Characteristics Of Macrozoobenthos Community For Different Fisheries Habitats In Poyang Lake

Macrozoobenthos play an important role in aquatic ecosystems.Changes in community structure can affect phytoplankton,fishes,and other aquatic organisms,and are of great significance to the health and stability of the entire food web and aquatic ecosystem.Poyang Lake and its surrounding sub-lakes are affected by human disturbance,resulting in the degradation of overall ecological functions.It is not yet clear that the impact of the driving factors of degradation on the community structure of macrozoobenthos.In 2019-2020,a survey of macrozoobenthos in seven habitats in Poyang Lake was conducted.The main findings are as follows:1.A total of 97 species of macrozoobenthos were identified in the habitats of Poyang Lake,belonging to 42 families,9 classes and 4 phylums.There were 13 species,11 species,9 species and 14 species of dominant species in the four sampling periods of spring,summer,autumn and winter,respectively.Nephtys oligobranchia,Bellamya purificata,Corbicula fluminea,Pelopia sp.and Chironomus sp.are all taking the dominant position in each sampling period.The dominant species in channel connect of Yangtze River and main lake of Poyang Lake were the Nephtys oligobranchia and Corbicula fluminea adapted to the sandy sediment,and the Chironom.id Larva are the dominant species in sub-lake area.2.The mean density and biomass of macrozoobenthos in different habitats of Poyang Lake was 217.55 ind./m2 and 85.33 g/m2.The temporal and spatial differences in the density and biomass of macrozoobenthos were significant(P<0.05).The density of macrozoobenthos was highest in winter(288.32 ind./m2)and lowest in summer(144.67 ind./m2).The biomass was highest in autumn(122.85 g/m2)and lowest in summer(44.63 g/m2).The density of macrozoobenthos in Qinglan lake was the greatest(467.73 ind./m2),the middle reach of Yangtze River was the lowest(l6.89 ind./m2),The biomass of Nanjishan reserve was the highest(238.33 g/m2)and the middle reach of Yangtze River was the lowest(0.02 g/m2).3.The species,density and biomass of macrozoobenthos feeding group did not significant in season while differences in spatial.Among them,there were 26 species of Scraper and 4 species of Shredder.Collector-gatherer accounted for 35.2%of the total density,followed by Collector-filterer(23.42%)and Shredder(6%).The biomass of Scraper and Collector-filterer accounted for more than 98%of the total biomass.The density and biomass of Collector-filterer and Scraper were higher in the channel connect of Yangtze River,Poyang Lake and Nanjishan reserve,while the density and biomass of Collector-gatherer and Predator were lower.In the middle reach of Yangtze River,Junshan lake,Qinglan lake and Shahu lake,the density of Predators was higher,the Scraper was lower.While the biomass at here was reverse.4.Cluster analysis showed that the channel connect of Yangtze River,Poyang Lake and the middle reach of Yangtze River was grouped into one group,Junshan lake,Qinglan lake and Shahu lake were grouped into one group,and Nanjishan reserve was grouped into one group.The structure of macrozoobenthos communities was significantly different in different seasons.NMDS analysis showed that in winter,the middle reach of the Yangtze river,Junshan lake,Qinglan lake and Shahu lake were grouped into one category,and the channel connect of Yangtze River,Poyang Lake and the Nanjishan reserve were grouped into one category.In spring,Junshan lake and Qinglan lake are of the same category;the channel connect of Yangtze River,Poyang Lake,Nanjishan reserve and Shahu lake are of the same category;the middle reach of the Yangtze river is of the same category.Junshan lake and Qinglan lake are grouped into one group in summer,and macrozoobenthos structures in other areas tend to be integrated.In autumn,the structure of macrozoobenthos communities in different regions tends to beintegrated.5.Environmental factors have important influence on the community structure of macrozoobenthos.RDA analysis showed that water depth,turbidity,dissolved oxygen and chlorophyll were the main affective factors in the study area.Annelids are mainly related to turbidity and chlorophyll,while molluscs are mainly related to total nitrogen,total phosphorus,salinity,water depth and pH,which are obvious in autumn and winter.Arthropods are mainly related to temperature,chlorophyll and turbidity,which are more obvious in winter and spring.