博斯腾湖过去百年来枝角类种群变化特征及生态意义OA

As essential primary consumers and secondary producers in freshwater lake ecosystems,the composition and abundance of Cladocera directly reflect the status of lake ecosystems.Bosten Lake is one of the most important fresh-water lakes in northwestern China.This study analyzes the zooplankton Cladocera subfossils in a sediment core from the central point of Bosten Lake,combined with measurements of 210Pb and 137Cs activity to establish an accurate chronological sequence for the core.The study reveals the succession characteristics and ecological significance of the Cladocera population structure in Bosten Lake over the past century.The results show that 17 genera and 25 species of Cladocera were identified in the sediments of the lake.The dominant species include Bosmina spp.,Monospilus dispar,Alona spp.,and Chydorus sphaericus s.l.Over the past century,the population structure and diversity of Cladocera in Bosten Lake exhibited notable phase changes.Prior to the 1867,the total abundance of Cladocera was low,with dominance by littoral species and high diversity indices,indicating that the lake was in a low water-level,grass-dominated environment.From the 1884-1909,the total abundance of Cladocera increased rapidly,reaching its hig-hest level in the core,with dominant species still being littoral types,but with an increase in the concentration of planktonic Bosmina spp.and rising diversity,suggesting increased water levels and nutrient levels in the lake.From the 1909-1963,Cladocera abundance and diversity levels decreased,with the dominant species shifting from Monospilus dispar to Chydorus sphaericus s.l.This indicates the increased nutrient levels and turbidity in the lake.Since the 1963,the total abundance of Cladocera has rapidly increased,with Bosmina spp.becoming the dominant species and further declines in diversity,reflecting significant degradation of the lake's water quality.The plankto-nic-to-littoral species ratio(P/L)significantly increased,indicating rising water levels in the lake.This study provides effective biological indicators to support the reconstruction of freshwater lake ecosystems in arid and semia-rid regions.