宁波市某人工泻湖浮游生物变化特征及影响因素分析

以宁波市北仑区梅山水道形成的人工泻湖为研究对象,在不同季节进行水质及浮游生物调查,分析其浮游生物时空分布特征与水质的关系。4个采样点共检出浮游植物66种,以硅藻为绝对优势种,检出浮游动物25种,主要为桡足类、少量轮虫及网纹虫;拦坝后水道内浮游生物密度有了数量级增长,各项生物评价指数降低,但各采样点仍处于中污染水平。监测理化参数表明,研究水域在拦坝后盐度下降、悬浮物浓度下降,氮磷含量无明显变化;水域大部分点位处于中度富营养化水平。结合浮游生物分布与理化参数进行分析,发现堤坝合龙后,水道内侧海水淡化、悬浮物含量下降,导致浮游生物密度上升、生物多样性下降、出现淡水优势种群;营养盐含量不是浮游生物生长的限制因子,对浮游生物分布无显著影响。

Distribution and Influencing Factors of Plankton in an Artificial Lagoon in Ningbo

The water quality and plankton survey were investigated in different seasons in an artificial lagoon formed by the course of Meishan Channel in Beilun District of Ningbo. The relationship between the spatial and temporal distribution characteristics of plankton and the water quality was analyzed. A total of 66 species of phytoplankton and 25 species of zooplankton were found, mainly including diatom species, copepods species, and a small amount of rotifer and Favella. The abundance of the phytoplankton increased by orders of magnitude while the biological indices decreased after building the dam. The biological indices of all samples indicated that water quality of the course was still in moderate level pollution. The physicochemical indexes showed that both the salinity and the suspended matter concentration decreased after the dam was built, but the concentrations of nitrogen and phosphorus had no obvious change. Most of the samples were mesotrophic or even eutrophic. The relationship between the distribution of plankton and the physicochemical indexes showed that the desalination of the sea water and the decrease of suspended matter concentration resulted in the increase of plankton density and the decline of biodiversity, which further induced the emergence of freshwater species. The nitrogen and phosphorous nutrition was not a limiting factor for plankton growth.