横岗水库富营养化特征分析

于2005年5月和11月调查了横岗水库的营养盐、叶绿素a(Chl.a)和浮游植物,对水库富营养化特征进行了分析。5月的总氮(TN)平均浓度为3.810mg·L^-1,总磷(TP)平均浓度为0.172mg·L^-1,Chl.a平均浓度为17.888mg·m^-3,综合营养状态指数(TSI_M)为73.3,该水库已达重度富营养化;11月份TSI_M下降到55.6,处于轻度富营养化状态,TN和TP平均浓度分别下降到1.302mg·L^-1和0.096mg·L^-1,Chl.a平均浓度却上升到26.935mg·m^-3,Chl.a浓度的上升与氨氮(NH₃-N)和正磷(PO₄-P)浓度上升以及浮游植物群落组成改变有关。从5月到11月,水库由蓝藻型富营养化水体变为绿藻型富营养化水体。5月浮游植物平均细胞密度高达2.75×10⁸cells·L^-1,优势种为美丽平裂藻和银灰平裂藻,其中平裂藻细胞数约占总细胞数的90%。11月浮游植物平均细胞密度降低到1.27×10⁷cells·L^-1,平裂藻的优势度下降,只占总细胞数的14.89%,绿藻成为主优势类群,其中栅藻是优势种之一,占总细胞数的11.52%。

Analysis on eutrophication characteristics of Henggang reservoir

The nutrients,chlorophyll a and phytoplankton in the Henggang Reservoir were monitored in May and November,2005.In May,the mean concentration of TN,TP and Chlorophyll a were 3.810 mg·L^-1,0.172 mg·L^-1 and 17.888 mg·m^-3,respectively.Comprehensive Trophic State Index(TSI_M),was 73.3,indicating that the Reservoir was hypertrophic.In November,the mean concentration of TN and TP were 1.302 mg·L^-1 and 0.096 mg·L^-1,respectively.The TSI_M decreased to 55.6,indicating that the Reservoir was lightly eutrophic.However,the mean Chlorophyll a increased to 26.935 mg·m^-3.The increase of chlorophyll a concentration was positively related to NH₃-N and PO₄-P,and changes in phytoplankton community composition.The phytoplankton community was dominated by Cyanophyta in May,but by Chlorophyta in November.In May,the mean cell abundance of phytoplankton was 2.75×10⁸ cells·L^-1.The dominant species were Merismopedia elegans and M.glauca,which composed about 90% of the total phytoplankton.In November,the mean cell abundance of phytoplankton was 1.27×10⁷ cells·L^-1.The dominance of Merismopedia reduced to 14.89% of total phytoplankton cells.Scenedesmus became one of dominant species,which composed 11.52% of total phytoplankton cells.