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Assessment, maintenance, and implementation of environmental flow (hereafter e-flow) in rivers and wetlands have been recognized as a vital tool for sustaining freshwater ecosystems in several countries including India. In this view, the paper intends to review the current understanding of e-flow concept in India. This can be accomplished by reviewing case studies reported for different river basins across India and documented literature, legislative and water policy reports, minutes of meetings, workshops, and conferences. with the aim, On the other hand, its aims to briefly trace the history of e-flow assessment studies as well as the progress that has been achieved so far since 1998s. Role of enabling factors and constraints for e-flow implementation in India at a macro scale is also highlighted, which shows e-flow understanding has received considerable attention over the past two decades for the conservation of freshwater ecosystems and is still evolving. This paper also concludes with identifying a range of actions and gives some directions for future research that requires for e-flow implementation in a river basin. [ABSTRACT FROM AUTHOR]

Fish constitutes the main protein source for the Amazonian population. However, the impact of different anthropogenic activities on trace element and metal accumulation in fish and their risks for human health at a regional scale remain largely unexplored. Here we assessed exposure levels of 10 trace elements and metals (Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Pb, and Hg) in 56 samples belonging to 11 different species of fish from the Brazilian Amazon. We studied the relationship between exposure levels, fish origin, and fish feeding habits, and assessed toxicological and carcinogenic risks for the Amazonian population. No significant correlation was found between sampling site and exposure levels to the studied elements, but a significant difference was found between the accumulation of some metals and the position of the fish species in the food chain. The concentrations of Cr and Hg in fish flesh were found to exceed the Brazilian limits for human consumption. This study shows that current fish consumption patterns can lead to estimated daily intakes of Hg, As and Cr that exceed the oral reference dose, thus posing a toxicological concern. Furthermore, carcinogenic risks may be expected due to the continued exposure to Cr and As. The results of this study show that the consumption of wild caught fish in the Amazon region should be controlled. Moreover, continued monitoring of trace element and metal contamination in fish and on the health of the Amazonian population is recommended, particularly for riverine and indigenous communities. [Display omitted] [ABSTRACT FROM AUTHOR]

Antibiotics and herbicides are contaminants of emerging concern in aquatic environments. Lake Villarrica is a relevant freshwater body in Chile and was recently designated a 'saturated nutrient zone'. Here, we investigated the occurrence of multiple antibiotic resistance (MAR) and herbicide catabolic profiles among bacteria present in the surface sediments of Lake Villarrica. The occurrence of antibiotic-resistant genes (ARGs; bla TEM, cat A and tet M) and herbicide-catabolic genes (HCGs; phn J and atzA) was investigated by qPCR. Subsequently, the presence of culturable bacteria with multiple resistance to amoxicillin (AMX), chloramphenicol (CHL) and oxytetracycline (OXT) was studied. Forty-six culturable MAR (AMX + CHL + OXT) strains were isolated and characterized with respect to their resistance to 11 antibiotics by using a disc diffusion assay and testing their ability to use herbicides as a nutrient source. qPCR analyses revealed that ARGs and HCGs were present in all sediment samples (101 to 103 gene copies g−1), with significant (P ≤ 0.05) higher values in sites near Villarrica city and cattle pastures. The plate method was used to recover MAR isolates from sediment (103–106 CFU g−1), and most of the 46 isolates also showed resistance to oxacillin (100%), cefotaxime (83%), erythromycin (96%) and vancomycin (93%). Additionally, 54 and 57% of the MAR isolates were able to grow on agar supplemented (50 mg L−1) with atrazine and glyphosate as nutrient sources, respectively. Most of the MAR isolates were taxonomically close to Pseudomonas (76.1%) and Pantoea (17.4%), particularly those isolated from urbanized sites (Pucón city). This study shows the presence of MAR bacteria with herbicide catabolic activity in sediments, which is valuable for conservation strategies and risk assessments of Lake Villarrica. However, major integrative studies on sediments as reservoirs or on the fate of MAR strains and traces of antibiotics and herbicides as a result of anthropic pressure are still needed. [Display omitted] • Lake sediment bacteria harbor antibiotic–resistance and herbicide–catabolic genes. • 46 multiple antibiotic resistance (MAR) bacteria were isolated from lake sediments. • 54–57% of MAR bacteria can use atrazine or glyphosate as a nutrient source. • 93.5% of MAR bacteria were identified (16S rRNA) as Pseudomonas or Pantoea. [ABSTRACT FROM AUTHOR]

Micro(nano)plastics (MNPs) are pervasive pollutants posing significant environmental and health risks. Selecting appropriate sentinel species to assess MNPs in terrestrial and aquatic environments involves considering factors such as species behavior, habitat, exposure pathways, and the feasibility of sampling. For these reasons, it was imperative to launch a virtual special issue (VSI) in Ecological Indicators. This editorial summarizes the contributions submitted to the VSI, which invited research on bioindicators of MNPs, including sampling protocols, monitoring strategies, and analytical methods, to advance our understanding and management of plastic pollution. The VSI received a total of 12 contributions from four countries, with a significant majority originating from Italy. To present the contributions, we have organized the sections into original articles and reviews. The original articles are further divided into sections on the occurrence of MNPs in biotic and abiotic compartments, the selection of bioindicators, and the effects and risk assessment of MPs. The reviews are categorized based on their focus on aquatic and terrestrial ecosystems. Future ecotoxicology studies should select bioindicators based on exposure to MNPs, conservation status, ecological roles, and human consumption. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are crucial in regulating microbial communities, thereby influencing greenhouse gas (GHG) emissions in freshwater ecosystems. MPs' presence in lake sediment has been confirmed to be aged, necessitating a reassessment of their influence on GHG emissions. This study aims to investigate the impacts of MPs with various aging methods on organic carbon decomposition and GHG release in urban lake sediments. During the four-week duration of the microcosm experiment, the conventional polyethylene (PE) and biodegradable Poly (butylene-adipate-co-terephthalate) (PBAT) MPs were subjected to ultraviolet (UV) radiation, advanced oxidation processes (AOPs) and biological aging methods to investigate their impacts on carbon dioxide (CO 2) and methane (CH 4) emissions from lake sediment. Compared to pristine PE, pristine PBAT significantly exacerbated the detrimental impact on CO 2 and CH 4 emissions by 21.61% and 43.13%, respectively, mainly due to 10% increase in dissolved organic carbon (DOC) and 22.65% increase in microbial biomass carbon (MBC). The surface morphology and functional groups of MPs were changed obviously after aging, thereby influencing the decomposition potential of organic carbon and the capacity of microbial reproduction. The aging process of PBAT reduced the available nutrients for microbial activity due to its rapid degradation, leading to a pronounced inhibitory effect on microbial respiration. Besides, MPs aging altered the microbial relative abundance of phyla Firmicutes , Actinobacteria , as well as families Lutispora and Azospirillaceae , thus exerting influence on capacity and anaerobic proportion of microbial respiration. [Display omitted] • The addition of PBAT aggravated GHG emissions from lake sediment compared to PE. • Aged MPs altered the sediment properties and microbial activity and structure. • The aging process changed the surface morphology and functional groups of MPs. [ABSTRACT FROM AUTHOR]

Cultural eutrophication is the main cause of the decline of submerged plants in freshwater ecosystems. While many studies have focused on the nutrient uptake by the roots of these plants, less attention has been given to the effects of eutrophication on root structure. We designed a mesocosm experiment with Eurasian watermilfoil (Myriophyllum spicatum), a submerged plant indigenous to the Eurasian continent. The responses of plant functional traits, including growth traits, morphological traits and root topological indices, to different nitrogen (N) and phosphorus (P) concentrations were elucidated. We found that high P concentrations suppressed all the morphological traits and reduced the root topological traits, whereas N concentrations had a comparatively minor effect. Although the root branching of M. spicatum did not change, its root topology became more dichotomous with fewer exterior root links being formed in nutrient-rich habitats, and the root form changed from deep and thin to shallow and dense with increasing P concentrations. The root nutrient absorption ability of M. spicatum may decrease with cultural eutrophication, and this change most likely reduces its anchoring ability and increases its sensitivity to dislodge from the sediment if disturbed by hydraulic forces. • The responses of plant traits of Myriophyllum spicatum to different nutrient concentrations were studied. • M. spicatum did not change its root architecture with increasing P concentrations. • Nutrient addition may reduce the anchoring ability of M. spicatum. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • 111 emerging contaminants were identified in Dongting Lake, a typical wetland ecosystem. • Multi-level risk assessment revealed non-negligible mixture toxicity of ECs to biota. • Neonicotinoids identified as main risk contributors via prioritization screening method. • Cropland area and precipitation levels drive ECs distribution and ecological risks. [ABSTRACT FROM AUTHOR]

In recent years, the concern derived from the presence of emerging contaminants in the environment and the possible effects on the One Health trilogy has increased. This study determined the concentration of pharmaceutical contaminants of emerging concern and their relationship with the extracellular enzymatic activity of microbial communities from two rivers in western Cuba. Two sampling stations were analyzed; one in the Almendares River (urban) and the other in the San Juan River (rural), taking into account the pollution sources that arrive at these stations and previous physicochemical characterizations. Extracellular protease, acid phosphatase, alkaline phosphatase, lipase, and catalase activities in water and sediments were determined and correlated with contaminants of emerging concern determined by liquid chromatography with mass spectrometry. This study evidenced the presence of different pharmaceutical contaminants found in the categories of antihypertensives, stimulants, anti-inflammatories, and antibiotics in both rivers. Concentrations of contaminants of emerging concern were greater in the Almendares River compared to the San Juan River. In addition, through the canonical redundancy analysis, the influence of these contaminants on the extracellular enzymatic activities of microbial communities was documented, where in most cases they inhibit protease, phosphatase, and lipase activities and enhance catalase activity in response to oxidative stress. The present investigation constitutes the first report in Cuba of the presence of pharmaceutical contaminants of emerging concern and one of the few works that exist in the Latin American region. [Display omitted] • First determination of pharmaceutical emerging contaminants in Cuban rivers. • Antihypertensives, stimulants, antiinflammatories and antibiotics where detected. • Contaminants of emerging concern inhibit protease, phosphatases and lipase activity. • Contaminants of emerging concern enhance catalase activity. [ABSTRACT FROM AUTHOR]

• Peatlands, land use and lake cover control water color variation in boreal forest streams. • Lake cover and water color exert strong control on stream invertebrate communities. • The effects of lake cover and water color on stream invertebrates are independent. • Strongly lake-influenced streams might be better protected from browning. • The effects of browning are likely similar, irrespective of catchment lake cover. Browning of streams due to increased export of dissolved organic carbon (DOC) and iron has been observed in vast areas of the northern hemisphere with likely adverse ecological effects. Lake basins in stream catchments can moderate DOC export and influence stream communities, which complicates understanding of the effects of DOC. In this study, we explored the independent and interactive effects of water color (proxy for DOC and iron) and catchment lake cover on benthic macroinvertebrate communities in 94 medium-sized boreal forest streams. We first investigated the role of lake basins and other catchment characteristics in controlling water color. We then studied the effects of water color and catchment lake cover on macroinvertebrate community composition, biodiversity, and functional feeding traits. Water color correlated negatively with catchment lake cover, whereas the correlation with peatland cover and drainage intensity was positive. PERMANOVA and GLS analyses indicated that both color and catchment lake cover had a distinct independent effect on invertebrate community composition and community attributes, without significant interactions. Color had an independent negative effect on EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa richness irrespective of lake cover. Increasing water color had negative effect on relative abundance of grazer, but no significant effect on shredder trait, while lake cover had a negative effect on both of the traits. Lake cover exhibited a negative influence on collector-gatherers, and a positive effect on filter feeders, while the predators were positively affected by both factors. The results highlight that water color influences the community structure of boreal stream ecosystems, and the effects are similar regardless of catchment lake cover. Mitigation measures should be emphasized, aimed at reducing DOC and iron runoff, in land use planning and river basin management. [Display omitted] [ABSTRACT FROM AUTHOR]

There is growing concern regarding the lack of evidence on the effects bioplastics may have on natural ecosystems, whilst their production continues to increase as they are considered as a greener alternative to conventional plastics. Most research is limited to investigations of the response of individual taxa under laboratory conditions, with few experiments undertaken at the community or ecosystem scale, either investigating microplastics independently or in combination with other pollutants, such as nutrient enrichment. The aim of this study is to experimentally compare the effects of oil-based (high density polyethylene – HDPE) with those of bio-based biodegradable (polylactic acid – PLA) microplastics and their interaction with nutrient enrichment on freshwater macroinvertebrate communities under seminatural conditions. There were no significant differences in total abundance, alpha and beta diversities, or community composition attributable to the type of microplastics, their concentration, or nutrient enrichment compared with the control. However, there was a significant difference in macroinvertebrate alpha diversity between high concentrations of both microplastic types under ambient nutrient conditions, with lower diversity in communities exposed to HDPE compared with PLA. Nutrient enrichment mediated the effect of microplastic type, such that the diversity of macroinvertebrate communities exposed to HDPE were similar to those communities exposed to PLA. These findings suggest that the effects of microplastic pollution on macroinvertebrate communities are very weak at large-scale settings under seminatural conditions and that these effects might be mediated by the nutrient status of freshwater ecosystems. More research under large-scale, long-term, seminatural settings are needed in order to elucidate the impact of both conventional plastics and bioplastics on natural environments and their interactive effect with other occurring stressors and pollutants. [Display omitted] • Species-specific toxicological effects of MPs were not realised in this study • Microplastic and nutrient pollution did not affect the structure of the communities • Alpha Diversity was higher with PLA compared with HDPE under ambient conditions • Nutrients moderated the difference in diversity of the communities between both MPs [ABSTRACT FROM AUTHOR]

• Benthic macroinvertebrates effects on the efficiency of Floc & Lock are species-dependent. • Chironomid larvae aid in phosphorus removal from water by depositing it in sediment. • Snails resuspend the sediment, reducing the effectiveness of Floc & Lock. • Snails consumed the sedimented flocs within 72 h. • Considering benthic invertebrates is crucial for effective eutrophication management. Anthropogenic activities have led to excessive loading of phosphorus and nitrogen into water bodies, leading to eutrophication and promoting the growth of cyanobacteria, posing a threat to the health of humans and aquatic animals. Techniques such as Floc & Lock have been developed to mitigate eutrophication by reducing phosphorus concentrations in water and preventing algal blooms. However, little attention has been given to the impact of phosphorus resuspension by sediment-associated organisms such as benthic macroinvertebrates, on the effectiveness of this technique. Here, we experimentally evaluated whether the presence of snails Melanoides tuberculata (Müller, 1774) and larvae of Chironomus sancticaroli (Strixino and Strixino, 1981) affects the efficiency of the Floc & Lock technique. Snails and chironomid larvae are benthic macroinvertebrates commonly found in high abundance in eutrophic reservoirs. Specifically, we tested the hypotheses that (i) the presence of benthic macroinvertebrates reduces the efficiency of coagulants and clays in removing phosphorus and algal biomass from the water column, and (ii) this effect is species-dependent, as some organisms such as the snails, revolve the substrate and resuspend sedimented particles, while other ones, such as chironomid larvae, aid in the removal of phosphorus from the water column by depositing them in the sediment. Our findings revealed that the impact of benthic macroinvertebrates on the effectiveness of the Floc & Lock technique is species-dependent. Chironomid larvae positively influenced the efficiency of the technique by aiding in the removal of total phosphorus, soluble reactive phosphorus, and algal biomass from the water column, depositing them in the sediment. In contrast, the presence of snails had the opposite effect, resulting in increased phosphorus concentration and algal biomass in the water. Surprisingly, the snails consumed the flocs formed by the coagulant and clay within a short time interval of 72 h, raising concerns due to the presence of toxic cyanobacterial biomass in these flocs. Our study emphasizes the importance of considering benthic macroinvertebrates and their impact on the effectiveness of eutrophication management techniques. [Display omitted] [ABSTRACT FROM AUTHOR]

Production of engineered carbon-based nanomaterials (CNMs) is rising, with increased risk of release to the environment during production, use, and disposal. This trend highlights a need to understand potential impacts of CNMs on the natural environment. Fullerenes are an emerging class of CNMs that are insoluble in water, and form aggregates that settle quickly, suggesting higher relative vulnerability of aquatic benthic ecosystems. This study assessed eco-toxicity of fullerenes (C60, C70) and the functionalized derivative, phenyl-C61-butyric acid methyl ester (PCBM), on functionally representative benthic organisms in traditional laboratory assays, and evaluated how the potential lethal and sub-lethal effects of fullerenes may indirectly impact benthic ecosystem function, including decomposition, primary productivity and nutrient cycling in lake microcosms with natural sediments. Standard toxicity tests indicated that population growth of Lumbriculus variegatus was reduced at 25 to 150 mg C60 kg−1, but C70 and PCBM did not affect growth or weight of organisms in artificial sediments at 25 mg kg−1. Survivorship and growth were lower in natural sediments with historic contamination, but C60 did not exacerbate this effect. C60 inhibited photosynthesis by the benthic diatom Nitzschia palea , and at high exposure chlorophyll a increased, suggesting a shading response. L. variegatus had strong effects on benthic ecosystem function, especially metabolism and nitrogen cycling, but C60 ≤ 30 mg kg−1 sediment did not influence the role of L. variegatus in driving benthic processes. These observations suggest that at moderate to high concentrations, C60 may directly impact benthic organisms. However, under natural conditions with low to moderate concentrations, C60 has little effect and does not indirectly impact the ecosystem processes maintained by such organisms. These results are a step further towards a better understanding of potential impacts of fullerenes on aquatic ecosystems, and can aid in the development of regulatory policies. Unlabelled Image • Fullerenes are emerging contaminants with unique nano-scale properties. • Benthic organisms and associated biogeochemical cycles face unknown exposure risks. • We assessed effects on model organisms and ecosystem functions in lake microcosms. • Fullerene affected organism growth, but not indirect control of benthic processes. • Results can inform potential risks of using fullerenes in products and technologies. [ABSTRACT FROM AUTHOR]

• Urbanization has an overall negative effect on the diversity of macroinvertebrates. • This finding is based mainly on the study of lotic ecosystems. • Analyses show significant heterogeneity among case studies. • We identified knowledge gaps regarding studied habitats and concepts of diversity. • We provided recommendation for the future research. Understanding the effects of urbanization on the diversity of freshwater macroinvertebrates is an important topic of biodiversity research and has direct conservation relevance. The absence of evidence-based systematic overviews on this topic motivated us to perform meta-analyses and to synthetize the present state of knowledge. We observed significant heterogeneity among individual case studies, reporting negative, neutral and positive effects. As expected, urbanization had an overall negative effect on the diversity of freshwater macroinvertebrates. These results are based mainly on the study of lotic (stream and river) ecosystems because there are insufficient data available for lentic (pond and lake) ecosystems. Compared to individual case studies, the present review reports an evidence-based synthesis for the first time. We identified knowledge gaps regarding case studies reporting the effects of urbanization on pond and lake ecosystems, case studies examining the phylogenetic and functional facets of biodiversity, as well case studies investigating the effect of urbanization on the beta diversity component of macroinvertebrate communities. The identification of these knowledge gaps allowed us to make recommendations for future research: (1) report results on specific taxonomic groups and not only the entire macroinvertebrate community, (2) study the impacts of urbanization on macroinvertebrate diversity in different habitat types and understudied continents, (3) focus on the functional and phylogenetic facets of diversity and (4) examine community differentiation (e.g. beta diversity) in urban freshwater ecosystems. Our results also suggested that the analysis of diversity- environment relationships is crucial for developing macroinvertebrate indicators especially in the increasingly urbanized world. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Annual growth, growth constants, and asymptotic lengths increased downstream. • Rising summer, spring, and winter temperatures positively affected mussel growth. • Rising autumn temperatures negatively affected annual mussel growth. • Growth and temperature relationships suggest that annuli can document climate. • Unio tumidus may be the best species to document long-term temperature changes. Abstract Sclerochronology provides an important and widely used tool to examine annual environmental patterns in marine systems, but few similar tools have been developed to establish ecological indicators in freshwaters on a seasonal scale. Previous work using marine mussels as ecological indicators have practiced shell ashing, acetate peels, and thin sectioning, all of which destroy the specimens. We studied the external annual rings of three freshwater mussel species with clear annual bands from the River Medway, UK, in order to non-invasively investigate the relationship between banding patterns, growth parameters, location, and seasonal water temperatures. We tested the accuracy and precision of this method through repetition of measurements and the reproduction of results through separate agers. Overall, mussels living downstream had higher length-at-age curves, asymptotic lengths (L ∞), and growth constants (k) than those living upstream. In Unio pictorum and Unio tumidus , there was a negative relationship between asymptotic lengths and growth constants, indicating that larger asymptotic lengths took more time to reach. Unio tumidus had the highest asymptotic lengths and the lowest growth constants across sites while Unio pictorum had the lowest asymptotic lengths and the highest growth constants across sites. Anodonta anatina showed simultaneously increasing asymptotic lengths with increasing growth constants and had the highest overall lengths of all three species. Summer water temperatures had the largest positive effect on annual growth, followed by spring and winter water temperatures, while autumnal temperatures had a negative impact on growth. The findings of this study suggest that through their annual banding, freshwater mussels can be used as tools to document historical water temperatures, especially in the warmer months of spring and summer, and can therefore serve as powerful indicators of spatial and temporal patterns in water temperature. Such tools can help infer palaeoclimatic conditions from fossil and subfossil shells, establish baselines for understanding future climatic change, and support conservation efforts aimed at protecting temperature-sensitive taxa. [ABSTRACT FROM AUTHOR]

Nanosized plastics are an emerging concern in freshwater ecosystems, raising the question whether they put freshwater ecological processes at risk. Litter decomposition is a major ecological function in forested streams which is mainly driven by aquatic hyphomycetes. Here we investigated whether increasing concentrations (up to 102.4 mg/L) of nanosized polystyrene plastics (NPPs; 100nm) affect litter decomposition by five widely distributed species of aquatic hyphomycetes. Results showed that average litter decomposition decreased by 8% relative to the control when exposed to 102.4 mg/L NPPs. Aquatic hyphomycete species differed in their sensitivity to NPPs. The greatest inhibition of litter decomposition was found with Tetracladium marchalianum , where it dropped from 37 (control) to 16% (102.4 mg/L of NPP). Overall our study highlights the emerging risks and potential dangers of NPPs to freshwater ecosystem functioning. It also indicates that the impact of NPPs may be species specific. • We examined if nanosized polystyrene plastics (100 nm; NPPs) impacted leaf litter decomposition. • Five species of worldwide-distributed aquatic hyphomycetes were isolated and used in this study. • Fungal species were exposed to increasing concentrations of NPPs and mass loss was measured. • Both concentrations of NPPs and fungal species had an impact on litter decomposition. • Our study provides novel insights on the emerging risks of NPPs to freshwater ecosystem functioning. [ABSTRACT FROM AUTHOR]

Abstract Freshwater ecosystems face many threats in the form of reduced water quantity, poor water quality and the loss of biodiversity. As a result, aquatic biomonitoring tools are required to enable the evaluation of these critical changes. Currently, macroinvertebrate-based indices are globally the most widely used biomonitoring tools in fluvial ecosystems. However, very little is known about the potential effects of changes in taxonomic understanding (updating of classification and nomenclature) or the presence of new non-native species for biotic indices calculation. This is especially relevant given that errors, incorrect classification or exclusion of new/updated nomenclature may affect ecological status evaluations and have direct consequences for the management and conservation of freshwater systems. In this discussion paper the main constraints, challenges and implications of these issues are outlined and case studies from a range of European countries are discussed. However, similar challenges affect rivers and managers globally and will potentially be amplified further in the future. Bioassessment science needs to be open to improvements, and current tools and protocols need to be flexible so that they can be updated and revised rapidly to allow new scientific developments to be integrated. This discussion highlights specific examples and new ideas that may contribute to the future development of aquatic biomonitoring using macroinvertebrates and other faunal and floral groups in riverine ecosystems. Highlights • Biomonitoring tools are required to address new and critical changes to rivers. • Taxonomic constraints and non-native species represent new biomonitoring challenges. • Existing tools need to be flexible so new scientific developments can be integrated. • Mismatches in status classifications may affect management and conservation policies. [ABSTRACT FROM AUTHOR]

Abstract Urban growth is a key process affecting the functioning of natural ecosystems, and consequently the global land-surface process. This work aimed at establishing the link between land cover changes around Harare Metropolitan city and the proliferation of aquatic hyacinth (Eichhornia crassipes) in Lake Chivero. Remotely sensed Landsat series acquired in the year 1973, 1981, 1994, 1998, 2008, 2009 and 2014 was used. Image classification was implemented to map the associated changes over time using discriminant analysis algorithm. Derived thematic land cover maps showed that agricultural land increased from 2% in 1973 to a 5% in 1981 reaching up to 30% in 2014, whereas the city's land area significantly (p < 0.05) increased between 1973 and 1994. However, water hyacinth constantly increased over time. The spatial and temporal resolution of Landsat images detected land cover changes and the proliferation of aquatic hyacinth (Eichhornia crassipes) in the Lake Chivero over time. Highlights • Fast urban expansion is a key factor affecting global climate change. • Remote sensing shows the potential in monitoring and understanding complex urban land use and land cover changes. • Post hoc test showed that water hyacinth can be accurately be discriminated from other land cover types. • Band 4, 5, 6 and 7 of the Landsat series data can be used to successfully map land cover changes. [ABSTRACT FROM AUTHOR]

The potential impacts of metallic nanoparticles (NPs) at environmental levels on freshwater ecosystems cannot be ignored due to their frequent release. The most widely used metallic oxide, ZnO NPs and TiO 2 NPs (100 ng L−1) were applied to explore their single and combined effects on leaf litter decomposition. Although ZnO NPs and TiO 2 NPs alone or in combination increased 22.68%–41.17% of the leaf decomposition rate, they performed different toxic mechanisms in ecological processes. The microbial mass and enzyme activities significantly increased after acute exposure, but significantly decreased after chronic exposure to ZnO NPs. The activity of BG was the most sensitive factor that was decreased by 66.22%, 56.97%, and 39.39% after 21-day exposure to ZnO NPs, TiO 2 NPs, and in combination, respectively. In addition, the analysis of Fourier transform infrared spectroscopy suggested a novel perspective on understanding the promoting mechanism. The promotion effect of ZnO NPs relied on the enhanced decomposition of refractory organics and easily degradable substances due to the contribution of Anguillospora , Pyrenochaetopsis , and Bipolaris. The single exposure to TiO 2 NPs and combined exposure with ZnO NPs promoted microbial mass and hydrolase activities, with the stimulating effect attributed to the enhanced decomposition of soluble substances. Therefore, the results highlight the importance of chemical analysis of decomposed leaves to evaluate the potential threat of metallic NPs to the function of freshwater ecosystems. [Display omitted] • TiO 2 NPs promoted the dissolution of ZnO NPs. • TiO 2 NPs reversed the inhibitory effect of ZnO NPs on microbial activity. • ZnO NPs and TiO 2 NPs promoted leaf litter decomposition with different mechanisms. • ZnO NPs accelerated the decomposition of soluble and refractory substances. • TiO 2 NPs was only beneficial for the decomposition of easily degradable substances. [ABSTRACT FROM AUTHOR]

The Amazon is the largest river by discharge volume and one of the most biodiverse biomes in the world. Lately, there has been a rapid increase of the urban population in the region, which has been translated into a growing emission of organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) into surface water bodies. This study provides the most comprehensive evaluation of the PAH contamination levels in surface waters of the Amazon basin. We investigated the occurrence and potential sources of 16 priority PAHs and characterised their risks for freshwater ecosystems. For this, we took 40 water samples from different sites along the Brazilian part of the Amazon River, including three major tributaries, and smaller rivers crossing the main urban areas. The results of this study show that PAHs are widespread contaminants in rivers of the Brazilian Amazon. The sum of the total concentration of the 16 priority PAHs reached values of 134 ng L−1 in the Amazon River, and 163 ng L−1 near densely populated areas. On the other hand, the total PAH concentration was generally lower in the monitored tributaries. In most samples, the contamination pattern was dominated by high molecular weight PAHs, suggesting a major contribution of pyrogenic sources, although petrogenic contamination was also present in some locations near urban areas. We assessed ecological risks posed by PAH mixtures using a hazard index. The results indicated that PAH contamination is not likely to pose direct toxic effects for Amazonian freshwater organisms, however continued monitoring is recommended near densely populated areas. [Display omitted] • The presence of 16 priority PAHs was investigated in Amazonian surface waters. • PAHs were found in all samples, with total concentrations up to 163 ng L−1. • Higher concentrations were found next to large urban areas. • In most samples, PAH contamination was of pyrogenic origin. • PAHs may not directly harm Amazonian freshwater ecosystems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Incorporate functional metrics into the development of a D-IBI. • Functional metrics differ significantly at the reference and impaired sites. • Most sites are in "Fair" and "Good" states. • The selection of metrics needs to remove the influence of spatial processes. Incorporating functional metrics into the development of a diatom-based index of biotic integrity (D-IBI) is conducive to a more comprehensive assessment of water quality and the degree of external impact on ecosystem function. A D-IBI was developed by incorporating functional metrics to candidate metrics. Four metrics were selected and divided into five levels to evaluate 147 sampling sites. By comparing the D-IBI scores in Thousand Islands Lake (TIL) catchment, we found that the total D-IBI score ranged from 20 to 100 (median was 45). Compared with reference sites, the resource competition of impaired sites was weaker, and the community was more stable. In response to basin damage, we recommend source protection, long-term monitoring, increased hydrological connectivity, and ecological management of small watersheds. For the assessment of water environmental health, we suggest that the functional metrics should be included in the biological assessment, and the candidate metrics that are greatly affected by the dispersal process should be excluded. Moreover, the assessment should be conducted at the multi-dimension level and watershed scale. [ABSTRACT FROM AUTHOR]

The effects of Hg contamination are presumably widespread across the components of aquatic ecosystems, but investigations have been mainly focused on freshwater fish, because this biota represents a major source of Hg for human populations. Yet, the possible bioaccumulation of Hg on other freshwater meso- and apex-predators (e.g., amphibians, reptiles) has been largely overlooked, especially in Western Europe. In this study, the determinants of Hg concentrations were assessed for the viperine snake ( Natrix maura ) across 6 populations (>130 individuals sampled in 2016 and 2017) in France and Spain. Specifically, body size, sex, and diet were compared with Hg concentrations measured in ventral scales. Overall, N. maura accumulated Hg in their scales. Sex did not seem to influence Hg concentrations in this species. Significant differences in Hg concentrations were observed between study sites, and these differences were likely to be mediated by site-specific diet. Frog-eating individuals were characterized not only by lower mean values of Hg (0.194 ± 0.018 μg·g −1 versus 0.386 ± 0.032 μg·g −1 for piscivorous individuals), but also by weaker slopes of the body size-Hg relationship as compared to fish-eating snakes, suggesting strong differences in accumulation rates due to food resources. Importantly, the highest slope of the body size-Hg relationship and the highest values of Hg were found in individuals foraging on trout raised by a fish farm, suggesting that fish farming may contribute to Hg contamination in inland freshwater systems. Finally, our results are compared with data on Hg concentrations in other species of aquatic snakes, in order to provide a comparative point for future studies. [ABSTRACT FROM AUTHOR]

Decaying experiments of four major aquatic macrophyte detritus, namely cattail ( Typha orientalis ), water lettuce ( Pistia stratiotes ), hydrilla ( Hydrilla verticillata ) and maidencane ( Panicum hemitomon ), were conducted using the litterbag technique in the stormwater detention pond of South Florida, USA. Dry weight and chemical composition of remaining biomass were dynamically determined during the 185-day decay experiment. The results showed that decomposition rates ( k ), and the derived turnover ( t 50% and t 95% ) were species specific. The k values decreased in the order of hydrilla (0.0123 g day −1 ) > water lettuce (0.0082 g day −1 ) > maidencane (0.0049 g day −1 ) > cattail (0.0031 g day −1 ), whereas t 50% and t 95% varied in the reverse way. Biomass properties including concentrations of C, N, P, lignin, cellulose, hemicellulose, and the ratios of C/N, C/P, N/P and lignin/N affected decaying rate of the studied aquatic plants. The dry mass loss and concentrations of C, N, P, lead (Pb), chromium (Cr), copper (Cu), manganese (Mn), zinc (Zn), lignin, cellulose, hemicellulose and ratios C/N, C/P, N/P and Lignin/N of plant detritus were significantly affected by species, decaying time, and their interactions. However, the influence of species differences was greater than that of decaying time on those indexes. The estimated amounts (kg) of nutrients and metals released based on k values for the waterways of the IRL basin (water surface area 15.6 km 2 ) were N 126.85 × 10 3 , P 8.89 × 10 3 , Zn 408.20, Pb 97.95, Cr 128.99, Mn 313.03, and Cu 82.40. Water lettuce contributed most, accounting for 52.13% N, 56.81% P, 74.95% Zn, 59.58% Pb, and 74.65% Mn, followed by hydrilla, cattail and maidencane. For Cr and Cu, cattail had the greatest contribution of 65.77% and 54.15%, respectively, followed by water lettuce, hydrilla and maidencane. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems sustain human society through the provision of a range of services. However, the status of these ecosystems is threatened by a multitude of pressures, including point sources of wastewater. Future treatment of wastewater will increasingly require new forms of decentralised infrastructure. The research reported here sought to enhance pollutant removal within a novel wastewater treatment technology, based on un-planted, artificially aerated, horizontal subsurface flow constructed wetlands. The potential for these systems to treat de-icer contaminated runoff from airports, a source of wastewater that is likely to grow in importance alongside the expansion of air travel and under future climate scenarios, was evaluated. A new configuration for the delivery of air to aerated treatment systems was developed and tested, based on a phased-aeration approach. This new aeration approach significantly improved pollutant removal efficiency compared to alternative aeration configurations, achieving >90% removal of influent load for COD, BOD 5 and TOC. Optimised operating conditions under phased aeration were also determined. Based on a hydraulic retention time of 1.5 d and a pollutant mass loading rate of 0.10 kg d −1  m −2 BOD 5 , >95% BOD 5 removal, alongside final effluent BOD 5 concentrations <21 mg L −1 , could be achieved from an influent characterised by a BOD 5 concentration > 800 mg L −1 . Key controls on oxygen transfer efficiency within the aerated treatment system were also determined, revealing that standard oxygen transfer efficiency was inversely related to aeration rate between 1 L and 3 L min −1 and positively related to bed media depth between 1500 mm and 3000 mm. The research reported here highlights the potential for optimisation and subsequent widespread application of the aerated wetland technology, in order to protect and restore freshwater ecosystems and the services that they provide to human society. [ABSTRACT FROM AUTHOR]

Degradation of freshwater ecosystems and the services they provide is a primary cause of increasing water insecurity, raising the need for integrated solutions to freshwater management. While methods for characterizing the multi-faceted challenges of managing freshwater ecosystems abound, they tend to emphasize either social or ecological dimensions and fall short of being truly integrative. This paper suggests that management for sustainability of freshwater systems needs to consider the linkages between human water uses, freshwater ecosystems and governance. We present a conceptualization of freshwater resources as part of an integrated social-ecological system and propose a set of corresponding indicators to monitor freshwater ecosystem health and to highlight priorities for management. We demonstrate an application of this new framework —the Freshwater Health Index (FHI) — in the Dongjiang River Basin in southern China, where stakeholders are addressing multiple and conflicting freshwater demands. By combining empirical and modeled datasets with surveys to gauge stakeholders' preferences and elicit expert information about governance mechanisms, the FHI helps stakeholders understand the status of freshwater ecosystems in their basin, how ecosystems are being manipulated to enhance or decrease water-related services, and how well the existing water resource management regime is equipped to govern these dynamics over time. This framework helps to operationalize a truly integrated approach to water resource management by recognizing the interplay between governance, stakeholders, freshwater ecosystems and the services they provide. [ABSTRACT FROM AUTHOR]

This study seeks to understand the general distribution of virome abundance and diversity in tropical freshwater ecosystems in Singapore and the geospatial distribution of the virome under different landuse patterns. Correlations between diversity, environmental parameters and land use patterns were analyzed and significant correlations were highlighted. Overall, the majority (65.5%) of the annotated virome belonged to bacteriophages. The percentage of Caudovirales was higher in reservoirs whereas the percentages of Dicistroviridae , Microviridae and Circoviridae were higher in tributaries. Reservoirs showed a higher Shannon-index virome diversity compared to upstream tributaries. Land use (urbanized, agriculture and parkland areas) influenced the characteristics of the virome distribution pattern. Dicistroviridae and Microviridae were enriched in urbanized tributaries while Mimiviridae, Phycodnaviridae , Siphoviridae and Podoviridae were enriched in parkland reservoirs. Several sequences closely related to the emerging zoonotic virus, cyclovirus, and the human-related virus (human picobirnavirus), were also detected. In addition, the relative abundance of PMMoV (pepper mild mottle virus) sequences was significantly correlated with RT-qPCR measurements (0.588 < r < 0.879, p < 0.05). This study shows that spatial factors (e.g., reservoirs/tributaries, land use) are the main drivers of the viral community structure in tropical freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Climate change impact on species is commonly assessed by predicting species' range change, a measure of a species' extrinsic exposure. However, this is only one dimension of species' vulnerability to climate change. Spatial arrangement of suitable habitats (e.g., fragmentation), their degree of protection or human disturbance, as well as species' intrinsic sensitivity, such as climatic tolerances, are often neglected. Here, we consider components of species' intrinsic sensitivity to climate change (climatic niche specialization and marginality) together with components of extrinsic exposure (changes in range extent, fragmentation, coverage of protected areas, and human footprint) to develop an integrated vulnerability index to climate change for world's freshwater otters. As top freshwater predators, otters are among the most vulnerable mammals, with most species being threatened by habitat loss and degradation. All dimensions of climate change exposure were based on present and future predictions of species distributions. Annual mean temperature, mean diurnal temperature range, mean temperature of the wettest quarter, precipitation during the wettest quarter, and precipitation seasonality prove the most important variables for otters . All species are vulnerable to climate change, with global vulnerability index ranging from −0.19 for Lontra longicaudis to −36,9 for Aonyx congicus . However, we found that, for a given species, climate change can have both positive and negative effects on different components of extrinsic exposure, and that measures of species' sensitivity are not necessarily congruent with measures of exposure. For instance, the range of all African species would be negatively affected by climate change, but their different sensitivity offers a more ( Hydrictis maculicollis , Aonyx capensis ) or less ( Aonyx congicus ) pessimistic perspective on their ability to cope with climate change. Also, highly sensitive species like the South-American Pteronura brasiliensis , Lontra provocax , and Lutra perspicillata might face no exposure to climate change. For the Asian Lutra sumatrana , climate change would instead lead to an increased, less fragmented, and more protected range extent, but the range extent would also be shifted into areas with higher human disturbances. Our study represents a balanced example of how to develop an index aimed at comparatively evaluating vulnerability to climate change of different species by combining different aspects of sensitivity and exposure, providing additional information on which to base more efficient conservation strategies. [ABSTRACT FROM AUTHOR]

Thermal quality in river ecosystems is a fundamental property for the development of biological processes and many of the human activities linked to the aquatic environment. In the future, this property is going to be threatened due to global change impacts, and basin managers will need useful tools to evaluate these impacts. Currently, future projections in temperature modelling are based on the historical data for air and water temperatures, and the relationship with past temperature scenarios; however, this represents a problem when evaluating future scenarios with new thermal impacts. Here, we analysed the thermal impacts produced by several human activities, and linked them with the decoupling degree of the thermal transfer mechanism from natural systems measured with frequency analysis tools (wavelet coherence). Once this relationship has been established we develop a new methodology for simulating different thermal impacts scenarios in order to project them into future. Finally, we validate this methodology using a site that changed its thermal quality during the studied period due to human impacts. Results showed a high correlation (r 2 = 0.84) between the decoupling degree of the thermal transfer mechanisms and the quantified human impacts, obtaining 3 thermal impact scenarios. Furthermore, the graphic representation of these thermal scenarios with its wavelet coherence spectrums showed the impacts of an extreme drought period and the agricultural management. The inter-conversion between the scenarios gave high morphological similarities in the obtained wavelet coherence spectrums, and the validation process clearly showed high efficiency of the developed model against old methodologies when comparing with Nash-Stucliffe criterion. Although there is need for further investigation with different climatic and anthropic management conditions, the developed frequency models could be useful in decision-making processes by managers when faced with future global change impacts. [ABSTRACT FROM AUTHOR]

Large protected areas have been created in Brazilian Amazon intending to safeguard as much of its biodiversity as possible. Despite these intentions, such megareserves were created predominantly focusing on terrestrial organisms and ecosystems. Here, we assessed the ability of the current Brazilian Amazon protected areas network to efficiently safeguard its stream-dwelling fish fauna. Ecological niche models were built for 138 stream fish species using MaxEnt software. We performed a gap analysis and spatial prioritization under three different Amazon protected areas scenarios: (1) strictly protected areas (SPAs) only; (2) SPA plus sustainable use areas (SPA + SUA); and (3) SPA + SUA plus indigenous territories (SPA + SUA + IT). The species were classified according to their distribution range size and required representation targets. Widespread species usually had lower area under the curve (AUC) and true skill statistics (TSS) values, which would be expected for large and heterogeneous areas such as the Amazon. Only partial gap species were found, with 20% to 90% of required representation targets included in PAs, which was not enough for a complete protection. Most of the officially protected areas in the Brazilian Amazon do not correspond to areas with high direct conservation values for stream fishes, once the priority areas for these species conservation were outside the PAs, leaving a high portion of the regional vertebrate fauna inadequately protected. We conclude that fishes and other freshwater organisms and habitats should be explicitly included during systematic conservation planning in order to thoroughly protect the Brazilian Amazon biodiversity. [ABSTRACT FROM AUTHOR]

Land use and climate change are increasingly important stressors affecting freshwater ecosystems. Although their effects on freshwater organisms have been widely studied, most studies applied traditional statistical methods, which only focus on single stressor and simple cause-effect relationships without considering the complex interactions among stressors. Therefore, we developed an integrated method by combining Structure Equation Modeling (SEM) and Bayesian Networks (BNs) to estimate the interactive effect of land use and climate change on freshwater macroinvertebrates. A field investigation was conducted in August 2009 in Taizi River Basin, Northeast China, and samples of stream macroinverterbates and water chemistry were collected from 211 sites. The SEM-BN models were developed to explore the complex relationships among land use cover (crop, forest and residential land), water quality (total phosphorus, total nitrogen and dissolved oxygen), physical factors influenced by climate change (water temperature, flow velocity), other habitat characteristics (slope and substrate composition) and macroinvertebrate EPT (Ephemeroptera, Plecoptera and Trichoptera) indices (the percentage of EPT taxa, EPT richness, EPT abundance and the Shannon-Weiner Diversity Index of EPT). Three scenarios were designed to assess the possible responses of EPT indices to land use change, climate change and their interactions. Our results showed that when the change of land use and climate were considered alone, increasing crop and urban land led to declines in EPT indices whereas moderate rise of air temperature and more rainfall had opposite effects. However, the combined effect showed that the positive effects caused by climate change could weaken some negative effects, but land use change still had stronger effect on EPT indices. Our results provided more detailed understanding on how environmental stressors affect freshwater organisms, and further catchment management should integrate the combined effect of different environmental stressors on streams. [ABSTRACT FROM AUTHOR]

Despite the worldwide concern over the impact of microplastics (MPs) and associated organic contaminants, the information regarding the occurrence and characteristics of these emerging class of pollutants is limited in freshwater environment. We present data on the distribution and concentration levels of MPs and phthalate esters (PAEs) from Rewalsar Lake, a shallow eutrophic lake in Northwest Himalaya. The MPs were identified in all samples, with concentration of 13–238 particles L−1 and 750 to 3020 particles kg−1 dry weight (dw) in surface water and sediments respectively. Majority of MPs were dominated by polystyrene, polyethylene, polypropylene polymers that principally occurred in the form of pellets and fragments. The MPs distribution was different among sampling sites, being more abundant to sites in the proximity of domestic sewage effluents and high level of religious and tourist activities. The di-isobutyl phthalate, dibutyl phthalate (DBP) and its branched isomer, di(2-ethylhexyl) phthalate (DEHP) are the identified PAE congeners in sediments, and the measured total concentrations of Σ 3 PAE ranged from 1.69 μg/g to 4.03 μg/g dw. Notably, concentration values of DEHP were higher as compared to other detected phthalates, and exceeded recommended environmental risk limit. The findings of this study emphasize the requirement for proper waste management measures in the region to reduce entry of these pollutants into the ecosystem. Further, this work contributes to the understanding of MPs and PAEs potential contamination profiles and sources in freshwater environments, and provides valuable information for future management decisions. [Display omitted] • Microplastics and phthalate compounds were ubiquitous in the Rewalsar Lake. • The microplastic abundance was higher at the marginal areas. • Polystyrene, polyethylene and polypropylene are abundant polymers. • The PAE congeners identified in surface sediments were DIBP, DBP and DEHP. • The high concentration levels of DEHP in sediments posed a high potential environmental risk. [ABSTRACT FROM AUTHOR]

More recently, the number of studies on the impacts of microplastics (MPs) on plants has drawn attention considerably. However, many of these studies focused on terrestrial plants, with vascular plants from freshwater ecosystems being little studied. Thus, we aimed to evaluate the possible effects of exposure of Salvinia auriculata , for 28 days, to different concentrations of polyethylene MPs (PE MPs – diameter: 35.46 ± 18.17 µm) (2.7 ×108 and 8.1 ×108 particles/m3), using different biomarkers. Our data indicated that exposure to PE MPs caused alterations in plant growth/development (inferred by the lower floating frond number, "root" length, and the number of "roots"), as well as lower dispersion of individuals in the experimental units. Plants exposed to PE MPs also showed lower epidermal thickness (abaxial leaf face) and a longer length of the central leaf vein and vascular bundle area. Ultrastructural analyses of S. auriculata exposed to MPs revealed rupture of some epidermal cells and trichomes on the adaxial and abaxial, leaf necrosis, and chlorosis. In the "roots", we observed dehydrated filamentous structures with evident deformations in plants exposed to the pollutants. Both on the abaxial leaf face and on the "roots", the adherence of PE MPs was observed. Furthermore, exposure to PE MPs induced lower chlorophyll content, cell membrane damage, and redox imbalance, marked by reduced catalase and superoxide dismutase activity and increased production of reactive oxygen and nitrogen species as well as malondialdehyde. However, in general, we did not observe the dose-response effect for the evaluated biomarkers. The values of the integrated biomarker response index, the principal component analysis (PCA) results and the hierarchical clustering analysis confirmed the similarity between the responses of plants exposed to different PE MPs concentrations. Therefore, our study sheds light on how PE MPs can affect S. auriculata and reinforces that putting these pollutants in freshwater environments might be hazardous from an ecotoxicological point of view. [Display omitted] • Exposure to PE MPs affects the growth and development of Salvinia auriculata. • Histomorphological changes are induced by exposure to PE MPs in S. auriculata. • Antioxidant activity is reduced in S. auriculata exposed to PE MPs. • PE MPs induces oxidative and nitrosative stress in S. auriculata. • PE MPs adheres to leaf and root structures of S. auriculata. [ABSTRACT FROM AUTHOR]

Frequent drying of ponded water, and support of unique, highly specialized assemblages of often rare species, characterize temporary wetlands, such as vernal pools, gilgais, and prairie potholes. As small aquatic features embedded in a terrestrial landscape, temporary wetlands enhance biodiversity and provide aesthetic, biogeochemical, and hydrologic functions. Challenges to conserving temporary wetlands include the need to: (1) integrate freshwater and terrestrial biodiversity priorities; (2) conserve entire ‘pondscapes’ defined by connections to other aquatic and terrestrial systems; (3) maintain natural heterogeneity in environmental gradients across and within wetlands, especially gradients in hydroperiod; (4) address economic impact on landowners and developers; (5) act without complete inventories of these wetlands; and (6) work within limited or non-existent regulatory protections. Because temporary wetlands function as integral landscape components, not singly as isolated entities, their cumulative loss is ecologically detrimental yet not currently part of the conservation calculus. We highlight approaches that use strategies for conserving temporary wetlands in increasingly human-dominated landscapes that integrate top-down management and bottom-up collaborative approaches. Diverse conservation activities (including education, inventory, protection, sustainable management, and restoration) that reduce landowner and manager costs while achieving desired ecological objectives will have the greatest probability of success in meeting conservation goals. [ABSTRACT FROM AUTHOR]

Detecting and monitoring the spatial distribution, configuration and propagation rates of aquatic water weeds (i.e. water hyacinth ) in freshwater ecosystems, is arguably important to water resources managers, hydrologists and policy makers, for sustainable water resources management and planning purposes. The principal objective of this work was to develop a model that can satisfactorily detect and map the spatial distribution and configuration of water hyacinth ( Eichhornia crassipes ) in freshwater ecosystems, using both visible, near-infrared and thermal band information derived from the Landsat 8 multispectral sensor. Statistical analysis was done, using two machine learning classification ensembles, which are the Discriminant Analysis (DA) and Partial Least Squares Discriminant Analysis (PLS-DA). Our results have shown that the spatial distribution and configuration of water hyacinth can be accurately detected and mapped with an overall classification accuracy of 95% using Landsat 8 data. The results have further shown that the different growing stages (i.e. young, intermediate and old water hyacinth) could be spectrally detected and mapped, using the new Landsat 8 sensor. In addition, the findings of this study have demonstrated that Landsat 8 bands 5, 6, 7, 8, 10 and 11 are the most influential in detecting and mapping water hyacinth in freshwater ecosystems. Furthermore, allocation of agreement results showed that the DA classification algorithm outperformed PLS-DA in the detection and mapping the distribution and spatial configuration of water hyacinth in freshwater ecosystems. Overall, the derived water hyacinth maps provide critical information required for the development of effective and robust water hyacinth control and eradication programmes. [ABSTRACT FROM AUTHOR]

One method with considerable potential for understanding fishing and environmental impacts on fish assemblages is size spectra (SS) and diversity size spectra (DSS) analysis—a regression of Ln abundance or Shannon diversity against the natural logarithm of body size of fish assemblages. But the usefulness of this method for application to tropical freshwater fish assemblages is uncertain. Here, we assessed the extent to which SS and DSS analyses explained changes in the exploited fish assemblage related to fishing effort and river droughts. To do this, we used correlation analyses on historical datasets of river water level, fishing effort, and fish length measurements for 56 fish species in three of the largest rivers of the Amazon Basin. In calculating the SS and DSS analysis statistics, we found that linear regressions adjusted well to the diversity and Ln(abundance) data plotted against Ln(fork length). In analysing SS and DSS statistics in relation to fishing and environmental impacts, we found that the slope of SS was negatively correlated to drought intensity with a lag of zero years in all rivers. The slope of SS also was negatively correlated to fishing effort with a lag of three years in two rivers and a lag of two years in one year. The slope of DSS was not correlated to drought intensity and fishing effort in any of the rivers. Our results provide support for the use of SS analysis to investigate fishing and environmental effects on exploited fish assemblages in tropical freshwater environments. [ABSTRACT FROM AUTHOR]

Recently, biodegradable plastics (BPs) are emerging as a sustainable alternative to traditional plastics. When released into an aquatic environment, the biodegradable performance of BPs is influenced by biochemical processes, especially the developed plastisphere. However, studies addressing the biodegrading capacity of BPs and traditional plastics within the plastisphere are still limited. Here, we investigated plastisphere community variations and their capacity to biodegrade polyethylene terephthalate (PET) and starch-based plastics (SBP) for four time periods (15, 30, 45, and 80 days) in three freshwaters. Unexpectedly, there is no significant difference in the microbial communities and network structure of the plastisphere between SBP and PET. Moreover, SBP tended to age rapidly at the early stage (0–15 days), while the aging degree of SBP and PET did not display an obvious difference at 80 days. Partial least squares path modeling suggested that plastic aging was mainly dominated by keystone taxa of network and aquatic environmental factors. These results suggest that the aging rate of commercial BPs may not be as fast as we imagine in freshwaters (SBP ≈ PET), and the environmental behaviors of BPs in the aquatic environment should be paid more attention to. [Display omitted] • Studied effects of microbial succession on aging of BPs and PET in freshwaters. • Similar microbial community and structure of plastisphere observed on SBP and PET. • Similar aging degree of SBP and PET was observed at 80 days in freshwaters. • Microbial keystone taxa and environmental factors co-dominated the plastic aging. [ABSTRACT FROM AUTHOR]

• We develop an integrated method for assessing lake ecosystem health. • Lake ecosystem degradation shows clear spatial heterogeneity patterns in East China. • Identifying the nonlinear contribution of multiple stressors to lake degradation. • Lake ecosystem health is significantly influenced by its distance from the city. Freshwater lake ecosystems face unprecedented challenges with escalating anthropogenic pressure worldwide. An improved understanding of how environmental and socioeconomic factors impact lake health is crucial for strategic conservation and management. Here, we compiled data from 85 lakes from China's most densely populated regions and proposed an integrated index to examine spatial patterns of lake ecosystem health. We further evaluated how 16 socioeconomic drivers and environmental conditions drive these changes by using the Bayesian hierarchical model and Gradient boosting decision tree models. Our results suggest the integrated index can provide a comprehensive picture of lake ecosystem quality from a systems perspective combining water bodies and lakeshore zones. We find that lake degradation shows clear spatial heterogeneity patterns given the common forcings associated with climate factors and land-use practices within this region. We further reveal the non-linear relationships between the social and economic factors (distance, population, food production, gross domestic product [GDP], etc.) and lake ecology, and find that distance of the lake from the city center was the predominant factor that influenced the lake system health among these multiple drivers. This study contributes to the understanding of the differences and driving mechanisms of lake ecological degradation in areas of high human activity as a basis for further identifying environmental conflicts and recommendations to improve the state of lake ecosystems. [ABSTRACT FROM AUTHOR]

The plastisphere has been widely studied in the oceans; however, there is little information on how living organisms interact with the plastisphere in freshwater ecosystems, and particularly on how this interaction changes over time. We have characterized, over one year, the evolution of the eukaryotic and bacterial communities colonizing four everyday plastic items deployed in two sites of the same river with different anthropogenic impact. α-diversity analyses showed that site had a significant role in bacterial and eukaryotic diversity, with the most impacted site having higher values of the Shannon diversity index. β-diversity analyses showed that site explained most of the sample variation followed by substrate type (i.e., plastic item) and time since first colonization. In this regard, core microbiomes/biomes in each plastic at 1, 3, 6 and 12 months could be identified at genus level, giving a global overview of the evolution of the plastisphere over time. The measured concentration of antibiotics in the river water positively correlated with the abundance of antibiotic resistance genes (ARGs) on the plastics. These results provide relevant information on the temporal dynamics of the plastisphere in freshwater ecosystems and emphasize the potential contribution of plastic items to the global spread of antibiotic resistance. [Display omitted] • The evolution of microbial communities in the plastisphere was studied for one year. • Site, substrate, and colonization time were relevant in shaping the plastisphere. • Core microbiome/biomes could be identified in each plastic item along time. • Everyday plastic items can be considered reservoirs of antibiotic resistance genes. [ABSTRACT FROM AUTHOR]

• Bacterial succession affects biodegrading BPs and non-BPs within freshwaters. • Plastic type potentially influences plastisphere succession. • Biodegrading plastisphere reached faster to mature phase. • BPs have the ability to gather the potentially degradable microorganisms. Plastics in the environment provide a new and unique habitat for microorganisms - known as the plastisphere. The microbial succession within the plastisphere and their potentials for plastic degradation in freshwater ecosystems is still not clear. Here, we investigated variation of microbial communities in plastisphere and their capacity to biodegrade non-biodegradable plastics (non-BPs), i.e., polypropylene (PP) and polyethylene (PE), and biodegradable plastics (BPs), i.e., polylactic acid+polybutylene adipate-co-terephthalate (PLA+PBAT) for four-time periods (15, 30, 45, and 80 days) in three freshwaters. Results showed that the aging degree of plastics increased with succession of plastisphere, with higher degradation rates of BP blends than those of non-BPs. High-throughput sequencing from 112 biofilm samples revealed that bacterial and fungal community structure of the plastisphere were potentially affected by plastic types and gradually converge during biofilm succession. The plastisphere of BPs reached the mature phase more quickly than those of non-BPs and increased co-exclusion to complete for resources. Furthermore, ecological networks involving plastic aging indices, environmental factors and bacterial and fungal operational taxonomic units were established. Ecological networks revealed that BPs may pose the ability to attract and retain key microorganisms (of the orders Bacillales, Myxococcales and Xanthomonadales) that significantly influence community composition such that biodegradative functions were increased in freshwaters. [Display omitted] [ABSTRACT FROM AUTHOR]

Multiple stressors threaten biodiversity and ecosystem integrity, imposing new challenges to ecosystem management and restoration. Ecosystem managers are required to address and mitigate the impact of multiple stressors, yet the knowledge required to disentangle multiple-stressor effects is still incomplete. Experimental studies have advanced the understanding of single and combined stressor effects, but there is a lack of a robust analytical framework, to address the impact of multiple stressors based on monitoring data. Since 2000, the monitoring of Europe's waters has resulted in a vast amount of biological and environmental (stressor) data of about 120,000 water bodies. For many reasons, this data is rarely exploited in the multiple-stressor context, probably because of its rather heterogeneous nature: stressors vary and are mixed with broad-scale proxies of environmental stress (e.g. land cover), missing values and zero-inflated data limit the application of statistical methods and biological indicators are often aggregated (e.g. taxon richness) and do not respond stressor-specific. Here, we present a ‘cookbook’ to analyse the biological response to multiple stressors using data from biomonitoring schemes. Our ‘cookbook’ includes guidance for the analytical process and the interpretation of results. The ‘cookbook’ is accompanied by scripts, which allow the user to run a stepwise analysis based on his/her own data in R, an open-source language and environment for statistical computing and graphics. Using simulated and real data, we show that the recommended procedure is capable of identifying stressor hierarchy (importance) and interaction in large datasets. We recommend a minimum number of 150 independent observations and a minimum stressor gradient length of 75% (of the most relevant stressor's gradient in nature), to be able to reliably rank the stressor's importance, detect relevant interactions and estimate their standardised effect size. We conclude with a brief discussion of the advantages and limitations of this protocol. [ABSTRACT FROM AUTHOR]

Global change is transforming freshwater ecosystems, mainly through changes in basin flow dynamics. This study assessed how the combination of climate change and human management of river flow impacts metabolism of the Ebro River (the largest river basin in Spain, 86,100 km 2 ), assessed as gross primary production—GPP—and ecosystem respiration—ER. In order to investigate the influence of global change on freshwater ecosystems, an analysis of trends and frequencies from 25 sampling sites of the Ebro river basin was conducted. For this purpose, we examined the effect of anthropogenic flow control on river metabolism with a Granger causality study; simultaneously, took into account the effects of climate change, a period of extraordinary drought (largest in past 140 years). We identified periods of sudden flow changes resulting from both human management and global climate effects. From 1998 to 2012, the Ebro River basin was trending toward a more autotrophic condition indicated by P/R ratio. Particularly, the results show that floods that occurred after long periods of low flows had a dramatic impact on the respiration (i.e., mineralization) capacity of the river. This approach allowed for a detailed characterization of the relationships between river metabolism and drought impacts at the watershed level. These findings may allow for a better understanding of the ecological impacts provoked by flow management, thus contributing to maintain the health of freshwater communities and ecosystem services that rely on their integrity. [ABSTRACT FROM AUTHOR]