中国主要河口海湾富营养化特征及差异分析

针对我国65个沿海河口海湾,基于自然地理数据及2007~2012年水质监测数据,采用箱须图法、聚类分析、相关性分析和主成分分析等方法,探讨河口海湾间富营养化特征、差异性及主要原因.结果表明,大型河口海湾的富营养化状态指标值相对较高,但河口海湾间富营养化响应指标值存在一定差异.DIN、PO₄^3--P和COD是河口海湾富营养化特征的第1主成分,DO和Chl-a是第2主成分,盐度、水深、潮差和面积等是第3主成分,河口海湾水体Chl-a浓度与TN入海量(P<0.01)、DIN(P<0.01)、PO₄^3--P(P<0.05)、流量(P<0.01)、温度(P<0.05)呈显著性正相关,同时与潮差(P<0.05)和盐度(P<0.01)和DO(P<0.01)呈显著性负相关.表明营养盐入海量增多是引起河口海湾一系列富营养化症状的主要因素,但河口海湾自然属性会调节其富营养化状态,造成系统间响应特征的差异.潮差小于2.5m的河口海湾,其营养盐转化效率明显高于潮差大于2.5m的河口海湾.说明河口海湾潮差可通过改变水体滞留时间、垂直混合和光照条件等,调节浮游植物生物量对营养盐的敏感性.此外,与外海的水体交换,海洋生物的捕食,及其他形态营养盐的供给等作用,也会影响河口海湾水体Chl-a的水平.人类活动带来的营养盐输入,以及河口海湾特有的自然属性,共同决定了其富营养化特征的差异和程度.

Eutrophication characteristics and variation analysis of estuaries in China

Eutrophication characteristics and variations were analyzed using four main statistical methods of box-plot analysis, cluster analysis, correlation analysis and principal component analysis, which were conducted based on natural geographic data and water quality monitoring data of 65 estuaries from 2007 to 2012 years in China. The results showed there was significant difference in eutrophication response indicators between the large-scale estuaries and small-scale estuaries. The eutrophication states of large-scale estuaries were more serious. It was also showed DIN, PO₄^3--P and COD were the first principal component of eutrophication characteristics, followed as DO and Chl-a for second, and Depth, Tidal and Area for third. In addition, there was significant positive correlation between the Chl-a and TN input (P<0.01), DIN (P<0.01), PO₄^3--P (P<0.05), inflow (P<0.01) and temperature (P<0.05), while there was significant negative correlation between chlorophyll a and tidal (P<0.05), salinity (P<0.01) and DO (P<0.01) in estuaries. It indicated the increase in nutrient input was the main factor which resulted in eutrophication symptoms. However, eutrophication state would be adjusted by typological factors and lead to different response characteristics among estuaries. The nutrient conversion efficiencies of estuarine tidal below 2.5m were higher than the ones above 2.5m. It is implied the eutrophication susceptibility to nutrient load could be regulated by changing water residence time, vertical mixing and light conditions. Furthermore, the Chl-a concentration were also influenced by water exchange with offshore area, biological predation and other nutrient forms supply in estuary. The differences and extent of eutrophication among estuaries were determined synthetically by nutrient inputs from human activities, as well as natural attributes of the estuary.