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Wetland ecosystems are vital for both biodiversity and communities that depend on them. The Ligawasan Marsh in the southern part of the Philippines is one of the most threatened wetlands in the country. Apart from increasing anthropogenic development, wetlands have faced warfare-driven threats that have hindered research and conservation efforts in the area for many decades. Our study is the first to investigate the patterns of physicochemical parameters, patterns of land use cover, and the relationship between land use change and marshland environmental status. We also developed the Marshland Impact Area (MARia) index to assess the potential impact contributions of the surrounding towns. We found a strong negative correlation between dissolved oxygen (DO) and indicators of pollution such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), and heavy metals. Interestingly, we observed elevated levels of phosphate and mercury at all sampling sites in the Ligawasan Marsh. Our landscape-level modelling showed that these elevated levels are associated with expanding croplands and urbanisation surrounding the marsh. We found that the potential impact contribution of cropland and urbanisation from surrounding towns of the Ligawasan Marsh varied significantly, suggesting the importance of implementing local policies to reduce land use change impacts. With the current yet remaims limited knowledge and beyond safe pollution levels in the Ligawasan Marsh, it is crucial to implement collaborative and science-based governance to integrate conservation initiatives with the priorities of global targets, such as the Kunming-Montreal Global Biodiversity Framework, for a comprehensive and sustainable approach to Ligawasan Marsh conservation. [ABSTRACT FROM AUTHOR]

The present study recorded a total of 30 species of diving beetles (Dytiscidae) under 12 genera and 5 subfamilies from the central region of Kerala State, India, of which Copelatus neelumae, Hydaticus discindens, Hydaticus incertus, Sandracottus festivus, Hydrovatus picipennis, Hydroglyphus pendjabensis, Clypeodytes bufo, Microdytes cameroni cf., Laccophilus auropictus cf., Laccophilus elegans and Cybister tripunctatus lateralis are new records to Kerala. The genus Clypeodytes is a first report from Kerala. Hydrovatus picipennis and Hydaticus incertus are new reports from South India. Short diagnoses of the new records are provided. A checklist of 62 species of diving beetles of Kerala is furnished by compiling the 30 species from this study with previous relevant studies. The updated checklist has 11 additions. A brief account of habitat preference and co-existence among Dytiscidae and an identification key for 30 species of diving beetles from the study area is provided. [ABSTRACT FROM AUTHOR]

Mediterranean high-mountain lakes are being increasingly affected by strong Saharan dust deposition events. However, the ecological impacts of these severe atmospheric episodes remain largely unknown. We examined the effects of a strong Saharan dust intrusion to the Iberian Peninsula in 2022 on the physicochemical parameters and prokaryotic communities in sediments of nine high-mountain lakes of Sierra Nevada (Spain) located above 2800 m.a.s.l and in different orientations (north vs. south). A previous year (2021), with lower Saharan dust deposition with respect to 2022, was used for interannual comparisons. The strong dust deposition to the high-mountain lakes resulted in a significant increase in sediment nutrient availability which was linked to changes in the composition of prokaryotic communities. Decreases in alpha diversity and changes in beta diversity of prokaryotic communities were mainly observed in lakes located in the south compared to the north orientation likely because the former was more affected by the atmospheric dust deposition episode. Dust intrusion to the high-mountain lakes resulted in significant changes in the relative abundance of specific genera involved in important nutrient cycling processes such as phosphate solubilization, nitrogen fixation, nitrification, and denitrification. Saharan dust deposition also increased predicted microbial functionality in all lakes. Our findings show that severe atmospheric dust inputs to remote high-mountain lakes of Sierra Nevada can have significant biogeochemical and biodiversity consequences through changes in nutrient availability and prokaryotic communities in sediments of these freshwater ecosystems. This information contributes to understanding how Mediterranean high-mountain lakes of Sierra Nevada face strong intrusions of Saharan dust and their ecological consequences. [ABSTRACT FROM AUTHOR]

Riverine environments host diverse microbial communities, exhibiting distinctive assemblies at both microscopic and macroscopic levels. Despite the complexity of microbial life in rivers, the underlying factors that shape the community structure across different compartments remain elusive. Herein, we characterized microbial community composition of biofilm and planktonic (water column) compartments in five naturally saline inland streams and a freshwater stream to examine changes in microbial communities following salinization via sequencing of the microbial 16S rRNA gene. Significant differences in specific conductivity, oxidation–reduction potential, dissolved oxygen, and pH among the sampled streams were measured, as were significant differences in the microbial community composition between the planktonic and biofilm. The bacterial families Bacillaceae, Vicinamibacterceae, and Micrococcaceae were significantly more abundant in the biofilm compartment, while Methylophilaceae, Alcaligenaceae, Spirosomaceae, Burkholderiaceae, and Comamonadaceae were more abundant in the planktonic compartment. In addition, salinity (based on specific conductivity) influenced the microbial community composition in both compartments, with higher sensitivity of the planktonic compartment. Increases in the bacterial families Shewanellaceae, Marinomonadaceae, and Saccharospirillaceae or loss of Anaeromyxobacteraceae could be indicative of increased salinity within inland streams. Our results suggest that monitoring of microbial assemblages of freshwater ecosystems could be used as early warning signs of increased salinization levels. [ABSTRACT FROM AUTHOR]

A novel assessment of the content of microplastics in the surface waters of Lake Khanka and its tributaries is performed. Collection, preparation, and analysis of samples were carried out in 2021‒2022. Five geographical sites were selected (the source of the Sungacha River, the mouth of the Spasovka River, the Vostochnyi cordon, the Ilistaya River, and the Komissarovka River) as areas most susceptible to pollution. Scanning spectrophotometry with an AIM-9000 SHIMADZU IR microscope detected the presence of microplastic particles (MPs) in all the water samples. The microplastics are predominantly of mixed and synthetic nature; the concentration varies depending on the season, amounting to 6–27 units/m3 in the spring–summer and 5–24 units/m3 in the autumn–winter sampling period. The detected microplastics are of mostly secondary origin and are overwhelmingly identified as fibers. Spectral analysis of the particles show that polyester and organic fibers are the most common types of microplastics. An increased concentration of microplastics is observed at the mouths of the Spasovka and Komissarovka rivers; in the area of the Vostochnyi cordon, which is located in the eastern coastal region of the lake on the territory of the Khanka Nature Reserve; and at the source of the Sungacha, the drainage river of Lake Khanka. It is concluded that the likely sources of microplastic pollution in Lake Khanka and rivers of its basin are runoff from wastewater treatment plants carried in by river flow, runoff from agricultural land, and precipitation and/or untreated wastewater. A comparative analysis of the surface waters of Lake Khanka, the Hai River (China), the Songhua River (China), and rivers of Japan and South Korea is performed. In all the considered water bodies, the predominant type of microplastics is fibers of synthetic origin. The average concentration of microplastics in Lake Khanka is found to be noticeably lower than in the other water bodies, with only that in the Hai River lower. [ABSTRACT FROM AUTHOR]

The rapid deterioration of freshwater ecosystems, particularly rivers, has threatened many living organisms, including human beings. In order to comprehend and maintain the well-being of a river ecosystem, it is important to assess the spatial and temporal variations in its physico-chemical parameters. The aim of the present study was to examine spatial and temporal physico-chemical parameters of snow-fed River Poonch in the Northwest Himalayas from July 2021 to June 2023. In order to generate precise and reliable data, one-way ANOVA, Duncan's multiple range test, Pearson correlation, linear regression, principal component analysis (PCA) and cluster analysis (CA) were used to analyse a total of fifteen physico-chemical parameters of the river. Significant (p < 0.05) differences spatio-temporally in physico-chemical parameters were found through one-way ANOVA followed by Duncan's multiple range test. Pearson correlation revealed that majority of the examined physico-chemical parameters exhibited a robust positive association (r > 0.70) in most cases, apart from DO (r ≥ − 0.80). Linear regression indicated significant (p < 0.05) associations among various physico-chemical parameters, which were substantial both in nature and size, with a coefficient of determination (r2 > 0.70) in most of the cases. PCA showed that physico-chemical parameters such as AT, WT, EC, TDS, FCO2, TA, TH, NO2-N, NO3-N, TP, SO42− and F− were significant for the determination of qualitative characteristics of River Poonch. In CA, two distinct clusters, viz. Cluster-I consisting of Site-III, downstream site prone to pollution and Cluster-II consisting of Site-II and Site-I, mid and upstream sites, respectively, less prone to pollution were obtained. The results of the study revealed that the water quality parameters were found well within the recommended ranges, suggesting that they are conducive for the existence of inhabitant fish species, which influence the local economy of the region. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are among the most threatened worldwide. A great part of this threat comes from climate and land cover changes. This situation is specially worrying in areas and ecosystems that are highly relevant in terms of biodiversity but severely impacted by these two factors, such as water bodies in North Africa. Using water beetles as surrogates of freshwater biodiversity, we present a novel approach to identify priority basins for the preservation of freshwater biodiversity in Morocco, using Species Distribution Models to identify potential biodiversity hotspots under future climate change scenarios, and estimates of future Land Cover dynamics. The mountainous areas of the Rif and Prerif, Middle Atlas and northern Central Plateau areas, as well as some Atlantic coastal basins were identified as priority areas for water beetles conservation and will play a crucial role for the conservation of freshwater biodiversity. Indeed, these areas can act as a dead end for a number of African species in the future. However, most of these areas are poorly covered by the national protected areas network (i.e., protected area extent < 10%). In addition, our analyses revealed a general negative trend of the natural vegetation coverage in the study area, and an increase of non-irrigated cropland. Finally, we identified specific areas that need special attention because are priority for conservation but are expected to suffer intense land cover changes. These results, which consider not only biodiversity values, but also the potential threats driven by climate and land cover changes, can provide a solid scientific basis to policy-makers to define specific conservation measures to anticipate freshwater biodiversity loss in North Africa. [ABSTRACT FROM AUTHOR]

Seasonal changes in environmental conditions drive phenology, i.e., the annual timing of biological events ranging from the individual to the ecosystem. Phenological patterns and successional abundance cycles have been particularly well studied in temperate freshwater systems, showing strong and predictable synchrony with seasonal changes. However, seasonal successional changes in the abundance of parasites or their infection levels in aquatic hosts have not yet been shown to follow universal patterns. Here, using a compilation of several hundred estimates of spring-to-summer changes in infection by trematodes in their intermediate and definitive hosts, spanning multiple species and habitats, we test for general patterns of seasonal (temperature) driven changes in infection levels. The data include almost as many decreases in infection levels from spring to summer as there are increases, across different host types. Our results reveal that the magnitude of the spring-to-summer change in temperature had a weak positive effect on the concurrent change in prevalence of infection in first intermediate hosts, but no effect on the change in prevalence or abundance of infection in second intermediate or definitive hosts. This was true across habitat types and host taxa, indicating no universal effect of seasonal temperature increase on trematode infections. This surprising variation across systems suggests a predominance of idiosyncratic and species-specific responses in trematode infection levels, at odds with any clear phenological or successional pattern. We discuss possible reasons for the minimal and variable effect of seasonal temperature regimes, and emphasise the challenges this poses for predicting ecosystem responses to future climate change. [ABSTRACT FROM AUTHOR]

Little is known about microplastics (MPs) in adult frogs. We investigated MPs in adult Common River Frogs (Amietia delalandii) from Potchefstroom, South Africa. Five kinds of samples were analysed: natural water, water used to rinse the skin, skin, intestine, and the remainder of the body (corpus). Tissues were digested. Microplastics occurred in all frogs and sample types (1128 MPs counted). Fibres were the most prevalent MP. Fibre lengths were between 28 and 4300 μm, either polyester or polyvinyl alcohol. MPs in skin were likely derived from the ambient, and MPs in the corpus from translocation via the skin. Fibres in tissues were significantly shorter in larger frogs, a phenomenon we provisionally assign to in situ biodegradation. Microplastics in frogs can potentially be transferred through the food web to higher trophic levels. This study provides the first evidence of MPs in adult frog tissues and avenues for further investigations. [ABSTRACT FROM AUTHOR]

The Media Luna spring, Mexico, is the main reservoir of the endemic and endangered fish Ataeniobius toweri. In the last decades, the ecosystem has been modified by tourism, and the habitat has changed for this species. Therefore, for better conservation management of the natural fish population, it is necessary to understand its abundance status and suitable habitat conditions, in ecological and spatial scenarios, on a temporal scale. In the present study, we modeled A. toweri's ecological responses and spatial distribution for adult and juvenile life stages, in three summer periods (years 1999, 2009, and 2019). As habitat variables, we used water depth and underwater coverage. Ecological response curves were obtained from a Generalized Linear Model; distribution models were obtained with DOMAIN. In the modeling evaluation, for the Linear Regression Model, we obtained true statistical skills metric > 0.30 and, for DOMAIN, an area under the curve (AUC) > 0.70 with an AUC ratio > 1.00. In general, as the summer periods progressed, we found the highest probability of occurrence (P > 0.20) and distribution (P > 0.60) in areas with conditions of large coverage of underwater vegetation, in the first 1.5 m of depth, and near the shores of the spring. Also, the variations of relative abundance were always observed at sites with these habitat conditions. Thus, we concluded that our models had the performance to discern between suitable and unsuitable habitat conditions for A. toweri, and that areas with little or no anthropogenic pressure are more important for this species. [ABSTRACT FROM AUTHOR]

Results of a study of Lake Tolpanjärvi's ecosystem are reported. Its hydrological and geochemical indices, as well as the current condition of biotic communities (the zooplankton, benthos, and fish population), were studied and analyzed. Analysis of the chemical composition of water indicates that the lake has a low organic-matter content (total phosphorus 0.007 mg/L, nitrogen 0.26 mg/L). Lake Tolpanjärvi is an oligotrophic lake, as indicated by the abundance of zooplankton (with a biomass of less than 1 g/m3) and zoobenthos (biomass 0.44 g/m2). The lake is of an oligosaprobic class (second-quality class, clean natural water), as evidenced by its saprobity index estimated using the Pantle–Buck method. The quantitative indices of the zoobenthos varied from 120 individuals/m2 and 0.08 g/m2 in the profundal zone to 1200 inds./m2 and 0.86 g/m2 in the quiet littoral zone. The lake is more similar in the chironomid index (K 2.10) to clean natural water. It is inhabited by eight fish species of five families. The fish population is dominated by the whitefish Coregonus lavaretus, the perch Perca fluviatilis, and the roach Rutilus rutilus. Two ecological forms of whitefish, differing in both the number of gill rakers (sparsely rakered 18–24 and medium-rakered 28–36) and biological indices (size–weight, maturation, fertility, and feeding), occur in the lake. Stable highly diverse ecosystems were shown to form the basis for the preservation of the gene pool and for assessment of the current condition of water bodies heavily affected by human activities. [ABSTRACT FROM AUTHOR]

Invasive alien species have become the second major threat to biodiversity affecting all three major ecosystems (terrestrial, marine, and freshwater). Increasing drivers such as habitat destruction, expanding horticulture and aquaculture industries, and global pet and food trade have created pathways for exotic species to be introduced leading to severe impacts on recipient ecosystems. Although relatively less studied than terrestrial ecosystems, freshwater ecosystems are highly susceptible to biological invasions. In India, there has been a noticeable increase in the introduction of alien fish species in freshwater environments. In the current study, we aimed to understand how climate change can affect the dynamics of the biological invasion of invasive alien fishes in India. We also evaluated the river-linking project's impact on the homogenization of biota in Indian freshwater bodies. We used species occurrence records with selected environmental variables to assess vulnerable locations for current and future biological invasion using species distribution models. Our study has identified and mapped the vulnerable regions to invasion in India. Our research indicates that the interlinking of rivers connects susceptible regions housing endangered fish species with invasive hotspots. Invasive alien fishes from the source basin may invade vulnerable basins and compete with the native species. Based on the results, we discuss some of the key areas for the management of these invasive alien species in the freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Freshwater planarians of the genus Girardia have been introduced all over the world, but little is known about the species involved and their possible impact on autochthonous ecosystems. Using molecular phylogenetics and niche modelling under different climatic scenarios we examine the human-induced spread of alien Girardia species from their original areas of distribution in the Americas to other areas. Our results corroborate that Girardia populations spreading worldwide belong to three species: G. dorotocephala, G. sinensis, and G. tigrina. Our study emphasizes that G. sinensis is native to North America and shows that G. dorotocephala has a broader range of introduced localities than previously known. Niche modelling revealed that the three species have a broad range of potential distribution in extensive regions of the Northern Hemisphere. Regardless of the future climatic scenario, their distributional range will increase towards northern Europe, without diminishing the high suitability of regions in the south. Their environmental requirements, being generalists with high suitability for human-modified habitats, and fissiparous reproduction explain their successful colonization. In the Iberian Peninsula, G. tigrina and G. sinensis have extensive areas of high suitability, overlapping with the more limited suitable areas of autochthonous planarians, pointing to potential detrimental effects of Girardia invaders. [ABSTRACT FROM AUTHOR]

Planorbellatrivolvis (ramshorn snail) is one of India's most extensively sold exotic aquarium pet snails. The unintentional or deliberate release of P. trivolvis may result in the colonisation and establishment as an invasive snail in freshwater ecosystems. However, the successful invasion of P. trivolvis will depend on several abiotic and biotic factors of the concerned freshwater ecosystem. We have assessed the possibility of overcoming the opposing factors in P. trivolvis invasion through laboratory-based experiments and examined the effects of household-derived pollutants on egg hatchability, adult survivability and fecundity, and temperature (15 to 35 °C) on growth, sexual maturity, and reproduction. Additionally, we have evaluated the potential of native predators as biotic resistance to invasion by prey-choice experiment. The results indicated that egg hatchability, adult survivability, and fecundity were reduced with increasing pollutant concentration. However, the same traits did not differ from a native freshwater snail, Indoplanorbis exustus. The fecundity of P. trivolvis increased with increasing body size, but no considerable differences at different temperature levels suggest a wide range of adaptation to temperature. Faster growth and the requirement of comparatively few days to attain sexual maturity were observed in the higher temperatures. The native predators, Glossiphonia weberi and Diplonychus rusticus, avoided P. trivolvis as prey over the alternative prey snails in most instances, suggesting the masking of biotic resistance against the colonisation. Our observations indicate that the chance dispersal of P. trivolvis from household or commercial aquaria may lead to a possible invasion of freshwater ecosystems under suitable conditions. [ABSTRACT FROM AUTHOR]

Turkey has many ecological characteristics due to its geographical location, allowing it to have a rich biodiversity in freshwater ecosystems. This study was carried out on the Kızılırmak river, the longest river (1.355 km) in the country; it originates and empties into the sea within its borders. The Kızılırmak river serves various agricultural, industrial, drinking water-related, and recreational purposes and greatly contributes to the region's economy. This study aimed to determine the distribution of the river's macroinvertebrate fauna and evaluate the impact of environmental variables on species distribution. In addition, using species-based biodiversity indices such as the Biological Monitoring Working Party (BMWP), Average Score per Taxon (ASPT), the Shannon–Wiener index, and evenness analysis, spatial and temporal similarities and differences were determined. According to the results, the ten taxonomic groups in the Kızılırmak river belong to the following categories: Gastropoda (81.5%), Gammaridae (9.8%), Oligochaeta (6.2%) Chironomidae (2.1%), Hirudinea (0.3%), and various others (0.1%). The Shannon–Wiener and evenness indexes were 0.29–1.9 and 0.46–0.14, respectively. TR-BMWP scores are in the poor to very poor water quality classes, and the ASPT ranges from moderate to poor water quality. Correlation analysis between species and physicochemical parameters indicated that the benthic macroinvertebrate fauna diversity of the river is affected by natural and anthropogenic factors. [ABSTRACT FROM AUTHOR]

This paper presents the results of methane flux field measurements on thermokarst lakes of the Russian north on three key sites: foothills of the Polar Urals, coast of the Kara Sea and the northwestern part of the Yamal Peninsula. 13 lakes were studied and about 500 methane fluxes were measured by the floating closed chamber method. The results showed most of the fluxes does not exceed 8 mgCH4 m–2 h–1. For larger values, a statistically significant correlation with the wind speed was found, determining in high degree the intensity of gas exchange on the water–atmosphere boundary. The exceptions are measurements in zone of lake methane seeps. For most lakes, the greatest scatter of measured fluxes was observed in the shallow part. The diurnal dynamics of methane fluxes was approximated by a sinusoidal function. For the presented lakes, the range of emission assessment is 0.23–775.38 gCH4 h–1. Obtained results are important material for estimating regional methane emission from the surface of thermokarst lakes in the tundra zone. [ABSTRACT FROM AUTHOR]

Leptopanchax opalescens is a critically endangered small annual fish. Reproductive traits of this species were studied to improve our understanding of the strategies that facilitate the occupation of temporary wetlands. We compiled egg diameter and maximum total length data from 136 neotropical killifishes (Rivulidae) to establish comparisons between species with different life histories. We tested the hypothesis that annual killifishes have smaller body sizes and eggs than non-annual killifishes, which may be associated with different life spans and embryonic diapause. Fish were collected from the Guandu River Hydrographic Region (southeastern Brazil). DNA barcoding was employed to confirm the species’ identity. The phases of gonadal development and spawn type were described using histological techniques. Egg size and fecundity were determined. Females with batch spawning and males with continuous spawning were detected. The batch fecundity ranged from 22 to 32 vitellogenic oocytes (mean 27 ± 7 SD). Maximum body size was similar between the two life cycles (p = 0.24), but egg size was smaller for annual killifishes (p < 0.001). Spawning in batches, synchronous modal development of oocytes, continued production of sperm in males, and a complex process of embryonic diapause are reproductive traits that favor the resilience of L. opalescens and other annual fish in temporary wetlands. We conclude that body size is not related to lifespan and that factors underlying the selection of different egg sizes between annual and non-annual killifish species may be associated with different life history strategies to deal with stressful habitats. [ABSTRACT FROM AUTHOR]

Inland capture fisheries in rivers, wetlands, lakes, tanks, and dam reservoirs support millions of marginalized people in countries like India. While being a critical resource for many, fishing also has negative impacts on threatened wildlife, through net entanglement and mortality, and fishery-associated hunting or poaching activities. Also, both fishing and river wildlife have declined due to dams affecting river flows, water pollution, and other anthropogenic threats. A dominant approach to protect terrestrial wildlife in India has been the creation of Protected Areas (PAs) where human activities detrimental to wildlife, including fishing, are banned or significantly regulated. But PAs in India have been historically sited in and near dam reservoirs, where culture-based fisheries are often allowed. This triad of PAs, dams, and reservoir/river fisheries can lead to inequitable outcomes, tradeoffs, and conflicts between wildlife conservation and fishery-dependent livelihoods. Hence there is a need to understand factors leading to fishery-wildlife conservation conflicts across PAs. In this review paper, attribute data on ecotype, area, number of dams, fishing intensity levels, and conservation status were compiled for non-marine PAs across India to understand their broad correlations with fishery-conservation conflict intensity levels. Conflict intensity levels were correlated with PA area, PA conservation status, and fishing intensity, and with the number of dams associated with PAs. These results are discussed and specific institutional gaps and management limitations in India are identified, that need to be addressed to prevent negative fishing impacts on wildlife and secure human livelihoods dependent on fisheries. [ABSTRACT FROM AUTHOR]

Conservation-planning approaches must be supported by a good understanding of the geographical distribution of species. Despite the efforts conducted so far to compile data on aquatic insects, the information on the distribution of water beetles in Morocco is scarce. In this study, we assess for the first time the degree of inventory quality of aquatic insects in Africa. Using an exhaustive database of Moroccan water beetles, likely the most complete database for any group of aquatic insects in Africa (with 11,229 records for 305 species), we specifically aim to explore the patterns of species richness, sampling effort and inventory completeness at four different spatial resolutions, identifying those spatial units that can be considered as sufficiently surveyed, and locating areas in need of further sampling effort. Our results showed a lack of complete and extensive inventory data; as less than 12% of Moroccan cells at the coarsest resolution assessed (45′) can be considered as well surveyed (slope < 0.1 and survey completeness > 70%), while at the finest resolution (7′), only 1% of Moroccan cells could be identified as being well prospected. Finally, we highlight the importance of these procedures to improve monitoring planning of aquatic fauna and to improve their effective conservation and management. Implications for insect conservation: Considerable information is still required to provide an accurate picture of the richness patterns of aquatic insects in North-Western Africa. Thus, results on the pattern of species richness must be used cautiously, as they could be just mirroring the pattern of sampling effort carried out. We recommend the use of modelling procedures as a shortcut to improve our knowledge on the biodiversity patterns of aquatic insects in North-Western Africa and to establish efficient conservation strategies for their protection. [ABSTRACT FROM AUTHOR]

Plastic wastes in the environment ultimately reach to the aquatic habitats and become available to aquatic organisms. The pathway of microplastic in aquatic ecosystem is very less investigated specially in freshwater. There have been evidences of MPs ingestion by freshwater biota but the fate of these MPs further in the food chain is unexplored. Thus, we reviewed the status of MPs in freshwater biota and tried to compare the studies to merge the available information, concepts, and perspectives in order to draw a conclusion on bioaccumulation potential, trophic transfer possibilities, biomagnification, and trends of ingesting MPs by the biota. In this review, the previously available information about MPs in aquatic biota is arranged, analyzed, and interpreted to understand all possible routes of MPs in freshwater habitats. The review further provides a better understanding about the lack of information and research gaps that are needed to be explored to develop a solution to the problem of MPs in near future. [ABSTRACT FROM AUTHOR]

It has been well documented that periphyton communities play a key role in primary productivity, nutrient cycling, and food web interactions. However, a worldwide overview of research on the key themes, current situation, and major trends within the field is lacking. In this study, we applied the machine learning technique (latent Dirichlet allocation, LDA) to analyze the abstracts of 6690 publications related to periphyton from 1991 to 2020 based on the Web of Science database. The relative frequency of classical and basic research on periphyton related to colonization, biomass, growth rate, and habitats has been clearly decreasing. The increasing trends of research on periphyton are embodied in the periphyton function in freshwater ecosystems (e.g., application as ecological indicators, function in the removal of nutrients, and application in paleolimnology), the research at macroscales (e.g., spatial–temporal variation, and functional and taxonomic diversity), and the anthropogenic themes (e.g., climate warming, response to multiple stressors, and land use type). The keyword and title analysis showed that the periphyton studies are concentrated mainly on diatom aspects, especially with respect to streams relative to lakes. The thematic space based on non-metric multidimensional scaling (NMDS) showed that the classical themes such as growth rate, colonization, and environmental factors (e.g., multiple stressors and climate warming) were most linked to other research themes. We proposed that future trends in the periphyton should focus on the function of periphyton in lakes and their response to multiple environmental pressures with the increasingly extensive eutrophication in lakes and the increasingly significant change in the climate. [ABSTRACT FROM AUTHOR]

Construction of dams on rivers can lead to changes in water flow and nutrient cycling due to impediments to the flow of basic nutrients. The hypothesis that the division of fish into guilds of benthic, demersal and pelagic would in a man-made lake explain the variation in the community structure was tested. The structure of vertical fish communities was described using two isometric log-ratio variables. The first variable was found to reflect the ratio of benthopelagic and demersal fish species, while the second indicated the proportion of pelagic to other fish species. The canonical correspondence analysis on these variables explained 6.4% of the observed community variations. The analysis axes reflected the variability in the fish community structure, which depends on the vertical preference of fish. During the study period in the lake ecosystem, the importance of benthopelagic guild was decreasing which was followed by a decrease in the abundance and diversity of the fish community. The lake ecosystems are located at different distances from the Dnipro River bed, and this pattern appeared to be stronger as the distance became greater. The observed temporal changes in the ecological guilds structure of the fish community were due to eutrophication and oxygen deficiency. [ABSTRACT FROM AUTHOR]

Identifying and quantifying global change impacts on biotic and abiotic components of ecosystems is critical to promote an effective adaptation that increases the success of conservation strategies. To achieve this goal, global and regional assessment efforts require certain degree of harmonization on local monitoring programs to establish relevant comparisons at different spatio-temporal scales. Otherwise, the lack of harmonization might hinder the detection and assessment on the effects of human impacts. In this work we have compiled information on freshwater monitoring programs located in areas of intensive research and conservation interest: International Long Term Ecological Research (ILTER) nodes and mountain National Parks. We aimed at evaluating the quality and robustness of these programs to assess the impact of global change, addressing from the worldwide to the European and Spanish national scale. Results highlighted that freshwater monitoring programs lack a common strategy to monitor these ecosystems. Even at the continental and national scales, contrasting strategies and level of detail have been historically applied. Water quality, habitat and biodiversity are more commonly monitored than community structure and ecosystem functioning. Monitoring efforts on the Spanish Mountain National parks indicated differences on the targeted aquatic ecosystems. Rivers and lakes received a higher attention, while mires were rarely considered. Our results provide evidence that greater efforts should be directed towards constructing a coordinated strategy to monitor freshwater ecosystems at national, continental, and global scales. This strategy should involve a shared backbone of biophysical and biogeochemical variables for each habitat type on agreed protocols that are implemented across regions and administrative borders. Achieving this will support a substantial advance on the ecological research to further delineate proper conservation strategies to face the challenges imposed by global change. [ABSTRACT FROM AUTHOR]

The present study reports a potentially toxic cyanobacterial species, Woronichinia naegeliana, which was observed along with a continuous bloom of Microcystis from a freshwater pond while monitoring cyanobacterial blooms along central Kerala, south India. Woronichinia is a toxic cyanobacterium usually found in freshwater ecosystems associated with other harmful cyanobacterial blooms. The monitoring was carried out from 2019 to 2020, and the high cell density of Woronichinia was observed in March 2020 (8.4 × 104 cells L−1). Hydrographic parameters studied revealed that the abundance of Woronichinia species was favoured by higher temperature (29 °C) with comparatively low nutrient values (NO3: 10.5 μmol L−1; PO4: 2.3 μmol L−1) while Microcystis desired a higher temperature (31 °C) with increased nutrient values (NO3: 96.78 μmol L−1; PO4: 5.88 μmol L−1). [ABSTRACT FROM AUTHOR]

Despite the biodiversity and ecosystem services provided by lotic ecosystems, they are strongly affected by anthropogenic activities. Therefore, biological monitoring and assessment strategies are crucial in helping maintain these ecosystems and developing mitigation policies. We provide a global overview of the use of benthic diatoms as bioindicators in lotic environments, by analyzing 764 articles published in the past 20 years. We analyzed the influence of substrate type on samplings, which species have been highlighted as indicators and for which type of impacts, which anthropogenic impacts have been most commonly evaluated, and which metrics have been commonly used in studies using diatoms to assess and monitor the quality of lotic environments. We found that the most studied anthropogenic impact is artificial eutrophication and that some species, especially Nitzschia palea, have been thoroughly mentioned as indicators of this impact. Indicator species related to other types of impact are less common, demonstrating the need for studies on this issue. Moreover, we verified that traditional taxonomic metrics, such as diversity and diatom indices, have been widely used. Some alternative metrics have been used recently, such as those based on teratological valves, lipid bodies, valve size, and DNA metabarcoding. The number of biomonitoring and assessment studies based on diatoms has increased considerably in the past 20 years. Nonetheless, the demand for natural resources and consequently the degradation of lotic ecosystems have accelerated significantly. Thus, the development of low-cost and time-efficient biological assessment and monitoring strategies is essential for evaluating the health of lotic environments. [ABSTRACT FROM AUTHOR]

Southern Vietnam, particularly the Mekong Delta, is popular in inland fish species diversity. In this study, fish species diversity across six stations from the estuary to the upstream of Cua Tieu River, which is situated in the Tien Giang province in Southern Vietnam, has been studied from January 2018 to June 2020. Altogether, 2088 specimens were collected and classified, and these belonged to 115 species, 98 genera, and 54 families of 15 orders that were recognized and identified. The names of species, genera, families, and orders are cited. In the total of 115 species, the Perch-like order (Perciformes) is the most diverse group, with 50 species (consist of 43.48% of total species). The catfish order (Siluriformes) is the second-most diverse group, consisting of 19 species (16.52% of total species). The carp order (Cypriniformes) consists of 8 species (6.96%), and the herring order (Clupeiformes) consists of 7 species (6.09%). Three orders of fishes, needle fish order (Beloniformes), Spiny eel order (Synbranchiformes), and flounder order (Pleuronectiformes), consist of 6 species (5.22%), and other orders consist of 1–3 species (0.87–2.61%). Among the 115 species recorded, 4 species were classified as vulnerable (VU) in the Red Data Book of Viet Nam (2007) (which is 3.48% of the total species collected). These are Elops saurus, Anodontostoma chacunda, Datnioides polota, and Toxotes chatareus. According to the IUCN Red list (2020), 1 species is endangered (EN) (0.87%), 1 species is vulnerable (VU) (0.87%), 3 species of fish are near threatened (NT) (2.61%), 6 species are data deficient (DD) (5.22%), and 58 species are least concern (LC) (50.43%). The result also recorded 41 fish as migratory species (26 freshwater species and 15 marine species), which is 35.65% of total species collected. Some migratory species are important and endemic species of the Mekong River, such as Bagarius yarrelli, Boesemania microlepis, Yasuhikotakia modesta, Cyclocheilos enoplos, Pangasianodon hypophthalmus, Pangasius conchophilus, Pangasius krempfi, Pangasius pleurotaenia, Phalacronotus bleekeri. [ABSTRACT FROM AUTHOR]

Investigating the influence of biodiversity on ecosystem functioning over environmental gradients is needed to anticipate ecosystem responses to global change. However, our understanding of the functional role of freshwater biodiversity, especially for microbes, is mainly based on manipulative experiments, where biodiversity and environmental variability are minimized. Here, we combined observational and manipulative experiments to analyse how fungal biodiversity responds to and mediates the impacts of drying on two key ecosystem processes: organic matter decomposition and fungal biomass accrual. Our observational data set consists of fungal biodiversity and ecosystem processes from 15 streams spanning a natural gradient of flow intermittence. Our manipulative design evaluates the responses of ecosystem processes to two fungal richness levels crossed with three levels of drying. For the observational experiment, we found that increasing the duration of drying reduced fungal species richness and caused compositional changes. Changes in species composition were driven by species turnover, suggesting resistance mechanisms to cope with drying. We also found that fungal richness had a positive effect on organic matter decomposition and fungal biomass accrual. Positive effects of fungal biodiversity were consistent when controlling for the effects of drying duration on richness by means of structural equation modelling. In addition, our results for the manipulative experiment showed that the positive effects of higher richness on both ecosystem processes were evident even when exposed to short or long simulated drying. Overall, our study suggests that maintaining high levels of biodiversity is crucial for maintaining functional freshwater ecosystems in response to ongoing and future environmental changes. [ABSTRACT FROM AUTHOR]

Metal pollution is one of the main environmental threats in freshwater ecosystems. Aquatic animals can accumulate these substances and transfer them across the food web, posing risks for both predators and humans. Accumulation patterns strongly vary depending on the location, species, and size (which in fish and crayfish is related to age) of individuals. Moreover, high metal concentrations can negatively affect animals' health. To assess the intraspecific relationship between metal accumulation and size and health (proxied by the body condition) of individuals, the concentration of 14 metals (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, Zn) was analyzed in six alien species from the highly anthropogenically altered Arno River (Central Italy): five fish (Alburnus alburnus, Pseudorasbora parva, Lepomis gibbosus, Ictalurus punctatus, and Silurus glanis) and one crayfish (Procambarus clarkii). We found that in P. clarkii, Cu was negatively related to size, as well as Al in L. gibbosus and Mg for adult I. punctatus. Positive size-dependent relationships were found for Hg in L. gibbosus, Fe in S. glanis, and Cr in juvenile I. punctatus. Only Co and Mg in S. glanis were found to negatively correlate with individual health. Since metal concentrations in animal tissue depend on trade-offs between uptake and excretion, the few significant results suggest different types of trade-offs across different species and age classes. However, only predatory fish species (L. gibbosus, I. punctatus, and S. glanis) presented significant relationships, suggesting that feeding habits are one of the primary drivers of metal accumulation. [ABSTRACT FROM AUTHOR]

Water crises in Latin America are more a consequence of poor management than resource scarcity. Addressing water management issues through better coordination, identification of problems and solutions, and agreement on common objectives to operationalize integrated water resources management (IWRM) could greatly improve water governance in the region. Composite indices have great potential to help overcome capacity and information challenges while supporting better IWRM. We applied one such index, the Freshwater Health Index (FHI) in three river basins in Latin America (Alto Mayo, Perú; Bogotá, Colombia; and Guandu, Brazil) to assess freshwater ecosystem vitality, ecosystem services, and the water governance system in place. The approach included convening management agencies, water utilities, planning authorities, local NGOs and industries, community groups and researchers to co-implement the FHI. The results provide detailed information on the ecological integrity of each basin and the sustainability of the ecosystem services being provided. All three basins show very low scores for governance and stakeholder engagement, thus improving both in the region should be a priority. The results also shed light on how the FHI framework can help inform decision-making to improve IWRM implementation by facilitating stakeholder engagement while contributing to coordination, identification of problems and solutions as well as agreement on common objectives. Because implementation of IWRM is part of the solution for the United Nations Sustainable Development Goal (SDG) 6.5 ("By 2030, implement IWRM at all levels, including through transboundary cooperation as appropriate"), our case studies can serve as examples to other Latin American countries to achieve SDG 6.5. [ABSTRACT FROM AUTHOR]

A revised environmental licence that authorises the disposal of coal mine effluent has reduced the severity and spatial extent of water pollution and associated ecological impairment of a high conservation-value river flowing into and within the Greater Blue Mountains World Heritage Area. This study investigated water quality and the ecological condition of the Wollangambe River above and below a colliery effluent outfall and assessed the longitudinal impact 22 km downstream. Results are compared to a previous study conducted in 2012/2013 when the environmental licence allowed hazardous pollutant discharges (zinc, nickel) from the colliery. The current study revealed that water quality and river sediment at sampling sites in close proximity (< 2 km) to the effluent outfall continues to contribute ecologically hazardous concentrations of metals and river macroinvertebrates reflect diminished ecological health. However, further downstream monitoring has revealed a significant improvement in ecological condition that can be directly attributed to the revised pollution licence. We hypothesise that the ecological recovery of the most contaminated reaches of the river that lies proximate to the discharge point is constrained by four decades of accumulated zinc and nickel within river sediments. Nickel (978 mg/kg) and zinc (2080 mg/kg) exceeded ecosystem protection guidelines by 45 and 10 times, respectively. The study highlights the importance of appropriate and site-specific environmental licencing to protect riverine ecosystems of conservation significance from long-term contamination. [ABSTRACT FROM AUTHOR]

Hybridization has been associated with increased invasiveness in plants. In North America, the hybrid aquatic plant Myriophyllum spicatum × Myriophyllum sibiricum (hybrid watermilfoil, hereafter HWM) is a cross between non-native invasive Eurasian watermilfoil (M. spicatum, EWM) and native northern watermilfoil (M. sibiricum, NWM). Lab-based trials have demonstrated higher growth rates in HWM compared to EWM and NWM, but these patterns have not been systematically examined in the field. In this study, we compared the invasiveness of HWM to its parental taxa, EWM and NWM, by examining the amount and timing of: (1) flowering, (2) surface cover, and (3) biomass (using stem counts as a proxy). We conducted repeat surveys of Myriophyllum beds at eight lakes (2–3 lakes/taxon) in the Minneapolis–St. Paul Metropolitan area (Minnesota, USA) between June 2017 and November 2018. HWM produced more flower spikes earlier and overall, and maintained consistently more flower spikes throughout the growing season than EWM and NWM. In addition, surface cover reached greater annual peaks and was higher for longer throughout the growing season for HWM than for both parental taxa. We did not observe a significant difference in stem counts among the three taxa, but HWM did reach a higher maximum number of stems than either parental taxon. This study provides field-based evidence of increased invasiveness associated with hybridization between EWM and NWM; specifically, greater reproductive potential via flowering and greater surface cover may increase HWM spread, have greater impacts on native species, and pose more of a nuisance to lake users. [ABSTRACT FROM AUTHOR]

Plants are key elements of wetlands due to their evolutionary strategies for coping with life in a water-saturated environment, providing the basis for supporting nearly all wetland biota and habitat structure for other taxonomic groups. Sardinia, the second largest island of the Mediterranean Basin, hosts a great variety of wetlands, of which 16 are included in eight Ramsar sites. The 119 hydro- and hygrophilous vascular plant taxa from Sardinia represent the 42.6% and 37.9% of the number estimated for Italy and Europe, respectively. Moreover, around 30% of Sardinia’s bryological flora, which is made up of 498 taxa, is present in temporary ponds. An overview at regional scale considering algae is not available, to our knowledge, even though several specific studies have contributed to their knowledge. In order to find the most investigated research themes and wetland types, identify knowledge gaps and suggest recommendations for further research, we present a first attempt to outline the work that has been hitherto done on plants in lentic habitats in Sardinia. Three plant groups (algae, bryophytes and vascular plants), and five research themes (conservation, ecology, inventory, palaeobotany and taxonomy) were considered. After a literature review, we retained 202 papers published from 1960 to 2019. We found that studies on vascular plants, as plant group, were disproportionately more numerous, and inventories and ecology were the most investigated research themes. Although efforts have recently been made to fill these long-lasting gaps, there is a need for updating the existing information through innovative methods and integrative approaches. [ABSTRACT FROM AUTHOR]

An assessment of the species composition, abundance, biomass, and pigment characteristics of phytoperiphyton and phytoplankton of Lake Pyasino, its tributaries (Bezymyannyi Stream, Daldykan, Ambarnaya, and Norilskaya rivers), and the head of the Pyasina River has been carried out after a manmade accident (a diesel-fuel spill near the city of Norilsk in May 2020). A significant decline in the biomass and changes in the species composition of phytoperiphyton after the water was contaminated by fuel is revealed only near the spillage site (in the Daldykan River and the Ambarnaya River downstream the mouth of the Daldykan). Downstream, in the Ambarnaya mouth zone, as a response to the release of a large amount of nutrients during the decomposition of fuel products and dead organisms, as well as the mechanical cleaning of the bank line, there has been a massive growth of diatom and green algae (Tabularia tabulata, Spirogyra sp.) in the water column and the appearance of indicators of organic pollution (Euglenophyceae and Cryptophyceae). No significant changes in the plankton of Lake Pyasino and the Pyasina River in comparison with the data obtained in the second half of the 20th century (i.e., long before the accident) are found. Species composition and quantitative features, as well as amount and ratio of pigments, characterized the phytoplankton and phytoperiphyton of Lake Pyasino and the Pyasina River as a normally functioning freshwater community of oligotrophic waters. All this indicates the absence of a negative impact of the accidental fuel spill on the ecosystem of Lake Pyasino and the Pyasina River. [ABSTRACT FROM AUTHOR]

Shihoudian Lake is one of the ecological restoration engineering pilot sites of Baiyangdian Lake, China. To evaluate the phytoplankton characteristics and eutrophication status in Shihoudian Lake, we investigated the community structure of phytoplankton, including the species composition, density, biomass dominance, biodiversity and water quality parameters, in autumn 2018 and spring and summer 2019. The relationships between the community structure and the main environmental factors were analysed using a multivariate statistical method. A total of 143 species of phytoplankton were identified, belonging to 53 genera and eight phyla, and Cyanophyta and Prochlorophyta were the most dominant phyla. Both the density and the biomass were the highest in the summer. A redundancy analysis showed that total phosphorus and chemical oxygen demand were the primary influencing factors of the community distribution of Cyanophyta. Evaluation of the comprehensive diversity index and water quality index revealed that the water of Shihoudian Lake was lightly to moderately polluted, providing scientific evidence for eco-environmental protection and remediation. [ABSTRACT FROM AUTHOR]

In the Tapajós River, Brazilian Amazon, fishing is an important activity, especially for low-income riverine populations. Unfortunately, the Tapajós River fish diversity and abundance are threatened by several anthropogenic drivers, including deforestation and overfishing. We modeled the lower Tapajós River's food web and simulated changes in biomass compartments as a response to increases in deforestation (loss of floodplain forest habitat) and on artisanal fishing pressure over 30 years. According to our simulations, the large-bodied species could be reduced drastically while small-bodied and fast-growing species could be favored by fishing effort increasing. The loss of floodplain forest is expected to cause a general decline (23%) of the total standing fish biomass. This reduction could reflect greater losses on species that are directly dependent on resources from the floodplain forests, such as fruits and seeds. These results indicated that the food web of the lower Tapajós River is structurally characterized by bottom-up control, through the use of basal resources, such as detritus (mostly from decomposing plants), fruits, seeds, terrestrial, and aquatic invertebrates. Furthermore, the simulations' results highlight that the protection of the floodplain forest through the existing protected areas will be of essential importance in the future to maintain fish biomass, sustainable artisanal fishing, and improve the food security of Amazonian riverine inhabitants. [ABSTRACT FROM AUTHOR]

This study investigated whether aquaculture facilities drive the introduction and establishment of the non-native Nile tilapia (Orechromis niloticus) in Neotropical streams, Brazil. Samples were taken from nine streams with different aquaculture occupation intensities (no, moderate, and intense) using the percentage of occupation of micro-watersheds by aquaculture ponds as a proxy for propagule pressure. The presence of aquaculture facilities and the percentage of aquaculture occupation were good predictors of the catch frequency and of densities of tilapias in the adjacent natural environment. In the streams under intense propagule pressure, females prevailed and high densities of young individuals comparing to adults were recorded. It suggests that the species was reproductively successful in the natural environment. In the streams under moderate propagule pressure, males prevailed, which indicates the likely capture of individuals escaped from aquaculture facilities. In general, our results show the positive influence of propagule pressure on the introduction and establishment of Nile tilapia in natural ecosystems, showing that aquaculture expansion of O. niloticus poses a threat to the conservation of aquatic biodiversity. [ABSTRACT FROM AUTHOR]

The concept of native range in invasion biology is difficult to define since, in many cases, this type of range is unknown and cannot be determined. We investigate the uncertainties related to this concept by focusing on the distribution of Faxonius rusticus (Girard, 1852), also known as the rusty crayfish, which is perceived as possibly the worst invasive crayfish species in North America. In this study, we undertake a comprehensive literature review, which includes 430 studies published between 1852 and 2018, in order to analyze the native and introduced ranges of this species. The rusty crayfish was reported to occur in 33 states in the U.S.A. and 3 Canadian Provinces. Ten of these U.S. states and one Canadian Province have been included multiple times in both the native and the non-native ranges of this crayfish. The confusion regarding the limits and history of the native range of the rusty crayfish has implications for the conservation of this species in various jurisdictions. This review also demonstrates that even for intensely studied species perceived as invasive, we often do not have a clear understanding of essential concepts such as native and non-native range. [ABSTRACT FROM AUTHOR]

Context: Functional connectivity of semiaquatic species is poorly studied despite that freshwater ecosystems are amongst the most threatened worldwide due to habitat deterioration. The Neotropical otter, Lontra longicaudis, is a threatened species that represents a good model to evaluate the effect of landscape-riverscape features on genetic structure and gene flow of freshwater species. Objectives: We aimed to assess the spatial genetic structure of L. longicaudis and to evaluate the landscape-riverscape attributes that shape its genetic structure and gene flow at local sites (habitat patches) and between sites (landscape matrix). Methods: We conducted the study in three basins located in Veracruz, Mexico, which have a high degree of ecosystem deterioration. We used a non-invasive genetic sampling and a landscape genetics individual-based approach to test the effect stream hierarchical structure, isolation-by-distance, and isolation-by-resistance on genetic structure and gene flow. Results: We found genetic structure that corresponded to the latitudinal and altitudinal heterogeneity of the landscape and riverscape, as well as to the hierarchical structure of the streams. Open areas and steep slopes were the variables affecting genetic structure at local sites, whereas areas with suitable habitat conditions, higher ecosystem integrity and larger streams enhanced gene flow between sites. Conclusions: The landscape-riverscape characteristics that maintain functional connectivity of L. longicaudis differed between the upper, middle, and lower basins. Our results have important implications for the conservation of the species, including the maintenance of larger suitable areas in Actopan and the necessity to improve connectivity in Jamapa, through the establishment of biological corridors. [ABSTRACT FROM AUTHOR]

For the first time, the concentration of plastic particles in surface water of Lake Baikal was evaluated. The concentrations of plastic particles were evaluated in trawl samples taken in the coastal zone of the most densely populated southeastern coast and in the Maloe More―one of the most popular tourist zones in Baikal. Converted to water surface area, the concentration of plastic particles varied from 19 000 to 75 000 per 1 km2, at an average of 42 000 particles per 1 km2, suggesting a high level of plastic pollution. By their chemistry, the particles were classified as polyethylene, polypropylene, and polystyrene. The microplastic found in the study is assumed to be the product of decay of various domestic packing materials. [ABSTRACT FROM AUTHOR]

In river ecosystems, spatial complexity as well as anthropogenic factors operating at different temporal and spatial scales are shaping demography, connectivity and population genetic structure of species inhabiting these habitats. Chilina dombeiana is a freshwater gastropod with direct development (absence of a free larval phase) that inhabits the Biobío river basin in Chile (36°S). No studies have yet evaluated the spatial patterns of the genetic diversity of this species and the potential factors that influence these patterns. Consequently, in this study, we analyzed the population genetics of C. dombeiana based on 15 locations along the Biobío river. Eight microsatellite loci were genotyped. Also, at each sampling site, 40 environmental parameters were recorded to characterize them. Results showed that C. dombeiana has low genetic variability with high population structure. In addition, we detected signs of historical decreases in effective population sizes, unidirectional gene flow (upstream to downstream) and contemporary demographic bottleneck. Spatial subdivisions in populations showed a pattern of isolation by distance. The redundancy analysis and variance partitioning showed that spatial components and dissolved oxygen could explain 28% of the interpopulation genetic variation, while the Random Forest analysis identified significant effects of dissolved oxygen, nitrite and total coliforms on the genetic variability of populations (22%). Although C. dombeiana is widely distributed in Chilean rivers, its low dispersal and specific habitat requirements make this species very sensitive to the severe increase in anthropogenic disturbances affecting river ecosystems in recent decades. Long-term monitoring of genetic population conditions and environmental parameters are needed to implement robust management and conservation policies. [ABSTRACT FROM AUTHOR]

We compare invertebrate herbivory upon 13 macrophyte species in freshwater wetland systems located in two global ecozones, the Afrotropics and Neotropics, in the context of biotic and environmental factors influencing these wetlands. The two ecozones are climatically similar regions, with similar water chemistry, but experience contrasting grazing and disturbance pressures from large mammalian herbivores. Our results for macrophytes show that small invertebrates removed significantly more lamina biomass per leaf in Neotropical macrophytes (6.55%) than Afrotropical ones (4.99%). Overall, the results indicate that underestimation of up to 15.6% of leaf biomass may occur if plant tissue removal by invertebrate herbivores is not included in estimates of plant biomass. Regarding the contrasting grazing and disturbance pressures from large herbivores influencing these wetlands, seven mammal species (especially the Black Lechwe antelope, Kobus leche) were observed impacting macrophytes in the Afrotropical wetlands, while in the Neotropics, only much smaller rodents, capybara, (Hydrochoerus hydrochaeris) were sporadically observed. We discuss the relevance of results for invertebrate herbivory in the context of both the methodological approach and the importance of large mammalian herbivores as biotic factors additionally impacting macrophyte populations in these subtropical to tropical wetlands. [ABSTRACT FROM AUTHOR]

The enzymatic reactions of microbial communities are rapid and adequate to changes in the composition of organic matter and environmental factors; therefore, they can be used as descriptors of biological responses in freshwater systems. The objective of this work was to determine the proteolytic enzymatic activity in the Almendares and San Juan rivers (western Cuba) and their relationship with physicochemical and microbiological indicators. The Almendares River (Havana, Cuba) presented water quality index between very poor and unusable for consumption, which makes impossible for recreational uses. In contrast, the waters of the San Juan River (Artemisa, Cuba) are classified as excellent and good in most of the sampling stations during the study period. The greatest proteolytic activities were detected in the San Juan River compared to the Almendares River, which indicates that in more contaminated ecosystems, the proteolytic enzyme activity decreases compared to another less impacted system. In addition, the annual variation in the proteolytic activity of both rivers was evidenced. In the San Juan River, a correlation was observed among proteolytic activity, the concentration of proteolytic bacteria and the physicochemical indicators of water quality, suggesting that proteolytic activity is related to naturally occurring contaminants. In contrast, in the Almendares River, this relationship was not observed, which suggests that the proteolytic activity is not directly affected by the indicators measured in this study. [ABSTRACT FROM AUTHOR]

Different techniques have been employed for fish surveys in freshwater impoundments, however, despite the increasing applicability of underwater video systems for fish sampling in different aquatic ecosystems, such technology has not been tested in reservoirs. This study compares estimates of fish species richness, community composition, and size structure derived from visual census (VC) and underwater video (UWV) in two Neotropical reservoirs. The total number of species recorded by both sampling methods was similar, even though UWV recorded higher mean number of species than VC, in both reservoirs. In general, VC was more efficient in recording cryptic and resident species, while UWV, was better for highly mobile species. Considering size classes, VC was more efficient than UWV in detecting smaller individuals (i.e., 31–79 mm total length). Although observational sampling methods depend on water transparency, UWV can be considered a complementary and promising technique for fish surveys in shallow areas of clear reservoirs. [ABSTRACT FROM AUTHOR]

The picture emerging from the rapidly growing literature on host-associated microbiota is that host traits and fitness often depend on interactive effects of host genotype, microbiota, and abiotic environment. However, testing interactive effects typically requires large, multi-factorial experiments and thus remains challenging in many systems. Furthermore, most studies of plant microbiomes focus on terrestrial hosts and microbes. Aquatic habitats may confer unique properties to microbiomes. We grew different populations of duckweed (Lemna minor), a floating aquatic plant, in three microbial treatments (adding no, "home", or "away" microbes) at two levels of zinc, a common water contaminant in urban areas, and measured both plant and microbial performance. Thus, we simultaneously manipulated plant source population, microbial community, and abiotic environment. We found strong effects of plant source, microbial treatment, and zinc on duckweed and microbial growth, with significant variation among duckweed genotypes and microbial communities. However, we found little evidence of interactive effects: zinc did not alter effects of host genotype or microbial community, and host genotype did not alter effects of microbial communities. Despite strong positive correlations between duckweed and microbe growth, zinc consistently decreased plant growth, but increased microbial growth. Furthermore, as in recent studies of terrestrial plants, microbial interactions altered a duckweed phenotype (frond aggregation). Our results suggest that duckweed source population, associated microbiome, and contaminant environment should all be considered for duckweed applications, such as phytoremediation. Lastly, we propose that duckweed microbes offer a robust experimental system for study of host–microbiota interactions under a range of environmental stresses. [ABSTRACT FROM AUTHOR]

Research on carbon gas flux to and from inland waters has increased over the past two decades, driven mainly by the need to understand (1) the global carbon budget in regard to stabilizing earth's climate, and (2) how aquatic ecosystems and the services they provide change in response to anthropogenic pressures like climate and land use change. This paper reviews carbon flux research in support of a proposed global carbon monitoring network to inform public policy. It begins with an overview of the physical–chemical processes and quantification tools for carbon gas flux, and then highlights their application to streams, rivers, lakes, reservoirs and estuaries. Research outcomes to date point to spatiotemporal coverage gaps owing to the complexity of the aquatic ecosystems and land–water interactions, suggesting that long-term monitoring is needed to better understand their signals in response to changes in climate and land management. While better monitoring of gas flux is an important piece of the global carbon budget resolution problem, new information will need to be developed and integrated to adequately inform carbon policymaking. This information can stem from developments in large-scale carbon status and flux assessment tools, such as via remote sensing platforms, and from improved integrated watershed-to-water body modeling efforts. [ABSTRACT FROM AUTHOR]

Habitat deterioration and fragmentation increase the risk of wildlife extirpation as they have strong impacts on population size, genetic diversity and gene flow. Small populations are more susceptible to these factors because the loss of genetic diversity by drift and inbreeding occurs at faster rates. Therefore, estimates of genetic diversity and population sizes of threatened and small wildlife populations in deteriorated landscapes are critical for managing and conservation. Here, we used a non-invasive sampling approach in combination with eleven microsatellite loci to evaluate genetic diversity, genetic structure, and demographic parameters of the Neotropical otter (Lontra longicaudis) in three river basins (Actopan, La Antigua and Jamapa), which are priority conservation areas for Veracruz, Mexico. Our results revealed moderate genetic diversity and genetic structure among river basins. However, we detected first-generation migrants among basins, suggesting current gene flow. Effective population size for each basin was considerably lower than the value (Ne < 100) suggested to maintain genetic variation of populations in the short-term. Similarly, census population size was lower than estimates reported for L. longicaudis in a conserved region in Mexico. We did not find evidence of recent genetic bottlenecks for any basin. Our genetic and demographic results suggest that L. longicaudis in the three river basins could be experiencing genetic isolation and erosion, with La Antigua being the most vulnerable basin. Natural fragmentation and habitat deterioration seem to be shaping the observed patterns of genetic variation in the Neotropical otter. [ABSTRACT FROM AUTHOR]

An approach to complex assessment of permissible pollutant loads for aquatic and terrestrial ecosystems has been proposed. The approach is based on evaluation of the contaminant removal (assimilation) or inflow rate on the basis of the difference between the mass flow rates at the lower and upper gauging stations of the selected river section. The removal (assimilation) or inflow rate is considered to be the current pollutant load on the river ecosystem (CLR). The maximum permissible pollutant inflow between the stations calculated on the basis of its maximum permissible concentration (MPC) is the maximum permissible load (MPLR). The difference between the MPLR and the CLR is considered the remainder of the pollution limit of the river ecosystem or the permissible load. The atmospheric deposition rate of the pollutant is considered its current load on the whole geosystem (CLG). The sum of the pollutant removal rate due to forest felling and the pollutant assimilation/inflow rate in the river, divided by the area of the drained portion of the water catchment area, is considered the maximum permissible load on the geosystems (MPLG). The difference between the MPLG and CLG is considered the remainder of the pollution limit of the terrestrial ecosystem or the permissible load. [ABSTRACT FROM AUTHOR]

Wide adaptive capabilities of fish introduced into new water bodies are shown by the example of vendace Coregonus albula and European smelt Osmerus eperlanus. Analysis of monitoring studies has shown that invading species are able to change their morphology and mode of life up to the formation of new ecological forms compared to the original population, which are known in the species in other areas of their habitat. New data have been obtained on the structure and functioning of aquatic ecosystems under the changing conditions. [ABSTRACT FROM AUTHOR]

Invasive alien species (IAS) have become an important driver of biodiversity change and exert severe pressure on natural ecosystems. The development of modelling approaches to assess and predict their distributions and impacts, and evaluate management options has increased substantially. We reviewed these modelling approaches, applied in aquatic ecosystems, using a systematic review approach in line with the preferred reporting items for systematic reviews and meta-analyses. According to our results, multispecies/ecosystem models dominated the applications, with dynamic and non-spatial models being the most prevalent. Most of the models included an additional stressor, mainly fisheries, climate change or nutrient loading. The impacts on biota focused on predation, but also on competition and ecosystem functioning, while the impacts on ecosystem services focused on food provision and water purification. At species/population level, most of the studies reported negative impacts; while at multispecies/ecosystem level, negative and both negative and positive impacts were similarly represented. We reflect on the ability of current models to assess different impacts of IAS populations and highlight the need to advance their capabilities to predict future impacts. Further development of models that allow capturing the arrival, establishment and spread of IAS and assess their impacts in an integrated way is still needed. Spatial–temporal modelling techniques bridging with novel analytical capabilities (such as environmental DNA to investigate the presence of IAS and metabarcoding and machine learning to predict future trophic behavior and distributions) may be the key for future achievement. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) analysis has been used as a cost-efficient and non-invasive tool for monitoring invasive and threatened species. Previous studies typically involve two approaches; species-specific detection via PCR and multiple species detection via metabarcoding. However, the former could be costly when several species are targeted, and the latter could sometimes be insufficient to distinguish closely related species. Here, the simultaneous eDNA detection from multiple species via multiplex real-time PCR was applied to 99 ponds to evaluate the distribution of three exotic and three threatened native fish species over different seasons. We detected bluegill sunfish (Lepomis macrochirus) eDNA at 31 sites, largemouth bass (Micropterus salmoides) eDNA at 22 sites, smallmouth bass (Micropterus dolomieu) eDNA at one site, golden venus chub (Hemigrammocypris rasborella) eDNA at 11 sites, Japanese medaka (Oryzias latipes) eDNA at 26 sites, and weather loach (Misgurnus anguillicaudatus) eDNA at 41 sites. We found that eDNA detection rates were higher in early summer for all fish species. Moreover, exotic fish eDNA was detected more frequently in ponds which were easier to access by car and which have a larger surface area and higher pH. Furthermore, the detection rates of native fish eDNA were generally lower in the ponds where exotic fish eDNA was detected more frequently. Multiplex real-time PCR can help detect the distribution of exotic and threatened native species for conservation and ecosystem management. This method is expected to substantially contribute to the early detection of invasive species and the efficient protection of threatened species' habitat. [ABSTRACT FROM AUTHOR]