洱海北部湖区轮虫群落季节演替特征

Seasonal succession of rotifer communities in northern Lake Erhai,Southwest China

洱海是位于我国西南亚热带高原地区的重要淡水生态系统,在高强度的人类活动与气候变化的影响下出现了较为严重的水质退化与富营养化现象,其中北部湖区的问题最为突出。本文以北部湖区为对象,设置了喜洲等5个样点,于2020年3、6、9和12月对该湖北部的轮虫群落及环境因子进行了季节性调查,分析了轮虫群落的季节演替特征及主要影响因子。本次调查共检出26属48种轮虫,多数种类为广布种或暖水种,其中无柄轮属、晶囊轮属、胶鞘轮属、须足轮属、龟甲轮属、多肢轮属在4个季节均出现。异尾轮属的种类数最多,共计9种。螺形龟甲轮虫、长肢多肢轮虫和前节晶囊轮虫是主要的优势种类。其中,螺形龟甲轮虫在4个季节均为丰度优势种,而前节晶囊轮虫在4个季节均为生物量优势种。非度量多维尺度分析表明,洱海北部湖区轮虫群落结构存在显著的季节差异。这种季节差异主要反映了水温的直接与间接影响,后者主要表现为鱼类捕食压力与食物资源的季节性。冗余分析表明,透明度、温度和浮游植物丰度为解释轮虫群落结构变化的重要变量。群落的物种组成与季节变化反映了主要轮虫优势种类对水温和水质变化的敏感性。

Lake Erhai,a significant freshwater lake located in the subtropical plateau of southwest China(Yunnan),has experienced water quality degradation and eutrophication under the influence of intensive human activities and recent climate change,especially in the northern zone of the lake.In this study,rotifer communities and environmental factors were seasonally investigated in 2020 at five sites in the northern zone of the lake.The seasonal succession of the rotifer communities and the associated environmental factors were explored by multivariate analyses.A total of 48 rotifer species from 26 genera were identified in this investigation,most of which were cosmopolitan or warm-water species.Ascomorpha,Asplanchna,Collotheca,Euchlanis,Keratella and Polyarthra appeared in all the investigated seasons.Trichocerca was the genus contributing the most species,including nine species.K.cochlearis,P.dolichoptera and A.priodonta were the dominant species.In the investigated seasons,K.cochlearis was the first dominant species in abundance,and A.priodonta was the first dominant species in biomass.Nonmetric multidimensional scaling analysis(NMDS)showed a significant seasonal difference in the community structure of rotifers in the northern zone of the lake.The significant seasonal difference of rotifer communities mainly reflected the direct and indirect effects of temperature,among which the indirect effects mainly included the seasonality of fish predation pressure and food resource.Redundancy analysis(RDA)showed that temperature,transparency and phytoplankton abundance were the important variables explaining the community variation and the seasonal succession of rotifers.Both seasonality and species composition of rotifer communities indicate the sensitivity of abundant species to the change of water quality and water temperature.