Analysis of productivity plankton and trophic status Beratan Lake ecosystem Tabanan Regency, Bali Province

Beratan Lake is used for fish cultivation activity, tourism, agriculture, and disposal activity. Utilization level is too high and makes lake ecosystem disturbed especially phytoplankton. Phytoplankton existence in water is acting as primary production and act to determine water quality on physical or chemical. The purpose of this research is to know plankton productivity and trophic status ecosystem Beratan Lake. Beratan Lake utilization that too high will impact in ecological pressure at lake ecosystem like decreasing water productivity and quality. The result of the research can conclude that water premier productivity of Beratan Lake is too low especially in cultivation fish territory that has phytoplankton abundance is 4585 individuals per ml that make Beratan Lake is classified to a lake that its trophic status is oligotrophic. The variety of phytoplankton and zooplankton that found in Beratan Lake shows low variety where it only found 5 classes and 11 species of phytoplankton and also 2 classes dan 3 species of zooplankton