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Biodiversity of rivers
\"Discusses the variety of living things in the ecosystem of a river\"--Provided by publisher.
Book
The curious and neglected soft-bodied meiofauna: Rouphozoa (Gastrotricha and Platyhelminthes)
Gastrotricha and Platyhelminthes form a clade called Rouphozoa. Representatives of both taxa are main components of meiofaunal communities, but their role in the trophic ecology of marine and freshwater communities is not sufficiently studied. Traditional collection methods for meiofauna are optimized for Ecdysozoa, and include the use of fixatives or flotation techniques that are unsuitable for the preservation and identification of soft-bodied meiofauna. As a result, rouphozoans are usually underestimated in conventional biodiversity surveys and ecological studies. Here, we give an updated outline of their diversity and taxonomy, with some phylogenetic considerations. We describe successfully tested techniques for their recovery and study, and emphasize current knowledge on the ecology, distribution, and dispersal of freshwater gastrotrichs and microturbellarians. We also discuss the opportunities and pitfalls of (meta)barcoding studies as a means of overcoming the taxonomic impediment. Finally, we discuss the importance of rouphozoans in aquatic ecosystems and provide future research directions to fill in crucial gaps in the biology of these organisms needed for understanding their basic role in the ecology of benthos and their place in the trophic networks linking micro-, meio-, and macrofauna of freshwater ecosystems.
Journal Article
Quantifying Biological Integrity by Taxonomic Completeness: Its Utility in Regional and Global Assessments
Water resources managers and conservation biologists need reliable, quantitative, and directly comparable methods for assessing the biological integrity of the world's aquatic ecosystems. Large-scale assessments are constrained by the lack of consistency in the indicators used to assess biological integrity and our current inability to translate between indicators. In theory, assessments based on estimates of taxonomic completeness, i.e., the proportion of expected taxa that were observed (observed/expected, O/E) are directly comparable to one another and should therefore allow regionally and globally consistent summaries of the biological integrity of freshwater ecosystems. However, we know little about the true comparability of O/E assessments derived from different data sets or how well O/E assessments perform relative to other indicators in use. I compared the performance (precision, bias, and sensitivity to stressors) of O/E assessments based on five different data sets with the performance of the indicators previously applied to these data (three multimetric indices, a biotic index, and a hybrid method used by the state of Maine). Analyses were based on data collected from U.S. stream ecosystems in North Carolina, the Mid-Atlantic Highlands, Maine, and Ohio. O/E assessments resulted in very similar estimates of mean regional conditions compared with most other indicators once these indicators' values were standardized relative to reference-site means. However, other indicators tended to be biased estimators of O/E, a consequence of differences in their response to natural environmental gradients and sensitivity to stressors. These results imply that, in some cases, it may be possible to compare assessments derived from different indicators by standardizing their values (a statistical approach to data harmonization). In situations where it is difficult to standardize or otherwise harmonize two or more indicators, O/E values can easily be derived from existing raw sample data. With some caveats, O/E should provide more directly comparable assessments of biological integrity across regions than is possible by harmonizing values of a mix of indicators.
Journal Article
Climate change may reduce suitable habitat for freshwater fish in a tropical watershed
Freshwater ecosystems have been increasingly threatened due to the impacts of climate change. Fishes have shifted their geographic distribution in response to these environmental changes. By forecasting biodiversity changes, we may provide knowledge for more effective conservation actions. Here, our aim is to assess the alpha and beta spatio-temporal patterns in the climate change context of freshwater fishes in the Brazilian portion of the Upper Paraguay River Basin (UPRB). We use ecological niche models which correlate fish occurrence with environmental variables such as BIO 2, BIO 5, BIO 7, BIO 12, BIO 13, BIO 14, elevation, and stream order. Then, we predicted species distribution current and future and evaluated both the alpha and beta diversity pattern changes over time. Overall, our modeling had good predictive performance (mean ± SD, AUC 0.8 ± 0.04; TSS 0.5 ± 0.08). The future projections reveal a progressive reduction in the species number over time, with alpha diversity decreasing 85%, together with the reduction forecast between 13 and 74% of gamma diversity until the end of the century. The loss of freshwater fishes can result in an ecosystem imbalance because different ecosystem services play in the aquatic environment. Yet it is expected that turnover contributes to promoting future temporal beta diversity in the UPRB. Our results provide at a spatial large scale the impact of climate change on fish diversity, indicating directions to protect ecosystems and socioeconomic processes dependent on fish diversity.
Journal Article
Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget
Because freshwater covers such a small fraction of the Earth's surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y-¹ from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y-¹ is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described.
Journal Article
Comprehensive study of the microplastic footprint in the urban pond and river of Eastern India
Freshwater ecosystems, comprising lakes, ponds, rivers, and groundwater, provides essential resources that support life on Earth. Though, during last few decades, the increasing concentrations of microplastics (MPs) in freshwater ecosystems are becoming a serious environmental concern with far-reaching and unpredictable consequences for human health and aquatic life. This study aimed to quantify and assess the dynamic footprint of MPs in the urban river and pond with their potential risks. The quantitative analyses revealed the presence of MPs in surface water and sediment of study sites between the range of 59–100 particles/l and 167–193 particles/g, respectively. According to the size distribution, 56.98% of the MPs were between 300 and 1180 μm, and 43.02% were between 1180 and 5000 μm. Further polymer characterization confirmed the presence of nylon (36%) as the dominant type, followed by polyethylene (25%), polyethylene terephthalate (18%), polyvinyl chloride (9%), polyurethane (5%), polypropylene (5%), and polystyrene (2%) in the available MPs. The film (39.07%) shaped MPs were dominant throughout the samples, followed by fragments (22.2%), particles (12.63%), fibre (9.73%), pellets (9.3%), foam (1.7%), and others. Following the risk analyses, the polymer hazard index and polymer load index values were above the crisis level (V and IV level), and potential ecological risk index for river water and pond surface water were extremely danger and danger levels.
Journal Article
Quantifying the effects of water hyacinth (Pontederia crassipes) on freshwater ecosystems: a meta-analysis
Water hyacinth (
Pontederia crassipes
, used to be
Eichhornia crassipes
), one of the world's most notorious invasive species, poses significant threats to freshwater ecosystems worldwide. Despite its widespread presence in over 70 countries, there is a lack of comprehensive analyses about the impacts of water hyacinth. To fill this knowledge gap and to explore the multi-dimensional (physical, chemical, and biological) impacts of water hyacinth on freshwater ecosystems, we conducted a meta-analysis that synthesized data from 25 original studies encompassing 12 countries and three continents. We found that water hyacinth invasions lead to significant reductions in water dissolved oxygen levels (Standardized Mean Difference (SMD) = −2.26, 95% CI: [−3.94, −0.56];
p
= 0.001) and nitrogen (SMD = −1.70, 95% CI: [−3.19, − 0.20];
p
= 0.01). We also observed non-significant but notable trends of decreased water pH levels and increased macroinvertebrates abundance, suggesting complex interactions between water hyacinth and abiotic factors. Our analysis underscores the need for more localized studies to better understand the general impacts of water hyacinth invasions. Given the significant ecological disruptions caused by water hyacinth, effective management strategies are imperative to mitigate the adverse effects of this invasive species. Overall, this meta-analysis provides valuable insights into the ecological consequences of water hyacinth invasion, highlighting the urgent need for targeted research and intervention strategies to protect and restore affected freshwater ecosystems.
Journal Article
Preface: Patterns and processes of meiofauna in freshwater ecosystems
Never heard of harpacticoids, ostracods, gastrotrichs or microturbellarians? This is no surprise, they are so tiny! Yet these taxa and many others more famous (nematodes, rotifers, or tardigrades) show complex behaviours and extraordinary physiologies that allow them to colonize inland waters worldwide. This exuberant fauna is better known as the meiofauna (or meiobenthos). Meiofaunal organisms have been fascinating study objects for zoologists since the seventeenth century and recent research has demonstrated their intermediate role in benthic food webs. This special issue highlights how meiofauna can help freshwater ecologists to describe and predict species distribution patterns, to assess production of biomass and trait functions relationships, as well as to examine the trophic links between microscopic and macroscopic worlds and to better understand species’ resilience to environmental extremes. Overall, meiofaunal organisms are bridging scales, and as such they deserve better integration to develop more comprehensive concepts and theories in ecology.
Journal Article
Hydrochemical and Seasonally Conditioned Changes of Microbial Communities in the Tufa-Forming Freshwater Network Ecosystem
Plitvice Lakes represent a rare freshwater ecosystem consisting of a complex network of lakes and waterfalls connecting them, as well as rivers and streams supplying water to the lake basin. The unique geomorphological, hydrological, biogeochemical, and biological phenomenon of Plitvice Lakes lies in the biodynamic process of forming tufa barriers. Freshwater network ecosystems consist of interconnected lotic and lentic environments within the same catchment area. Using Plitvice Lakes as an example, we studied the changes in environmental conditions and microbial communities (bacteria and fungi) that occur with downstream flow. Water samples from tributaries, interlake streams, connections of the cascading lakes, and the Korana River, the main outflow of the system, were characterized using amplicon sequencing of bacterial 16S rRNA and fungal ITS2 genes. Our results show that different environmental conditions and bacterial and fungal communities prevail among the three stream types within the freshwater network ecosystem during multiple sampling seasons. Microbial community differences were also confirmed along the longitudinal gradient between the most distant sampling sites. The higher impact of “mass effect” was evident during spring and winter, while “species sorting” and “environmental selection” was more pronounced during summer. Prokaryotic community assembly was majorly influenced by deterministic processes, while fungal community assembly was highly dominated by stochastic processes, more precisely by the undominated fraction, which is not dominated by any process. Despite the differences between stream types, the microbial community of Plitvice Lakes is shown to be very stable by the core microbiome that makes up the majority of stream communities. Our results suggest microbial community succession along the river-lake continuum of microbial communities in small freshwater network ecosystems with developed tufa barriers. IMPORTANCE Plitvice Lakes represent a rare freshwater ecosystem consisting of a complex network of lakes and waterfalls connecting them, as well as rivers and streams supplying water to the lake basin. The unique geomorphological, hydrological, biogeochemical, and biological phenomenon of Plitvice Lakes lies in the biodynamic process of forming tufa barriers. In addition to microbial communities, abiotic water factors also have a major influence on the formation of tufa. Therefore, it is important to understand how changes in environmental conditions and microbial community assembly affect the functioning of the ecosystem of a freshwater network with developed tufa barriers.
Journal Article
Web-Based Decision Support System for Managing the Food–Water–Soil–Ecosystem Nexus in the Kolleru Freshwater Lake of Andhra Pradesh in South India
Most of the world’s freshwater lake ecosystems are endangered due to intensive land use conditions. They are subjected to anthropogenic stress and severely degraded because of large-scale aquafarming, agricultural expansion, urbanization, and industrialization. In the case of India’s largest freshwater lake, the Kolleru freshwater ecosystem, environmental resources such as water and soil have been adversely impacted by an increase in food production, particularly through aquaculture. There are numerous instances where aqua farmers have indulged in constructing illegal fishponds. This process of aquafarming through illegal fishponds has continued even after significant restoration efforts, which started in 2006. This underlines the necessity of continuous monitoring of the state of the lake ecosystem in order to survey the effectiveness of restoration and protection measures. Hence, to better understand the processes of ecosystem degradation and derive recommendations for future management, we developed a web mapping application (WMA). The WMA aims to provide fishpond data from the current monitoring program, allowing users to access the fishpond data location across the lake region, demanding lake digitization and analysis. We used a machine learning algorithm for training the composite series of Landsat images obtained from Google Earth Engine to digitize the lake ecosystem and further analyze current and past land use classes. An open-source geographic information system (GIS) software and JavaScript library plugins including a PostGIS database, GeoServer, and Leaflet library were used for WMA. To enable the interactive features, such as editing or updating the latest construction of fishponds into the database, a client–server architecture interface was provided, finally resulting in the web-based model application for the Kolleru Lake aquaculture system. Overall, we believe that providing expanded access to the fishpond data using such tools will help government organizations, resource managers, stakeholders, and decision makers better understand the lake ecosystem dynamics and plan any upcoming restoration measures.
Journal Article