Potential Use of Cyclopoida (Crustacea, Copepoda) as Trophic State Indicators in Tropical Reservoirs

Abstract

The pelagic zones of fifty three Sao Paulo State reservoirs were sampled as a part of the project “Diversity of zooplankton in relation to conservation and degradation of aquatic ecosystems in the State of Sao Paulo”, within the Biota/Fapesp Program (1999 – 2003). The trophic state index (TSI) was calculated, using total phosphorus and chlorophyll a. The Cyclopoida (Copepoda) populations were analyzed, and richness and relative abundance of the dominant species determined. Most values of the TSI ranged from oligotrophic to mesotrophic. The species richness did not present linear relationships with the TSI values. Nine species of Cyclopoida were dominant. Thermocyclops decipiens was the most frequently dominant species, followed by T. minutus, Mesocyclops ogunnus, T. inversus, T. iguapensis, Microcyclops anceps, Tropocyclops prasinus, Microcyclops alius and Mesocyclops longisetus. Correlations between the abundances of different species were highly negative, with values over 85%, especially between the Thermocyclops species. The species that are potential bioindicators due to the relationship between their dominance and reservoir trophic state are the following: Thermocyclops decipiens and Tropocyclops prasinus as indicators of mesotrophic/eutrophic systems; Thermocyclops inversus and Microcyclops anceps as indicators of oligotrophic/mesotrophic systems, Thermocyclops minutus and T. iguapensis as indicators of oligotrophic systems and Mesocyclops ogunnus as indicator of eutrophic systems.