t-SNE) unveiled distinct patterns in MP distribution with a higher similarity exhibited in the MPs found in fish gill and gut samples, unlike water and sediment, which shared certain characteristics. The findings in the current study contribute to filling the knowledge gap of MP assessment and accumulation in global freshwater systems and highlight the microplastic contamination and accumulation in fish with its potential implications on human health.

Severe Microplastic Pollution Risks in Urban Freshwater System Post-Landfill Fire: A Case Study from Brahmapuram, India

To investigate the escalating issue of microplastic (MP), pollution in urban water bodies, this study focuses on the aftermath of the Brahmapuram landfill fire in Kochi, India, analyzing its impact on MP concentrations in nearby freshwater system. The study conducted sampling sessions at the landfill site immediately before and after the fire. Post-fire, findings demonstrated a substantial increase in MP concentrations in surface waters, with levels rising from an average 25793.33 to 44863.33 particles /m³, featuring a notable presence of larger, predominantly black MPs. Sediment samples showed no significant change in MP count, but there was a significant increase in mass concentration. SEM/EDS analysis revealed changes in surface morphology and elemental composition, suggesting thermal degradation. Risk assessment using the Microplastic Pollution Index (MPI) and Risk Quotient (RQ) methods indicated heightened MP pollution risk in surface water post-fire. Hierarchical cluster analysis revealed the landfill's proximity as a significant factor influencing MP characteristics in the aquatic system. The study highlights the escalated challenge of MP pollution in urban water bodies following environmental disasters like landfill fires, underscoring the urgent need for policy and environmental management strategies.

Natural shorelines support greater diversity and abundances of fishes than armoured shores along Chicago's waterways

Abstract Shoreline armouring is one of the most ubiquitous alterations to aquatic systems globally. Armouring and hardening to prevent erosion and maintain land uses reduce or eliminate habitat complexity that softer and more natural, vegetated shorelines offer. The effects that shoreline armouring has had on biodiversity of coastal and estuarine communities are well studied, while studies in freshwater systems remain sparse. Data collected during a large‐scale long‐term fish survey with high spatial resolution from the Invasive Carp Regional Coordinating Committee's Monitoring and Response Work Group were re‐analysed to assess the effects that bulkhead versus natural shorelines have on fish diversity and abundance. Lengths of bulkhead, natural and riprap shoreline were calculated within 300 m of each sampling location, which occur every 100 m throughout the Chicago Area Waterway System. Water depths of each sampling location were also classified into deep (&gt;6 m), mid‐range (4–6 m) or shallow (&lt;4 m) to account for potential variations in gear efficiencies. Fish species richness and abundance increased with increasing proportions of natural shoreline, which can be contrasted with stronger (i.e., steeper slope) decreases as proportions of bulkhead shorelines increased. The results show strong evidence for the negative effects of shoreline armouring of freshwater ecosystems and are consistent with those shown in coastal ecosystems studies. As cities continue to encroach on freshwater systems, greater emphasis on maintaining natural riparian shorelines and ecoengineering hardscapes will increasingly be important for freshwater conservation.

Cyanopeptides occurrence and diversity in a Brazilian tropical reservoir: Exploring relationships with water quality

Microcystins (MCs) are a class of toxic secondary metabolites produced by some cyanobacteria strains that endanger aquatic and terrestrial organisms in various freshwater systems. Although patterns in MC occurrence are being recognized, divergences in the global data still hamper our ability to predict the toxicity of cyanobacterial blooms. This study aimed (i) to determine the dynamics of MCs and other cyanopeptides in a tropical reservoir, (ii) to investigate the correlation between peptides and potential cyanotoxin producers (iii) identifying the possible abiotic factors that influence the peptides. We analyzed, monthly, eight MC variants (MC-RR, -LA, -LF, -LR, -LW, -YR, [D-Asp3]-RR and [D-Asp3]-LR) and other peptides in 47 water samples collected monthly, all season long, from two sampling sites in a tropical eutrophic freshwater reservoir, in southeastern Brazil. The cyanopeptides were assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The biomass of potential cyanobacterial producers and water quality variables were measured. MCs were detected in both sampling sites year-round; the total MC concentration varied from 0.21 to 4.04 μg L−1, and three MC variants were identified and quantified (MC-RR, [D-Asp3]-RR, -LR). Additionally, we identified 28 compounds belonging to three other cyanopeptide classes: aeruginosin, microginin, and cyanopeptolin. As potential MC producers, Microcystis spp. and Dolichospermum circinalis were dominant during the study, representing up to 75% of the total phytoplankton. Correlational and redundancy analysis suggested positive effects of dissolved oxygen, nitrate, and total phosphorus on MC and microginins concentration, while water temperature appeared to favor aeruginosins. A comparison between our results and historical data showed a reduction in total phosphorus and cyanobacteria, suggesting increased water quality in the reservoir. However, the current MC concentrations indicate a rise in cyanobacterial toxicity over the last eight years. Moreover, our study underscores the pressing need to explore cyanopeptides other than MCs in tropical aquatic systems.

Past and present sawfish (Pristidae) records from India

Overfishing, as well as habitat loss and degradation, has led to major population declines and local extinctions of sawfishes (Pristidae) globally. Four sawfish species reportedly occur in India; however, records have been limited to opportunistic commercial catch and landing reports. Here, we provide the first comprehensive review of published and grey literature on sawfish records from India, including opportunistic observations of sawfish rostra offerings to religious places, highlighting the cultural significance of these species locally. In total, 223 recorded capture events were compiled between 1794 and 2022, with largetooth sawfish Pristis pristis (n = 82), followed by narrow sawfish Anoxypristis cuspidata (n = 32), being the dominant species reported. In addition to marine fisheries, 8 reports of sawfish were reported from freshwater systems. The wide range of rostra sizes and total lengths recorded also suggests that India’s waters harbour various life history stages of sawfish. When caught, sawfish livers were utilised to produce oil, meat was locally consumed, and fins were exported. Despite being legally protected in India since 2001, 63 incidental captures were recorded from landings, suggesting various levels of awareness and enforcement of catch bans across the country. To avoid extinction of these species in India, we emphasise the need to conduct culturally associated awareness programs with coastal communities, encourage safe release and improve handling practices with fishers, identify critical habitats, and strengthen enforcement for mandatory live release.

Incidence of microplastic contamination in fishes of the Ramsar Wetland, Loktak – The world's only floating lake from the Indian Himalayan region

Microplastics are ubiquitous, and their widespread prevalence in the ecosphere has generated concerns about their potential effects on terrestrial and aquatic organisms. However, studies pertaining to ecologically sensitive freshwater ecosystems, such as Ramsar wetlands, is scarce. Therefore, the study was conducted in Loktak, the world's only floating lake, and one of the largest wetland in the Indian Himalayan region. The wetland's degradation and pollution have resulted its inclusion in the Montreux Record, underscoring the need for studying this eco-sensitive freshwater system. This work investigated the (i) abundance, morphotype and size of microplastics in fish, and (ii) chemical composition of the microplastics consumed and accumulated in the fish of Loktak lake. Fish samples representing eight species were collected and analyzed for microplastics. Results revealed that ∼91% of the sampled fish ingested microplastics. Fragment was identified as the predominant morphotype (∼82%). Plastic polymers including polyamide (PA), polystyrene (PS), polycarbonate (PC) and carboxymethyl cellulose (CMC) were detected. The occurrence of heavy metals - chlorine (Cl), palladium (Pd), sodium (Na), zinc (Zn), lead (Pb) and copper (Cu) suggests their adhesion on the microplastics. The occurrence of microplastics in fish indicates pollution in the lake and poses a potential health risks to humans through consumption. Therefore, implementing comprehensive management approaches is imperative to mitigate this emerging pollution and uphold the ecological integrity of the Ramsar site. Substantial information on microplastics and their potential human exposure through fish consumption, particularly in the Indian Himalayan region, remains to be assessed, underscoring the need for extensive study.

Spatial and temporal analysis of physical and chemical properties of Short Creek

Freshwater systems are vitally important. Ecologically, rivers and streams are responsible for immense biodiversity, providing habitat for terrestrial and aquatic flora and fauna. Freshwater systems benefit humans in innumerable ways, providing drinking water to millions of people, means of transportation, food sources, and recreation areas. Nevertheless, the degradation of freshwater ecosystems continues to worsen at alarming rates. Long-term water quality monitoring can help determine the best management practices to improve and restore waterways. This study assessed changes in water chemistry in the Short Creek tributary located in Wheeling, WV, comparing historical data to current, focusing on physical and chemical water quality parameters data recorded from single monthly points obtained from historical data and averaged monthly points from current data. Short Creek represents 4 of 11 sites where data is collected weekly year-round. This data collection has been ongoing since 2018 and is part of a more extensive compilation hosted by Three Rivers Quest and the WVU Water Resource Research Institute. Water temperature, dissolved oxygen, chloride, specific conductivity, pH, and turbidity were recorded and analyzed utilizing Excel and RStudio. The increased frequency of monitoring provides a more accurate representation of Short Creek's overall condition. Both historical and current datasets were incomplete but generally did not show declines. A concerted effort in long-term water quality monitoring is necessary for understanding stream health. Current and historical data combined give us more resolution to estimate trends in water chemistry, better determine stream health progress, and assist in implementing best management practices.

Bioelectrochemical reactor to manage anthropogenic sulfate pollution for freshwater ecosystems: Mathematical modeling and experimental validation

Anthropogenic sulfate loading into otherwise low-sulfate freshwater systems can cause significant ecological consequences as a biogeochemical stressor. To address this challenge, in situ bioremediation technologies have been developed to leverage naturally occurring microorganisms that transform sulfate into sulfide rather than implementing resource-intensive physio-chemical processes. However, bioremediation technologies often require the supply of electron donors to facilitate biological sulfate reduction. Bioelectrochemical systems (BES) can be an alternative approach for supplying molecular hydrogen as an electron donor for sulfate-reducing bacteria through water electrolysis. Although the fundamental mechanisms behind BESs have been studied, limited research has evaluated the design and operational parameters of treatment systems when developing BESs on a scale relevant to environmental systems. This study aimed to develop an application-based mathematical model to evaluate the performance of BESs across a range of reactor configurations and operational modes. The model was based on sulfate transformation by hydrogenotrophic sulfate-reducing bacteria coupled with the recovery of solid iron sulfide species formed by the oxidative dissolution of dissolved ferrous iron from a stainless steel anode. Sulfate removal closely corresponded to the rate of electrolytic hydrogen production and hydraulic residence time but was less sensitive to specific microbial rate constants. The mathematical model results were compared to experimental data from a pilot-scale BES tested with nonacidic mine drainage as a case study. The close agreement between the mathematical model and the pilot-scale BES experiment highlights the efficacy of using a mathematical model as a tool to develop a conceptual design of a scaled-up treatment system.

Ecotoxicological evaluation of surface waters in Northern Namibia.

The increasing pressure on freshwater systems due to intensive anthropogenic use is a big challenge in central-northern Namibia and its catchment areas, the Kunene and the Kavango Rivers, and the Cuvelai-Etosha Basin, that provide water for more than 1 million people. So far, there is no comprehensive knowledge about the ecological status and only few knowledge about the water quality. Therefore, it is crucial to learn about the state of the ecosystem and the ecological effects of pollutants to ensure the safe use of these resources. The surface waters of the three systems were sampled, and three bioassays were applied on three trophic levels: algae, daphnia, and zebrafish embryos. Additionally, in vitro assays were performed to analyze mutagenicity (Ames fluctuation), dioxin-like potential (micro-EROD), and estrogenicity (YES) by mechanism-specific effects. The results show that acute toxicity to fish embryos and daphnia has mainly been detected at all sites in the three catchment areas. The systems differ significantly from each other, with the sites in the Iishana system showing the highest acute toxicity. At the cellular level, only weak effects were identified, although these were stronger in the Iishana system than in the two perennial systems. Algae growth was not inhibited, and no cytotoxic effects could be detected in any of the samples. Mutagenic effects and an estrogenic potential were detected at three sites in the Iishana system. These findings are critical in water resource management as the effects can adversely impact the health of aquatic ecosystems and the organisms within them.

Multi-criteria optimization of a combined power and freshwater system using modified NSGA-II and AHP-entropy-topsis

This paper proposed an innovative hybrid system to generate electricity and fresh water with higher energy efficiency. A subsystem is employed by integrating DCMD and heat pump to recover waste heat of PEMFC to produce fresh water. The thermodynamic and exergoeconomic models are established to evaluate the system comprehensive performance. Compared with the PEMFC alone, the results demonstrated that the proposed hybrid system achieves a 42.07 % increase in energy efficiency and provides 177.86 kg/h of fresh water. The components with high exergy destruction are PEMFC, Relief value, Inverter, Separator 2 and DCMD with the exergy destruction rate of PEMFC stack accounting for 54.55 %. The parametric analysis results indicate that the variation of the membrane filament number, feed and permeate flow rates all have evident impacts on the thermodynamic and economic performances of the hybrid system. The multi-objective optimization is conducted by adopting NSGA-II and three decision-making methods. The optimal solution obtained by AHP-entropy-TOPSIS approach for the net power out, exergy efficiency, WPC, and total exergy cost rate are 96059W, 0.5293, 0.2995 $/m3, and 14.27 $/h, respectively. In addition, the obtained results shown that the simulation times of NSGA-II are significantly reduced from 89.30 to 11.20 h by introducing BP-ANN to improve the simulation efficiency.

Sucralose (C12H19Cl3O8) impact on microbial activity in estuarine and freshwater marsh soils.

As the general population's diet has shifted to reflect current weight-loss trends, there has been an increase in zero-calorie artificial sweetener usage. Sucralose (C12H19Cl3O8), commonly known as Splenda® in the USA, is a primary example of these sweeteners. In recent years, sucralose has been identified as an environmental contaminant that cannot easily be broken down via bacterial decomposition. This study focuses on the impact of sucralose presence on microbial communities in brackish and freshwater systems. Microbial respiration and fluorescence were measured as indicators of microbial activity in sucralose-dosed samples taken from both freshwater and estuarine marsh environments. Results showed a significant difference between microbial concentration and respiration when dosed with varying levels of sucralose. Diatom respiration implied a negative correlation of community abundance with sucralose concentration. The freshwater cyanobacterial respiration increased in the presence of sucralose, implying a positive correlation of community abundance with sucralose concentration. This was in direct contrast to its brackish water counterpart. However, further investigation is necessary to confirm any potential utility of these communities in the breakdown of sucralose in the marsh environment.

Microalgae for freshwater arsenic bioremediation: examining cellular toxicity, bioconcentration factor and eluding an alternative arsenic detoxification pathway

Microalgae are photoautotrophic organisms in freshwater systems known to uptake and bioremediate arsenic, a heavy metal. In this study, we compared the growth and arsenic uptake of two microalgae strains, Nostoc and Chlorella, to determine their suitability for arsenic bioremediation. As compared to the control, our results showed that treatment with As (III) enhanced the Nostoc growth by approximately 15% when grown in the absence of phosphate. The highest bioconcentration factor of Nostoc at this treatment was 1463.6, whereas 0.10 mg L−1 As (V) treatment improved the Chlorella growth by 25%, in the presence of phosphate. However, arsenic uptake reduced from 175.7 to 32.3 throughout the cultivation period for Chlorella. This suggests that Nostoc has an upper advantage in the bioremediation of arsenic as compared to the Chlorella strain. To gain insights into the potential of Nostoc in arsenic bioremediation, we further conducted SEM analysis on the vegetative cell surface. The SEM results showed that As (III) disrupted the Nostoc vegetative cell surface and structure. Further to this, pathway analysis and polymerase chain reaction (PCR) were conducted to identify the potential arsenic pathway regulated by Nostoc. The primary As (III)-related pathways elucidated include the arsA transporter and arsD complex that require ATP and As (III) methylation to S-adenosylmethionine. The phosphate deficiency condition resulting in the inability to generate ATP caused As (III) could not be excreted from the Nostoc cells, potentially contributing to the high arsenic concentration accumulated under phosphate-depleted conditions. These insights contribute to understanding the efficacy of microalgae strains in freshwater arsenic bioremediation.

Characteristics, fate, and sources of microplastics contaminant in surface water and sediments of river water

Although developing countries are huge producers of plastic debris, few studies on MPs in freshwater systems, a major contributor to oceans, have been done. In this investigation, we estimated the abundance, shape, size, and potential sources of MPs in river water and sediments taken from the freshwater of the Subarnarekha and Kharkai rivers in Jamshedpur. Four types of MPs were identified among the analyzed data: fragments, films, foams, and fibers. These MPs were examined using a stereomicroscope and their polymer composition was identified using ATR-FTIR spectroscopy. The quantitative assessment of our study revealed a mean abundance of MPs 9.55 ± 4.87 items/L (average ± SD, n = 9) in water and 270.88 ± 105.89 items/kg (average ± SD, n = 9) in sediment samples. The morphological distribution of MP particles revealed that fibers account of 44.2 % of MPs particles, followed by film (24.4 %), fragments (20.9 %), and pellets/foam (10.5 %) in water. Fiber accounts 48.3 % of total MPs shape followed by fragments (20.6 %), foam/pellets (16.4 %) and film (14.7 %) in sediments. According to the MP size distribution, 84.9 % of the MPs were between <125 μm and 1000 μm in water, while 94.0 % of the particles were between 125 μm and 5000 μm. The black color MPs accounted for 27. 0 % in water and 20.0 % in sediments, followed by blue (24.0 %), and white (19.0 %) in water and sediments, respectively. The most abundant polymer composition found was 30.0 % and 28.2 % of polyester in water and sediment samples respectively, which was followed by polypropylene 37.7 %, polyvinyl chloride 36.2 %, polyethylene 29.7 %, polystyrene 25.1 %, and polyamide 13.1 % in water and sediments. To reduce microplastic pollution, focus on mitigation of plastic waste, improving waste management, and implementing practical solutions.

Exploring tradeoffs among diet quality and environmental impacts in self-selected diets: a population-based study.

Proposed sustainable diets often deviate dramatically from currently consumed diets, excluding or drastically reducing entire food groups. Moreover, their environmental sustainability tends to be measured only in terms of greenhouse gases emissions. The aim of this study was to overcome these limitations and identify a cluster of already adopted, relatively healthy diets with substantially lower environmental impacts than the average diet. We also aimed to estimate the reduction in multiple environmental impacts that could be achieved by shifting to this diet cluster and highlight possible tradeoffs among environmental impacts. The diet clusters were identified by applying energy-adjusted multiple factor analysis and hierarchical clustering to the dietary data of the National FinHealth 2017 Study (n = 5125) harmonized with life cycle assessment data on food products from Agribalyse 3.0 and Agri-Footprint using nutrient intakes and global warming potential, land use, and eutrophication of marine and freshwater systems as the active variables. We identified five diet clusters, none of which had the highest overall diet quality and lowest impact for all four environmental indicators. One cluster, including twenty percent of the individuals in the sample was identified asa "best compromise" diet with the highest diet quality and the second lowest environmental impacts of all clusters, except for freshwater eutrophication. The cluster did not exclude any food groups, but included more fruits, vegetables, and fish and less of all other animal-source foods than average. Shifting to this cluster diet could raise diet quality while achieving significant reductions in most but not all environmental impacts. There are tradeoffs among the environmental impacts of diets. Thus, future dietary analyses should consider multiple sustainability indicators simultaneously. Cluster analysis is a useful tool to help design tailored, socio-culturally acceptable dietary transition paths towards high diet quality and lower environmental impact.

Introduction of Native Submerged Macrophytes to Restore Biodiversity in Streams.

Streams are biodiversity hotspots that provide numerous ecosystem services. Safeguarding this biodiversity is crucial to uphold sustainable ecosystem functioning and to ensure the continuation of these ecosystem services in the future. However, in recent decades, streams have witnessed a disproportionate decline in biodiversity compared to other ecosystems, and are currently considered among the most threatened ecosystems worldwide. This is the result of the combined effect of a multitude of stressors. For freshwater systems in general, these have been classified into five main pressures: water pollution, overexploitation, habitat degradation and destruction, alien invasive species, and hydromorphological pressures. On top of these direct stressors, the effects of global processes like environmental and climate change must be considered. The intricate and interconnected nature of various stressors affecting streams has made it challenging to formulate effective policies and management strategies. As a result, restoration efforts have not always been successful in creating a large-scale shift towards a better ecological status. In order to achieve an improved status in these systems, situation-specific management strategies tailored to specific stressor combinations may be needed. In this paper, we examine the potential of introducing native submerged macrophyte species to advance the restoration of stream ecosystems. Through successful introductions, we anticipate positive ecological outcomes, including enhanced water quality and increased biodiversity. This research is significant, as the potential success in restoring stream biodiversity not only represents progress in ecological understanding but also offers valuable insights for future restoration and management strategies for these vital ecosystems.

Microplastics alter the leaf litter breakdown rates and the decomposer community in subtropical lentic microhabitats

Microplastics, pervasive pollutants in aquatic environments, have been primarily studied for their impact on marine ecosystems. However, their effects on freshwater systems, particularly in forested phytotelmata habitats, remain understudied in Subtropical systems. This research examines the influence of varying microplastic concentrations (0.0, 200, 2,000, 20,000, and 200,000 ppm) on leaf litter breakdown of Inga vera (in bags of 10 and 0.05 mm mesh) and the naturally associated invertebrate community occurring in forested phytotelmata. The study employs an experimental design with microplastic concentration treatments in artificial microcosms (buckets with 800 mL of rainwater) arranged in an area of Atlantic Rain Forest native vegetation of Subtropical systems. The results indicate that elevated concentrations of microplastics may enhance leaf litter breakdown (6–8%), irrespective of the bag mesh, attributed to heightened decomposer activity and biofilm formation. Consequently, this contributes to increased invertebrate richness (33–37%) and greater shredder abundance (21–37%). Indicator analysis revealed that Culicidae, Stratiomyidae, Chironomidae, Empididae, Planorbidae, and Ceratopogonidae were indicative of some microplastic concentrations. These findings underscore the significance of accounting for microplastics when evaluating the taxonomic and trophic characteristics of invertebrate communities, as well as the leaf breakdown process in Subtropical systems.

Freshwater Malacofauna and Distribution of Trabzon, Türkiye

In this study, freshwater molluscs and their zoogeographical distributions in Trabzon were investigated. During the period of June-December 2021, samples were collected from 38 freshwater river localities. From the study area, Ancylus fluviatilis from Gastropoda class, Planorbidae family, non-native species Physella acuta from Physidae family, and Dreissena polymorpha from Bivalvia class and Dreissenidae family were identified. While A. fluviatilis specimens were found from all freshwater systems in Trabzon region, the non native P. acuta could be identified from Fol Stream, Yıldızlı Stream, Sera Lake and Manahoz River. Empty shells belonging to the D. polymorpha species were identified from the area where Çatalzeytin Stream joins the sea. P. acuta and D. polymorpha are new records for the freshwater streams of Trabzon region.

Combined effect of freshwater salinization and harmful algae on the benthic invertebrate Chironomus pallidivittatus

Global climate change as well as human activities have been reported to increase the frequency and severity of both salinization and harmful algal blooms (HABs) in many freshwater systems, but their co-effect on benthic invertebrates has rarely been studied. This study simultaneously examined the joint toxicity of salinity and different cyanobacterial diets on the behavior, development, select biomarkers, and partial life cycle of Chironomus pallidivittatus (Diptera). High concentrations of salts (e.g., 1 g/L Ca2+ and Mg2+) and toxic Microcystis had synergistic toxicity, inhibiting development, burrowing ability and causing high mortality of C. pallidivittatus, especially for the Mg2+ treatment, which caused around 90% death. Low Ca2+ concentration (e.g., 0.01 g/L) promoted larval burrowing ability and inhibited toxin accumulation, which increased the tolerance of Chironomus to toxic Microcystis. However, low Mg2+ concentration (e.g., 0.01 g/L) was shown to inhibit the behavior, development and increase algal toxicity to Chironomus. Toxic Microcystis resulted in microcystin (MC) accumulation, inhibited the burrowing ability of larvae, and increased the proportion of male adults (>50%). The combined toxicity level from low to high was verified by the weight of evidence and the grey TOPSIS model, which integrated five lines of evidence to increase the risk assessment accuracy and efficiency. This is the first study that provided insights into ecological risk arising from the joint effect of salinity and harmful algae on benthic organisms. We suggest that freshwater salinization and HABs should be considered together when assessing ecological threats that arise from external stress.

Thermal tolerance of cultured and wild Icelandic arctic charr (Salvelinus alpinus) at self-selected flow rates

Climate change is predicted to change not only the temperature of many freshwater systems but also flow dynamics. Understanding how fishes will fare in the future requires knowing how they will respond to both extended variations of temperature and flow. Arctic charr have had their thermal tolerance measured, but never with respect to flow. Additionally, this circumpolar species has multiple populations exhibiting dramatic phenotypic plasticity which may mean that regional differences in thermal tolerance are unaccounted for. In Iceland, Arctic charr populations have experienced highly variable flow and temperature conditions over the past 10,000 years. The Icelandic climate, topography and geothermal activity have created a mosaic of freshwater habitats inhabited by charr that vary substantially in both temperature and flow. Our purpose was to test whether populations from these varied environments had altered thermal tolerance and whether phenotypic plasticity of thermal tolerance in charr depends on flow. We raised cultured Icelandic charr from hatch under a 2 X 2 matrix of flow and temperature and compared them to wild charr captured from matching flow and temperature environments. Wild fish were more thermally tolerant than cultured fish at both acclimation temperatures and were more thermally plastic. Icelandic Arctic charr were more thermally tolerant than comparison charr populations across Europe and North America, but only when acclimated to 13 °C; fish acclimated to 5 °C compared equably with comparison charr populations. Icelandic Arctic charr were also more thermally plastic than all but one other salmonine species. Neither flow of rearing or the flow selected during a thermal tolerance (CTmax) test factored into thermal tolerance. Thermal tolerance was also independent of body size, condition factor, heart and gill size. In summary, wild Icelandic Arctic charr have greater thermal tolerance and plasticity than predicted from the literature and their latitude, but artificial selection for properties like growth rate or fecundity may be breeding that increased tolerance out of cultured fish. As the world moves toward a warmer climate and increased dependence on cultured fish, this is a noteworthy result and merits further study.