A new coastal marine ecosystem model study coupled with hydrodynamics and tidal flat ecosystem effect

A new coastal marine ecosystem model was developed, which was composed of p elagic and benthic ecosystems, and was applied to Mikawa Bay, Japan. This m odel deals with variations of biochemical and physical interactions among d issolved oxygen and C-N-P species (composition formed out of carbon, nitrog en and phosphorus elements) so that it resolves the flux dynamics of carbon , nitrogen, phosphorus and oxygen elements. The physical and biochemical me chanism figured in this model is constructed for the purpose of simulating the estuarine lower trophic ecosystem, in areas where the sea was too deep for light to reach the sea-bottom. As a result of coupling the benthic with pelagic system, the effect of process of sedimentation and nutrient diffus ion back to the pelagic system could be indicated. In addition, by implemen ting the tidal flat ecosystem model's calculation result, the integrated mo del can include the effect of water purification in tidal flats where the l ight can reach the sea-bottom, and where seaweed, sea grass and benthic alg ae exist. In this study, the model indicates that oxygen-depleted water exi sts at the sea-bottom especially in summer mainly caused by an increase of oxygen consumption in the benthic system and a decrease of the vertical mix ing water process. Furthermore, by comparing the case - with the tidal flat ecosystem model and the case without it, the effect of water purification of tidal flat estuaries was indicated. From the viewpoint of a short time s cale, the tidal flat has the potential to restrict red tide (rapid increase of phytoplankton), and from the viewpoint of a long time scale, it restric ts the sedimentation of detritus. Restricting the sedimentation prevents ox ygen-depleted water occurring in the coastal marine system of Mikawa Bay. ( C) 2001 Elsevier Science Ltd. All rights reserved.