Study On The Habitat Suitability Of Macrozoobenthos In The Middle And Upper Reaches Of The Heihe River

In recent years,with the rapid socio-economic development,human development and influence on rivers have intensified,and the original river ecosystem has experienced a series of problems such as water pollution,reduction of aquatic biodiversity,a decrease of habitat suitability and weakening of river ecological service functions.As an indispensable part of river ecosystem operation,macrozoobenthos has been widely used in water quality assessment and habitat suitability assessment because of their role in purifying water bodies and promoting material exchange.At present,there are many studies on benthic habitats in China,but they are mainly focused on outflow river basins,and there are few studies on inland rivers,especially in high altitude areas.Therefore,this paper investigates the characteristics of macrobenthic communities and the spatial and temporal distribution of water environment factors in the middle and upper reaches of the Heihe River and conducts a study on the habitat suitability of macrobenthic habitats to provide scientific theoretical support and data reference for ecological restoration,aquatic biodiversity conservation and habitat restoration in the Heihe River basin.The main research results are as follows:(1)The overall preference of water quality in the middle and upper reaches of Heihe River has obvious spatial and temporal heterogeneity,showing that the upstream tributaries are better than the middle reaches and better in summer than in autumn.Spatially,the p H,electrical conductivity,total dissolved solids,dissolved oxygen,salinity,nitrate-nitrogen,total phosphorus,total nitrogen,five-day biochemical oxygen demand and chemical oxygen demand in the upper reaches of the river were all lower than those in the middle reaches in summer,while the resistivity,nitrite nitrogen and potassium permanganate index were greater than those in the middle reaches;in autumn,p H value,conductivity,total dissolved solids,salinity,nitrate-nitrogen,total nitrogen,ammonia nitrogen,biochemical oxygen demand and chemical oxygen demand in the upper reaches were lower than those in the middle reaches,while dissolved oxygen,electrical resistivity,chemical oxygen demand were smaller in the middle reaches,resistivity,total phosphorus,potassium permanganate index content and substrate particle size were greater in the upstream reaches than in the midstream reaches.Temporally,p H,electrical conductivity,total dissolved solids,dissolved oxygen,salinity,nitrate-nitrogen,total phosphorus,total nitrogen,ammonia nitrogen,five-day biochemical oxygen demand,and potassium permanganate index were lower in the summer streams than in the fall,with only the summer streams having lower resistivity and chemical oxygen demand.and chemical oxygen demand was higher than those in autumn,and the difference in substrate grain size between the two seasons was not significant.(2)The macrobenthic community structure and biodiversity in the middle and upper reaches of the Black River show significant spatial and temporal differences.In summer,a total of 1308 macrobenthic animals were collected,with 43 species belonging to 3 phyla,7orders and 14 orders;the number of species was 27 in both the upper and middle reaches,and the trend of species density and biomass along the range was that the middle reach(706ind·m^-2,45.3878 g·m^-2)>the upper tributaries(602 ind·m^-2,18.2318 g·m^-2).A total of 828macrobenthic animals were collected in autumn,with 38 species belonging to 3 phyla,7 orders,14 families and 24 families,of which the number of species was 28 in the middle reaches and24 in the upper reaches.The trends of species density and biomass along the range were 481ind·m^-2>343 ind·m^-2in the upstream section and 31.2105 g·m^-2>16.9966 g·m^-2in the upstream section.The biomass trends in summer and autumn were different,with summer biomass showing as mollusks>arthropods>annelids,while autumn showed arthropods>mollusks>annelids.(3)Statistical analysis of water environmental factors and macrozoobenthos in the middle and upper reaches of the Black River was conducted to screen three indicator factors of dissolved oxygen(DO),water temperature(WT)and substrate(SD)and one indicator species of the water spider,and the optimum range of water environmental factors of water spider was determined.The habitat suitability model was used to evaluate its habitat suitability quantitatively.The results show that the water spider likes to dwell in the pebble bed,and the optimal dissolved oxygen concentration is between 6.66 mg/L and 9.19 mg/L.The optimum water temperature ranged from 17.17 to 21.35?.The mean HSI values of each river section in summer were 0.66 in the upstream tributary,0.63 in the upstream mainstem and 0.81 in the midstream;the mean HSI values of each river section in autumn were 0.63 in the upstream tributary,0.38 in the upstream mainstem and 0.7 in the midstream.