Characteristics Of Polychaete Community And Its Environmental Indicating Function In Sansha Bay

With the continuous expansion of the scale of mariculture in our country,the environmental pollution caused by it follows.Sansha Bay is a typical compound aquaculture bay along the coast of China.In 2021,the output of large yellow croaker,seaweed and abalone in the bay has reached 19.16 million tons,20.42 million tons and50000 tons.Therefore,it is of great significance to study the ecological effects of mariculture activities in Sansha Bay.According to the study of the macrobenthic community in Sansha Bay,it was found that the community structure presented the characteristics of homogeneous distribution,and there was no significant difference in the community structure in different aquaculture waters.Therefore,further research on polychaete community in Sansha Bay is conducive to revealing the environmental impact of aquaculture activities.Polychaeta community structure and their responses to the impacts of marine exploitation activities in Sansha Bay,China,were studied based on fauna and concurrently obtained environmental samples collected in August 2016.Based on the biological samples and synchronous environmental data accumulated in the laboratory in recent years,the environmental indicators of polychaetes were studied.Our relevant research methods and conclusions are as follows:1.Status of polychaeta community structure and its relationship with environmental factors in Sansha BayThere are 41 stations in Sansha Bay,including four types of fish cage farming,seaweed raft farming,abalone cage farming and non-farming.A total of 48 species of polychaetes belonging to 27 families were collected.There are 41 species of polychaete animals in the fish cage farming;seaweed raft farming take the second place,with 27species;There are 10 and 13 species of polychaete animals in abalone cage farming and non-farming,respectively.The mean density of polychaete was 292.68 ind./m~2,and the mean biomass of polychaete was 13.06 g/m~2.The characteristics of the Polychaeta community in Sansha Bay was considered to be consistent with those reported in warm temperate waters in northwestern Pacific.The Onuphis sp.,Heteromastus filiformis,Sternaspis scutate,Ophelina acuminata,Lumbrineridae and Cirratulus sp.were dominant species in polychaeta community.The Shannon-Wiener diversity index in the above four types of waters was 2.37,2.18,2.03 and 1.52.The Pielou index was 0.88,0.81,0.73 and 0.72.The Margalef index was 0.76,0.70,0.70 and 0.44.The Simpson index was0.26,0.25,0.33 and 0.45.Kruskal-Wallis test showed that there was no significant difference(P>0.05)between the four community parameters in different aquaculture waters.Behrens-Fisher test showed that there were significant differences(P<0.05)in density between fish cage farming and non-farming,and between seaweed raft farming and fish cage farming.There were significant differences(P<0.05)in species between fish cage farming and non-farming.There were significant differences(P<0.05)in biomass between fish cage farming and non-farming,and between seaweed raft farming and fish cage farming.The results of cluster analysis showed that the similarity of polychaete community structure between different mariculture zone was low,and the spatial heterogeneity of polychaete community in the bay was high.Generalize linear model analysis shows that environmental factors such as depth,total phosphorus,stable carbon isotope and acid volatile sulfide in sediment have an impact on the distribution of most dominant polychaete species.Research has shown a significant correlation between environmental factors and the distribution characteristics of polychaete communities in the waters of Sansha Bay,indicating that the polychaete community in Sansha Bay responds to the impact of aquaculture activities.To sum up,our results showed that most fish cage farming activities in Sansha Bay have not caused significant negative ecological impact.However,the fish cage farming in some areas has had a negative impact,which is mainly reflected in the presence of"opportunistic"polychaete with high population density in some stations,such as Onuphis sp and Heteromastus filiformis.2.Study on the environmental indicator function of polychaetesBased on the biological samples and synchronous environmental data accumulated in the laboratory in recent years,the environmental indicators of benthic polychaetes were studied.This paper systematically describes 22 species of microcephala,Among them,there are 6 species of Capitellidea,13 species of Maldanidae,and 1 species of Sternaspidae,Arenicolidae and Oweniidae respectively.Firstly,the main environmental factors are determined by clustering,multi-dimensional ranking and canonical correspondence analysis.Classification of habitat types by major environmental factors and use ANOSIM to test the difference between different types.Secondly,based on the toxicological test data and environmental data,select the reference station and pollution station.The environmental characteristic value is calculated according to the projection of the sampling station on the vector formed by the median line between the reference station and the pollution station.Based on the environmental characteristic values and benthic species abundance data,the principal coordinate analysis method was used to construct the pollution gradient and calculate the pollution tolerance value of species on the main pollution gradient.According to the median and interquartile interval of the species pollution tolerance value,it was determined that in the aquaculture waters of the East China Sea area,Lumbrieris heteropoda and Moorella iridescens had the environmental indicator function,both of which were in favor of the polluted environment.