KARAKTERISTIK KOMUNITAS FITOPLANKTON DAN FAKTOR LINGKUNGAN DANAU-DANAU KECIL DI PULAU JAWA

Perluasan lahan pertanian dan pemukiman di daerah aliran sungai dan pemanfaatan danau yang intensif di Jawa menimbulkan masalah kualitas seperti eutrofikasi yang dicirikan oleh melimpahnya jenis fitoplankton tertentu. Penelitian ini bertujuan untuk mengetahui karakteristik komunitas fitoplankton dan faktor-faktor lingkungan yang menentukan distribusinya di danau-danau kecil di Pulau Jawa. Penelitian dilakukan di 12 danau kecil di Jawa pada tahun 2006. Parameter kualitas air diukur secara langsung menggunakan Horiba U 10. Alkalinitas, nutrient, dan klorofil-a dianalisis menggunakan standard method. Fitoplankton dianaliis secara kuantitatif menggunakan metode Lackey Drop Micro Transect termodifikasi. Pengelompokan komposisi fitoplankton dengan faktor lingkungan menggunakan principle component analysis dan keterkaitan distribusi jenis-jenis fitoplankton dengan faktor lingkungan dianalisis menggunakan canonical corespondence analysis. Komposisi fitoplankton pada umumnya didominansi oleh kelompok Chrysophyta. Pada umumnya kelimpahan fitoplankton dan indeks status trofik (trophic state index) masing-masing >15.000 ind./L dan >50, menunjukkan perairan danau yang subur, sedangkan indeks keragaman dan indeks dominan fitoplankton masing-masing berkisar 0,787-3,174 dan 0,15-0,941. Analisis principle component analysis menunjukkan bahwa alkalinitas, suhu dan pH mengelompokkan distribusi Chrysophyta and Euglenophyta. Nitrat, Total N, dan rasio TN/TP mengelompokkan distribusi Chlorophyta, Cyanophyta, dan Phyrrophyta. Analisis canonical corespondence analysis menunjukkan beberapa parameter lingkungan menentukan distribusi jenis-jenis fitoplankton di danau kecil di Jawa. The extension of agriculture area as well as urban and intensive utilization of lake in Java may rise quality problem such as eutrophication indicated by the high abundance of certain species. This study was aimed to elucidate the phytoplankton community characteristic and influence of environmental factors to their distribution in small lakes of Java. The study was conducted at 12 small lakes of Java in 2006. Water quality parameters were measured in situ using Horiba U-10 water quality checker. Alkalinity, nutrient and chlorophyll-a were analyzed according to Standard Method. Quantitative analysis of phytoplankton was done using modified Lackey Drop Micro transect. Principle component analysis was used to detect the major environmental variable that classify the composition of phytoplankton. Canonical component analysis was used to elucidate the relationship between phytoplankton species and their environmental factors. The results show that in general Chrysophyta was a dominant group of phytoplankton composition of small lakes of Java. In most cases, the phytoplankton abundance was more than 15,000 ind./L and trophic state index was >50 indicating a eutrophic waters. The diversity and dominant indexes of phytoplankton ranged 0.787-3.174 and 0.15- 0.941, respectively. The principle component analysis show that alkalinity, temperature, and pH determined in classifying the Chrysophyta while nitrate, TN, and TN/TP ratio were determinants in classifiying the Cyanophyta, Chlorophyta, and Phyrophyta group. Canonical component analysis analysis show that some environmental factors determined the distribution of phytoplankton species in small lakes of Java