苏北浅滩辐射沙洲海域浮游植物分布特征

Distribution of Phytoplankton in Radial Sand Ridge Area in North Jiangsu Shoal

为探讨浅滩沙脊潮沟系统特殊的地形对浮游植物分布特征的影响,根据苏北浅滩中部2010年11月(秋季)、2011年5月(春季)辐射沙洲北部,以及2011年11月(秋季)辐射沙洲南部浮游植物调查数据,分析这一海域浮游植物的分布特征及其与地形等环境因子的关系.结果表明:共发现浮游植物3门25属81种,硅藻从物种数量和细胞丰度上都占绝对优势.2010年秋季(北部)、2011年春季(北部)和2011年秋季(南部)浮游植物细胞平均丰度分别为351.74、126.52、240.44 cells/mL.从丰度平面分布可看出,受苏北浅滩沙脊潮沟系统特殊的地形以及变化复杂的潮流场共同影响,个别优势种呈现明显的聚集特性.秋季南部海域细弱圆筛藻优势度为0.49,显著高于其他优势种,其平均丰度(123.88 cells/mL)也高于其他优势种平均丰度的总和,成为秋季南部海域的绝对优势种.优势种的聚集特性使浮游植物细胞丰度的平面分布不均匀,南、北部海域浮游植物细胞丰度均表现为潮沟内高于沙脊,特别是潮流汇集区附近的潮沟末端站位丰度更高,即沟底>中部>沟口.浮游植物丰度水平分布与优势种特征关系密切,南部海域与北部海域优势种差异较大,与南北海域分属不同潮波系统控制有关.多变量相关性分析得出,浮游植物分布特征与环境因子的关系并不密切,而沙脊潮沟系统地形和潮流特征,造成了浮游植物在不同环境水体的聚集,是这一海域浮游植物分布特征形成的重要原因.

This paper investigated from November 2010 to November 2011 the distribution of phytoplankton in the area of radiate sand ridges of north Jiangsu shoal, and analyzed the effect of topography and environmental factors on distribution of phytoplankton. Our results identified a total of 81 species of 25 genera and 3 classes, with diatoms the predominant in both species number and total phytoplankton cell abundance. The average abundance of phytoplankton were 351.74 cells/mL, 126.52 cells/mL and 240.44 cells/mL in three areas （north area in spring, north area in autumn, south area in autumn） respectively. Horizontal distribution of phytoplankton abundance showed an apparent trend of aggregation of individual dominant species, probably due to the combined action of the unique topography of sandbanks and tidal creeks and tidal current in the shoal. In autumn, Coscinodiscus subtilis was the most dominant species （0.49 of degree of dominance） in the south area, with an average abundance of phytoplankton 123.88 cells/mL. The asymmetry in abundance of horizontal distribution of phytoplankton showed a higher abundance in tidal creek terminals and sandbanks in the south and north areas, with the highest phytoplankton abundance found at the joint water of tidal creek terminals and sandbanks. Because of the different tidal wave systems, the dominant species were different at both vertical and horizontal scales. In conclusion, this study suggested that the unique topography of sandbanks and tidal creeks rather than the environmental factors play a crucial role in the formation of phytoplankton distribution patterns. Fig 4, Tab 3, Ref 19