大亚湾生态监控区的浮游植物年际变化

依据国家海洋局、国家海洋局第三海洋研究所等权威机构2004~2007年所获的数据和资料,对大亚湾生态监控区近4a长时间尺度的浮游植物群落年际变化进行分析,通过物种组成、丰度变化、优势类群演替、群落结构及赤潮灾害事件来反映生境的退化,探讨其变化的主要原因及趋势。结果表明,浮游植物群落由暖水种占绝对优势转变为广温广布种占主导地位。种类与丰度呈逐年下降的态势,浮游植物丰度的分布保持西高东低,近岸高于远岸的特征,浮游植物的高丰度与营养盐丰富及温排水有关。终年以硅藻为优势种群,优势种演替具有明显的季节与年际变化,细长翼根管藻(Rhizosolenia alataf.gracillima)是春季稳定的优势种,柔弱拟菱形藻(Pseudo-nitzschia delicatissma)是夏季稳定的优势种,春末甲藻的优势度增加明显。浮游植物群落多样性指数呈逐年下降趋势,均匀度呈逐年上升态势。浮游植物的异常增殖及过度集中导致多样性较低,种间比例不均匀,群落结构单一。赤潮季节性发生频繁,发生频率及引发种类呈上升趋势,海洋环境脆弱。

Yearly changes of phytoplankton in the ecological monitoring zone of Daya Bay

Based on a great deal of monitoring data and information obtained from National Oceanic Administration, the Third Institute of Oceanography and other authorities, the yearly changes and spatial variation of phytoplankton community in the Ecological Monitoring Zone of Daya Bay were studied. To assess the current status and further trend, the phytoplankton composition, abundance, dominant species, diversity and harmful algae bloom events from 2004 to 2007 were analyzed. Results showed that the main principal phytoplankton ecotypes were changed from warm-water species to eurythermy species. The species and abundance were yearly degressive. The distribution of phytoplankton abundance kept a trend of higher in the west coast and lower in the east and southeast coast, and higher alongshore and lower offshore. It is presented that the rich nutrients and warm water discharge affected the phytoplankton abundance. In the Ecological Monitoring Zone of Daya Bay the dominant species were mostly diatom with seasonal and yearly diversity and variability. Rhizosolenia alata f. gracillima was the predominant species in spring and Pseudo-nitzschia delicatissma was the predominant species in summer. Pyrrophyta started to be the ascendancy at the end of spring. The diversity of phytoplankton community was yearly decreased and the evenness of phytoplankton community was yearly increased. The unconventionality of phytoplankton multiplication led to lower diversity, species imbalance, monotony of community. Harmful algae bloom occurred frequently in spring and summer, and its frequency and classes were increased year by year. All of these indicated that the ecosystem of the Ecological Monitoring Zone of Daya Bay was vulnerable and undergoing a rapid deterioration.