Phytoplankton, Macrophytes and Macroinvertebrates in Reservoirs: Response to Eutrophication.

Eutrophication impact on key aquatic communities (phytoplankton, macrophytes and macrozoobenthos) was studied in three standing water bodies in Bulgaria (Kardzhali, Koprinka and Batak). The reservoirs had a high summer nutrient level and were between eu- and hypertrophic category. In the meso-eutrophic condition the highest number of phytoplankton species and functional diversity (Kardzhali Reservoir) and domination of functional groups (FGs) B, F, X3 and T were registered. The most intensive cyanobacterial growth was recorded in eu- to hypertrophic conditions (Koprinka Reservoir), as well as lower functional and species diversity, and domination of FGs M and J. Hydrological regime in hydroelectric reservoirs was a serious pressure for aquatic macrophytes and macrozoobenthos. Along the nutrient gradient, the Batak Reservoir had highest phytoplankton biovolume and macroinvertebrate taxa richness, well developed macrophyte community, dominated by eutrophication-tolerant species. The results suggested that measures for mitigating ecological impacts from pressures should be implemented without significant adverse effect on water use. [ABSTRACT FROM AUTHOR]