富营养水体中浮游植物生长的营养限制研究

LIMITING NUTRIENT OF PHYTOPLANKTON GROWTH IN 30 EUTROPHIC PONDS

选取位于武汉城郊汤逊湖畔的30个养殖池塘作为研究对象,运用营养盐加富试验评价了浮游植物生长的氮磷限制类型。研究发现这些池塘的氮磷含量均较高,尤其是TP,绝大部分都在0.4 mg/L以上,TN/TP(原子比)变化范围为1.7~20.3。相关分析显示,浮游植物的生物量与氮素(TN,TDN,NO3-,NH4+,NO2-)显著正相关(r=0.402~0.677,P【0.05);但与磷素(TP,TDP,PO43-)无显著相关性(P】0.05)。营养盐加富试验显示浮游植物群落对加N的响应程度要显著大于加P;受N限制的池塘数量占50%;P限制的占13.3%;N、P共同限制的占23.3%;而不受N、P影响的仅占13.3%。这些结果表明:在富营养的水体中,当TP浓度】0.4 mg/L且TN/TP【20时,N是限制浮游植物生长的主要因子,P处于第二位。

A total of 30 ponds,located near Lake Tangxun in the suburb of Wuhan,were selected for this study.Nutrient enrichment bioassays(NEBs) were performed to identify which nutrient is limiting phytoplankton growth.These ponds were rich in nutrients,especially for phosphorus,with most ponds having TP>0.4mg/L.Atomic TN/TP ratio ranged from 1.7~20.3.Correlation analysis showed that phytoplankton biomass was significantly correlated with N(TN,TDN,NO3-,NH4+,NO2-)(r=0.402~0.677,P<0.05)but not with P(TP,TDP,PO43-)(P>0.05).The NEBs demonstrated that the addition of N induced significant responses of phytoplankton growth compared to the addition of P.Phytoplankton growth was limited by N in 50% and by P in 13.3% and by N+P in 23.3% of the study ponds,respectively.Only 13.3% of the ponds were not limited by N or P.These results suggest that phytoplankton growth was primarily limited by N,with P being a secondarily limiting nutrient when TP>0.4mg/L and TN/TP<20 in eutrophic waterbodies.