Eutrophication Status And Its Ecological Effects In The Changjiang Estuary And Adjacent Coastal Waters

Estuarine and coastal eutrophication has been one of the primary environmental problems worrying the coastal countries; it is also the hotspot of marine ecological and environmental research. In this dissertation, the Changjiang estuary and its adjacent coastal waters was chosen as the research object. Based on the data of field surveys during the period of 1997 to 1999 and 2002 to 2003, nutrient distributions, transportation and their limitation for phytoplankton growth in the Changjiang estuary and its adjacent coastal waters were studied; the contribution of the upwelled nutrients to the euphotic zone through coastal upwelling in the East China Sea was also discussed. Moreover, the evolvement process of eutrophication status and its long-term ecological effects were discussed in the Changjiang estuary and its adjacent coastal waters by use of long-term series data. Finally, the ASSETS method, which is the representative approach of the "Phase II" models for the assessment of estuarine and coastal eutrophication status, was modified and applied to the assessment of eutrophication status in the Changjiang estuary and its adjacent coastal waters. The main results are as the following:1) The nutrient condition in the Changjiang estuary and adjacent coastal waters represents as "overabundance for nitrogen, deficient for phosphate, and insufficient for silicate "Being influenced by nutrient inputs from the Changjiang, the Changjiang estuary and adjacent coastal waters is a high nutrient concentration region in all the time of a year. The nutrients in the Changjiang Diluted Water are transported bi-directionally simultaneously, but the proportions are different in different season. In the wet season, they are expanded primarily northeastward and secondarily southward; in the dry season, however, they are expanded primarily southward along the bank and secondarily northeastward. With regard to the mixing behaviors of nutrients in the estuary, it is quite different in different season and different salinity zone even for the same kind of nutrient, both addition and removing effects occurs. This indicated that both biotic and-...