砷污染下阳宗海浮游动物群落特征及其影响因素

Characteristics and driving factors of zooplankton community in arsenic-polluted Yangzong Lake

砷污染是云南阳宗海近年来面临的主要环境问题之一,目前仍缺乏关于其对浮游动物这一重要生物类群影响的研究。为了科学评价砷污染对阳宗海浮游动物的健康风险,于2015—2016年对该湖的轮虫和浮游甲壳动物进行了每季度一次的采样调查。共发现浮游动物32种,且基本为广温性种类。浮游动物丰度变化范围为2~18 ind·L^(-1),平均丰度为8.5 ind·L^(-1)。三大类群的丰度以轮虫最高,而生物量则是桡足类占优势。浮游动物丰度和生物量在季节上差异显著(P<0.05),而在空间上差异不显著(P>0.05)。浮游甲壳动物(不含无节幼体)的体长范围为180~1780μm,以小个体为主,其中枝角类均为小个体种类。冗余分析结果显示,总磷、总氮、p H、砷、叶绿素a和蓝藻是影响浮游动物群落变化的主要环境因子。与历史数据及相关湖泊的比较表明,阳宗海浮游动物群落在砷污染后受到明显的抑制,其种类数、丰度均不同程度下降。

Arsenic pollution is a major environmental problem in Yangzong Lake,one of the largest lakes located in Yunnan Province of southwest China.However,its impact on zooplankton remains unknown.To evaluate the ecological risk of arsenic contamination to zooplankton in Yangzong Lake,we conducted seasonal investigations of rotifers and crustaceans(i.e.cladocerans and copepods)during 2015 and 2016.A total of 32 zooplankton species was recorded,which were mainly cosmopolitan ones.The total abundance of zooplankton ranged from 2 to 18 ind·L^(-1),with a mean of 8.5 ind·L^(-1).Among the three taxonomic groups,rotifers had the highest abundance,while copepods dominated community biomass.There was a significant difference in zooplankton abundance and biomass among seasons(P<0.05),but no difference among sampling sites(P>0.05).Crustaceans(excluding nauplii)had a mean body length ranging from 180 to 1780μm,and were dominated by small-sized individuals.In particular,cladocerans were all small-sized species.Results of RDA analysis showed that water total phosphorus,total nitrogen,p H,arsenic concentration,chlorophyll a,and cyanobacteria biomass were the main factors driving seasonal and spatial variations in zooplankton community.Compared to previous records from Yangzong Lake and neighboring lakes with similar trophic states,zooplankton species richness and abundance were significantly lower during 2015 to 2016,reflecting the detrimental effect of arsenic contamination on zooplankton in Yangzong Lake.