春旱期间小清河济南段浮游动物群落演替特征OA

The North China Plain experienced consecutive spring droughts in 2024 with precipitation 20%to 40%below the multi-year average,which had significant impacts on river eco-hydrological environments.While there is extensive research on zooplankton community structure in the Xiaoqing River under normal hydrological conditions,studies on drought-induced responses of population and functional group structures are limited.Therefore,to identify changes in aquatic ecosystem stability and to provide scientific support for water ecological protection and restoration strategies during drought periods,an analysis of the evolutionary trends of zooplankton community structure and biodiversity under drought stress was undertaken. From January to June 2024,thorough monthly analyses of zooplankton and water environment parameters were carried out at six sampling locations along the Xiaoqing River's main stem.Community metrics such as dominance,Margalef richness index,Pielou evenness index,and Shannon-Weiner diversity index were calculated using species identification and density data.In order to determine the driving mechanisms between zooplankton communities and environmental factors while evaluating the effects of drought,non-metric multidimensional scaling and Mantel tests were used to compare community structure and biodiversity variations between drought and non-drought years. Investigation revealed one hundred and three zooplankton species belonging to four taxonomic groups in the Jinan section,categorized into seven functional groups.Both populations and functional groups showed little spatiotemporal variation in species composition,with protozoans and rotifers dominating populations and filter-feeders and predator-flagellates dominating functional groups.Density composition showed significant temporal variation,with protozoan dominance from January to March and rotifer prevalence from April to June.Functional group densities shifted from piercer-carnivores and predator-flagellates toward raptorial-carnivores and filter-feeders.In comparison to non-drought conditions,the drought year had lower water levels but generally higher water quality parameters,as well as lower species density and biomass but increased species richness and biodiversity indices. Water temperature fluctuations were the primary driver of community succession during a drought.Rotifers,copepods,and specific functional groups demonstrated significant correlations with chemical oxygen demand and five-day biochemical oxygen demand,whereas zooplankton biodiversity and dominant species showed weaker relationships with nutrients,including total nitrogen.The pattern of elevated water quality parameters coupled with reduced zooplankton density and biomass but enhanced species richness and biodiversity during the 2024 drought indicates that mild drought conditions may improve zooplankton community diversity and stability while simultaneously suppressing growth and reproduction,ultimately reducing overall density and biomass.