Abstract:
Water-level fluctuations are reported to be key processes influencing ecosystem
structure and functions in lentic aquatic ecosystems such as reservoirs. The plankton
community structure in reservoirs, being useful mon1toring tools as reservoir trophic
status indicators, are influenced by water quality parameters and water-level fluctuations.
The present study tested the hypothesis that plankton community properties in
irrigation reservoirs are influenced by hydrological regimes and physical and chemical
parameters. Accordingly, the effects of physical, chemical and hydrological parameters
on plankton density and taxa richness were Investigated for 10 selected irrigation
reservoirs of Sri Lanka. The relative reservoir level fluctuation (RRLF), an index
of the magnitude of water-level fluctuation In relation to mean depth, had a positive
influence on phytoplankton density. Because the RRLF positively influenced phytoplankton
density, this index appeared to favour eutrophy in reservoirs. Canonical
correspondence analysis (CCA) indicated both the phytoplankton and zooplankton
community structure in the study reservoirs was influenced by physical and chemical
characteristics. CCA also indicated the plankton taxa abundance and water quality
parameters could be used for the trophic classification of irrigation reservoirs. The
results of the present study highlight the need for examining attributes based on hydrological
regimes in the context of reservoir water quality management.
