Study On The Community Structure Of Nekton And Their Correlation With Environmental Factors In Eastern Laizhou Bay

In order to understand the characteristics and seasonal variation of the community structure of swimmers in the eastern waters of Laizhou Bay,the environmental factors related to the community structure of swimmers in the eastern waters of Laizhou Bay were explored.This paper is based on four bottom-season trawl surveys conducted in the eastern waters of Laizhou Bay from 2020 to 2021.Using species similarity index,dominant species(IRI)and replacement rate,cluster analysis,non-metric multidimensional scaling analysis(n MDS),biodiversity,niche width and overlap index,ABC curve and correlation analysis of environmental factors,The community structure characteristics and seasonal variation trend of the swimmers in the eastern part of Laizhou Bay were analyzed.The main research results are as follows:The most swimmers were captured in spring(49 species),followed by autumn and summer(47 species,42 species),and winter(40 species).The highest dominant species were in autumn(6 species),followed by spring(5 species),and the lowest were winter(3 species)and summer(3 species).In the index of species similarity,the similarity level between spring and summer was medium.The level of dissimilarity between autumn and winter and winter and spring was moderate,which might be related to seasonal changes.The seasonal replacement rate of dominant species of swimming animals in the eastern waters of Laizhou Bay showed a decreasing trend,and the seasonal replacement of dominant species was relatively large.Hierarchical cluster analysis showed that there were more groups in summer(4groups)and winter(3 groups),but less groups in autumn(2 groups)and spring(2groups).Non-metric multidimensional scaling analysis showed that the results of community clustering and grouping had certain explanatory significance and were basically reliable.The single factor similarity analysis among the groups showed that the difference was very significant in the four seasons(P < 0.01),indicating that the clustering results of the communities in the four seasons were better.The results of similarity percentage analysis showed that the similarity contribution rate within each group and the difference contribution rate between groups were different in the four seasons.In terms of biodiversity,the four seasonal Shannon-Wiener(H ’),Pielou(J ’)and Margalef(D)did not fluctuate significantly in the eastern Laizhou Bay.In the four seasons,the biodiversity index was higher in the northeast and southwest regions,and the regions with higher evenness index and higher richness index were in the west and north regions of the survey sea area,respectively.The niche width index of main swimming animals in autumn ranged from 0.14 to1.09,with an average value of 0.83.There were 6 species in the middle niche and 7species in the narrow niche.In winter,it ranged from 0.45 to 1.10,with an average of0.76.There were 1 meso-niche species and 9 narrow niche species.In spring,the range was 0.15 to 1.13,with an average of 0.88.There were 4 species in the middle niche and13 species in the narrow niche.In summer,the values ranged from 0.02 to 1.11,with an average of 0.85.There were only 2 species in the middle niche,and the other 14 species were narrow niche species.In general,species with higher ecological niche in autumn are dominated by higher trophic organisms such as Portunus trituberculatus and SP(Platycephalus indicus).However,species with higher niche in winter,spring and summer are predominantly omnivorous species such as Chaeturichthys stigmatias and short-rosed red-tongue sole(Cynoglossus joyeri).The niche overlap values of main swimming animals in autumn ranged from 0.11 to 0.94.Among 78 species pairs,39 pairs(50.00%)had significant niche overlap,35pairs(44.87%)had significant niche overlap,and 4 pairs(5.13%)had niche overlap less than 0.3.In winter,niche overlap values ranged from 0.13 to 0.93.Among the 45 species pairs,29(64.44 %)had significant niche overlap,12(26.67 %)had significant niche overlap,and 4(8.89%)had niche overlap.In spring,niche overlap values ranged from 0.56 to 0.94.Among 136 species pairs,135(99.26 %)had significant niche overlap,while only 1(0.74 %)had significant niche overlap.The niche overlap values of main swimming animals in summer ranged from 0 to 0.96.Among 120 species pairs,93(77.50%)had significant niche overlap,15(12.50%)had significant niche overlap,and 12(10.00%)had niche overlap less than 0.3.In general,the species pairs with higher niche overlap values in the four seasons were mainly small and of low economic value,while the larger species pairs had lower niche overlap values.On the whole,the W value in ABC curve analysis showed a trend of spring(-0.009)< winter(-0.08)< autumn(0.05)< summer(0.086),which indicated that the community structure of swimmers in the eastern waters of Laizhou Bay was unstable in spring and winter and was highly disturbed by the outside world.The community structure of swimming animals in summer and autumn was stable and less disturbed.The hydrology and water quality of the eastern sea area of Laizhou Bay did not change greatly in the four seasons,and all showed the first class standard.Through the analysis of the correlation between the biomass of main swimming animals and environmental factors,in general,the correlation between swimming animals and environmental factors in the eastern Laizhou Bay showed seasonal differences.The environmental factors affecting the community structure of swimming animals in the four seasons were mainly Temp,Depth,DIP,DIN and pH.