Freshwater Organisms Research Articles

Excess chloride and impervious surfaces reduce over-winter quality of stream algal assemblages

Winter road salt use leads to the salinization of freshwater habitats. Freshwater organisms experience negative effects due to increased chloride ions, including algae in periphyton biofilms. This study examines the effects of road salt on algal assemblage composition, lipid production, and enzyme activity. Five streams throughout Erie County, New York, US were sampled monthly from October 2018 to March 2019. Chloride concentrations in all streams averaged 203.6 Cl- mg/L throughout the winter and had a highly significant relationship (rs = 0.82) with developed land use. Algal biodiversity scores decreased with elevated salinity (rs = 0.11). Algae exhibited the greatest total lipids in January (2.92 mg/m2) and the lowest in March (1.03 mg/m2). Similar trends were observed with ω3 and ω6 compounds. Overall desaturase Δ6 activity trended with stream Cl- concentrations, mainly along ω6 pathways, suggesting an inflammatory stress response. Algal assemblages exhibited evidence of chronic salt exposure through impaired taxonomic composition and patterns of lipid production that followed trends in stream water salinity. These effects suggest road salt applications have negative effects on stream primary producers with consequences for higher trophic levels.

Nanoplastic exposure inhibits feeding and delays regeneration in a freshwater planarian

The concentration of nanoplastics (NPs) is expected to increase in aquatic environments thus potentially threatening freshwater organisms through interactions with plastic particles that variously float, circulate in the water column or sink into the benthos. Studies into the mechanisms of any NP effects are still scarce, particularly with respect to the regenerative ability of biota for which there is no recognised model organism. The present study therefore aimed to investigate behavioural and regeneration responses of the freshwater planarian Girardia tigrina after 10 days exposed to along a gradient 0.01–10 mg/L of poly (styrene-co-methyl methacrylate) NPs (∼426 ± 175 nm). Exposure to NPs induced a significant reduction in planarian feeding rate even at low concentrations (LOEC of 0.01 mg/L), while head regeneration was delayed in a clear dose response way (LOEC of 0.1 mg/L for blastema length). Planaria locomotion assessed was not affected. Our results highlight the potential adverse effects of exposure to poly (styrene-co-methyl methacrylate) NPs and show that feeding behaviour and regeneration of a freshwater benthic organism can be indicators of the resulting toxicity. Planarians are becoming widely used model organisms in ecotoxicology and can help to address potential effects of plastic polymers on regeneration.

Adverse effects of sulfamethoxazole on locomotor behavior and lipid metabolism by inhibiting acetylcholinesterase and lipase in Daphnia magna

Sulfamethoxazole (SMZ), a kind of sulfonamide antibiotic, is widely used in both human and veterinary medicine. Frequent detection of SMZ in natural aquatic environments has prompted growing attention and posed ecological risks to the ecosystem and human health. In this study, we investigated the ecotoxicological properties of SMZ upon Daphnia magna, and the mechanisms of the deleterious effects of SMZ were attempted to be elucidated by investigating a chain of parameters, including survival, reproduction, growth, locomotor behavior, metabolism, as well as levels of related enzyme activity and gene expression. After a 14-d sub-chronic exposure to SMZ at environmentally relevant concentrations, we observed virtually no lethal effect, weak growth inhibition, significant reproductive damage, evident ingestion rate decline, obvious change in locomotor behavior, and remarkable metabolic disorder. Notably, we identified SMZ as an inhibitor against acetylcholinesterase (AChE)/lipase in D. magna both in vivo and in vitro, which explained the adverse effects of SMZ on locomotor ability and lipid metabolism at the molecular levels. Furthermore, the direct interactions between SMZ and AChE/lipase were confirmed by using fluorescence spectrum and molecular docking. Together, our findings provide a new insight to advance the understanding of the environmental effects of SMZ on freshwater organisms.

Lake water chemistry and population of origin interact to shape fecundity and growth in Daphnia ambigua.

Freshwater environments vary widely in ion availability, owing to both natural and anthropogenic drivers. Field and laboratory work point to the importance of overall salinity, as well as cation depletion, in shaping the physiology, behavior, and ecology of freshwater taxa. Yet, we currently have a poor understanding of the degree to which populations may vary in response to ion availability. Using Daphnia collected from three lakes that differ greatly in salinity and calcium availability, we conducted a laboratory reciprocal transplant experiment to assess how animals representing these populations vary in fecundity, body size, and survival when reared in lake water from each environment. The lake water environment and population of origin strongly interacted to shape Daphnia growth and reproduction. Surprisingly, we found only modest evidence that lake water with abundant calcium (5.5 vs. 1.2-2.3 mg/L) increased Daphnia growth or reproduction. By contrast, water from a relatively ion-rich lake (400 μS/cm specific conductance) strongly boosted Daphnia fecundity over lower-ion lake water (20-50 μS/cm), especially for the population originating from the high-ion environment. Our results suggest that ion-poor conditions common in regions around the world may exert stress on freshwater organisms, even for populations inhabiting these environments. Meanwhile, moderate salt enrichment may not prove harmful but could even benefit freshwater taxa in these ion-poor regions. The context dependence of how and when lake water chemistry affects Daphnia and other freshwater taxa deserves greater attention, in both ion-depleted and ion-rich conditions. Daphnia are key members of lake food webs and serve as an important model for ecology, evolution, and toxicology research. Consideration of how lake water chemistry may influence how Daphnia populations respond to abiotic and biotic stress may improve the ability to evaluate and predict ecological and evolutionary dynamics in lakes of varying chemical composition.

Hydrothermal co-carbonization of sewage sludge and whey: Enhancement of product properties and potential application in agriculture

The impacts of operating conditions on hydrothermal carbonization of sewage sludge (SS) in water media were investigated in this study. Hydrothermal co-carbonization (co-HTC) of SS and cheese whey was also carried out under selected conditions (T = 250 °C, t = 5 h), to investigate the effects of replacing water with whey on product properties. Besides, the potential application was also tested of HTC products for agricultural use.The HTC treatment increased the content of nutrients (P, Ca, and Mg) in hydrochars compared to untreated SS, but fuel properties were not improved. Increasing the operating temperature and time increased the contents of nitrogen and volatile fatty acids in the process liquids. The replacement of water with whey resulted in remarkable improvement of the fuel properties of hydrochar, as the hydrochar yield increased from 57.10 to 64.14 wt%, the calorific value from 14.75 to 18.29 MJ/kg, and carbon content from 36.89 to 45.24 wt%. The ash content decreased from 46.55 to 40.06 wt%. The content of N, P, Ca, Mg and K increased significantly. SEM-EDS, FTIR and thermogravimetric analysis revealed the strong influence of the co-carbonization on the thermogravimetric behaviour of the hydrochars and their chemical properties. The HTC products proved efficient as fertiliser in a germination test with plants. Process liquids can be used as an N fertiliser, while hydrochars as a P fertiliser. Undiluted process liquids were toxic to the freshwater organisms Daphnia magna.

The Behavioral and physiological impacts of the hormesis of chemical contaminants on embryonic zebrafish

Pharmaceutical chemicals are being produced, consumed, and excreted in human civilization at an increasing rate. These chemicals have the capacity to accumulate, especially in environments such as freshwater systems, but there have not been any major responses to this threat yet as the present concentrations of the chemicals is not viewed as dangerous. Previous research has shown that the developing concentrations of chemicals is an issue, supporting that these chemicals, though not present in large doses, have impacts on exposed organisms. However, prior research has not been conducted to examine the specific effects of chemicals at hormetic concentrations on freshwater organisms. “Hormetic concentration” defines the concentrations of chemicals at specific levels where the response to a low dose of chemical differs from the response to the high dose, and these were the ranges of concentration that were tested in this experiment. Zebrafish were acquired at zero days post fertilization, transferred to the medium containing the appropriate concentration of chemicals for the group that they would be a part of, and used as a model for aquatic organisms to show the resulting chemical, neural, and physical response to the chemical concentrations. The zebrafish were euthanized via bleaching and freezing prior to seven days post fertilization. The results of this experiment show that there is an ecological risk associated with the environmental accumulation of pharmaceutical chemical contaminants that is inherent to their use in human civilization, a result which makes it clear that this issue needs to be addressed.

Ponticolaalasanicus sp. n. (Gobiiformes, Gobiidae) from the Alazani River Basin, Georgia.

The South Caucasus Region and Georgia, in particular, is a biodiversity hotspot and characterised by high diversity of landscapes and ecosystems, as well as high levels of endemism. At the same time, diversity of freshwater organisms in the region remains poorly studied, including fishes. The freshwater fish fauna of the South Caucasus Region consists of 119 fish species, of which 13 species belong to the order Gobiiformes. It should be noted that gobies are amongst the poorly studied taxa in Georgia and probably unknown/undescribed species still living in the Georgian freshwater ecosystems which requires further research. Ponticolaalasanicus, a new species is described from the Alazani River, western Caspian Sea Basin, Georgia. It is distinguished from its congeners in the Caspian and Black Sea Basins by having the following features: dorsal fin with VI-VII spines and 15½-16½ branched rays, anal fin with 10½-12½ branched rays; lateral line with 48-55 scales; laterally compressed body with dark brown and black blotches - scales ctenoid; first and second dorsal fins almost touching with dorsal fins bases; head large, depressed, wider than deep, its length approaches almost 3.4th of standard length; nape scaled completely; cycloid scales cover upper part of opercle, cheeks noticeably swollen; snout longer than eye, eye diameter 4.5 times its head length; lower jaw slightly protruding; upper lip is uniform; pelvic disc short, elongated and flat, not reaching the anus; the pectoral fins extends vertically through first branched dorsal fin; caudal fin rounded. Ponticolaalasanicus sp. n. belongs to P.syrman group and it is separated by a minimum Kimura 2-parameter distance of 3.5, 3.6 and 4.8% from P.syrman, P.iranicus and P.patimari, respectively.

Trophic transfer of microplastics from producer (Lemna minuta) to primary consumer (Cataclysta lemnata) in a freshwater food chain

Contamination by microplastics (0.1 μm–5 mm plastic fragments) is currently one of the major threats to the conservation of aquatic and terrestrial ecosystems worldwide. Growing awareness on this issue has led to an increase in studies on the effects of microplastics on freshwater organisms, although there are still few investigations on possible transfer of this contaminant along water trophic chains from producers to primary consumers. In this study, aquatic herbivorous larvae of the moth Cataclysta lemnata were fed on microplastic-free (control) and contaminated (MPs treatment) Lemna minuta fronds. For treatments, Lemna fronds were grown in mineral water enriched with fluorescent microparticles of poly(styrene-co-methyl methacrylate) (MPs, 100 mg/L) and then fed to the larvae as a food source. Microplastics effects on larvae were tested at 0, 7, 14 and 21 days of exposure, corresponding to sensitive phases of the insect life cycle. Contaminant impact was assessed based on some parameters such as viability, larva body size/weight, feeding alterations and regularity of the insect life cycle. Using scanning electron and fluorescence microscopy, the presence of microplastics in the larvae was verified. The finding of fluorescent microplastics in both the intestinal lumen and excrement samples showed that larvae ingested contaminated Lemna fronds. In addition, larvae fed contaminated fronds were strongly affected by the presence of microplastic contaminant over time, showing high mortality (90 %) and total inability to complete the life cycle after 21 days by failing to reach the winged adult phase. In control tests, survival rates were higher than in treatments, and 50 % of the larvae managed to pupate and emerge as moths, reaching the adult phase. The results show that there was a trophic transfer of microplastics from producer to primary consumer along a freshwater food chain, generating negative effects on the life cycle of this aquatic herbivore.

Systematic Review of Nano- and Microplastics' (NMP) Influence on the Bioaccumulation of Environmental Contaminants: Part II-Freshwater Organisms.

Nano- and microplastic fragments (NMPs) exist ubiquitously in all environmental compartments. The literature-based evidence suggests that NMPs interact with other environmental contaminants in freshwater ecosystems through sorption mechanisms, thereby playing a vector role. Chemically bound NMPs can translocate throughout the environment, reaching long distances from the contaminant discharge site. In addition, they can be ab/adsorbed by freshwater organisms. Although many studies show that NMPs can increase toxicity towards freshwater biota through the carrier role, little is known regarding their potential to influence the bioaccumulation of environmental contaminants (EC) in freshwater species. This review is part II of a systematic literature review regarding the influence of NMPs on bioaccumulation. Part I deals with terrestrial organisms and part II is devoted to freshwater organisms. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA ScR) was used for the literature search and selection. Only studies that assessed the bioaccumulation of EC in the presence of NMPs and compared this with the bioaccumulation of the isolated EC were considered. Here, we discuss the outcome of 46 papers, considering NMPs that induced an increase, induced a decrease, or caused no effect on bioaccumulation. Lastly, knowledge gaps are identified, and future directives for this area of research are discussed.

Nanotechnology-based pesticides: Environmental fate and ecotoxicity

The imminent increase in global food demand inevitably leads to an increase in agricultural practices, with an emphasis on pesticide applications. Nanotechnology-based pesticides, or nanopesticides, have gained importance as they are more efficient and, in some cases, less toxic than their conventional counterparts. However, concerns about these novel products have arisen as evidence about their (eco)safety is controversial. This review aims to: (1) introduce the currently applied nanotechnology-based pesticides and their mechanisms of toxic action; (2) describe their fate when released into the environment, with an emphasis on aquatic environments; (3) summarize available research on ecotoxicological studies in freshwater non-target organisms through a bibliometric analysis; and (4) identify gaps in knowledge from an ecotoxicological perspective. Our results show that the environmental fate of nanopesticides is poorly studied and depends on both intrinsic and external factors. There is also a need for comparative research into their ecotoxicity between conventional pesticide formulations and their nano-based counterparts. Among the few available studies, most considered fish species as test organisms, compared to algae and invertebrates. Overall, these new materials generate toxic effects on non-target organisms and threaten the integrity of the environment. Therefore, deepening the understanding of their ecotoxicity is crucial.

Potential thyroid hormone disorder risks of tire antioxidants to aquatic food chain organisms after absorbing free radicals in marine and freshwater environments

Tire antioxidants are essential functional chemical additives in tire rubber production. Because of the characteristic easy precipitation in the water environment, the environmental pollution problem caused by tire antioxidants is concerning. To reveal the mechanism by which tire antioxidants reduce common oxidative factors (free radicals) in the environment and to control the potential biological thyroid hormone disorder risk of tire antioxidant derivatives, eight commonly used antioxidants in tire production were selected for analysis. Firstly, the ability of tire antioxidants to reduce three different free radicals was quantitatively characterized based on Gaussian calculation method and inferring the radical reduction mechanism of tire antioxidants. Moreover, using the PaDEL-Descriptor software and random forest algorithm found that the N-octanol/water partition coefficient, a structure descriptor of tire antioxidant molecules, significantly correlated with their reducing ability. Second, molecular docking and molecular dynamics methods were used to assess the thyroid hormone disorder risk to aquatic organisms of eight antioxidants after reducing three free radicals. And this is the first study to construct an assessment score list of potential thyroid hormone disorder risk of the derivatives of tire antioxidants after reducing free radicals to marine and freshwater aquatic organisms based on the risk entropy method. Through the screening of this list, it was found that the derivative of the antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline oxidized by free radicals had the highest risk of thyroid hormone disorder. In addition, the top organism in the aquatic food chain was the most affected. This study also revealed that van der Waals interactions and hydrogen bonding were the main influencing factors of thyroid hormone disorder risk to aquatic organisms of the derivatives of tire antioxidants that reduce free radicals based on amino acid residue analysis. Overall, the results provide theoretical support for the selection of antioxidants and the avoidance and control of environmental risks in the tire rubber production process.

Elevated dissolved carbon dioxide and associated acidification delays maturation and decreases calcification and survival in the freshwater crustacean Daphnia magna

AbstractIncreasing pCO2 in freshwaters across the globe will likely be accompanied by acidification. Although this has been linked to reduced calcification, growth, and survival in several marine species, similar responses in freshwater organisms remain largely unexplored. Here, we investigated the direct effects of elevated pCO2 and associated acidification on the water flea Daphnia magna. As a highly efficient filter feeder, this crustacean is a dominant primary consumer in freshwater zooplankton assemblages, capable of controlling algal growth. It has a high calcium content compared to other zooplankton species, which might make it particularly sensitive since calcification may be impaired under elevated pCO2. We exposed newly hatched individuals of four clonal lineages to 27,000 ppm pCO2 corresponding to a pH of 6.7 in a controlled laboratory experiment. Both survival and calcium content were reduced and juveniles grew slower and matured later under elevated pCO2. Adult growth rate was not affected by pCO2 suggesting that surviving adults are less sensitive or may acclimate over time but at the cost of reduced offspring size. We hypothesize that the combination of elevated pCO2 and low pH interferes with the calcification process, reflected in slower growth, smaller body size and reduced calcification in D. magna. In turn, this might lead to less efficient control of phytoplankton as an ecosystem service and reduce their competitive advantage over other zooplankters with less calcified bodies.

Transcriptome analysis revealed the mechanism of Luciobarbus capito (L. capito) adapting high salinity: Antioxidant capacity, heat shock proteins, immunity

Salinity has a significant influence on the physiology of freshwater aquatic organisms. However, there are few studies on the hematology and immunology of freshwater fish under high salinity. In the current study, we aimed to analyze the adaptive effect of salt stress on L. capito spleen immune function and hematology using transcriptomic analysis. We replicated a L. capito acute salinity stress model, and collected blood and spleens from freshwater and saltwater fish. It was found that salinity affected significantly the numbers of leukocytes, lymphocytes, neutrophils, and red blood cells, as well as the content of haemoglobin. Salt treatment resulted in a significant increase in the expression of HSP70, HSP90, CAT, SOD, and GPX1 genes in L. capito spleens. Transcriptomic analysis revealed a total of 546 differentially expressed genes (DEGs) in spleens, including 224 up-regulated DEGs and 322 down-regulated DEGs. In addition, GO enrichment analysis revealed immune system process, multicellular organismal process, and biological regulation of genes with the most differences in biological processes. KEGG enrichment analysis showed that the regulation of lipolysis in adipocyte, FoxO signaling pathway, Hematopoietic cell lineage signaling pathway, and HIF-1 signaling pathway were significantly enriched. L. capito adapted oxidative to high salinity through FoxO signaling pathway and immune to high salinity through Hematopoietic cell lineage signaling pathway. At the same time, we selected 10 DEGs for qRT-PCR detection, and the results showed that the qRT-PCR results were consistent with our RNA-Seq results, indicating that transcriptome sequencing was accurate and reliable. In conclusion, our results demonstrated that the improvement of antioxidant capacity, heat shock protein and immunity are involved in the molecular mechanism of L. capito adapting to high salinity. Our findings provided a rationale for further study on high salinity adaptation and related enrichment pathways.

Comparative ecotoxicity of graphene, functionalized multi-walled CNTs, and their mixture in freshwater microalgae, Scenedesmus obliquus: analyzing the role of oxidative stress.

Due to their remarkable properties, the applications of carbon-based nanomaterials (CNMs) such as graphene and functionalized multi-walled carbon nanotubes (f-MWCNTs) are increasing. These CNMs can enter the freshwater environment via numerous routes, potentially exposing various organisms. The current study assesses the effects of graphene, f-MWCNTs, and their binary mixture on the freshwater algal species Scenedesmus obliquus. The concentration for the individual materials was kept at 1mg L-1, while graphene and f-MWCNTs were taken at 0.5mg L-1 each for the combination. Both the CNMs caused a decrease in cell viability, esterase activity, and photosynthetic efficiency in the cells. The cytotoxic effects were accompanied by increased hydroxyl and superoxide radical generation, lipid peroxidation, antioxidant enzyme activity (catalase and superoxide dismutase), and mitochondrial membrane potential. Graphene was more toxic compared to f-MWCNTs. The binary mixture of the pollutants demonstrated a synergistic enhancement of the toxic potential. Oxidative stress generation played a critical role in toxicity responses, as noted by a strong correlation between the physiological parameters and the biomarkers of oxidative stress. The outcomes from this study emphasize the significance of considering the combined effects of various CNMs as part of a thorough evaluation of ecotoxicity in freshwater organisms.

Direct and indirect effects of salinisation on riverine biota: a case study from river Wipper, Germany

Salinisation has direct and detrimental physiological effects on freshwater organisms, yet little is known about its indirect effects. Here, we present a study that investigated the primary and secondary effects of salinisation on aquatic macroinvertebrates. We analysed macroinvertebrate samples from nine sites in river Wipper, Germany against nine stressor variables (water quality, salinisation, hydromorphological degradation). A Principal Component Analysis showed water quality deterioration and physical habitat degradation to constitute the main stressor gradients. Two macroinvertebrate community metrics (index of general degradation and percent Ephemeroptera-Plecoptera-Trichoptera specimens) revealed strong and significant positive correlations with water quality, but only weak and insignificant positive correlations with hydromorphological quality. High-resolution temporal measurements revealed notable oxygen deficits at a salinised and macrophyte-rich site that was dominated by the salt-tolerant macrophyte species Stuckenia [Potamogeton] pectinata (L.) Börner. At the site, oxygen levels frequently dropped below 6 mg/L during nighttime, suggesting an interaction of osmoregulatory stress (through salinisation) and respiratory stress (through plant mitochondrial respiration) that is caused by the mass development of a salt-tolerant macrophyte species. This biologically driven interaction of direct and indirect salinisation effects adds another level of complexity to the influence of multiple stressors in lotic systems and requires consideration in river management and restoration.

Freshwater salinization reduces vertical movement rate and abundance of Daphnia: Interactions with predatory stress

Contaminants in human-dominated landscapes are changing ecological interactions. The global increase in freshwater salinity is likely to change predator-prey interactions due to the potential interactive effects between predatory stress and salt stress. We conducted two experiments to assess the interactions between the non-consumptive effects of predation and elevated salinity on the abundance and vertical movement rate of a common lake zooplankton species (Daphnia mendotae). Our results revealed an antagonism rather than a synergism between predatory stress and salinity on zooplankton abundance. Elevated salinity and predator cues triggered a >50% reduction in abundance at salt concentrations of 230 and 860 mg Cl−/L, two thresholds designed to protect freshwater organisms from chronic and acute effects due to salt pollution. We found a masking effect between salinity and predation on vertical movement rate of zooplankton. Elevated salinity reduced zooplankton vertical movement rate by 22–47%. A longer exposure history only magnified the reduction in vertical movement rate when compared to naïve individuals (no prior salinity exposure). Downward movement rate under the influence of predatory stress in elevated salinity was similar to the control, which may enhance the energetic costs of predator avoidance in salinized ecosystems. Our results suggest antagonistic and masking effects between elevated salinity and predatory stress will have consequences for fish-zooplankton interactions in salinized lakes. Elevated salinity could impose additional energetic constraints on zooplankton predator avoidance behaviors and vertical migration, which may reduce zooplankton population size and community interactions supporting the functioning of lake ecosystems.

Scaling the invisible wall: Molecular acclimation of a salinity-tolerant diatom to freshwater.

In aquatic ecosystems, marine and freshwater environments are separated by steep salinity gradients. The osmotic stress induced by this 'invisible wall' forms an insurmountable barrier for many aquatic lifeforms, including bacteria, algae and animals. Because the osmotic differences when transiting a salinity divide are so hard to overcome, most species have adapted exclusively to a marine or a freshwater lifestyle. A major consequence of this physiological specialization into marine and freshwater organisms is that transitions are relatively rare, impeding regular contact and colonization. While some animals use specialized organs or behaviour to cope with unfavourable salinity levels, unicellular algae such as diatoms are completely dependent on cellular mechanisms to mitigate salinity stress. In this issue of Molecular Ecology, Downey and colleagues investigate the transcriptomic response of a salinity-tolerant diatom to a shock treatment with freshwater (Molecular Ecology, 2023). Through frequent sampling and integration of existing RNA sequencing data, a fine-grained model of the acclimation to hypo-osmotic stress emerges. Deciphering the pathways that drive the acute and long-term acclimation to freshwater has major implications for diatom ecology, diversification and resilience to global change.

Effects of Spontaneous Fluorescent Polystyrene on Nostocaceae and Daphnia Magna

Microplastic pollution is widespread around the world and inevitably comes into contact with organisms. With the accumulation of microplastics in the environment, the negative impact of microplastics on organisms has become the main focus in the field of microplastics. In this study, the different particle and concentration effects of fluorescent polystyrene microplastics (PS-MPs) on Nostocaceae and Daphnia Magna were researched. The results indicate that PS-MPs adhered to Nostocaceae through static electricity, which hindered the absorption of photons and CO2 by Nostocaceae, resulting in a decrease in chlorophyll, a low growth rate and high mortality for Nostocaceae. PS-MPs with very small particles may be integrated into the blood of Daphnia Magna, leading to an increasing trend of mortality and a decrease in spawning rate. The research provides basic data and a reference for the effect of PS-MPs on freshwater organisms and has implications for the further study of microplastics.

Distribution of Freshwater Organisms in the Pyeonggang Stream and Application Effects of Hydrothermal Energy on Variations in Water Temperature by Return Flow in a Stream Ecosystem

Distribution of Freshwater Organisms in the Pyeonggang Stream and Application Effects of Hydrothermal Energy on Variations in Water Temperature by Return Flow in a Stream Ecosystem

Shortfalls in our understanding of the causes and consequences of functional and phylogenetic variation of freshwater communities across continents

Freshwater ecosystems harbour a disproportionately high biodiversity relative to their area, being also one of the most threatened ecosystem types worldwide. However, our capacity to design evidence-based conservation plans for this realm is restricted by all biodiversity shortfalls that have been recognized so far. In this context, the paucity of comparable field data and information on traits and phylogenies of freshwater organisms should be emphasized. Here, we highlight how increased knowledge could be gained and where we should aim at in research on the functional and phylogenetic features of freshwater communities. First, attempts to combine datasets from different sources should pay careful attention to data harmonization. Second, more effort should be focused on natural history observations on species habitats and life histories, providing the backbone of information for multi-trait databases. Third, fully resolved phylogenies would be required for deciphering the evolutionary relationships of freshwater organisms. Provided that these three hurdles can be overcome, conducting studies of local freshwater communities across continental spatial extents would pave the way for mapping functionally important ecosystems and evolutionarily valuable areas for the conservation of freshwater organisms and their habitats.