ABSTRAKTelah dilakukan penelitian tentang komunitas plankton di Danau Segara Anak, Pulau Lombok, Indonesia. Danau tersebut adalah danau vulkanik tertinggi di Indonesia. Tujuan penelitian ini adalah untuk mendeskripsikan struktur komunitas plankton dan mengeksplorasi pola perubahan komunitas secara spasial dan temporal. Hasil penelitian ini mengungkapkan bahwa komunitas plankton terdiri dari 39 spesies fitoplankton dan 5 spesies zooplankton. Indeks keanekaragaman dan keseragaman spesies fitoplankton berturut-turut 3,064 dan 0,029, sedangkan indeks keanekaragaman dan keseragaman spesies untuk zooplankton berturut-turut 1,352 dan 0,060. Hasil analisis statistik menunjukkan tidak terdapat perbedaan signifikan secara spasial dan temporal pada kekayaan spesies, kemelimpahan dan indeks keanekragaman fitoplankton dan zooplankton di Danau Segara Anak. Perbedaan signifikan hanya terlihat pada kekayaan spesies dan indeks keanekaragaman spesies zooplankton antara bagian permukaan dan dasar danau.Kata kunci : keanekaragaman, fitoplankton, zooplankton, Danau Segara Anak. ABSTRACTPlankton community was studied at the Lake of Segara Anak, Lombok Island, Indonesia. The purpose of this study was to describe community structure of plankton and to explore spatial and temporal pattern. The results show there were 39 species of phytoplankton and 5 species of zooplankton. Species diversity and similarity indices of phytoplankton were 3.064 and 0.029 respectively, while the species diversity and similarity indices of zooplankton were 1.352 and 0.060 respectively. Statistical analysis showed no significant difference spatially and temporally on the species richness, abundance, diversity index and similarity index of zooplankton and phytoplankton. Significant difference was only found on the average of species richnes and diversity index of zooplankton between the surface and the bottom of the lake.

Segara Anak is a volcanic lake located in the Mount Rinjani National Park, West Nusa Tenggara, Indonesia. It covers an area of ± 11.3 km2 with a maximum depth of 230 m at 2010 m.a.s.l. Segara Anak one of tourism object around Rinjani Mountain. The purpose of this research was to study the phytoplankton community structure and physical and nutritional factors correlation in Segara Anak spatially and temporally. The sampling technique used was a purposive sampling method. The samples were taken at five stations with an increasing depth of 1 m, 5 m, and 10 m respectively. The sample collection was started from October to December 2017. The data were analyzed using One-way ANOVA, Kruskal Wallis, Cluster Analysis and Principal Component Analysis. We identified 19 phytoplankton genera with 4 classes. The phytoplankton structure, nutrient, and physical factors are significantly different in spatial depth and temporal sampling. The abundance of phytoplankton in Segara Anak is dominated by the Cyanophyceae class.