Study On The Characteristics Of Zooplankton Communities And Construction Mechanisms In The Yanhe River Basin

The Yan River,a typical right-bank tributary of the middle reaches of the Yellow River,has a complex natural,cultural,and geographic environment,with a fragile ecological system.Zooplankton are an important component of freshwater ecosystems and are highly responsive to changes in water quality.Therefore,their community characteristics have an important indicative role in maintaining the health of aquatic ecosystems.With the aim of better understanding the current state of water ecology in the Yanhe River Basin and promoting more scientifically sound ecological protection measures,a systematic investigation was conducted in the spring and autumn of 2021(April and October,respectively)to study the water quality and zooplankton in the Yanhe River main stream,5 tributaries,and 3 reservoirs.Principal component analysis was used to analyze the water environment characteristics of the three types of water bodies in the Yanhe River Basin and the overall water environment characteristics in spring and autumn.The current abundance and diversity indices of zooplankton in the Yanhe River Basin were calculated and analyzed,and the temporal and spatial differences in the community characteristics of zooplankton in the Yanhe River Basin were analyzed using NMDS and ANOSIM analysis methods,with functional groups of zooplankton used as basic units.In addition,neutral models were used to explore the construction mechanism of zooplankton communities in the Yanhe River Basin,and the effects of neutral processes and niche processes on the construction of zooplankton communities in the Yanhe River Basin were studied using distance decay models and ecological niche analysis.The results of this study included the following achievements:(1)During two seasons,a total of 64 genera and 114 species of zooplanktons were identified in the Yan River Basin,with rotifers being the most dominant species.Specifically,87 species of zooplanktons were identified in the spring season,and 61 species in the autumn season.Furthermore,the abundance,dominant species,and diversity index of zooplanktons were generally higher in the spring than in the autumn season.It is worth noting that the abundance of zooplanktons was far higher in reservoirs than in rivers,indicating that zooplanktons tend to preferentially inhabit reservoirs.(2)The water environmental characteristics of the Yan River Basin exhibit significant spatiotemporal heterogeneity.Spatially,the water environmental characteristics among river water bodies are relatively similar,while there are larger differences between the reservoir water bodies and river water bodies.Temporally,the Yan River Basin’s overall water environmental characteristics also exhibit significant seasonal differences,and there are significant differences in environmental factors spatiotemporally.Based on the water quality index(WQI)and the diversity index of zooplanktons,the water quality evaluation shows that the overall water quality in the Yan River Basin is better in spring than in autumn.(3)In spring,87 species of zooplanktons can be divided into seven functional groups:PF,RF,RC,SCF,MCF,MCC,and LCF.In autumn,the zooplanktons in the Yan River Basin can be divided into nine functional groups,with two new predatory functional groups(PC and LCC)compared to spring.The community structure of zooplanktons(functional groups)in the Yan River Basin also exhibits significant spatiotemporal heterogeneity:in spring,the river water bodies are similar,while the reservoir water bodies are different from the river water bodies,which is consistent with the rule of water environmental characteristics;and the differences in zooplankton community characteristics among the three types of water bodies in autumn are not significant.(4)Niche processes primarily shape the community structure of zooplanktons in the Yantze River Basin.Nutrients,water temperature,pH,and turbidity are the primary environmental factors that promote the dynamic changes in the community structure of zooplanktons.In terms of biological interactions,during the spring season the competition among the functional groups of zooplanktons is weak and the populations enter mutualistic symbiosis,leading to a positive development succession in the community structure of zooplanktons.However,during fall season,competition and predatory relationships among the functional groups of zooplanktons become intense,leading to a negative development succession in the community structure.This intense ecological niche process determines the dominant species and eliminates weaker ones,only species with ecological differentiation can survive better.Niche processes enable the functional groups in zooplanktons to become more consistent across the three types of water bodies in the Yantze River Basin during autumn.This study contributes to a better understanding of the diversity and community construction mechanisms of freshwater zooplanktons,providing comprehensive data for a better understanding of the response of biological communities to environmental changes,and making contribution to the protection of water ecological health.