The Current Status Of Biological Habitats In The Middle And Lower Reaches Of The Ganjiang River And Their Responses To Environmental Factors

By arranging 12 sampling sections in the middle and lower reaches of the Ganjiang River(from the intersection of Zhangjiang and Gongshui to the section that merges into Poyang Lake),and through detailed recording of site conditions(weather,temperature,environmental status,water level changes,etc.),in 2019 On-site sampling of benthic animals and plankton in the Ganjiang River will be conducted on January,April,July,October,and January and April 2020.Use statistical methods to analyze the community characteristics and spatial distribution characteristics of benthic animals and plankton within the year,year,and under different water regimes,and compare with the measured data from 2009 to 2010,and analyze the changes in the water ecosystem of the middle and lower reaches of the Gan River in the past 10 years,And discuss the influence of the Gan River water quality status,hydrological situation and habitat area changes on the abundance of benthic fauna and plankton.Finally,the main environmental factors that affect the abundance of aquatic organisms,different water regimes,and the size of the habitat area are obtained,which can provide reliable data for the protection of the species diversity of the biological habitats in the middle and lower reaches of the Ganjiang River and the healthy ecosystem of the Ganjiang River.During the sampling survey,a total of 21 species of benthic animals were detected,with a maximum of 10 species of mollusks;followed by arthropods and annelids,with 6species and 5 species respectively;accounting for 47.62%,28.57% and 23.81%respectively.The number of benthic animals in different sections of the year varies greatly.The biological density of each section of the river is 0?425.8ind./m2,and the biomass range is 0?857.8g/m2;18 benthic animals were detected in the dry season under different water conditions.The genus,accounting for 50%,has 3 dominant species,namely Bellamya aeruginosa(Y=0.1548),Branchiura sowerbyi(Y=0.0443)and Chironomus(Y=0.0443)Glyptotendipes pallens)(Y=0.0248);a total of 12 genera were detected in the normal water period,and there are 2 dominant species,namely Bellamya aeruginosa(Y=0.2691)and Corbicula fluminea(Y=0.0243);Three genera were detected in the wet season,and the dominant species was Bone river snail(Y=0.0595).The average range of the annual Shannon Wiener Index H'of benthic animals is between 0 and 0.95,while the relatively high average range of the richness index d M is 1.03 to 2.62,and the evenness index J'has the worst average range of the year.0?0.33.A total of 41 genera,17 families and 4 classes were detected in zooplankton.Among them,there are the most rotifers,25 species,mainly crystal capsule wheels,accounting for60.98%,followed by cladocerans and copepods,with 7 species and 5 species,accounting for 17.07% and 12.20%,native The least biological species,only 4 species were detected,accounting for 9.76%.The dominant species is the crystal capsule wheel.The averagedensity in the wet season is 407/L,while in the dry season it is only 189/L.Phytoplankton is composed of cyanobacteria,green algae,diatoms,euglena,dinoflagellate and cryptophytes.Among them,there are many types of green algae,diatoms and cyanobacteria,15,12,and 8 species were detected in sequence,and the remaining three species of algae The same,2 types are detected.29 species of 6 phyla were detected during the dry season,among which 13 species of green algae are at most,and 4dominant species in the dry season are cyanobacteria(Y=0.5524),cryptophyta(Y=0.0244),diatoms(diatom)(Y=0.0674)and green algae(Y=0.2300);24 species in 6 phyla were detected in normal water period,including 10 species of diatom and 4 dominant species,namely cyanobacteria(Y =0.1073),cryptophyta(Y=0.0412),diatom(Y=0.4378)and green algae(Y=0.2279);19 species in 6 phyla were detected in high water period,dominant species There are 3 species,namely cyanobacteria(Y=0.2587),diatoms(Y=0.1254)and green algae(Y=0.4627).The density range of phytoplankton in each section is 131400 ind./L?2714500 ind./L,the biomass range is 0.1752 mg/L?4.6513 mg/L,dry period(2.3886 mg/L)> normal water period(0.7540 mg/L)> High water period(0.4292 mg/L).The annual average range of Shannon Wiener Index H'is 1.1525?1.3342,while the relatively high average range of richness index d M is 1.1767?1.8255,and the average range of evenness index J'is only 0.3423?0.4297..The average abundance of benthic animals in 2009-2010 was higher than that of2019-2020,67.6 ind./m2.Among them,the difference in abundance during normal water period was the largest,and the wet period and dry period were smaller;the order of biomass was normal water period> dry period> abundance Water period.Compared with the abundance and biomass of benthic animals in the Ganjiang River Basin around ten years ago,the abundance has changed significantly,and the overall biomass has also shown a downward trend,but the change is small.The average abundance of zooplankton is higher than 96.21 ind./m2 ten years ago,and the difference in wet season is the largest.In terms of biomass,the average biomass in 2019-2020 is higher than 0.235 mg/L in2009-2010,among which the difference in dry season is the largest,and the difference in biomass in wet and flat periods is smaller,and the order of biomass is in dry season>High-water period> normal water period;in terms of abundance of phytoplankton,the average abundance of phytoplankton during 2009-2010 was only 809967 ind./L,which was only one third of that in the past two years.Among them,the difference in dry season is the largest,followed by the difference in normal and wet periods;and the biomass change trend is basically consistent with abundance.The change trend of the average annual flow in the middle and lower reaches of the Ganjiang River from 1959 to 2010 is the same in the four hydrological stations as a whole,showing an increasing trend.According to the average flow,the order is Waizhou Station>Xiajiang Station>Ji'an Station>Dongbei Station.The change trend of the monthlyaverage flow before and after the construction of the dam at Dongbei Station shows that the flow rate increased during the dry season and the discharge flow rate decreased during the wet season,reflecting the flood control and irrigation regulation and storage effects of the Wan'an Reservoir;Short,the analysis results have not yet played the role of flood prevention.The TLI value of each section in the middle and lower reaches of the Ganjiang River is in the range of 42.2-46.2,with an average value of 44.31,indicating that the water quality of the middle and lower reaches of the Ganjiang River is relatively good and in a moderately nutrient state.The abundance,biomass and 8 environmental factors of aquatic organisms and water samples in the Ganjiang River Basin were processed to perform correlation analysis and CCA analysis between the two.Obtained ammonia nitrogen,phosphate and COD are the main environmental factors affecting the abundance of aquatic organisms in the Ganjiang River Basin.Analyzing the hydrological situation and aquatic abundance in the middle and lower reaches of the Ganjiang River for many years,it is found that in terms of benthic fauna,the flow of the middle reaches is positively correlated with the abundance of benthic animals,and there is indeed no obvious correlation in the lower reaches;For animals,the flow in the middle reaches has a negative correlation with zooplankton;for phytoplankton,the flow in the middle reaches has a positive correlation with the abundance of phytoplankton in dry and wet periods,and the lower reaches of the Gan River is only Ji'an-The Xiajiang section has a negative correlation;while the normal water period is basically the opposite of the results obtained during the dry and wet periods.In short,the increase in flow along the Ganjiang River will promote the abundance of benthic and phytoplankton,but will have a smaller impact on the abundance of zooplankton.The impact of habitat area changes on benthic organisms and phytoplankton: By analyzing the changes in the area of the river section and its abundance trend,it is concluded that the changes in the area of the biological habitat in the middle and lower reaches of the Gan River are basically related to the abundance of benthic animals in the river.The change trend of zooplankton abundance and habitat area is basically the same as that of benthos;analysis of phytoplankton abundance and habitat area change shows that phytoplankton abundance and habitat area change are negative relationship.