Research On The Correlation Between Macrobenthos Community Structure And Environmental Factors In The Lower Reaches Of The Mudanjiang River Basin

This paper systematically investigated the community distribution of macrobenthos in the lower reaches of the Mudanjiang River,and then analyzed the connection between macrobenthos and environmental factors,that provided basic knowledge for the analysis of macrobenthos variety within the Mudanjiang River basin and scientific basis for water ecological protection of the Mudanjiang River.The main research results are as follows.1.Five investigations were carried out in the lower reaches of the Mudanjiang River from January 2020 to December 2020,and a complete of 32 species of macrobenthos were identified,happiness to 4 phyla,7 classes,11 orders and 23 families.Among them,aquatic insects were the majority,that accounting for 43%of the full species.Molluscs(Granulifusus Kiranus)and crustaceans(Malacostraca)accounted for 31%and 19%,respectively.Annelida was the least abundant species,accounting for only 7%.The absolute dominant species within the lower reaches of Mudanjiang River are Palaemonetes sinensis,arthropod genus Substriata and Semisulcospira amurensis.absolutely the dominant species within the lower reaches of the Mudanjiang River are:Palaemonetes sinensis,Corixa substriata and Semisulcospira amurensis;The common species are Macrobrachium sp.and Heptagenia sp.In addition,the dominant species modified considerably with the seasons.2.The average quantitative biomass of macrobenthos within the lower reaches of the Mudanjiang River is 130ind/m~2,including 81ind/m~2for aquatic insects,23ind/m~2 for mollusks,19ind/m~2 for crustaceans and 7ind/m~2 for aquatic annelids.The variation range between different river segments is 5-240ind/m~2,and the variation range between different seasons is 59-165ind/m~2,and the seasonal variation trend of the quantitative biomass is Summer(165ind/m~2)>Autumn(120ind/m~2)>Winter(63ind/m~2)>Spring(59ind/m~2).The average gravimetric biomass of macrobenthos within the lower reaches of the Mudanjiang River is 0.486 mg/m~2,in which the gravimetric biomass of aquatic insects,mollusks,crustaceans,and annelids is 0.031 mg/m~2,0.123 mg/m~2,0.32 mg/m~2and 0.012 mg/m~2 respectively;the gravimetric biomass of benthos varied from 0.01 to0.815 mg/m~2 in different river segments,and the seasonal range of variation is 0.041-1.01mg/m~2 with the seasonal variation trend of Summer(1.01 mg/m~2)>Spring(0.5 mg/m~2)>Autumn(0.107 mg/m~2)>Winter(0.041 mg/m~2).3.The average of Shannon-Wiener diversity index of macrobenthos within the lower reaches of the Mudanjiang stream equals 3.35.The spatial variation range of each river segment is 1.6-5,and the seasonal variation range is 2.3-5.1.Among them,the diversity index of aquatic insects was the highest,and the spatio-temporal trend was basically consistent with that of macrobenthos,while the Shannon-Wiener index of mollusks and aquatic annelids was lower.The Shannon-Wiener index was lower for mollusks and aquatic annelids,and the seasonal variation of aquatic annelids was not obvious in each river segment.4.Pearson correlation analysis showed that environmental factors such as water temperature(Wt),dissolved oxygen(Do),total nitrogen(TN),total phosphorus(TP),permanganate index and total dissolved solids were closely associated with the community structure of macrobenthos within the lower reaches of the Mudanjiang River.The results of the redundancy analysis(RDA)of benthic communities and environmental factors showed that water temperature,as the main environmental factor,influenced the spatial distribution of benthic fauna in the lower Mudan River mainstem in spring,summer and winter;in addition,ammonia and p H also influenced the spatial distribution of benthic fauna in spring as secondary factors;in addition,water temperature,together with total nitrogen and p H,influenced the spatial distribution of benthic fauna in summer.In addition,water temperature,together with total nitrogen and p H,influenced the spatial distribution of benthic fauna in summer;total ammonia and total phosphorus also influenced the spatial distribution of benthic fauna in the lower main stream of Mudan River in winter;compared with other influencing factors,water temperature had less influence on the spatial distribution of benthic fauna in autumn,when total ammonia,ammonia nitrogen and dissolved oxygen were the environmental influencing factors.