| Summary: | 碩士 === 國立成功大學 === 海洋科技與事務研究所 === 101 === Coastal eutrophication has become one of the main threats to the ocean environment, reducing the ecosystem services and causing changes in biological resources that lead to economy loss. The United States and EU have developed various assessment methods to analyze coastal eutrophication. However, there is no integrated analysis for coastal eutrophication in Taiwan. This study adopted and modified the methods used in other countries to evaluate coastal eutrophication and compared the advantages and disadvantages among them. In addition, the concentration of chlorophyll was discussed by examining MODIS monthly ocean color satellite images to investigate the susceptibility to eutrophication in Taiwan.
The assessment results showed that high susceptibility to eutrophication occurs mostly on the southwestern estuaries, including Beigang River, Puzih River, Bajhang River, Jishuei River, Zengwun River, Erren River, Agongdian River, Gaoping River, and Donggang River. Land-based pollutants are more likely to accumulate at estuaries that are highly susceptible to eutrophication. In addition, higher nutrient levels (Ni 〉 40) were found at Agongdian River, followed by Yenshui River, Fongshan River, Jhonggang River, and Houlong River. Higher nutrient levels indicated higher input of nutrients at these estuaries. For coastal waters beyond the estuaries, Dapeng Bay (Ni = 14.37) and Gaoping River (Ni = 9.69) had the highest nutrient levels. Regarding the assessment of coastal eutrophication, the coastal area of Gaoping River exhibited higher levels of orthophosphate (DIP 〉 0.05 mg/L) and dissolved inorganic nitrogen (DIN 〉 0.5 mg/L). Chlorophyll a, among other water quality indices, was also higher in the coastal area of Dapeng Bay (Chl-a = 15.6 μg/L), indicating symptoms of eutrophication. Moreover, the results of the comprehensive evaluation method showed low EQRS (〈 0.21) for the coastal areas beyond Erren estuary, Kao-Ping estuary, and Dapeng Bay. Analysis of chlorophyll a using MODIS images showed that the concentration of chlorophyll a was higher (Chl-a 〉 5 μg/L) in estuaries of Jhuoshuei River, Puzih River, and Zengwun River, and coastal waters beyond these estuaries, implying high possibility of nutrient accumulation.
Eutrophication is an environmental issue that draws more and more attention worldwide. Taiwan should establish integrated management plans to mitigate the problems of coastal eutrophication. The results in this study can serve as references for competent authorities to prevent coastal pollution as well as to reduce input of nutrients. Limited resources should be utilized for managing coastal waters exhibiting higher degree of eutrophication.
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