Spatial And Temporal Distribution Patterns And Driving Mechanisms Of Macroinvertebrate Communities In The Qinghai Lake Basin

A river-lake composite ecosystem is a large and open ecosystem,where rivers and lakes play a crucial role in maintaining ecological balance,material circulation,and energy transfer.However,with the aggravation of global warming and the increasing impacts of human activities,the high-altitude river-lake ecosystem is facing increasingly severe environmental problems.Macroinvertebrates,as an important component of aquatic ecosystems,are one of the most diverse biological groups in aquatic environments and play an irreplaceable role in maintaining the balance of aquatic ecosystems.The spatiotemporal distribution pattern of macroinvertebrates can reflect the dynamic environment changes between rivers and lakes.However,many surveys of macroinvertebrates in high-altitude lakes or rivers often only consider individual river or lake,and few studies combine lakes and rivers together.This paper selects Qinghai Lake and its inflowing tributaries as well as sub-lakes,to investigate the spatiotemporal patterns of macroinvertebrate communities and their relationship with environmental factors.Firstly,the changes in community structure in different regions and seasons are compared to explore the spatiotemporal distribution pattern of macroinvertebrate communities.Then,the key environmental factors affecting the macroinvertebrate community and the community-environment relationship are analyzed during different seasons.At the same time,this paper analyzes the spatiotemporal changes and influencing factors of alpha diversity of macroinvertebrates from the dimensions of species and functional diversity.The main research results of this paper are as follows:In the survey of the summer of 2020,a total of 127 macroinvertebrate species were recorded in the main lake area,sub-lake,and inflowing tributaries,including 102 aquatic insects,15annelids,8 mollusks.The inflowing tributaries supported the most diverse species,with 121species found,far more than the 15 species in the sub-lake and the 8 species in the main lake area.Overall,one-way analysis of variance and PERMNOVA analysis both showed significant differences in the macroinvertebrate community among the main lake area,sub-lake,and inflowing tributaries.The inflowing tributaries support the highest biodiversity index and relatively complex community structure,while the sub-lake and main lake area had fewer species and a relatively simple structure.The db RDA analysis showed that COD,salinity,altitude,and BOD₅were the key environmental factors affecting the distribution of macroinvertebrate communities throughout the basin.A spatial and temporal analysis of the macroinvertebrate community in the main Qinghai Lake was conducted.A total of 16 macroinvertebrate species were recorded in three surveys conducted in spring,summer,and autumn of 2020,including 9 species of Diptera,2 species of Mollusca,3 species of Annelida,and others two species（Gammarus sp.and Hydracarina spp.）.The dominant species in all three seasons and four lake areas were Chironomus salinarius,with a high proportion.The density and biomass of macroinvertebrates in spring were significantly higher than those in summer and autumn,mainly due to the highest abundance of Chironomidae in spring.The repeated measures ANOVA and PERMNOVA analyses showed no significant differences in community structure among the four lake areas（lakeside zone,shallow water zone,inflow zone,and deep water zone）.However,the density and biomass of macroinvertebrates generally decreased from the coastal zone to the lake center,especially in spring.The db RDA analysis showed that temperature and chloride ion（Cl^-）concentration were the key environmental factors affecting the distribution of macroinvertebrates.An analysis was conducted on the composition of macroinvertebrate communities,species diversity,and functional diversity patterns among different tributaries of a lake.The results showed that there were significant differences in the relative abundance of dominant taxa among different tributaries.The relative abundance of Gammaridae and Perloidea was higher in the Buha River basin,while Oligochaeta was lower.In the Ganzi River,the relative abundance of Gammaridae was lower,and the relative abundance of Chironomidae and Simuliidae was higher.In the Hargei River,the relative abundance of Simuliidae and Oligochaeta was higher.In seasonal rivers,the relative abundance of Chironomidae,Simuliidae,and Oligochaeta was higher.Regarding functional traits,the relative abundance of five traits,Size 2,Arm 1,Arm 2,Swim 2,and Hab 4,showed significant differences among different tributaries（P<0.05）.Among them,the relative abundance of Size2,Arm2,and Swim 2 was the highest in the Buha River and the lowest in the Ganzi River and Hargei River,while the other six tributaries were intermediate.The relative abundance of Arm1 was the lowest in the Buha River and the highest in the Ganzi River and Hargei River.The CAP analysis showed that there were significant differences in both taxonomic composition and functional trait composition among different tributaries.There were no significant differences in taxonomic and functional compositions among different tributaries.The db RDA analysis showed that total phosphorus was the main influencing factor of the alpha diversity index of various species,while altitude,water temperature,and dissolved oxygen were the main environmental factors influencing the alpha diversity index of function.The explanatory power of environmental factors for functional alpha diversity was generally higher than that for species diversity.