A Preliminary Study On The Pattern Of Benthic Diatom Diversity And Its Environmental Correlation In Urban Rivers

As an significant part of the river ecosystem,the composition and community structure of benthic diatom can reflect the water quality directly or indirectly.With the acceleration of urbanization,the impact of human activities on river ecosystem is increasingly serious.Therefore,research of benthic diatom diversity and its relationship with environmental parameters become more and more important.In this study,benthic diatoms were collected from Harbin urban river network including the Songhua River,Hulan River,Ashi River and Lalin River seasonally during2018 and 2019.A total of 179 samples were collected from 30 sampling sites.Benthic diatom diversity,compostion differences spatially and temporally,and physical and chemical parameters were investigated to analyse the diatom community structure,distribution pattern and assess the water quality.The main results are as follows:1.During the study period,202 species(including varieties and forms)belong to53 genera were identified.Ten taxa from 5 genera belonging to Centricae and 192 taxa from 48 genera belong to Pennatae.Gomphonema,Nitzschia and Navicula are sepcies rich genera,with 22 species(10.89%),20 species(10.89%),ands 19 species(9.41%)respectively.2.In total,45 dominant species belong to 21 genera were observed.The dominant species in the Songhua River Basin are: Ctenophora pulchella,Diatoma monilifonmis,Navicula radiosa,etc.;the dominant species in the Hulan River Basin are: Cocconeis placentula,Cymbella affinis,Achnanthidium minutissimum,etc.;the dominant species in the Ashi River Basin are: Cyclotella meneghiniana,Nitzschia palea,Navicula lanceolata,etc.;the dominant species in the Lalin River Basin are: Hannaea arcus,Encyonema silesiacum,Gomphonema parvulum,Encyonema minutum,etc.3.The benthic diatom community structure is different among different river basin.The results of the diversity index show that the benthic diatom community in Songhua River Basin and Ash River Basin is similar,and the other river basins have similar similarities.During the season,the structure of the diatom community changed significantly,and the two types of diatoms were the most during the two years.4.During the two years,water temperature(WT)varied between 5.7 ? and31.5 ?;pH varied from 6.8 to 9.9;dissolved oxygen(DO)were from 1.9 mg/L to 9.9mg/L;the specific conductance(SpCond.)ranged from 32.1 mS/cm to 975.13 mS/cm;the turbidity(Tur.)appeared between 1.7 NTU and 155.0 NTU;total nitrogen(TN)varied between 0.10 mg/L and 3.27 mg/L;total phosphorus(TP)were between 0.01mg/L and 3.88 mg/L;chemical oxygen demand(CODMn)varied between 1.0 mg/L and17.0 mg/L.Canonical correspondence analysis(CCA)showed that seven physical and chemical factors,including WT,pH,SpCond.,Tur.,TN and CODMn are the key factores affected the benthic diatom community structure in the study area.5.Based on the water environmental factors,water quality was preliminarily evaluated: according to the total nitrogen content the water quality showed abnormal eutrophication,through the evaluation of total phosphorus content,the water quality of the study area is light eutrophication.;chemical oxygen demand content indicated that the water quality was moderate eutrophication;utrition state index revealed that the water quality is light eutrophication.Based on the dominant species to evaluate water quality,the study area is eutrophic;Water quality evaluation based on diversity index showed: Shannon Wiener diversity index(H)performed light pollution or no pollution,and Pielou evenness index(J)performed light pollution or no pollution.