Algal Biodiversity as a Sentinel of Freshwater Ecosystem Health
DOI:
https://doi.org/10.67601/njbls.v3i2b.89Keywords:
Biomonitoring, Eutrophication, Harmful, Environmental DNA (eDNA), Remote sensingAbstract
Freshwater ecosystems are among the most biologically productive yet ecologically vulnerable habitats on Earth, facing escalating pressures from nutrient enrichment, climate change, industrial pollution, and expanding urbanization. Algae encompassing a phylogenetically diverse assemblage ranging from unicellular phytoplankton and benthic diatoms to filamentous green algae and colonial cyanobacteria serve simultaneously as foundational primary producers and sensitive environmental recorders. Their rapid, measurable responses to physicochemical perturbations make them unrivalled bioindicators for the integrated assessment of aquatic ecosystem integrity. This review synthesizes current knowledge on the taxonomy, structural diversity, ecological functions, and environmental sensitivity of freshwater algae, contextualized within a comprehensive framework for water quality monitoring. The principal drivers of algal community change including eutrophication, climate-induced thermal stratification, organic and metal pollution, and hydromorphological modifications was examined and discusses how shifts in assemblage composition, diversity indices, and functional traits reflect these stressors. A systematic evaluation of assessment methodologies is presented, and transformative emerging approaches including environmental DNA (eDNA) metabarcoding, satellite and drone-based remote sensing, and machine-learning-assisted predictive modeling are highlighted for their capacity to overcome the taxonomic, spatial, and temporal limitations of conventional morphology-based assessment. Special focus is directed to harmful algal blooms (HABs), particularly cyanobacterial blooms, and their compounding role as co-stressors alongside climate warming. The review concludes by identifying critical research gaps and advocating for the integration of molecular tools, standardized protocols, expanded genomic reference databases, and artificial intelligence into global algal biomonitoring frameworks.
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