浅水湖泊沉积物生源要素与浮游藻类和沉水植物的关系

Relationship of Biogenic Substances in Sediments with Phytoplankton and Submerged Macrophytes in Shallow Lakes

为探究长江中下游浅水湖泊沉积物碳、氮、磷等生源要素的含量及其对浮游藻类和沉水植物的影响,以长江中下游11个浅水湖泊为研究对象,分析2003-2020年夏季沉积物总氮(TN_(Sed))、总磷(TP_(Sed))和有机碳(TOC_(Sed))含量与浮游藻类和沉水植物的关系。结果表明:(1)在长江中下游湖泊中,TP_(Sed)在藻型湖泊中最高,为(0.71±0.21)g/kg,草型湖泊中最低,为(0.52±0.13)g/kg。TN_(Sed)和TOC_(Sed)则在草型湖泊中最高,分别为(4.64±3.57)g/kg和(55.89±50.28)g/kg,中间态湖泊最低,分别为TN_(Sed)(1.86±1.26)g/kg,TOC_(Sed)(20.00±12.13)g/kg。(2)回归分析结果显示,夏季浮游藻类Chl-a含量在TP_(Sed)较高的湖泊中更高(P=0.01),沉水植物生物量(BMac)则在TP_(Sed)较低的湖泊中更高(P=0.03),而TN_(Sed)和TOC_(Sed)与Chl-a和BMac的回归关系不显著(P>0.17)。(3)长江中下游湖泊夏季沉水植物消失的沉积物总磷阈值约为0.87~0.98 g/kg。在长江中下游湖泊的沉积物中,磷含量对浮游藻类和沉水植物生物量的预测力比碳、氮含量更高,进一步研究二者定量关系后可为评价水生态系统沉积物污染状况及确定水生植被修复的沉积物条件需求提供科学依据。

In this study,we explored the effects of biogenic substances in sediments on phytoplankton and submerged macrophytes in shallow lakes in the middle and lower reaches of the Yangtze River basin.The study was based on summer investigations of water quality,biogenic substances in sediments and submerged macrophytes in 11 shallow lakes from 2003 to 2020(Baoan Lake during the summers of 2003-2012,2020;Hongxing,Honghu,Nanhu,Qingling,Sanliqi and Zhangdu Lakes in the summer of 2003;Dianshan,Gehu,Wuchang and Yangcheng Lakes in the summer of 2004).The relationship between sediment nutrient content and algal or macrophyte dominance was analyzed using univariate linear regression.Results show that:(1)The total phosphorus content in sediment(TP_(Sed))was highest in algal-dominated lakes(0.71±0.21)g/kg and lowest in macrophyte-dominated lakes(0.52±0.13)g/kg.Total nitrogen content(TN_(Sed))and total organic carbon content(TOC_(Sed))in sediment were highest in macrophyte-dominated lakes[TN_(Sed):(4.64±3.57)g/kg;TOC_(Sed):(55.89±50.28)g/kg]and lowest in intermediate lakes[TN_(Sed):(1.86±1.26)g/kg;TOC_(Sed):(20.00±12.13)g/kg].(2)Regression analysis shows that phytoplankton chlorophyll-a content(Chl-a)increased and submerged macrophytes biomass(BMac)decreased significantly at high TP_(Sed)(P<0.05).However,TN_(Sed) and TOC_(Sed) had little effect on Chl-a and BMac(P>0.17).(3)TP_(Sed) thresholds for the disappearance of submerged macrophytes in summer was 0.87-0.98 g/kg in the lakes of the middle and lower reaches of the Yangtze River basin.Our results demonstrate that TP_(Sed) is a better predictor of Chl-a and BMac than TN_(Sed) and TOC_(Sed) in shallow lakes of the middle and lower reaches of the Yangtze River basin.More quantitative analysis of these relationships will provide a scientific basis for assessing sediment pollution in shallow lakes and determining sediment conditions necessary for restoring and maintaining the submerged macrophyte community.