长江口区浮游植物的数量变动及生态分析

长江口一带水系交汇复杂,海水理化环境多变,导致海洋生物资源量产生很大波动。预计在三峽水利枢工程建成调节入海径流量后,河口生态环境必将出现新的格局,对河口生态系、生物资源量和社会经济将产生很大影响。故在工程兴建前必须从多方面进行预测和研究,以便对工程作出科学评价。以往虽在河口附近进行过多次调查,但迄今仍缺长江口门水域及河道内的资料,难以全面说明径流对河口环境的影响。为此,在1985-1986年逐月进行了长江口区生态环境及生物资源的本底调查。本文旨在根据调查结果探讨工程建成后,对作为生态系基础环节的浮游植物可能产生的影响,并为河口区生物资源开发利用提供科学依据。

QUANTITATIVE VARIATION AND ECOLOGICAL ANALYSIS OF PHYTOPLANKTON IN THE ESTUARINE AREA OF THE CHANGJIANG RIVER

During the period of 1985-1986, the annual average of chlorophyll-a contents of sea water and phytoplankton cells in the estuarine area of the Changjiang River were 3.3mg/m3 and 3×107 cells/m3, respectively. The tendencies of the horizontal distribution and seasonal variation of the chlorophyll-a were very similar to those of the phytoplankton. In the flood season (from June to September) the phytoplankton patch of the largest range and the greatest density of cells occurred in the middle part of the investigated area and only a small patch whose cell density was one fifth of that of the flood season occurred near the estuary in the other months. In summer, the composition of the phytoplankton was very complex, the fresh-water species,Scenedesmus spp. and Pediatrum spp., speared in the estuary, the eurythermal and low saline species such as Skeletonema costatum(Grev.)Cleve occupied the mddle part and some tropical species, Hemidiscus hardmannicnus(Grev.) Mann and Amphisolenia bidentata Schroeder, etc, appeared in the southeastern and northeastern parts of the investigated area. The distribution patterns of the above phytoplankton species of different ecological natures showed the dynamic state of the different water masses in the investigated area. The main factor on the variation of phytoplankton cell numbers is the flow capacity of the Changjiang River. The phytoplankton peak(108 cells/m3) often occurred in the months with flow capacity of 34,000 to 40,000m3/s. When the flow capacity is more than 45,000m3/s, the transparency of the sea water falls to less than 0.5m, and becomes the limiting factor to the phytoplankton growth, although a great deal of nutrients were carried into the estuarine area by flood, yet those rich nutrients were not beneficial to the phytoplankton growth.