Study On Community Structure Of Zoobenthos And Comparison Of Different Conservation Waters In Lianhuazhou Port In The Lower Reaches Of Yangtze River

Due to various human activities,the biodiversity of the Yangtze River is decreasing continuously,general secretary Xi pointed out that the restoration of the Yangtze River's ecological environment should be placed in an overwhelming position,adhere to the protection in the course of development,and achieve coordination in all aspects.The waterway regulation of the Yangtze River trunk line is of significance to the economic development of the Yangtze River basin.In order to fully and effectively alleviate the bottleneck of navigation,waterway departments focus on the construction of the 6-meter waterway regulation project from Wuhan to Anqing.At the same time,for the purpose of ecological protection and restoration,the experimental area of ecological conservation was set up in Lianhuazhou port,and two local habitat improvement areas were set up in that port region.Eco-friendly structures such as fish nest frames and tetrahedron permeable frames were put in the habitat-improved area 1(G1)and 2(G2)respectively.At present,there are few reports about the ecological effect of structures designed or applied with ecological concept.Based on 12 sampling surveys of zoobenthos and environmental factors in Lianhuanzhou Port of the lower reaches of the Yangtze River,this paper analyzed the spatial and temporal distribution characteristics of zoobenthos community structure,feeding functional groups and their relationships with environmental factors,and also compared the habitat improvement areas with other areas.The main results are as follows:1.A total of 45 species of zoobenthos were collected at Lianhuazhou Port,belonging to 6 classes,15 orders,25 families and 39 genera,among which the number of arthropod species was the largest(25species),accounting for 55.56%of the total.The average density of zoobenthos was 49.08 ind./m~2,and the average biomass was 0.640 g/m~2.The composition of dominant species in Lianhuanzhou Port varied obviously in different months,with more dominant species of arthropods and less molluscs.The pielou index(J)and Shannon weiner index(H')of each station were relatively low in the middle stations of most sections,while the Margalef index(D)fluctuated little overall.The results of CCA analysis showed that dissolved oxygen,ammonia nitrogen,nitrate nitrogen,flow velocity and water depth were the main environmental factors affecting zoobenthos in Lianhuanzhou Port.2.The zoobenthos in Lianhuanzhou Port were composed of 5 feeding functional groups,among which the largest number of species were gather-collectors(22 species,48.89%),followed by filter-collectors and predators(7 species,respectively),with a small species number of scrapers(6 species)and shredders(3species).The average density showed gather-collectors(20.65 ind./m~2)>predators(15.42 ind./m~2)>shredders(7.82ind./m~2)>filter-collectors(3.96 ind./m~2)>scrapers(1.10 ind./m~2).The average biomass of filter-collectors was dominant(0.518 g/m~2),accounting for 80.93%of the total average biomass.3.Regional comparison found that the number of zoobenthos species in G1 and G2was less,and the species time variation was similar.At the beginning,crustaceans were the main species,and with the change of time,polychaetes were the main species,and then crustaceans with strong mobility were the dominant species.However,there was no obvious regularity in other areas,crustaceans were the dominant species in the later period.Similarity percentages showed that the average similarity within the habitat improved area was 66.69%,and the difference between the habitat-improved area and other areas was41.76%.The main divergent species between the habitat-improved area and the other areas are Perinereis sp.,Nephtys sp.,Nephtys polybranchia and Grandifoxus culpis.The average density of each area showed G2(93.44 ind./m~2)>G1(82.89 ind./m~2)>other areas(34.87ind./m~2),and the average biomass showed other areas(0.760 g/m~2)>G2(0.431 g/m~2)>G1(0.224 g/m~2).4.Regional comparison found that the density of feeding functional groups in G1 and G2 showed predators>gather-collectors>shredders>filter-collectors>scrapers.Other areas were different,the average density of gather-collectors was the highest(18.81ind./m~2),followed by shredders(6.72 ind./m~2),and scrapers was the lowest(1.27 ind./m~2).The bioamass of feeding functional groups in G1 and G2 showed filter-collectors>predators>gather-collectors>shredders>scrapers.In other areas,the biomass of each feeding functional group showed filter-collectors>scrapers>gather-collectors>predators>shredders.5.Compared with the other areas,G1 and G2 were favorable for the survival of zoobenthos,especially polychaetes and crustaceans,when the water regime is stable.The species number,density,biomass and biodiversity of zoobenthos in G2 were higher than those in G1,indicating that permeable frame was more conducive to the survival and recovery of zoobenthos than nest row.