Taxonomic and functional traits of macroinvertebrate community along fish farming pollution gradient: Taxonomic sufficiency for reliable bioassessment

Abstract

The expansion of fish farming globally, driven by rising demand for fish as a food source, has raised substantial environmental concerns due to its impact on aquatic ecosystems. This study investigates the effects of fish farming effluents on taxonomic and functional diversity of macroinvertebrate community and test how taxonomic resolution impacts their effectiveness as pollution indicators. Macroinvertebrate samples were collected from seven trout farms, with sampling sites categorized based on proximity to farm effluents. Results indicate that fish farming effluents significantly alter macroinvertebrate communities, with observable changes in both taxonomic and functional metrics. Although traditional taxonomic metrics revealed differences along the pollution gradient, functional diversity measures provided more sensitive indicators of ecological changes. Functional traits, even at coarse taxonomic resolutions, better reflected shifts in ecological processes than taxonomic diversity alone. The study supports integrating both taxonomic and functional diversity measures in river restoration and management practices to optimize pollution detection and ecological assessment. Combining taxonomic and functional approaches in bioassessment is recommended for better evaluation of water quality and ecosystem health. Functional attributes can simplify routine monitoring, especially for poorly known macroinvertebrate taxa. Nevertheless, metrics related to chironomids showed significant changes along the pollution gradient and were useful for detecting fish farm effluents. Chironomid data at both fine and coarse taxonomic levels revealed the impact of pollution effectively.