The Characteristics And Mechanism Of Eutrophication In Jiaozhou Bay

Jiaozhou Bay is atypical semi-closed and shallow Bay located in Temperate zone which has been greatly affected by anthropogenic activities Because it has been greatly affected by anthropogenic Jiaozhou Bay is a typical semi-closed and shallow Bay located in Temperate zone which has been greatly affected by anthropogenic activities. Because it has a representative location and ecologic conditions to a certain extent explored and it combines with ambient society and economy to be a multiplex ecosystem, it is a perfect object to study the effects of human activities on marine environment. This essay mainly researches on eutrophication and its formative mechanism in the Jiaozhou Bay. Based on the investigation data of May/August/November 2003 and February 2004, the horizontal distribution of nutrients and their structures, the relativity between nutrients and the relations between nutrients and salinity, chlorophyll-a are discussed with statistic method. At the same time, the relations between the seasonal changes of nutrients and their structures and chlorophyll-a are also studied. And which nutrient is the limiting factor of phytoplankton is probed into resorting to the analysis of nutrients structures. It is concluded that the concentrations of nutrients is the highest in the northeast of the bay and those are also high in the north and northwest and east. The values of isoclines becomes low from northeast to southwest and the mouth of the embayment. Generally DIN/PO4-P is higher in the west and northeast of the bay and lower to the mouth. The horizontal distribution of SiO3-Si/PO4-P and SiO3-Si/DIN are different in various season?Silicon is the limiting factor of phytoplankton. The nutrients were positive correlation that indicates their sources 3are resemble. And nutrients have strong negative correlation with salinity that implicates the hydrology controls the distribution of nutrients. The correlations between nutrients and Chla are stronger in autumn and winter than those in spring and summer because the inputs of nutrients are different in every season. The analysis between the seasonal changes of nutrients and the structures and Chl-a showes that abundant nutrients are the premise of high Chl-a and silicon may be important in the forming of eutrophication of Jiaozhou Bay. Based on the seasonal data of 2002 and 2003, a simple assessment model is applied to assess the trophic status of Jiaozhou Bay. As a result, the waters are eutrophic in the northeast and northwest of the bay, especially in the northeast. Based on the historical data of nutrients, the long-time changes of nutrients are discussed that show nutrients are increasing. The silicon is increasing rapidly in recent years which maybe the important reason of eutrophication. The precipitation, river runoff? point pollution, marine aquaculture and sediment release are the sources of nutrients. Among those sources the river runoff ,point pollution and sediment release are the more important ones to increase the nutrients in Jiaozhou Bay. This essay is the first time to systematically research the characteristics and mechanism of eutrophication in Jiaozhou Bay where the silicon is the limiting factor of phytoplankton.