Hubungan produktivitas fitoplankton dengan ketersediaan unsure hara berkenaan dengan beban masukan dari sungai dan laut di perairan Teluk Ambon Dalam

Abstract

The development of increasingly rapid development resulted in bay conditions, particularly in Ambon bay gets heavy pressure, resulting in changes in the aquatic environment. These changes further affect marine organisms that live in it. One of the marine organisms playing an important role for productivity is a water plankton community. Plankton community plays great role in marine ecosystems, particularly because phytoplankton are the foundation of the food chain so called primary producers. As primary producers, phytoplankton can form organic matter from inorganic matter through photosynthesis which in turn can be used directly by other living organisms. The purposes of this study were 1) to analyze seasonal changes in the distribution of temperature, salinity and density in the water; 2) to analyze the inter-relationship between the light intensity and the level of turbidity water; 3) to analyze the load level of nutrients in water derived from river and sea; 4) to analyze the spatial and temporal distribution of phytoplankton composition and abundance in the water; 5) to analyze seasonal changes in the level of productivity of phytoplankton in the water; and 6) to examine the inter-relationship between the succession of phytoplankton to changes in N:P ratio in the water of the Ambon bay. The results of this study indicate that temperature, salinity and density were low in East Season. In the Bay of Ambon there was stratification in temperature and salinity, while mixing was not occur either from surface to bottom water. Season were great influence on the distribution of nutrients in the water, again the average ammonia concentration was higher in East Season that indicate domestic sewage polluted water. Average NO3-N concentration of the lowest in the Western season (0.05 μm) and high in East Season (0.55 μm). Average concentration of nitrate in the East Season in Zone-1 was low and Zone-2 was high. In East Season high phosphate concentrations, so that phosphate stimulates rapid growth (blooming) Trichodesmium in water. Average concentration of silica in the East, Transition II, Western and Transition I Season highly significant, with the lowest concentrations in Transition Season I (1.29 μm) and high in East Season (35.61 μm). At the moment there was a high concentration of silica Bacillariophyceae low abundance in the eastern season. In the Transition II, the West, and the Transition I Season occurred increased abundance of Bacillariophyceae, along with decrease in the concentration of silica. Input nitrate and phosphate in East Season was very large from outside Ambon Bay compared to from river. Spatial and temporal waters in the Inner Ambon Bay were found oligotrofik and mesotrofik state. Flushing time were occured in Ambon Bay within 14 days. The average of chlorophyll-a concentration in the East, Transition II, West and Transition I Season were highly significant, the lowest concentration at West season (0.44 μg/l) and high in East season (0.94 μg/l). In the East Season, there was an increase of chlorophyll-a, but the low abundance of phytoplankton. In the East Season, chlorophyll-a negative correlation revealed in nitrate and nitrite, this is due to an increase in chlorophyll-a caused by decrease in nitrate and nitrite or instead. The value of primary productivity was influenced by chlorophyll-a, neither by abundance of phytoplankton. In addition, primary productivity in West Season showed a significant relationship with a correlation coefficient (r) of 0.81. It is caused by passes of ultra- and nano-phytoplankton from plankton nets when sampling. Primary productivity is determined by the intensity of light, temperature, nutrients (N, P, and Si) and chlorophyll-a. In West, Transition II and Transition I Season showed a significant correlation between the intensity of light with primary productivity, this suggests that the increase in the intensity of light would affect primary productivity. The relationship between temperature and primary productivity with a correlation coefficient (r) is the 0.664 Transition I Season. At the Transition II Season, there is a significant relationship between DIN-N and SiO2-Si with primary productivity with a correlation coefficient (r) for 0.794 and 0.746, respectively; while PO4-P with primary productivity showed no significant relationship at all seasons with values correlation coefficient (r) were smaller than 0.5. Composition of the phytoplankton were found in 4 classes Bacillario-phyceae with 38 genera, with 12 genera Dinophyceae, Cyanophyceae and Chrysophyceae with 1 genus with 2 genera. The average abundance of phyto-plankton in East, Transition II, Western and Transition I Season were highly significant, with the lowest density in the high season in the East and Transition I. Transitionally, starting from East to Transition II, to West and to Transition I Season were revealed succession of phytoplankton species, due to changes in the N and P ratio, as well as Si and N.