Scenario Prediction Of Future Ecological Environment Change In The Yellow Sea And East China Sea

The Yellow Sea and East China Sea is an important support of the economic and social development in China. In the past few decades, dramatic changes have taken place in the structure of ecosystem, which had a profound impact on the marine ecological health. The ecological environment change is driven by two forces, climate change and human activities. With global warming and intensified human activities, the pressure of marine ecological environment has further increased. The main goal of this paper is to predict future ecological environment in the Yellow Sea and East China Sea by a three dimensional physical-biological model. Climate prediction result in IPCC report is used to drive the regional marine hydrodynamic model and ecological model in downscaling method, combined with future river nutrient load to predict the ecological response to climate change and river nutrient emission.This paper utilizes FGOALS climate prediction under RCP4.5 scenario as the forcing field. Future river nutrient data in two extreme scenarios is from GlobalNEWS. Nutrient concentration, nutrient structure, primary production and phytoplankton community composition is analyzed in the Yellow Sea and East China Sea.The results show that, nutrient concentration will increase significantly in the central Yellow Sea, the Subei shoal and the vicinity of estuaries in the future. Silicate concentration increases in the Yellow Sea. Eutrophication will be heavier in both future scenarios. In GO scenario, due to the large increase of river DIN load, phosphorus limitation will be even more significant. In AM scenario, N/P ratio will decline, as the river DIP load increases sharply. The nitrogen and phosphorus concentration increase in the future, causing high primary production in the central Yellow Sea and northern East China Sea. The biggest increase locates in the west front of Yellow Sea Cold Water Mass and outside the Changjiang estuary. Primary production in AM scenario is higher than that in GO scenario. Silicate concentration. changes little in the future. So diatom biomass does not change significantly. The rise of nitrogen and phosphorus concentration makes flagellate biomass increase. The ratio of diatom to flagellate declines. Silicon becomes an important limiting factor in the future. Due to silicate supplement of Changjiang river, diatom and flagellate biomass both increase in the region offshore of the Changjiang estuary. As a result, the community composition changes little.Through sensitive experiment, we assess the relative contribution between hydrodynamic variation and river nutrient load variation in the future. Compared to hydrodynamic variation, increasing nutrient export by rivers is the main cause of the rise of nitrogen and phosphorus concentration in the future. Silicate export by rivers is not changed in the future, so silicate concentration is affected by transport from external. In addition, diatom and biogenic silica is transport by advection and diffusion, then remineralized in the local, led to silicate distribution changed. Hydrodynamic variation has a great contribution to silicate concentration.Nutrient budget analysis shows that the advection contributes to the rise of nutrient concentration in the Yellow Sea. Due to the increasing river export of nitrogen and phosphorus, increasing biomass causes more nutrients released by remineralization of sinking particulate organic matter in the bottom layer, then accumulated there in the stratified season. The region offshore of the Changjiang estuary is mainly influenced by Changjiang river plume. Biomass increase in the future. Biological process will accordingly enhance to consume more nutrients.Due to the lack of future open boundary condition, such as nutrient concentration and transport of the Kuroshio, this study only considers the variation of atmospheric dynamic and thermodynamic forcing at the upper boundary and river nutrient loads in the future. Our work preliminary complete the attempt on scenario prediction of marine ecological environment. Acquirement of more accurate data of future river nutrient load may improve the accuracy of ecological prediction.