Struktur Komunitas Plankton di Sekitar Keramba Jaring Apung Danau Toba, Kecamatan Haranggaol, Kabupaten Simalungun, Sumatera Utara

Abstract

Toba lake is an aquatic resources that has very important value. Utilization of Lake impact on water quality degradation due to local people activity, for example floating net cages. This activity can give a very significant influence to the reduction of abundance micro-organisms such as plankton. Purpose of this research was to determining the community structure of plankton in Toba Lake, Haranggaol sub-district. This research was carring out on May to June 2013 on waters of Lake Toba, Haranggaol sub-district, Simalungun regency. This research conducted by purpossive random sampling. There was two station location, first station, region which contain floating net cages activities, second station, region without floating net cages. Sampling activities conducted 4 times a month. The results showed that there were30 genus of plankton consisting of 19 fitoplankton genus and 11 zooplankton genus. Plankton abundance data in first station was 5812,66 ind/l and then second station was 4140,66 ind/l. The genus diversity index on first station and second station are 3,08 and 3,38. Uniformity index on first station is 0,39 and on second station is 0,34, this means uniformity values from both stations relatively low. The dominance index values of both stations is 0,04 which means there are no species is dominating other species. This means floating net cages cultivation activity affected the plankton community structure.