Impacts of multiple stressors on algal communities in freshwater ecosystems in rural areas

Rural lowland areas are mostly dominated by agricultural lands. Scattered freshwater ecosystems in these rural areas are consisted with agricultural streams and lentic small water bodies (LSWB). These ecosystems are exposing to multiple stressors such as hydrological disturbances, nutrient enrichment, and pesticide contamination and still mostly neglected by the environmental programs. Algal communities are efficient indicators of ecological impacts of these stressors by revealing consequences to microbial biodiversity and ecosystem functioning. This study aims to understand impacts of multiple stressors, particularly hydrological disturbances, nutrient enrichment, and pesticide contamination on algal communities in freshwater ecosystems in rural areas dominated by agricultural land use. We conducted (i) a thorough literature review, (ii) a field study in agricultural streams, (iii) a field study in LSWB and (iv) a microcosm experiment to gain a comprehensive understanding of the topic. The key findings of this study are: (i) Epiphytic biofilms are understudied in freshwater ecosystems and their interactions with macrophytes are essential to understand, maintain, and improve freshwater ecosystem integrity. (ii) Epiphyton and epilithon communities show distinct structural differences during an annual cycle in agricultural streams in terms of biomass, algal composition, and diatom species composition. Structural properties of epiphyton are less affected by hydrological regimes and water nutrient concentration than epilithon. (iii) High pesticide toxicity and PO4-P concentrations can shift phytoplankton community composition to less-sensitive, fast-adapting generalists. Functional features were negatively affected by nutrient enrichment. (iv) Environmentally realistic concentrations of metazachlor and flufenacet alter phytoplankon species composition and negatively affect taxonomic diversity and functional features