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Aim: Substantial progress has been made to map biodiversity and its drivers across the planet at multiple scales, yet studies that quantify the evolutionary processes that underpin this biodiversity, and test their drivers at multiple scales, are comparatively rare. Studying most fish species, we quantify rates of body size evolution to test the role of fundamental salinity habitats in shaping rates of evolution at multiple scales. We also determine how four additional factors shape evolutionary rates. Location: Global. Time Period: Extant species. Major Taxa Studied: Actinopterygii. Methods: In up to 1710 comparisons studying over 27,000 species, we compare rates of body size evolution among five salinity habits using 13 metrics. The comparisons span a molecular tree, 100 supertrees, and 10 scales of observation to test for robust patterns and reveal how patterns change with scale. Then, three approaches assess the role of three non‐salinity factors on rates, and an alternative habitat scheme tests if lakes influence evolutionary rates. Results: Rates of size evolution rarely differ consistently between salinity habitats; rate patterns are highly clade‐ and scale dependent. One exception is freshwater‐brackish fishes, which possess among the highest size rates of any salinity, showing higher rates than euryhaline fishes in most groupings studied at most scales, and versus marine, freshwater and marine–brackish habitats at numerous scales. Additionally, species richness had the greatest potential to predict phenotypic rates, followed by branch duration, then absolute values of body size. Lacustrine environments were consistently associated with high rates of size evolution. Main Conclusions: We reveal the rate patterns that underpin global body size diversity for fishes, identifying factors that play a limited role in shaping rates of size evolution, such as salinity, and those such as species richness, age and lake environments that consistently shape evolutionary rates across half of vertebrate diversity. [ABSTRACT FROM AUTHOR]

Although intraspecific trait variation is increasingly recognized as affecting ecosystem processes, few studies have examined the ecological significance of among-population variation in behavioral traits in natural ecosystems. In freshwater habitats, crayfish are consumers that can influence ecosystem structure (e.g., macroinvertebrate communities) and function (e.g., leaf litter breakdown). To test whether crayfish behavioral traits (activity, boldness, and foraging voracity) are major contributors of leaf litter breakdown rates in the field, we collected rusty crayfish (Faxonius rusticus) from eight streams across the midwestern USA and measured behaviors using laboratory assays. At the same streams, we measured breakdown rates of leaf packs that were accessible or inaccessible to crayfish. Our results provide evidence that among-population variation in crayfish boldness and foraging voracity was a strong predictor of leaf litter breakdown rates, even after accounting for commonly appreciated environmental drivers (water temperature and human land use). Our results suggest that less bold rusty populations (i.e., emerged from shelter more slowly) had greater direct impacts on leaf litter breakdown than bold populations (P = 0.001, r2 = 0.85), potentially because leaf packs can be both a shelter and food resource to crayfish. Additionally, we found that foraging voracity was negatively related to breakdown rates in leaf packs that were inaccessible to crayfish (P = 0.025, r2 = 0.60), potentially due to a trophic cascade from crayfish preying on other invertebrates that consume leaf litter. Overall, our results add to the growing evidence that trait variation in animals may be important for understanding freshwater ecosystem functioning. [ABSTRACT FROM AUTHOR]

Limnoperna fortunei (L. fortunei) (Dunker, 1857), the golden mussel, is an invasive species possessing exceptional environmental adaptability and a destructive impact on water systems and artificial structures. To better conservation of freshwater ecosystems by controlling this mussel, it is essential to study its distribution, potential for invasion, environmental tolerance and biological traits.This paper outlines the distribution of L. fortunei in Asia and South America, as well as its potential for future invasion in freshwater habitats, along with the research methods employed.We find that the mussel had a temperature tolerance range of 8–35 °C and a pH range was 5–10, with some individuals surviving in extreme conditions for extended periods.We find that temperature was a decisive factor for success at reproductive stages, larval development and adult growth.The biological traits of L. fortunei are discussed, focusing on feeding habits, attachment characteristics and locomotion, with an emphasis on byssus structure, foot proteins and adhesion mechanisms. The study elucidates the impact of flow velocity, light exposure and substrate material on their attachment, with the optimal attachment being identified at a flow velocity of 0.3–0.9 m/s. Additionally, the mussel exhibits strong light avoidance performances and a preference for rough surfaces.Extensively‐researched control strategies are classified and summarized, primarily categorized into physical, chemical and biological control, with an outline of their respective strengths and limitations. [ABSTRACT FROM AUTHOR]

The invasion process and the persistence of invasive species across environments can be explained by their tolerance to stressors, such as salinization. Urochloa arrecta (Poaceae) exhibits high invasive potential and has already established in various natural and artificial aquatic ecosystems. Here, we experimentally evaluate the effects of water salinity on the traits of three exotic populations of U. arrecta derived from naturally occurring populations across a salinity gradient. Specifically, we measured the difference in the number and perimeter of intercellular spaces for individuals from the different populations across three experimental treatments of salinity. Our results demonstrate that high water salinity levels affected anatomical traits in all populations. However, the traits of freshwater populations were the more significantly impacted by increasing salinity compared with populations sampled from naturally higher occurring salinity. Populations of U. arrecta established in places with certain degree of salinity can be more resistance to salt increases compared with populations established in freshwater habitats that are more distant geographically. However, the resistance of freshwater populations to certain high salinity levels suggests that these populations may exhibit rapid adaptation and to survive under some degree of salinity, demonstrating the species' high resilience across various environments. [ABSTRACT FROM AUTHOR]

An overview of freshwater fish variety worldwide and the variables influencing trends in variation between and within river basins are given in this review. Continental freshwater ecosystems are highly diverse and species-rich, housing nearly 18,000 species of fish (>50% of all fish species) in <0.5% of the total land area and providing a negligible (<0.01%) share of the planet's water supply. Large lowland tropical river basins such as the Amazon, Congo, and Mekong basins are home to the greatest freshwater fish diversity. Freshwater species of fish depth variation at the global magnitude is correlated with the total amount and variation of aquatic habitats and the environment's equilibrium overtime during the evolution of scales. The river continuum concept states that there is a predictable shift in fish species depth, diversity of species, and functional characteristics along gradients of environment from headwater to estuary. The ongoing trade of minerals and organic matter related to nearby floodplains is a strong factor in the number and variety of riverine fishes in most parts of the world (the flood pulse concept). Without coordinated conservation efforts, freshwater fishes will suffer significant losses in abundance and diversity due to the numerous threats they currently face worldwide. However, further development, adaptation, training, and guidance are needed. New technologies based on water conservation, suitable species, and local traditions are needed. Waste materials and local feed additives can also be used. Farmers should be provided with the necessary training and information. [ABSTRACT FROM AUTHOR]

A new genus and new species of sesarmid crab is described from Bogor in West Java Province, Indonesia. Chriselatium schubarti new genus, new species, is morphologically most similar to Selatium , and Lithoselatium , but differs markedly in a suite of carapace, cheliped, ambulatory leg, and male pleonal characters. While Selatium and Lithoselatium are found in mangroves and coastal habitats, Chriselatium new genus was collected in a freshwater habitat that is over 60 km from the nearest coastline. [ABSTRACT FROM AUTHOR]

Simple Summary: This study is a case study on the diversity patterns, population aspects, emergence and ecological drivers of the so-far poorly studied water beetle family Scirtidae. Although they can be very abundant in karstic lotic freshwater habitats, there are still insufficient data on their biology and ecology. The family was studied over a period of 15 years in specific lotic habitats of springs and tufa barriers in the karst freshwater ecosystem of Plitvice Lakes NP, Croatia. Scirtidae showed a longitudinal gradient, as the genus Elodes was recorded only in the spring area, while the genus Hydrocyphon was found only in downstream sites with tufa barriers. Their emergence showed a seasonal character, with males dominating earlier in the season and females appearing later. The type of substrate determined their distribution, with a preference for bryophytes. Their abundance and emergence were primarily determined according to the parameters that showed the greatest fluctuations over the 15-year period: water discharge, water temperature and oxygen saturation. Compared to previous results from similar studies on other insect groups, our results clearly show the high potential of the family Scirtidae as indicators of habitat quality. Due to ongoing changes and a decline in biodiversity, science today should rely on long-term species-based ecological studies. We have conducted a long-term ecological dynamics study on the water beetle family Scirtidae, which, although it is very abundant in benthic communities, is still poorly studied. The main objective of this study was to investigate the population aspects (composition, diversity, sex ratio) and ecological aspects (emergence patterns, seasonal dynamics and preferences for environmental factors) of the family Scirtidae over 15 years in Plitvice Lakes NP, Croatia. The study was conducted at three sites and in five different substrate types. A total of three taxa with different distributions were recorded in the study area: Hydrocyphon novaki and H. deflexicollis on the tufa barriers and the Elodes sp. in the spring area. The sex ratio was in favour of males in spring and early summer, while it shifted in favour of females towards the end of autumn. The abundance and emergence of the family were primarily determined by the environmental parameters which showed the greatest fluctuations over a period of 15 years: water temperature, water discharge and oxygen saturation. Our results clearly show that Scirtidae can be used as indicators of stream zonation and habitat quality. Based on the methodology and the results of this study, we conclude that Scirtidae should be used in future monitoring and protection measures in karst freshwater habitats in southeastern Europe. [ABSTRACT FROM AUTHOR]

Individual processes scale up: these are the unique phenotypes that undergo selection, constitute populations, interact with other species, and thus shape biological reality. Understanding how individual animals differ in behaviour, that is understanding how behavioural individualities (personalities) emerge and are selected, leads us to a better understanding of how higher level systems, such as food webs, communities, or ecosystems, function. As amidst the contemporary global environmental crisis, freshwater habitats and their fish inhabitants are disproportionately both biodiverse and threatened, it is of crucial importance to understand how individual fishes cope with the anthropogenic change. In the present work we first provide a snapshot view of what personalities in freshwater fish are, how they manifest in different species, are shaped under different selective pressures, emerge over ontogeny, and form complex traits. This includes the review of research on fish boldness, exploration, activity, aggressiveness and sociability, and on their consistency and correlations. We then focus on three major threats to freshwater fish, on how fish cope with them behaviourally, and on where personalities may have profound ecological and evolutionary outcomes. The chosen focus on habitat fragmentation by damming, climate change and chemical pollution provides us with an insight into the pervasive role fish personalities play in the contemporary world. [ABSTRACT FROM AUTHOR]

Many rivers and streams in Nigeria are habitats of freshwater snails. Many of these snails are edible, whereas others are intermediate hosts of various flatworms. Nine rivers and streams from three towns in Ekiti State, Nigeria, were examined for the presence of freshwater snails. Each freshwater habitat was sampled for snails at the designated sites for 15 min on a monthly basis using a 0.2 mm mesh scoop. The collected snails were transported to the laboratory in pre-labelled plastic containers. Two thousand three hundred and thirty-one (2331) freshwater snails were collected from all habitats. Lanistes libycus had the highest population, 1044 (44.8%). The other species were Melanoides tuberculata 550 (23.6%), Bulinus globosus 401 (17.2%), and Potadoma moerchi 336 (14.4%). Freshwater snails were more abundant at the beginning of the rainy season (March-May) than during heavy rainfall (July-October). The environmental conditions of the study area supported the occurrence of these snail species. Although some species of these snails are edible, others can serve as intermediate hosts for parasitic flatworms, which requires urgent attention. [ABSTRACT FROM AUTHOR]

Although scientific research has identified the causes of undesirable ecological changes in fresh waters, translating the results of research into practical conservation and management, and raising awareness of the need for action, is often inadequate.This Viewpoint considers the present coverage of conservation‐related freshwater research, the application of science to conservation, the extent of collaboration between international organizations, and the level of awareness of freshwater ecosystems and the need for their conservation.Far greater attention has been given to conservation in marine than freshwater areas. This is illustrated by the respective number of publications in the scientific literature, an imbalance in the UN Sustainable Development goals, and, until recently, the lack of an explicit reference to freshwater ecosystems in the UN Global Biodiversity Framework.Four case studies are presented as examples of how freshwater conservation can be made more effective: involving local communities in applying nature‐based solutions; bringing scientists and stakeholders together to discuss how to improve freshwater management; collaborating at a global scale in freshwater protection and restoration; and demonstrating how scientists and government can work together to reconcile the competing needs of nature and human society.Producing and implementing effective conservation and management plans needs a recognition of the extensive diversity of freshwater habitats and species, as well as a systematic evaluation of how scientific information can be translated into action at local, regional and global scales.Data on freshwater ecosystems need to be accessible, comprehensible, unambiguous and available to all those working on practical conservation projects. Many international organizations are already active in this field, but greater collaboration would make their work more effective.Raising awareness needs education and training, carefully targeted at a wide range of audiences, and communicated using the full range of media now available. [ABSTRACT FROM AUTHOR]

Although ostracods are important components in aquatic ecosystems, little is known about their microbiomes. Here, we analyzed the microbiomes of the putative ancient asexual ostracod species, Darwinula stevensoni, in three natural populations from different freshwater habitats in the UK, Belgium, and Spain. We applied high-throughput amplicon sequencing approaches to analyze the V3–V4 part of the bacterial 16S rRNA region. We tested for host-specific microbiomes by comparing bacterial assemblages of ostracods with those of sediment and water samples from the same locations. Around 2,200 Amplicon Sequence Variants (ASVs) were identified from ostracod samples with universal primers and 1,700 ASVs with endosymbiotic-specific primers, illustrating a high microbiome diversity in D. stevensoni. Most bacterial taxa were unique to the microbiome of D. stevensoni as compared to other freshwater invertebrates and to non-marine ostracods. Alpha diversity of ostracod microbiomes did not differ significantly between the three populations, but PERMANOVA detected significant differences in bacterial compositions. Microbiomes varied highly among ostracod specimens from the same population. Possible factors shaping ostracod microbiomes could be latitude, food, age, and environmental variables. Preliminary functionality analyses showed that Darwinula-specific microbiomes contribute to lipid, carbohydrate, nucleotide, and amino acid metabolic processes and the synthesis of co-factors and vitamins. [ABSTRACT FROM AUTHOR]

The efficiency of glass eel restocking as a conservation measure to restore the altered local eel stocks has never been evaluated by integrating the dimension of typological diversity of freshwater habitats in eel recruitment performance in terms of the abundance, density, growth, silvering, survival, catchability and eel yields. Here, we used the electrofishing method during a 6-year study to catch eels, and the most appropriate Jolly–Seber model was applied to estimate the demographic parameters in open populations. We found that most eels were yellow eels in the growth phase with a low abundance (eels 3+: 2.8% and eels 5+: 7.1%) of silver eels, which were only males at the MII migrating phase. Eel recruitment performance varied between sector/river habitats. Restocked eels showed annually positive allometric growth type with good length increments and better condition factors. They have survived in almost all sectors with a survival rate > 0.810. Eels were more abundant and denser (maximum 0.128 individuals m−2) in one sector with a high quality of habitats offering optimal living conditions in terms of the protection against predators and water flow, settlement and food availability, as revealed by it having the highest eel yields. In contrast, no eels were found in two sectors whose habitats offered a high threat of predation, poor burial properties and insufficient protection against water flow. Sector/river habitats play a key role in the success of yellow eel production and certainly, over time, future genitor production. This study provides recommendations for the management of eels and their habitats during restocking aimed at the conservation of this threatened species. [ABSTRACT FROM AUTHOR]

Brownification denotes increasing water color, partly caused by increasing dissolved organic matter of terrestrial origin in freshwater. Brownification has become a wide-spread environmental problem because water color alters the physicochemical environment and biological communities in aquatic ecosystems. However, our understanding of its ecological effects on aquatic macrophytes is limited. Here, an indoor mesocosm experiment with a common submerged macrophyte, Potamogeton crispus, along an increasing gradient of brownification was conducted over a period of 42 days. Results showed that P. crispus was able to overcome low degrees of brownification owing to the plasticity in morphological and physiological traits and P. crispus growth even benefitted from the concomitant nutrients along with brownification. However, the macrophyte growth was negatively affected by a 10-fold increase in water color beyond its current level. Additionally, collapse in antioxidant systems and potent photosynthesis inhibition implied that P. crispus could not adapt to the low-light stress generated under the high degree of brownification. Epiphytic bacteria are more sensitive to brownification than their hosts. Any degree of brownification initially caused a decrease in microbial diversity of epiphytic biofilm, whereafter the concomitant nutrients under brownification favored the growth of epiphytic microorganisms. The shading effect of a large number of epiphytic biofilms under brownification may further aggravate the low-light stress on macrophytes. Overall, the study provides new insights into the comprehensive effects and underlying mechanisms of brownification on macrophytes. [ABSTRACT FROM AUTHOR]

This study comprises the first fish inventory of the Água das Araras stream, a small tributary of the Laranjinha River, in the upper Paraná River basin. Four samplings were carried out seasonally between June 2010 and July 2011, in 12 collecting sites distributed from the headwater to the mouth of Água das Araras stream and its tributaries, using seines and gill nets to capture specimens. A total of 5,328 specimens were collected, distributed in six orders, 15 families, 33 genera, and 41 species. The most representative orders, in terms of species richness, were Siluriformes and Characiformes. Among the families, Characidae (eight species) and Loricariidae (seven species) presented higher richness contributing together with approximately 36.6% of all collected species. The most frequent species captured in ≥75% of the sampled sites were Astyanax lacustris, Characidium aff. zebra, Corydoras aeneus, and Imparfinis schubarti. The classification of species with the Kendeigh Index highlighted the following ranking of the more abundant species: Phalloceros harpagos, C. aeneus, A. lacustris, and I. schubarti. Finally, our results emphasize the importance of sampling small aquatic bodies, revealing their potential for maintaining a significant portion of fish diversity in Neotropical freshwater environments. [ABSTRACT FROM AUTHOR]

World produces 360 million tons of plastic every year, out of which only 7% plastic undergo recycling leaving majority of this waste lying around that get accumulated in the environment, thus posing a serious threat especially in the form of microplastics (MPs) to the large group of organisms on earth. Microplastics have been observed both in freshwater as well as in marine environment; however, recently, the occurrence of MPs in the fresh water that will ultimately lead to pollution in drinking water is emerging as one of the major concern for the scientific community. Till now, relative to the marine environment, the MPs pollution in the fresh water system is not very well understood and still an area of research that needs to be explored in detail. A detailed understanding of the origin, qualification, quantification, hazardous effects, etc. has be established to develop a proper waste management process for the MPs found in fresh water system. This review focuses on the sources, distribution, sampling methods, separation methods, methods of characterization and toxicological effects of microplastics in the freshwater environment. Various factors that affect the transportation and distribution of microplastics in fresh water system are reviewed. It is recommended that a standard protocol must be developed for identification of microplastics for scientific community across the world. The present study will help us to understand the source, transport, and effects of microplastics on the freshwater environment which would thereafter help to standardize the process for quantification and identification of microplastics in the freshwater environment. A combination of methods for the detection and prevention of microplastics in freshwater environment has also been suggested. [ABSTRACT FROM AUTHOR]

Mangrove environments are often characterized by large fluctuations in salinity, ranging from freshwater to hyper‐saline conditions. Most reports have focused on the mechanisms by which mangroves adapt to high salinity. However, how mangroves cope with seasonal freshwater habitats has seldom been studied. To address this question, we surveyed the river salinity and leaf traits (chlorophyll fluorescence, ion concentrations, carbon isotope ratios and osmolality) of Aegiceras corniculatum (L.) Blanco (river mangrove) along a freshwater‐dominated river. A. corniculatum at the upstream site was subjected low salinity, being in fresh water for a long period (up to 310 h) in the wet season, which drastically diminished during the dry season. At both sites, the actual photosystem II efficiency (ФPSII) and electron transport rates (ETR) of the leaves were higher in the wet season than in the dry season, and the carbon isotope (δ13C), ions (Na+ and Cl−) concentrations and osmolality showed no seasonal variations. However, the maximal quantum yield of PSII photochemistry (Fv/Fm), the proportion for closed PSII reaction centres (1 − qP) and non‐photochemical quenching (NPQ) of the leaves at the upstream site maintained high levels in the wet season. This quenching analysis indicated that there was a down‐regulation of photoprotection at the upstream site during wet season. An explanation for this is that long‐term freshwater is a stressful environment for A. corniculatum and maintaining certain level Na+ and Cl− in saline water episode is necessary for A. corniculatum to maintain low water potentials to take up water. [ABSTRACT FROM AUTHOR]

Introduction: The unpredictable evolution of avian influenza viruses (AIVs) presents an ongoing threat to agricultural production and public and wildlife health. Severe outbreaks of highly pathogenic H5N1 viruses in US poultry and wild birds since 2022 highlight the urgent need to understand the changing ecology of AIV. Surveillance of gulls in marine coastal environments has intensified in recent years to learn how their long-range pelagic movements potentially facilitate interhemispheric AIV movements. In contrast, little is known about inland gulls and their role in AIV spillover, maintenance, and long-range dissemination. Methods: To address this gap, we conducted active AIV surveillance in ring-billed gulls (Larus delawarensis) and Franklin's gulls (Leucophaeus pipixcan) in Minnesota's natural freshwater lakes during the summer breeding season and in landfills during fall migration (1,686 samples). Results: Whole-genome AIV sequences obtained from 40 individuals revealed three-lineage reassortants with a mix of genome segments from the avian Americas lineage, avian Eurasian lineage, and a global "Gull" lineage that diverged more than 50 years ago from the rest of the AIV global gene pool. No poultry viruses contained gull-adapted H13, NP, or NS genes, pointing to limited spillover. Geolocators traced gull migration routes across multiple North American flyways, explaining how inland gulls imported diverse AIV lineages from distant locations. Migration patterns were highly varied and deviated far from assumed "textbook" routes. Discussion: Viruses circulating in Minnesota gulls during the summer breeding season in freshwater environments reappeared in autumn landfills, evidence of AIV persistence in gulls between seasons and transmission between habitats. Going forward, wider adoption of technological advances in animal tracking devices and genetic sequencing is needed to expand AIV surveillance in understudied hosts and habitats. [ABSTRACT FROM AUTHOR]

The feeding characteristics of the nase, based on its mouth morphology and feeding behavior related to aquatic habitat substrata sediments make this fish a biological uptake vector for microplastics in freshwater ecosystems. Fibers may have limited absorption through the gastrointestinal tract therefore unlikely to be found in fish gastrointestinal tissue and muscle tissue. The presence of microplastic fibers in the gastrointestinal content is proof of how difficult it is for these fibers to become embedded in other organs. The absence of microplastic fibers in muscle tissue and gastrointestinal tissue is key information for microplastic fabrication and management in aquatic ecosystems. The majority of fish have relatively low levels of microplastics; however, a few individuals have a higher dose. This is true for all types of microplastics analyzed, with the exception of fish that had just one microplastic present in the analyzed matrix. The microplastics are not concentrated in the fish muscle tissue, gastrointestinal tissue and gastrointestinal content in relation to fish age, which may be due to their different mobility in the ecosystem, or due to the recent appearance of this type of contamination and the scale at which microplastics bioaccumulate. Such a relatively common fish species must be included in the assessment and monitoring systems of the Eurasian lotic systems. The risks involved include the transfer of the freshwater environments microplastics into human tissues via the food web of fishing species with the nase as a key basis. [ABSTRACT FROM AUTHOR]

Adaptation to one stressor can influence organismal responses to future environmental changes, either to the same or a novel stressor. But there is a lack of research on this topic, particularly in the context of freshwater habitats. Fluctuating salinity and heatwaves that are becoming more frequent and intensified are affecting freshwater ecosystems. We applied an experimental evolution approach to examine the influence of adaptation to elevated salinity on the population's responses to subsequent salt and heat stress. We conducted lab experiments using Daphnia pulicaria cultured from individuals with previous 8-week exposure history to two salinity treatments (6.5 or 350 mg Cl−/L). Iso-female lines with or without prior exposure to elevated salinity were assayed along a salt gradient (18.5 to 1500 mg Cl−/L) or an acute heat gradient treatment (20 to 35 °C). Our results showed that Daphnia survival, fecundity, and body length growth rate declined with increased salt concentration, with survival and fecundity being most sensitive. The treatment group with previous salt exposure history had higher survival and fecundity than the naïve treatment group when treated with salt, without loss of fitness under low-salinity conditions. Daphnia survival and growth rates were reduced in temperatures higher than 30 °C. Despite the fact that the two stressors can induce similar defense mechanisms, previous exposure history to salt did not prevent Daphnia populations from experiencing reduced survival and growth rates under heated conditions. Our work demonstrates that organisms can rapidly adapt to a stressor that protects them from later exposure to increases in this stressor, without a trade-off in fitness under undisturbed conditions, but this evolved tolerance cannot protect them from all levels of this stressor or alleviate damage by a novel one. [ABSTRACT FROM AUTHOR]

Understanding the effects of species invasions on vulnerable freshwater habitats is crucial to protecting those ecosystems. The vermiculated suckermouth sailfin armored catfish, an abundant, invasive grazer in Florida springs and around the world, may interact with native communities in complex ways, including alteration of nutrient availability, which in turn may influence primary production, with cascading effects through the food web. Armored catfish may differ from native fishes in their body nutrient content because of their high proportion of bony material; therefore, increasing densities of armored catfish may shift nutrient availability to primary producers due to their consumption, excretion, and egestion of nutrients. To evaluate this, we measured N:P ratio of catfish tissues compared to the N:P ratios of two abundant native species and found that catfish had a significantly lower body N:P than native species. We also measured the N and P in catfish gut contents and excreta and found that posterior gut (egesta) N:P was significantly higher than anterior gut (ingesta) N:P. Finally, we measured excreted N and P, finding that excreted N:P was high. These data demonstrate that, because high proportions of P are retained in the bodies of invasive armored catfish, they are a P sink and are, therefore, more likely to limit P availability than native fishes in freshwater spring ecosystems both in Florida and worldwide. [ABSTRACT FROM AUTHOR]

Fish are important elements of aquatic ecosystems. Their communities naturally follow the river continuum and have been well described in the western European freshwater watersheds. In regions of higher endemism, such as the Balkan Peninsula, the widely accepted fish zonation of Illies is doubtfully relevant. In this study, a more suitable categorization of lotic and lentic freshwater ecosystems in Bulgaria is proposed, based on 389 multimethodological and multihabitat fish sampling occasions. Referent-type communities have been determined for 33 types of recognized water bodies. Adapted zonation of Illies is a rough estimation of the real distribution of fish assemblances in the country; moreover, sensitive and/or endemic species are generally of restricted distribution and abundance. In view of the lentic ecosystems, they can be divided into salmonid and cyprinid, at approximately 1500 m above sea level. [ABSTRACT FROM AUTHOR]

Species of the genus Anaspides, known as mountain shrimps, are endemic to Tasmania and inhabit a variety of freshwater habitats such as mountain tarns, pools, creeks and runnels, as well as caves. Until 2015 only two species of Tasmanian mountain shrimps were recognized, A. tasmaniae (Thomson, 1893), which was believed to be widespread all over the island and A. spinulae from Lake St. Clair. Revision of the genus by Ahyong in 2016 recognized 7 species, most having narrow geographic distributions. Only two widespread species remained: A. richardsoni, occurring mainly on the Central Plateau and its margins, and A. swaini, occurring largely in south-western Tasmania. Notably, within A. swaini, three geographically correlated morphological forms were observed. We re-evaluated all three forms of A. swaini and herein describe one of the forms as a new species, A. driesseni, on the basis of morphological and molecular data. Anaspides driesseni corresponds to A. swaini form 3 and occurs mainly in south-eastern Tasmania from the Hartz Mountains over the Snowy Mountains to the Wellington Range. Telson structure, spination and male secondary sexual characters proved taxonomically instrumental. [ABSTRACT FROM AUTHOR]

Aim: Biological invasions are a major threat to biodiversity in aquatic and terrestrial habitats. Insects represent an important group of species in freshwater and terrestrial habitats, and they constitute a large proportion of non‐native species. However, while many non‐native insects are known from terrestrial ecosystems, they appear to be less represented in freshwater habitats. Comparisons between freshwater and terrestrial habitats of invader richness relative to native species richness are scarce, which hinders syntheses of invasion processes. Here, we used data from three regions on different continents to determine whether non‐native insects are indeed under‐represented in freshwater compared with terrestrial assemblages. Location: Europe, North America, New Zealand. Methods: We compiled a comprehensive inventory of native and non‐native insect species established in freshwater and terrestrial habitats of the three study regions. We then contrasted the richness of non‐native and native species among freshwater and terrestrial insects for all insect orders in each region. Using binomial regression, we analysed the proportions of non‐native species in freshwater and terrestrial habitats. Marine insect species were excluded from our analysis, and insects in low‐salinity brackish water were considered as freshwater insects. Results: In most insect orders living in freshwater, non‐native species were under‐represented, while they were over‐represented in a number of terrestrial orders. This pattern occurred in purely aquatic orders and in orders with both freshwater and terrestrial species. Overall, the proportion of non‐native species was significantly lower in freshwater than in terrestrial species. Main conclusions: Despite the numerical and ecological importance of insects among all non‐native species, non‐native insect species are surprisingly rare in freshwater habitats. This is consistent across the three investigated regions. We review hypotheses concerning species traits and invasion pathways that are most likely to explain these patterns. Our findings contribute to a growing appreciation of drivers and impacts of biological invasions. [ABSTRACT FROM AUTHOR]

The Konya Closed Basin (KCB) in Türkiye plays a key role in agricultural production and freshwater supply. However, the basin is impacted by humanly derived nitrogenous compounds and toxic metals. Keeping the water quality at a potable level in the basin is compulsory. This study was part of a project yielding monitoring of water quality in KCB in accordance with the Water Framework Directive (2000/60/EC). Eleven stations, except Beyşehir Lake and Mamasın Dam, were sampled for the first time for freshwater molluscs. Community structure indexes and multivariate statistical analyses were applied to determine the microhabitats of gastropods and their responses to environmental changes. The structure and distribution of gastropod assemblages differed depending on total phosphate, total nitrogen, dissolved oxygen, and pH. This study revealed that most of the gastropods in KCB are relatively tolerant to biodegradable pollution. However, there is a strong observed decline in population size requiring intensive future monitoring; measures have to be taken to preserve the remaining populations. Two endemic species need an urgent action plan to protect their habitats: Theodoxus anatolicus of Çeltik Canal and Bithynia pseudemmericia of Beyşehir Lake; a re-assessment of their extinction risk according to the IUCN rules is needed (2022). The results of this study will be useful for comparison with future studies to document potential improvements or continued ecological regression in the quality of aquatic ecosystems in the watershed. [ABSTRACT FROM AUTHOR]

Nucleic acids released by organisms and isolated from environmental substrates are increasingly being used for molecular biomonitoring. While environmental DNA (eDNA) has received much attention, the potential of environmental RNA as a biomonitoring tool remains under‐explored. Several recent studies using paired DNA and RNA metabarcoding of bulk samples suggest that RNA might better reflect "metabolically active" parts of the community. However, such studies mainly capture organismal eDNA and eRNA. For larger eukaryotes, isolation of extra‐organismal RNA will be important, but viability needs to be examined in a field‐based setting. In this study we evaluate (a) whether extra‐organismal eRNA release from macroeukaryotes can be detected given its supposedly rapid degradation, and (b) if the same field collection methods for eDNA can be applied to eRNA. We collected eDNA and eRNA from water in lakes where fish community composition is well documented, enabling a comparison between the two nucleic acids in two different seasons with monitoring using conventional methods. We found that eRNA is released from macroeukaryotes and can be filtered from water and metabarcoded in a similar manner as eDNA to reliably provide species composition information. eRNA had a small but significantly greater true positive rate than eDNA, indicating that it correctly detects more species known to exist in the lakes. Given relatively small differences between the two molecules in describing fish community composition, we conclude that if eRNA provides significant advantages in terms of lability, it is a strong candidate to add to the suite of molecular monitoring tools. [ABSTRACT FROM AUTHOR]

Surfactants are used to control microbial biofilms in industrial and medical settings. Their known toxicity on aquatic biota, and their longevity in the environment, has encouraged research on biodegradable alternatives such as rhamnolipids. While previous research has investigated the effects of biological surfactants on single species biofilms, there remains a lack of information regarding the effects of synthetic and biological surfactants in freshwater ecosystems. We conducted a mesocosm experiment to test how the surfactant sodium dodecyl sulfate (SDS) and the biological surfactant rhamnolipid altered community composition and metabolic activity of freshwater biofilms. Biofilms were cultured in the flumes using lake water from Lake Lunz in Austria, under high (300 ppm) and low (150 ppm) concentrations of either surfactant over a four-week period. Our results show that both surfactants significantly affected microbial diversity. Up to 36% of microbial operational taxonomic units were lost after surfactant exposure. Rhamnolipid exposure also increased the production of the extracellular enzymes, leucine aminopeptidase, and glucosidase, while SDS exposure reduced leucine aminopeptidase and glucosidase. This study demonstrates that exposure of freshwater biofilms to chemical and biological surfactants caused a reduction of microbial diversity and changes in biofilm metabolism, exemplified by shifts in extracellular enzyme activities. Key points: • Microbial biofilm diversity decreased significantly after surfactant exposure. • Exposure to either surfactant altered extracellular enzyme activity. • Overall metabolic activity was not altered, suggesting functional redundancy. [ABSTRACT FROM AUTHOR]

Freshwater ascomycetes are a group of fungi of great ecological importance because they are involved in decomposition processes and the recycling of organic matter in aquatic ecosystems. The taxonomy of these fungi is complex, with representatives in several orders of the phylum Ascomycota. In the present study, we collected ninety-two samples of plant debris submerged in freshwater in different locations in Spain. The plant specimens were placed in wet chambers and developed several fungi that were later isolated in pure culture. A main phylogenetic tree using the nucleotide sequences of D1–D2 domains of the 28S nrRNA gene (LSU) was built to show the taxonomic placement of all our fungal strains, and, later, individual phylogenies for the different families were built using single or concatenated nucleotide sequences of the most suitable molecular markers. As a result, we found a new species of Amniculicola that produces a coelomycetous asexual state, a new species of Elongatopedicellata that produces an asexual state, a new species of Neovaginatispora that forms both sexual and asexual states in vitro, and the sexual states of two species of Pyrenochaetopsis, none of which have been reported before for these genera. In addition, we describe a new species of Pilidium characterized by the production of copper-colored globose conidiomata, and of Pseudosigmoidea, which produces well-developed conidiophores. [ABSTRACT FROM AUTHOR]

Aquatic insects undergo substantial shifts in their ecology during development, such as changing from a benthic consumer stage (e.g., larva) to a pelagic non-consumer stage (e.g., non-feeding pupae). Fish may differentially target these life-stages during predation, but the prevalence of this feeding is largely unknown. To determine how stage-specific feeding varies among fish species, we sampled fish diets from four freshwater habitats in southeastern South Dakota, USA. We measured the fraction of gut contents in fish that consisted of prey that do not feed in the aquatic food web (e.g., terrestrial insects or non-consumer stages of aquatic insects). We also compared estimates of dietary overlap using methods that either included or did not include prey life-stage information. When averaged across 22 fish species, 17% (10 to 25%) of diet dry mass consisted of prey that were not consumers in the aquatic food web. Non-consumer prey came from a mix of terrestrial subsidies (11%) and non-feeding life-stages of aquatic prey (6%). The overall fraction of non-consumer prey varied widely among fish species, from ~ 2% in a darter (Etheostoma nigrum) to ~ 52% in a minnow (Notropis stramineus). Adding prey life-stage information to estimates of dietary overlap revealed the presence of prey life-stage specialists and generalists in the fish populations, causing overlap to decline. The magnitude of this decline increased as individual fish ate more non-larval stages of aquatic insects. These results reveal the importance of considering developmental changes in prey when estimating fish diets and indicate that stage-structured prey partitioning reduces dietary overlap. [ABSTRACT FROM AUTHOR]

Many biodiversity studies focus on explaining high tropical species richness, but an equally dramatic yet understudied pattern involves the divergent richness of land, sea and freshwater. Here, we reveal the origins of these richness differences among habitats across animals and plants. Most plant and animal species are terrestrial, although these habitats cover only ~28% of Earth's surface. Marine habitats have fewer species over a larger area (~70%). Freshwater habitats have relatively high richness and exceptional phylogenetic diversity given their tiny area (2%). The relative richness of habitats is related to variation in diversification rates. Based on ancestral reconstructions of habitat, we find that most marine species are descended from marine ancestors and most terrestrial species from freshwater ancestors. Yet, most extant animal richness in freshwater is derived from terrestrial ancestors. Overall, our results reveal the origins of fundamental but neglected biodiversity patterns, and highlight the conservation importance of freshwater habitats. [ABSTRACT FROM AUTHOR]

The intestinal microbiota of marine animals was influenced by the water and environment in which they live. The Amur ide (Leuciscus waleckii) adapts to extremely high alkalinity and is an ideal material for aquacultural studies of alkaline adaptation. In this study, we screened intestinal indicator flora and functional redundancy of intestinal colonies in alkaline-water species (AW) and freshwater species (FW) of Amur ide (L. waleckii) in these different aquatic environments. The available vs. community composition correlations were then predicted by contrasting each other with the flora contained in environmental water samples. Here, five microbial species and six genera were identified owing to the classifiable sequence. The intestinal microbiota that existed in AW and FW had approximately 1/3 of the operational taxonomic units in the respective living water environments, meaning gut microbes in the aqueous habitats will have an influential association with gut microbes in AW and FW. Compared to the bacterial composition of the FW intestine and that present in freshwater, Moraxella osloensis, Psychrobacter maritimus , and Psychrobacter faecalis were significantly enriched in the intestine of AW and alkaline water samples. In the FW intestine and freshwater samples, however, Cryptomonas curvata and Polynucleobacter asymbioticus were highly improved, which can be summarized as Enterobacter sp., the predominant population in the AW gut, while Aeromonas and Ralstonia being primarily present in FW intestines. Photosynthetic bacteria were most significant in both water samples. The results indicated that the intestinal microbiota composition, abundance, and diversity of AW and FW were quite different. In contrast, the microbial composition of the additional alkaline water and freshwater environments showed slight differences. This study expects to enhance our understanding of the alkalinity tolerance of L. waleckii , which will be provided for the breeding of fish living in alkaline water, and push the development of alkaline water resources with increased efficiency. [ABSTRACT FROM AUTHOR]

Foraminifera include diverse shell‐building lineages found in a wide array of aquatic habitats from the deep‐sea to intertidal zones to brackish and freshwater ecosystems. Recent estimates of morphological and molecular foraminifera diversity have increased the knowledge of foraminiferal diversity, which is critical as these lineages are used as bioindicators of past and present environmental perturbation. However, a comparative analysis of foraminiferal biodiversity between their major habitats (freshwater, brackish, intertidal, and marine) is underexplored, particularly using molecular tools. Here, we present a metabarcoding survey of foraminiferal diversity across different ecosystems using newly designed foraminifera‐specific primers that target the hypervariable regions of the foraminifera SSU‐rRNA gene (~250–300 bp long). We tested these primer sets on four foraminifera species and then across several environments: the intertidal zone, coastal ecosystems, and freshwater vernal pools. We retrieved 655 operational taxonomic units (OTUs); the majority of which are undetermined taxa that have no closely matching sequences in the reference database. Furthermore, we identified 163 OTUs with distinct habitat preferences. Most of the observed OTUs belonged to lineages of single‐chambered foraminifera, including poorly explored freshwater foraminifera which encompass a clade of Reticulomyxa‐like forms. Our pilot study provides the community with an additional set of newly designed and taxon‐specific primers to elucidate foraminiferal diversity across different habitats. [ABSTRACT FROM AUTHOR]

Indiscriminate plastic littering behaviour of inhabitants continues to pose a threat to water bodies with its repercussions on human health and the integrity of the environment. This paper assessed the ecological impact of plastics that are less than 5 mm on the longest dimension, hereinafter called microplastics. Sixty (60) residents were purposively sampled using a snow-balling approach for the study. Questionnaires, field observations of microplastics and sources, fish, and water sediments from the River were the data for the study. Data was analysed with SPSS version 20.0 and presented in tables and figures. Laboratory analysis of microplastics was run on sediments trawled, and on the digestive tracts and gills of fishes caught, all from the River, to assess the accumulation of microplastics. The study revealed that microplastics are present in the River and there is uptake of microplastics by some resident aquatic life which may pose threat to lives. The study further revealed positive correlations between number of fishes and microplastics loads in fish and between microplastic loads in water and loads in fish. Residents are aware of microplastics in the catchment area of the River. The unregulated gutters that flow directly into the River are the main sources. Wind and running water were discovered as the potential ways by which microplastics are deposited into the River. It is therefore recommended that wastewater be treated before reaching the River and gutters should be channelled out of the River where necessary and plastics usage should be regulated and if possible, banned. [ABSTRACT FROM AUTHOR]

The genus Pseudoblepharisma is currently comprised of only one species, P. tenue, and one variant, P. tenue var. viride, both described as free-living ciliates thriving in oxygen depleted freshwater habitats of Europe. Here we report on this genus being discovered from subtropical freshwaters of Florida, USA. The Florida strain diverges from the P. tenue by being much larger, as well as having a far higher density of intracellular symbiotic green algae, resembling P. tenue var. viride. Unlike its European counterparts, the North American strain was observed to build a lorica, likely useful for protection and feeding; this has not been previously described for this genus. In contrast to P. tenue, the Florida strain does not have endosymbiotic purple bacteria. Despite large distances between sampling zones, the species is a close match at a morphological level to Pseudoblepharisma tenue var. viride. We provide the first 18S rRNA gene sequence for this species, allowing future investigations into the biogeography of this genus. As intensive sampling efforts continue to increase, cryptic microbial species will continue to be recorded from diverse freshwater habitats at a global scale. [ABSTRACT FROM AUTHOR]

Worldwide, scientists are increasingly collaborating with the general public. Citizen science methods are readily applicable to freshwater research, monitoring, and education. In addition to providing cost‐effective data on spatial and temporal scales that are otherwise unattainable, citizen science provides unique opportunities for engagement with local communities and stakeholders in resource management and decision‐making. However, these methods are not infallible. Citizen science projects require deliberate planning in order to collect high data quality and sustain meaningful community partnerships. Citizen science practitioners also have an ethical responsibility to ensure that projects are not putting the safety of participants at stake. We discuss here how citizen science is being applied in freshwater research, emerging challenges in project planning and implementation, as well as how citizen science is shaping public understanding, policy, and management of freshwaters. This article is categorized under:Science of Water > Water QualityWater and Life > Conservation, Management, and AwarenessHuman Water > Water GovernanceWater and Life > Methods [ABSTRACT FROM AUTHOR]

Current knowledge on environmental distribution and taxon richness of free‐living bacteria is mainly based on cultivation‐independent investigations employing 16S rRNA gene sequencing methods. Yet, 16S rRNA genes are evolutionarily rather conserved, resulting in limited taxonomic and ecological resolutions provided by this marker. The faster evolving protein‐encoding gene priB was used to reveal ecological patterns hidden within a single operational taxonomic unit (OTU) defined by >99% 16S rRNA sequence similarity. The studied subcluster PnecC of the genus Polynucleobacter represents a ubiquitous group of abundant freshwater bacteria with cosmopolitan distribution, which is very frequently detected by diversity surveys of freshwater systems. Based on genome taxonomy and a large set of genome sequences, a sequence similarity threshold for delineation of species‐like taxa could be established. In total, 600 species‐like taxa were detected in 99 freshwater habitats scattered across three regions representing a latitudinal range of 3,400 km (42°N to 71°N) and a pH gradient of 4.2 to 8.6. In addition to the unexpectedly high richness, the increased taxonomic resolution revealed structuring of Polynucleobacter communities by a couple of macroecological trends, which was previously only demonstrated for phylogenetically much broader groups of bacteria. An unexpected pattern was the almost complete compositional separation of Polynucleobacter communities of Ca2+‐rich and Ca2+‐poor habitats. This compositional pattern strongly resembled the vicariance of plant species on silicate and limestone soils. The new cultivation‐independent approach presented opened a window to an incredible, previously unseen diversity, and enables investigations aiming on deeper understanding of how environmental conditions shape bacterial communities and drive evolution of free‐living bacteria. [ABSTRACT FROM AUTHOR]

The Eurytemora affinis species complex (Copepoda: Calanoida) is widespread in coastal and estuarine waters in the northern hemisphere. The species Eurytemora carolleeae belongs to this complex. It was recently described and recognized as an invasive copepod for European waters. Since then, it was found in a few European estuaries. Based on molecular and morphological studies, we observed that E. carolleeae has expanded into new freshwater habitats in Central Europe. We carried out detailed morphological analysis for this species which indicates the potential higher stability of the populations in freshwater habitats compared to brackish waters. Fluctuating asymmetry did not significantly differ between freshwater and brackish water habitats, but the share of deformed specimens was considerably larger in brackish waters. We also found that season and habitat influenced the morphology of Eurytemora. In the molecular analyses, we focused on mitochondrial (COI) as well as nuclear gene markers (18S rDNA, ITS1-2) in E. carolleeae. In addition, for the first time, we analyzed the cytochrome b gene of the latter species. A wide distribution of E. carolleeae in the Oder River system in Central Europe indicates that it is a suitable habitat for the present populations and suggests further expansion of the species into continental waters. [ABSTRACT FROM AUTHOR]

Identifying environmental predictors of phenotype is fundamentally important to many ecological questions, from revealing broadscale ecological processes to predicting extinction risk. However, establishing robust environment—phenotype relationships is challenging, as powerful case studies require diverse clades which repeatedly undergo environmental transitions at multiple taxonomic scales. Actinopterygian fishes, with 32,000+ species, fulfil these criteria for the fundamental habitat divisions in water. With four datasets of body size (ranging 10,905–27,226 species), I reveal highly consistent size‐by‐habitat‐use patterns across nine scales of observation. Taxa in marine, marine‐brackish, euryhaline and freshwater‐brackish habitats possess larger mean sizes than freshwater relatives, and the largest mean sizes consistently emerge within marine‐brackish and euryhaline taxa. These findings align with the predictions of seven mechanisms thought to drive larger size by promoting additional trophic levels. However, mismatches between size and trophic‐level patterns highlight a role for additional mechanisms, and support for viable candidates is examined in 3439 comparisons. [ABSTRACT FROM AUTHOR]

Local extinctions break species interactions and have cascading effects throughout ecosystems; parasites are often severely affected. The European bitterling, Rhodeus amarus, is a cyprinid fish that parasitizes unionid mussels by laying eggs into the mussel gill cavity, where embryos develop and emerge as active juveniles; this relationship is obligatory for the bitterling.This article describes a field experiment aimed at averting the secondary extinction of the European bitterling after a complete die‐off of a freshwater mussel community, as a result of habitat destruction.Approximately 5,000 unionid mussels were reintroduced within the short time frame in which the remnant bitterling population was still present at the site. Mussel survival was high, and bitterling resumed reproduction, with vigorous courtship observed within 24 hours of mussel release. Recruitment was successful, as evidenced by increased occupancy, densities, and relative frequencies in the fish assemblage. The frequency of sub‐adults and young‐of‐the‐year changed from 0% before mussel reintroduction to 80% a year later, and 50% 2 years later, when young‐of‐the‐year contributed to about half of the young fish. No bitterling were observed at two control sites where mussels were not reintroduced.This study exemplifies how the timely restitution of affiliate species can avert co‐extinction. It also shows how the conservation of the bitterling within its historical distribution range can serve mussel conservation, including species that although not legally protected, are important keystone species and ecosystem engineers, shaping the structure and function of a broad range of freshwater habitats. [ABSTRACT FROM AUTHOR]

High biodiversity is a prerequisite for the integrity, stability, and functioning of global aquatic ecosystems, but it is currently subject to anthropogenic threats. Small freshwater bodies with high habitat diversity are essential to sustain regional biodiversity, but species inventory and biodiversity are largely overlooked, especially in mountainous regions. In the Italian Alps, obligate assessments of freshwater biota (e.g., for the European water framework directive, WFD) are usually done in larger rivers or lakes only, which is why many taxa from small freshwater habitats might have been overlooked so far. Here we summarize and discuss the efforts to record aquatic invertebrates within the framework of so-called "Biodiversity Days", organized since 2001 at 13 different sites located across the North Italian province of South Tyrol. These events with voluntary participation of scientists and naturalists from universities and environmental agencies led to the detection of 334 benthic invertebrate taxa in streams and lakes (mostly at species or genus level), whereby higher taxa richness was found in streams. The overall hierarchy of species numbers within invertebrate orders or families corresponded to that of other Alpine regions (groups richest in taxa were Chironomidae and Trichoptera) and these Biodiversity Days contributed to biodiversity research of that region in detecting 167 additional taxa. Besides analyzing yearly gains in the regional taxa inventory, we predict that future surveys will lead to new discoveries of aquatic taxa for that province (i.e., current modeling estimates a regional inventory of more than 600 taxa). However, specific surveys in hitherto unconsidered habitats, such as morphologically modified or urban waters, might reveal even more taxa than currently estimated. Besides characterizing the invertebrate fauna of this region and providing a first reference list for future monitoring projects in the same region, this work demonstrates that such Biodiversity Days can contribute to biodiversity research. [ABSTRACT FROM AUTHOR]

Aim: Fish community composition is shaped by current and historical factors. In recently formed ecosystems, however, as the Quaternary coastal lagoons of South America, the influence of historical factors has less frequently been investigated. The low rate of endemism in these lagoons suggests a limited role for speciation while their dynamic formation history suggests local extinction and dispersal limitation could have affected present species composition. We aimed to assess the influence of past and current factors on the beta diversity of those communities and explore the main processes involved. Location: Atlantic coast of South America. Taxon: Fishes (173 species). Methods: We built a dataset of species occurrence in 129 lagoons across eight freshwater ecoregions of the world (FEOWs) located between latitudes 0° and 36°, and calculated beta diversity (βjac) and its turnover (βjtu) and nestedness (βjne) components. We used a partial Mantel test and multiple regressions on distance matrices to evaluate the importance of past and current factors, and of geographical distance in determining beta diversity. Past variables were those representing the historical freshwater habitat during the last glacial maximum (LGM), and contemporary variables were those related to current habitat. Results: We found high values of βjac within the FEOWs, with βjtu prevailing over βjne. Both past (palaeodrainage) and current (drainage area, salinity and lagoon area) factors affected species dissimilarity (βjac = 46%) and its components (βjtu = 44% and βjne = 20%), although explanation was, in part, shared with geographical distance. Individually, the influence of past factors was prevalent in beta diversity and its components. Main conclusions: The large influence of the past factors on beta diversity suggests that major changes in the availability of freshwater habitats and connectivity since the Pleistocene must have affected the colonization, extinction and recolonization processes of fishes along the eastern coast of South America. We suggest that the high beta diversity values result from limited dispersal after extinctions in the LGM. The dissimilar freshwater fish communities currently seen result from heterogeneous subsets of the regional species pool that persisted in landscape refuges during past sea level increases and then recolonized coastal lagoons. [ABSTRACT FROM AUTHOR]

Yellow flag iris (Iris pseudacorus L.) is a highly invasive aquatic plant that is primarily known to occupy freshwater habitats. We report the observation of multiple patches of reproductively mature I. pseudacorus persisting in coastal habitats devoid of consistent sources of freshwater. [ABSTRACT FROM AUTHOR]

Aim: Our ability to model species distributions and abundances is a valuable ecological tool in predicting future distributions of species. Effectively incorporating connectivity into these predictions is crucial; however, many connectivity measures utilize metrics which may not have a direct relation to the dispersal capacity of the species they are attempting to model. The identification of more relevant metrics is therefore a vital step forward in species distribution modelling. Location: 85 freshwater lakes across a latitudinal gradient in Sweden, and an additional 282 freshwater lakes in one drainage basin in northern Norway. Methods: To investigate the effect of different connectivity measures, we first record recolonization of fish into lakes previously treated with the piscicide rotenone. Two invasive fish species, the northern pike (Esox lucius) and the European perch (Perca fluviatilis), were used as focal study species. We model the distributions of these species in a drainage basin with snapshot data of present‐day distributions to see how well the effects of the different connectivity measures correspond to the effects seen in our recolonization study. Connectivity is quantified using slope and distance along streams connecting lacustrine populations. Results: The effects of connectivity variables were similar in both the recolonization study and the species distribution modelling. Incorporation of connectivity improved species distribution models significantly. There was little evidence for the inclusion of distance between populations, while there was strong evidence for the inclusion of different slope parameters for both species. Main conclusions: Our study demonstrates the need to ensure the relevance of connectivity measures when accounting for dispersal limitation in distribution models. The correspondence of estimated connectivity measures from recolonization studies to those estimated from species distribution models demonstrates a link between species dispersal capacity and the connectivity measures employed, and is likely to improve our ability to predict species future distributions. [ABSTRACT FROM AUTHOR]

Microplastic is a contaminant of concern in freshwater ecosystems worldwide. Microplastic particles within aquatic habitats are colonized by dense microbial biofilms, and previous studies have shown that microplastic microbiomes are distinct in taxonomic composition from bacterial assemblages in the surrounding environment. However, questions remain about the degree to which microplastic selects for specific bacterial taxa across diverse aquatic habitats. We used laboratory microcosms inoculated with water from 3 rivers in northern Illinois watersheds with distinct land-use types to test the hypothesis that microbiomes present on microplastic would be similar even when the microplastic was incubated with microbial assemblages from different source waters. When microplastic from a commercial soap and ceramic tiles were incubated with water from each of the 3 rivers for ~1 mo, the bacterial assemblages that colonized the microplastic were remarkably consistent in taxonomic composition, whereas the planktonic and tile bacterial assemblages originating from the 3 rivers were distinct. The number of bacterial operational taxonomic units found within the microplastic microbiomes was consistent across source water treatments and ~3× lower than in the surrounding water and tiles. Some of the bacterial taxa that were over-represented in the microplastic microbiomes in our experiment can metabolize plastic or plastic-associated compounds. If microplastic microbiomes are metabolizing plastic polymers, this process could have significant implications for the long-term fate of microplastic in freshwater habitats. [ABSTRACT FROM AUTHOR]

The phylogroup Chloromonadinia (Volvocales, Chlorophyceae) encompasses ecologically versatile green microalgae with a predominantly freshwater and snow lifestyle. Although a few species have been described from soils, the evolutionary history of terrestrial volvocalean flagellates is poorly known due to undersampling. Here we provide new insights into the phylogenetic position of terrestrial flagellates within the Chloromonadinia and investigate six unresolved strains from terrestrial and freshwater habitats in both hemispheres. The terrestrial strains differed in cell morphology, ultrastructure and lifestyle from the freshwater ones, therefore, we expected them to represent distinct evolutionary lineages (species or genera). While the terrestrial strain SAG 25.87 (Chloromonas gracillima comb. & stat. nov.) from Czech mountains clustered within the psychrotolerant core Chloromonas clade, the other terrestrial strains formed a phylogenetically separate lineage which we proposed as Ostravamonas gen. nov. The new genus differs from other closely related Chloromonadinia genera by chloroplast, eyespot, papilla and cell-wall morphology. Two terrestrial strains, CAUP G 1401 (coal spoil heap; Czechia) and SAG 12.72 (acidic soil; New Zealand), were designated as Ostravamonas chlorostellata comb. nov. and represent the first Chloromonadinia microalgae discovered in acidic terrestrial environments. Closely related 'Chlamydomonas' strains SAG 75.81 (ditch; France) and CCAP 11/108 (origin unknown) were reassigned to Ostravamonas meslinii comb. nov. and Ostravamonas tenuiincisa sp. nov., respectively. Our study shows that the traditional 'Chlamydomonas' still hides an overlooked diversity of species with a terrestrial lifestyle that are nested phylogenetically within the Chloromonadinia phylogroup. [ABSTRACT FROM AUTHOR]

With about 5,000 species worldwide, the Heteroptera or true bugs are the most diverse taxon among the hemimetabolous insects in aquatic and semi-aquatic ecosystems. Species may be found in almost every freshwater environment and have very specific habitat requirements, making them excellent bioindicator organisms for water quality. However, a correct determination by morphology is challenging in many species groups due to high morphological variability and polymorphisms within, but low variability between species. Furthermore, it is very difficult or even impossible to identify the immature life stages or females of some species, e.g., of the corixid genus Sigara. In this study we tested the effectiveness of a DNA barcode library to discriminate species of the Gerromorpha and Nepomorpha of Germany. We analyzed about 700 specimens of 67 species, with 63 species sampled in Germany, covering more than 90% of all recorded species. Our library included various morphological similar taxa, e.g., species within the genera Sigara and Notonecta as well as water striders of the genus Gerris. Fifty-five species (82%) were unambiguously assigned to a single Barcode Index Number (BIN) by their barcode sequences, whereas BIN sharing was observed for 10 species. Furthermore, we found monophyletic lineages for 52 analyzed species. Our data revealed interspecific K2P distances with below 2.2% for 18 species. Intraspecific distances above 2.2% were shown for 11 species. We found evidence for hybridization between various corixid species (Sigara, Callicorixa), but our molecular data also revealed exceptionally high intraspecific distances as a consequence of distinct mitochondrial lineages for Cymatia coleoptrata and the pygmy backswimmer Plea minutissima. Our study clearly demonstrates the usefulness of DNA barcodes for the identification of the aquatic Heteroptera of Germany and adjacent regions. In this context, our data set represents an essential baseline for a reference library for bioassessment studies of freshwater habitats using modern high-throughput technologies in the near future. The existing data also opens new questions regarding the causes of observed low inter- and high intraspecific genetic variation and furthermore highlight the necessity of taxonomic revisions for various taxa, combining both molecular and morphological data. [ABSTRACT FROM AUTHOR]

Elodea nuttallii is an invasive plant widely distributed in many European freshwater habitats. The species has been recently added to the list of invasive alien species of Union concern (European Union (EU) Regulation 1143/2014). We aim to investigate the species' potential distribution across the EU to provide a scientific basis for preventing further spread. To this end, we generated a model-based habitat suitability map for E. nuttallii in the EU, showing areas where the plant is most likely to establish and persist over time. The MaxEnt algorithm was used for implementing the map, taking into account environmental information and the most updated geographically referenced data on the species' occurrence. The R package ENMeval and extraction of occurrence data at three spatial scales were used to compensate for sampling bias and model overfitting. Our results suggest that most of the EU suitable areas for the establishment of E. nuttallii are already occupied by the species. Still, there are many non-infested areas across the EU, and considering the rapid spread of E. nuttallii and the highly connected waterbodies in Europe, it is likely that these areas will be invaded in the near future. Among these, several areas fall within sites of the Natura 2000 protected network. We suggest that these areas should receive conservation priority, and early warning and rapid response mechanisms should be locally developed against new introductions of the species. [ABSTRACT FROM AUTHOR]

We document the morphology of 15 species of Eunotia from freshwater habitats in the Falkland Islands using light and electron microscopy, and describe four new species, Eunotia australovalida, Eunotia inconspicua, Eunotia floweriana and Eunotia latecapitata. Diatom assemblages were studied from a range of habitats on East Falkland, West Falkland, Saunders Island and Pebble Island, which differed in water chemistry and hydrological conditions including streams, ponds, lakes, springs and damp terrestrial habitats. Significant site and species groups obtained by cluster analysis are related to environmental conditions. Island species-area relationships for Eunotia from the sub-Antarctic region, and the wider geographic distributions of seven Eunotia species from the Falkland Islands are shown. [ABSTRACT FROM AUTHOR]

With about 5,000 species worldwide, the Heteroptera or true bugs are the most diverse taxon among the hemimetabolous insects in aquatic and semi-aquatic ecosystems. Species may be found in almost every freshwater environment and have very specific habitat requirements, making them excellent bioindicator organisms for water quality. However, a correct determination by morphology is challenging in many species groups due to high morphological variability and polymorphisms within, but low variability between species. Furthermore, it is very difficult or even impossible to identify the immature life stages or females of some species, e.g., of the corixid genus Sigara. In this study we tested the effectiveness of a DNA barcode library to discriminate species of the Gerromorpha and Nepomorpha of Germany. We analyzed about 700 specimens of 67 species, with 63 species sampled in Germany, covering more than 90% of all recorded species. Our library included various morphological similar taxa, e.g., species within the genera Sigara and Notonecta as well as water striders of the genus Gerris. Fifty-five species (82%) were unambiguously assigned to a single Barcode Index Number (BIN) by their barcode sequences, whereas BIN sharing was observed for 10 species. Furthermore, we found monophyletic lineages for 52 analyzed species. Our data revealed interspecific K2P distances with below 2.2% for 18 species. Intraspecific distances above 2.2% were shown for 11 species. We found evidence for hybridization between various corixid species (Sigara, Callicorixa), but our molecular data also revealed exceptionally high intraspecific distances as a consequence of distinct mitochondrial lineages for Cymatia coleoptrata and the pygmy backswimmer Plea minutissima. Our study clearly demonstrates the usefulness of DNA barcodes for the identification of the aquatic Heteroptera of Germany and adjacent regions. In this context, our data set represents an essential baseline for a reference library for bioassessment studies of freshwater habitats using modern high-throughput technologies in the near future. The existing data also opens new questions regarding the causes of observed low inter- and high intraspecific genetic variation and furthermore highlight the necessity of taxonomic revisions for various taxa, combining both molecular and morphological data. [ABSTRACT FROM AUTHOR]

Connectivity between freshwater habitats and marine areas is heavily obstructed by anthropogenic structures (e.g. weirs, pumping stations, sluices…), leading to a high pressure on diadromous fish populations. A better understanding of fish migration behaviour in relation to these barriers is needed to take proper mitigation actions. We investigated the impact of migration barriers on downstream migrating European eel ( Anguilla anguilla L.) by tracking 50 acoustically tagged eels between July 2012 and March 2015 in a Belgian polder area. The study area was selected due to the presence of a wide range of migration barriers, such as two pumping stations, a weir and tidal sluices. These structures regulate the water level, resulting in discontinuous flow conditions. The results showed that migration was primarily nocturnal and discharge appeared to be the main trigger for migration in the polder. We also observed substantial delays and exploratory behaviour near barriers. Delays can have a serious impact on eels since their energy resources are limited for a successful trans -Atlantic migration. In addition, delays and exploratory behaviour can also increase predation and disease risk. The obtained knowledge can contribute to efficient management such as improved fish passage and guidance solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recovering salmon requires understanding effects of habitat degradation on populations. • Diverse relationships at finer scales highlight the complexity of salmon responses to habitat. • Relationships between salmon trends and habitat pressures broke down at the provincial scale. • Nonetheless, pressure indicators are still useful for province-wide land-use planning. Global freshwater biodiversity is declining at rates greater than in terrestrial or marine environments, largely due to habitat alteration and loss. Pacific salmon are declining throughout much of their southern range due to a combination of pressures in their marine and freshwater habitats. There is, therefore, an urgent need to understand the main drivers of decline to inform both fisheries and land-use management. Here, we draw on a suite of freshwater habitat pressure indicators to test whether we can detect relationships between them and trends in Pacific salmon spawner abundance throughout British Columbia. We related trends in spawner abundance (n = 3691 populations) to ten habitat pressure indicators that represent a snapshot in time of the level of degradation in salmon freshwater spawning habitats (e.g., Equivalent Clearcut Area, percent watershed area impacted by urban development or agriculture). Evidence of relationships between freshwater habitat pressure indicators and trends in spawner abundance was weak at the province-wide scale, while variable in both direction and magnitude at the watershed scale likely due to the mediating effects of regional biological and physical factors. We used these empirical relationships to assess the vulnerability of individual species and regions to increasing habitat pressures. Vulnerability was highest when multiple conditions coincided: when salmon were sensitive to the habitat pressure indicator, the current level of disturbance under that indicator was moderate or low, and populations were declining but not yet at rates high enough to be deemed "threatened". These findings highlight the need to consider the current state of the landscape and of populations when assessing where habitat protection might have the greatest benefit for biodiversity conservation. Strategic recovery planning for Pacific salmon requires multi-scale approaches that account for the diversity and complexity of relationships between habitat disturbance and population dynamics. [ABSTRACT FROM AUTHOR]