Effects of multiscale environmental variables on the taxonomic and functional structures of riverine microeukaryotic plankton communities: eDNA metabarcoding and metatranscriptomic perspectives
Introduction
Rivers are dynamic ecosystems where even microscopic life forms play crucial roles in nutrient cycling, food web stability, and ecological resilience. Among these, microeukaryotic plankton—tiny, diverse organisms such as protists and microalgae—form the foundation of freshwater biodiversity. But what governs their composition and function? Recent advances in molecular biology, particularly environmental DNA (eDNA) metabarcoding and metatranscriptomics, provide powerful tools to uncover the hidden complexities of these communities and the environmental factors influencing them.
Understanding Microeukaryotic Plankton
Microeukaryotic plankton are sensitive indicators of environmental change. They respond to a wide range of multiscale environmental variables, including water temperature, nutrient concentrations, pH, hydrology, and land use. These factors operate at local (e.g., site-specific water chemistry) to regional scales (e.g., watershed characteristics), influencing both the taxonomic diversity (which species are present) and functional diversity (what roles they play).
The Power of eDNA Metabarcoding and Metatranscriptomics
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eDNA metabarcoding allows researchers to identify a wide range of plankton species by analyzing DNA traces left in water samples. It reveals who is there.
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Metatranscriptomics goes a step further by analyzing RNA to reveal what those organisms are doing, providing insights into gene expression and ecological function.
Together, these approaches paint a holistic picture of the plankton community—linking biodiversity with ecosystem processes.
Key Findings from Multiscale Analyses
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Environmental Gradients Matter: Temperature, nutrient load, and flow variability were found to significantly influence both species composition and metabolic functions of riverine plankton.
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Functional Redundancy and Specialization: While many taxa may perform similar roles, certain environmental stressors lead to the dominance of specialists with unique functional capabilities.
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Spatial Scale is Crucial: Regional land use (agriculture, urbanization) had a larger influence on taxonomic diversity, while local water quality was more tightly linked to functional expression patterns.
Why It Matters
These insights are essential for river management and conservation, especially under the growing threats of climate change, pollution, and habitat modification. Understanding both who is present and how they function helps ecologists forecast how ecosystems respond to change and identify critical taxa that support ecological resilience.
Conclusion
The integration of eDNA metabarcoding and metatranscriptomics represents a new frontier in freshwater ecology. By linking multiscale environmental variables to the structure and function of microeukaryotic plankton communities, scientists can better monitor river health and design targeted conservation strategies.
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