Influences of Physical Processes and Anthropogenic Influx on Biogeochemical Cycle in the Java Sea: Numerical Model Experiment

Abstract

Three-dimensional coupled physical-biogeochemical model was utilized in order to investigate the influence of physical processes to biogeochemical cycle in the Java Sea. The biogeochemical model was consisted of nitrate, ammonium, phosphate, phytoplankton, zooplankton, pelagic detritus and benthic detritus. The coupled model could reproduce the basic condition of seasonal variability of surface Chl a distribution consistently with satellite data. Model results and satellite data clearly showed seasonal variability of Chl a distributions, influenced by monsoon, through water exchange with adjacent seas and nutrient supply from rivers discharges. Phytoplankton blooming during southeast monsoon is higher in general than northwest monsoon, due to upwelling event in the eastern Java Sea. On the other side, the role of nutrient riverine input during northwest monsoon (rainy season) is only limited in the region near river mouths or coastal regions. The calculated annual new productions (Rnew) suggested that the regenerated production is predominant in the Java Sea, except for some regions (e.g: Jakarta Bay and south-coast of Kalimantan) that is influenced by human activities in the land (anthropogenic perturbation). The anthropogenic impact through riverine input triggers high primary production in the regions, while it subsequently uptakes atmospheric CO2 in particular monsoon season. However, as a consequence of high sea surface temperature in the tropical region, annually the entire Java Sea acts as a source for CO2 even though the Java Sea is a net autotrophic.