阿哈水库叶绿素a时空分布特征及其与藻类、环境因子的关系

Spatial and Temporal Distribution of Chlorophyll a and Its Relationship to Algae and Environmental Factors in Aha Reservoir

为了解阿哈水库叶绿素a(Chl-a)时空分布特征及其与藻类、环境因子的关系,于2012年枯水期至2013年平水期、丰水期对藻类与理化指标进行分层采样.结果表明Chl-a季节变化明显,与藻类生物量季节变化较为一致,而与丰度差别较大,平水期发生甲藻水华,浓度最高(91μg·L^(-1)),枯水期与丰水期相对较低,分别为8μg·L^(-1)与16μg·L^(-1).枯水期与丰水期水体表层Chl-a浓度略高于中、底层,表层光照、溶解氧相对充足,利于藻类生长;平水期表层Chl-a浓度远高于中、底层,易在表层聚集的甲藻水华是主要原因.大坝Chl-a浓度高于库中,这可能是大坝位于金钟河入库口,营养盐高于库中的缘故.相关性分析得出Chl-a与甲藻门呈极显著正相关(R=0.798,P<0.01);Chl-a与TP、DO、pH呈极显著正相关(R=0.762,P<0.01;R=0.792,P<0.01;R=0.658,P<0.01),与TN显著正相关(R=0.388,P<0.05)与N/P、NO_3^--N显著负相关(R=-0.37,P<0.05;R=-0.435,P<0.05).逐步回归分析得出DO、TP、N/P为影响阿哈水库Chl-a分布的主要因子.此外热分层以及水温对Chl-a的影响也不容忽视.

As one of the drinking water sources for Guiyang City in southwest China,the Aha Reservoir has an area of 190 km2 and a volume of 5. 42 × 10-8m3. The water depth is less than 30 m,with an average depth of 13 m. Regulated by subtropical humid monsoon climate,it has cool summers and warm winters,with an annual mean air temperature of about 15. 3℃ and an annual normal rainfall of approximately 1,129 mm. Impacted heavily by human activity（ e. g.,untreated industrial and domestic sewage and agricultural nonpoint pollution sources）,the eutrophication problem in the Aha Reservoir has become more serious each year. In order to explore the spatial and temporal distribution characteristics of chlorophyll a（ Chl-a） and its relationship to algae and the driving factors in the Aha Reservoir,phytoplankton and water samples were collected in the dry period,normal period,and flood period. The results showed a significant seasonal variation in Chl-a,same as biomass,but not the same as the algal abundance. Highest Chl-a concentration（ 91μg·L^-1） occurred in the mean season with the dinoflagellate bloom but during dry and wet seasons,they were only 8 μg·L^-1and 16μg·L^-1,respectively. During the dry and flood periods,the Chl-a concentrations in surface waters were slightly higher than the other layers caused by sufficient light and dissolved oxygen. But in the normal period,the Chl-a concentrations in surface waters were far higher than the other layers because of the dinoflagellate bloom assembling in surface waters. Located at the reservoir entrance of Jinzhong River,Dam sampling point owned higher Chl-a concentration than Kuzhong as a result of higher nutrients. Correlation analysis indicated that Dinoflagellate was positively correlated with Chl-a（ R = 0. 798,P〈0. 01）. Chl-a was positively associated with total phosphorus,dissolved oxygen,pH value,and total nitrogen（ R = 0. 762,P〈0. 01; R = 0. 792,P〈0. 01; R = 0. 658,P〈0. 01; R= 0. 388,P〈0. 05） and it had a negative correlation with the N/P ratio and nitrate nitrogen（ R =-0. 37,P〈0. 05; R =-0. 435,P〈0. 05）. Stepwise regression analysis showed that TP,N/P ratio,and DO were the most important factors influencing the temporal and spatial distribution of Chl-a. Thermal stratification and water temperature were also the significant factors that could not be ignored.