Study On Benthic Diatom Diversity And Its Correlation With Environment In Lalin River

The river ecosystem is an important channel for the material cycle of the biosphere.It has many functions such as regulating climate,improving ecological environment and maintaining biodiversity.In highly mobile water bodies such as river ecosystems,the benthic properties of benthic diatoms are sensitive to nutrients,organic and inorganic pollutants,and play an important role in water quality assessment.As an important tributary of the Songhua River,the Lalin River flows through the agricultural activity area of the Songnen Plain and is an important agricultural irrigation water source.It is of great significance to establish an evaluation system for the response of benthic diatoms to water nutritional status by analyzing their community structure and biodiversity.In this study,benthic diatoms were collected and identified from 23 sampling sites in the Lalin River Basin in spring,summer,and autumn of 2021 and summer of 2022,and the physical and chemical indexes of water were determined.The spatial and temporal patterns of benthic diatom community structure in Lalin River were explored from the perspectives of richness,abundance,biomass,niche and interspecific association.The diversity characteristics of benthic diatoms were discussed from three dimensions of species diversity,functional trait diversity and phylogenetic diversity,and two levels ofαdiversity andβdiversity.The correlation between benthic diatom biodiversity and water environmental factors in Lalin River was revealed by using Pearson correlation,grey correlation analysis and structural equation model.At the same time,based on the methods of diatom indicator species,diatom index,and biological integrity,the water health status of the Lalin River Basin was preliminarily evaluated,which provided basic data and reference for the protection and maintenance of biodiversity in the Lalin River Basin and the database of benthic diatom resources in the cold zone affected by agriculture in China.The main research results of this paper are as follows:1.A total of 234 species of benthic diatoms were identified,belonging to 2 classes,6 orders,12 families,and 52 genera.The average abundance of benthic diatoms was4.08×10⁵ind./cm²,and the average biomass was 0.45 mg/cm².2.38 dominant species of benthic diatoms were identified,among which some species of Navicula were dominant.The seasonal succession characteristics of the dominant species are as follows:in spring,Hannaea arcus were successively replaced by Gyrosigma scalproides in summer,and finally replaced by Luticola goeppertiana in autumn.Among them.Spatially,there was a change from the clean or oligotrophic indicator species in the forest land area（Achnanthidium minutissimum）to the pollution-tolerant and eutrophic indicator species in the agricultural land area（Melosira varians,）.3.The niche overlap index(ΔO_ik)and ecological response rate（R）of most dominant species were positive,and the community as a whole was developmental.The interspecific association was mainly positive correlation,and the species showed strong mutually beneficial synergy.4.The species,functional traits and phylogenetic diversity of benthic diatoms in the Lalin River Basin are abundant.In terms of time,spring and autumn show a certain similarity;spatially,the diversity index showed that the forest land area was larger than the agricultural land,showing a high sensitivity to the impact of human activities.5.Theβdiversity of benthic diatoms in the Lalin River Basin showed certain differences in time and spatial distribution,and agricultural activities had a certain impact on theβdiversity of benthic diatoms.6.Land use and spatial interaction directly and indirectly affect the species,functional traits and phylogenetic diversity of benthic diatoms in the Lalin River Basin by affecting climate,hydrology and nutrients.Environmental selection and diffusion work together on the spatial pattern of benthic diatom communities.