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Plastic production has inevitably increased in the past few decades and is one of today's most diverse materials. With this growing production and broader use, aquatic ecosystems have become the trash barrel for all kinds of plastic, becoming a looming spectre to the habitat and functions of both inland and offshore ecosystems. Microplastics are a pollutant of growing concern, capable of harming aquatic organisms and entering the food web. While, freshwater microplastic research has expanded in recent years, much remains to be discovered regarding microplastic sources and delivery pathways in these environments. Plastic pollution is considered an emerging global environmental concern that could significantly affect biological diversity and potentially cause adverse effects on human health. Compared to the studies on microplastics in marine ecosystems, the studies on their presence in freshwater ecosystems have received relatively less attention. This review article focuses on the literature available on reports of microplastic occurrence, its distribution in freshwater ecosystems worldwide, and its insidious effects, which are of emerging concern. [ABSTRACT FROM AUTHOR]

The ecological significance of freshwater ecosystems for conservation in the temperate zone has been determined by aquatic biologists using a variety of ecological techniques. One such tool is the Community Conservation Index (CCI), which was primarily developed in Britain but is also recommended for international use. The current study intends to further test the CCI's applicability and its sensitivity in identifying freshwater systems of high conservation importance. The pristine condition of three natural monument (Arinta, Ekor, and Oowu waterfalls) streams was evaluated in this study using the macroinvertebrate metric indicators, and the results were compared with their CCIs. The relative compositions of stress-sensitive species, facultative species, functional feeding guilds (FFGs), and modes of locomotion or microhabitat preference (ML/MP) were selected as the macroinvertebrate metrics. The fauna was dominated by the taxonomic group EPT (Ephemeroptera, Plecoptera, Trichoptera), with the highest EPT-related metrics found at Oowu Waterfalls. Ironically, because a vulnerable species (i.e. Pentaphlebia stahli) is present there, the Ekor Waterfalls, which had the lowest values for the EPT-related metrics, had the highest CCI. Although both the CCI (>20) and macroinvertebrate metrics suggest that the three sites had high conservation value, the CCI proved to be more goal-oriented in determining the conservation value of pristine freshwater ecosystems. In light of the findings of this study, it is recommended that the CCI be utilized in conjunction with macroinvertebrate metric indicators for studies of a similar nature, particularly in Afrotropics' protected and pristine sites that are a potential refuge for rare and threatened species. [ABSTRACT FROM AUTHOR]

Multiple anthropogenic drivers are changing ecosystems globally, with a disproportionate and intensifying impact on freshwater habitats. A major impact of urbanization are inputs from wastewater treatment plants (WWTPs). Initially designed to reduce eutrophication and improve water quality, WWTPs increasingly release a multitude of micropollutants (MPs; i.e., synthetic chemicals) and microbes (including antibiotic‐resistant bacteria) to receiving environments. This pollution may have pervasive impacts on biodiversity and ecosystem services. Viewed through multiple lenses of macroecological and ecotoxicological theory, we combined field, flume, and laboratory experiments to determine the effects of wastewater (WW) on microbial communities and organic‐matter processing using a standardized decomposition assay. First, we conducted a mensurative experiment sampling 60 locations above and below WWTP discharges in 20 Swiss streams. Microbial respiration and decomposition rates were positively influenced by WW inputs via warming and nutrient enrichment, but with a notable exception: WW decreased the activation energy of decomposition, indicating a "slowing" of this fundamental ecosystem process in response to temperature. Second, next‐generation sequencing indicated that microbial community structure below WWTPs was altered, with significant compositional turnover, reduced richness, and evidence of negative MP influences. Third, a series of flume experiments confirmed that although diluted WW generally has positive influences on microbial‐mediated processes, the negative effects of MPs are "masked" by nutrient enrichment. Finally, transplant experiments suggested that WW‐borne microbes enhance decomposition rates. Taken together, our results affirm the multiple stressor paradigm by showing that different aspects of WW (warming, nutrients, microbes, and MPs) jointly influence ecosystem functioning in complex ways. Increased respiration rates below WWTPs potentially generate ecosystem "disservices" via greater carbon evasion from streams and rivers. However, toxic MP effects may fundamentally alter ecological scaling relationships, indicating the need for a rapprochement between ecotoxicological and macroecological perspectives. [ABSTRACT FROM AUTHOR]

Protists play a crucial role for ecosystem function(ing) and oxygen is one of the strongest barriers against their local dispersal. However, protistan diversity in freshwater habitats with oxygen gradients received very little attention. We applied high-throughput sequencing of the V9 region ( 18S rRNA gene) to provide a hitherto unique spatiotemporal analysis of protistan diversity along the oxygen gradient of a freshwater meromictic lake (Lake Alatsee, SW Germany). In the mixolimnion, the communities experienced most seasonal structural changes, with Stramenopiles dominating in autumn and Dinoflagellata in summer. The suboxic interface supported the highest diversity, but only 23 OTUs95% (mainly Euglenozoa, after quality check and removal of operational taxonomic units ( OTUs) with less than three sequences) were exclusively associated with this habitat. Eukaryotic communities in the anoxic monimolimnion showed the most stable seasonal pattern, with Chrysophyta and Bicosoecida being the dominant taxa. Our data pinpoint to the ecological role of the interface as a short-term 'meeting point' for protists, contributing to the coupling of the mixolimnion and the monimolimnion. Our analyses of divergent genetic diversity suggest a high degree of previously undescribed OTUs. Future research will have to reveal if this result actually points to a high number of undescribed species in such freshwater habitats. [ABSTRACT FROM AUTHOR]

The article reports that the Global Freshwater Biodiversity Atlas has been launched by the BioFresh Research Project, a collaboration of 12 European Union (EU) research institutions, in January 2014. It explains that the Atlas allows research scientists, resource managers, educators, and policy makers to view and share up-to-date geographic data on all freshwater habitats across the world, which would help them to make better decisions for protecting the biodiversity of freshwater ecosystems.