滆湖大洪港草、藻状态转换的磷阈值

Phosphorus threshold for the shift between grass- and algae-stable states in Dahong Harbor of Gehu Lake

以滆湖水草残存区——大洪港为对象,研究了自然条件下磷对大洪港草、藻状态转换的影响.对环境因子进行相关分析表明:总磷(TP)与叶绿素a(Chla)、透明度(SD)呈较好的线性相关关系.主成分分析结果表明,TP、总氮(TN)是影响水质变化的主要成分,其中主成分的贡献率及最大分量来源为TP.总磷浓度的变化影响大洪港草/藻型状态的转换,大洪港冬季处于草型状态,春季从草型状态转换为草-藻中间状态,夏秋季一直维持在草-藻中间状态.系统从草型状态向藻型状态转换的湖水总磷阈值为61μg·L-1,从草-藻中间状态向藻型状态转换的总磷阈值为115μg·L-1.可通过采取削减与控制污染源、底泥疏浚、构建沉水植被区等措施来改善湖区生境,使TP浓度降低到61μg·L-1以下,以维持大洪港处于草型状态.

Taking the macrophytes remaining area in Dahong Harbor of Gehu Lake as test object, this paper studied the phosphorus threshold for the shift between grass- and algae-stable states under natural conditions. The correlation analysis on the environmental factors showed that the total phosphorous in water body had better liner relationships with phytoplankton chlorophyll a and Secchi depth, and principal component analysis indicated that total phosphorous and nitrogen in the water body were the two main components affecting the water quality, among which, total phosphorous was the maximum weight source and played a determinant role in the shift between grass- and algae-stable states. The Harbor was in grass-stable state in winter, shifted to grass-algae intermediate state in spring, and kept the intermediate state in summer and autumn. The total phosphorous threshold for grass-stable state shifting to grass-algae intermediate state was 61 μg·L-1, and that for grass-algae intermediate state shifting to algae-stable state was 115 μg·L-1. In order to make the ecosystem shift from algae-stable state to grass-stable state, some measures such as cutting and controlling the Lake’s nutrient sources, removing the sediment rich in organic matter, and constructing submerged macrophytes areas should be adopted to make the total phosphorous threshold in the water body dropped to below 61 μg·L-1.