Study On Early Warning Evaluation On The Typical Mariculture Areas, Guangdong Province

During three decades, to solve the contradiction between supply and demandamong the population and marine fisheries resources, the mariculture has developedrapidly, which simultaneously leads to the degradation of the marine eco-environment.Ecosystem degeneration is the the process of change from a quantitative to qualitative.And therefore, to identify and prevent deterioration of the ecosystem in themariculture, it is very just significant to establish a set of operational applicability ofecological early warning assessment system.Through the analysis of domestic and foreign research on security early warningindicator system, chemometrics methods to select the evaluating factors were set up.The tools of fuzzy logic synthesis index were the construction of security alarmassessment system. The results are as following:1. The spatial-temporal eco-enviromental variation characteristics in themariculture area of Guangzhou were mainly affected by the subtropical monsoonclimate combined with the spatial patterns and seasonal productive procedures of thecage fish and oyster raft farming. During high temperature and humid in summer andautumn, abundant rainfall and surface runoff caused the decrease of salinity, while atthe same time which brought a large number of exogenous nutrients to promote thegrowth of phytoplankton. During low temperature and dry winter and spring, as theresult of less rain, higher salinity, the exogenous input of nutrients were relativelyreduced.2. It is closely related among temporal and spatial variation of fish cage cultureand oyster raft farming, the spatial layout of the ecological environment of theirrespective aquaculture production season, and the cyclical nature. In summer andautumn the mariculture eco-environment was mainly affected by fish farmingpollution caused by the lack of dissolved oxygen and the increasing of phosphate andsediment sulfide.3. On the basis of chemometrics methods above to select8index factors with thebehalf of the mariculture eco-environmental characteristics, the index factorsrespectively were dissolved oxygen, dissolved inorganic nitrogen, phosphorus,chemical oxygen demand, Chlorophyll a, transparency, sediment organic matter, sediment sulfide. In model, dissolved oxygen and sediment sulfide in the maricultureecosystem were emphasized.4. The results of case study in the fuzzy logic early warning model, revealed thateco-environment between Dapeng Cove and Baisha Bay had the consistency andheterogeneity. Consistency was reflected in the seasonal characteristic. Theheterogeneity was reflected in their different regions, as well as the structure of themariculture area, the environmental quality of Baisha Bay better than that of DapengCove.Dapeng Cove and Baisha Bay, generally in summer showing the low level ofdissolved oxygen, combined with the eutrophication of warning; In fall eutrophicationwarning; In winter and spring marine environment quality is slightly higher, did notshow obvious warning.This study revealed the spatial-temporal variations of mariculture environmentalfactors, and fuzzy logic early warning assessment model was constructed based onthis feature in-depth understanding of of fish cage culture and oyster raft farming theeco-environment in shallow sea. The paper aims to provide a reference on thesustainable management of the eco-environment of the mariculture area...