东南沿海河流-水库系统藻类生长营养盐限制季节变动

选取厦漳泉三地市饮用水源地九龙江20条支流以及4个水库开展2013~2014年为期一年的逐月水质与生态调查与监测,并借助GIS、统计分析方法,识别了氮磷营养盐和浮游植物藻类丰度和群落的时空变异性,河流与水库氮磷营养盐限制的差异性以及其控制性的季节性变化特征.结果表明,九龙江支流和水库的营养盐、藻类丰度和群落都分别展示出明显的时空变异性.支流和水库均呈现营养盐氮素浓度冬春季节较高,夏秋季节较低;营养盐磷素浓度大体与之相反.水库藻类丰度于夏季最高,而支流藻类丰度呈现冬春季节较高,夏秋季节较低的趋势.其中,汀溪水库于秋冬春季节和夏季呈现硅藻,绿藻演替;江东库区于冬春,夏秋季节呈现绿藻-隐藻、绿藻-蓝藻演替;石兜-坂头水库以及支流均未出现季节演替现象,优势藻分别为蓝藻、绿藻.RDA排序图较好地显示了浮游植物藻类与环境因子之间的关系.水库叶绿素a与氮磷营养盐之间呈现显著相关性,相关关系较强,并且其相关关系在冬春季节呈现营养盐磷的限制性,夏秋季节呈现营养盐氮的限制性.相比于水库,支流叶绿素a与营养盐之间只有夏秋季节呈现显著相关性,且相关关系较弱.

Seasonal Variation on Nutrient Limitation for Phytoplankton Growth in a Coastal River-Reservoir System, Southeast China

A comprehensive analysis was conducted using a dataset obtained from October in 2013 to October in 2014 monitoring in 20 headwater streams of Jiulong River and four reservoirs, situated in such a coastal river-reservoir system in Southeast China suffering from intensive anthropogenic disturbance. In-situ monitoring, GIS and statistical analysis were coupled in this study to identify the spatiotemporal variations of nutrients & phytoplankton abundance and community structure, the differentiation of nitrogen & phosphorus limitation of phytoplankton growth, and the seasonal variations in nutrient limitation of phytoplankton growth. The results showed that there were obvious spatiotemporal variations in terms of nutrients & phytoplankton abundance and community structure in the 20 headwater streams and four reservoirs. The concentration of nitrogen was higher in winter and spring whereas lower in summer and autumn for both 20 headwater streams and four reservoirs. However, the concentration of phosphorus showed an opposite trend. The phytoplankton's abundance was the highest in summer for four reservoirs while it was higher in winter and spring, lower in summer and autumn in the 20 headwater streams. Meanwhile, the main trend in the succession of phytoplankton was from Bacillariophyta in autumn, winter and spring to Chlorophyta in summer in Tingxi reservoir, from Chlorophyta-Cryptophyta in winter and spring to Chlorophyta-Cyanophyta in summer and autumn in Jiangdong reservoir. No obvious trend exhibited in phytoplankton succession in Shidou-Bantou reservoir and 20 headwater streams. The Redundancy analysis (RDA) ordination plots well displayed the phytoplankton's community structure and its relationships with environmental factors. Besides, according to linear regression analysis there was a closer correlation between chlorophyll-a and nutrients in four reservoirs than in 20 headwater streams. In four reservoirs, N limitation was preliminarily observed in autumn whereas P limitation exhibited in winter.