Implikasi perubahan ketersediaan nutrien terhadap perkembangan pesat (blooming) fitoplankton di Perairan Teluk Jakarta

Abstract

The main inorganic nutrients are necessary for phytoplankton to grow and develop are nitrogen, phosphorus, and silica. If the input of nutrients in marine waters beyond the optimal growth of phytoplankton, it will lead to rapid growth (blooming) of certain types of phytoplankton. This study aimed to analyze and determine the concentration and ratio of N : P as well as changes in nutrient availability to the population explosion and change the structure of phytoplankton communities in Jakarta Bay, to set the amount of nutrient preparations leading to population explosions of certain phytoplankton in the Jakarta Bay, as well as to examine the relationship between increased production phytoplankton biomass with nutrient availability in the dry season and rainy season and transitional season. The experiment was conducted in Jakarta Bay in August 2009 to May 2010. Sampling was performed six times at nine stations. Phytoplankton enumeration was performed by the method of deposition. Nutrient samples were analyzed using a spectrophotometer. Canonical correspondence analysis was used to determine the relationship between phytoplankton with physico-chemical parameters of water. The results showed that the spatially and temporally there were found 47 genera of phytoplankton from four classes : Bacillariophyceae (26 genera), Chlorophyceae (8 genera), Cyanophyceae (7 genera), and Dinophyceae (6 genera). Concentration of major nutrients (N, P, and Si) was high and the ratio of N : P was less than 16 resulted in very rapid growth (blooming) of certain types of phytoplankton in Jakarta Bay waters. Very rapid growth of phytoplankton occured in the range of concentrations of nutrients, namely nitrate: 0.0105-0.0829 mg.L-1, orthophosphate : 0.0114-0.3010 mg.L-1, and silica : 0.2787-5.9946 mg.L-1. Genera of phytoplankton that were experiencing rapid growth (blooming) in the dry season were Skeletonema and Rhizosolenia, while those of phytoplankton in the transitional season were Skeletonema, Chaetoceros, Rhizosolenia, and Noctiluca. How ever, in the rainy season there was no genus of phytoplankton that grew very rapidly. Physico-chemical parameters contributing to the blooming of Skeletonema were silica, nitrate, orthophosphate, and temperature. Parameters that contributing to the blooming of Chaetoceros were pH and silica. pH also played a role in the rapid growth of the genus Rhizosolenia.