Influence of estuarine circulation on the biological production of the northern Hiroshima Bay, Japan, in summer season

Abstract

An ecosystem model was constructed to evaluate the influence of estuarine circulation process on the biological production in the northern Hiroshima Bay, Japan. In summer season, of the estimated total input DIP (dissolved inorganic phosphate), decomposition of detritus, river discharge of the Ohta river and vertical advection and diffusion from the lower layer, amounted 44%, 12% and 44%, respectively. While, 80% DIP was estimated to be supplied by decomposition process in the lower layer. Total amount of DIP utilized by primary production in the area amounted 8.7-folds of that from the riverine input. Sensitivity analyses revealed that the biological production in northern Hiroshima Bay is most responsible to the variation of the nutrient concentration in the lower layer of neighboring southern area. In the viewpoint of environmental management of northern Hiroshima Bay, it is important to evaluate the influence of the estuarine circulation quantitatively in addition to the influence by land.