2009年湛江湾叶绿素a分布及其与主要环境因子的关系

2009-02—2009-11分4个季度调查了湛江湾叶绿素a的时空分布,并分析了其与主要环境因子的关系。结果表明,湛江湾海域叶绿素a变化范围为0.35～21.52mg/m3,年平均值4.47mg/m3;全海域叶绿素a呈现夏季(6.50mg/m3)>冬季(4.75mg/m3)>春季(3.58mg/m3)>秋季(3.01mg/m3)的季节变化模式;水平分布上,冬季的叶绿素a呈现由南三岛附近海域(即断面2和3)向外海和沿岸递减,春季、夏季和秋季呈现由外海向沿岸递减,年均值呈现由外海向沿岸递减的分布特征。主成分分析显示,湛江湾海域叶绿素a与pH、盐度呈极显著的正相关,与氨氮、硝氮、硅酸盐、磷酸盐和无机氮呈极显著负相关。以表征的叶绿素a为标准的水体营养状况评价结果显示湛江湾海域多为中营养或贫营养状态,与以营养盐和化学耗氧量为标准的评价结果不一,故湛江湾的水体营养状况评价需要综合多个因子考虑。

The Spatial and Temporal Distributions of Chlorophyll-a and Its Relationship With Main Environmental Factors in Zhanjiang Bay in 2009

The spatial and temporal distributions of chlorophyll-a in Zhanjiang Bay were surveyed in four seasons from Feb.to Nov.in 2009,and the relationship between chlorophyll-a and main environmental factors was studied.The chlorophyll-a ranged from 0.35 to21.52 mg/m3,with an annual average of 4.47 mg/m3.The seasonal change of chlorophyll-a was found in summer(6.50 mg/m3),followed by in winter(4.75 mg/m3),spring(3.58 mg/m3) and autumn(3.01 mg/m3) in turn.In horizontal distribution,the chlorophyll-a in winter was descending from middle Nansan Island sea area to coastal area and outside of the bay,while its degression was from outside bay to inner bay in spring,summer and autumn.The annual average distribution of the chlorophyll-a had a trend of descending from sea to coastal area.PCA analysis showed that the chlorophyll-a was significantly positive related to pH,salinity,but significantly negative correlated with NH+4-N,NO-3-N,SiO2-3-Si,PO3-4-P and DIN.Results indicated that the trophic status of the Zhanjiang Bay was middle-trophic or oligotrophic according to superficial chlorophyll-a as an assessment criterion.This was different from the criterion of nutrient and COD,suggesting the multiple ecological factors should be integratively considered for trophic assessment in this bay.