Ecological Monitoring And Assessing Based On Benthic Macrofauna In Sandy Intertidal Zone Where Chinese Horseshoe Crab Habitating

In recent years,due to excessive human fishing,coastal engineering and other human activities,Tachypleus tridentatus《resources reduced dramatically.Benthic macrofauna has the advantages of wide distribution,relatively stable living habits,and it can reflect the disturbance of the sediment,so it has great significance in the method of biological index to evaluate the marine environment.In this study,Benthic macrofauna monitoring was carried out in the sandy intertidal zone of three research areas,and macrofaunal species,density,biomass,functional group,biological index and Abundance Biomass Comparison were used to evaluate the ecological environment of sandy intertidal zone in research areas.The aim was to explore the reasons for the reduction of horseshoe crab in China and the results can provide a scientific basis for the protection of horseshoe crab.The main research results are as follows:1.Ninety-one species of benthic macrofauna were obtained in the horseshoe crab reserve of Pingtan Island.Polychaetes had a majority in the collection of benthic macrofauna,including 43 species,but horseshoe crab was not collected.The average density of benthic macrofauna in Pingtan area was 3162 ind.·m-2,the average biomass of benthic macrofauna was 140.78 g·m-2.Carnivores group was the main benthic macrofaunal functional group in Pingtan research area,with 29 species,and Phytophagous group had the least number of species,only 9 species.The sediments had a great influence on the distribution of macrobenthic functional groups.2.Thirty-four species of benthic macrofauna were identified in the sandy intertidal of Zhaoan Island.The number of polychaetes was the highest with 17 species,but horseshoe crab was not collected.The monthly average density of benthic macrofauna in Zhaoan research area was 202 ind.·m-2,and the monthly average biomass of benthic macrofauna was 2.40 g·m-2.Carnivorous group was the main benthic macrofaunal functional group in Zhaoan research area,with 29 species;followed by Omnivores group(10),Phytophagous group(5),Detritivorous group(4),and Planktophagous group has the least number of species,just only 1 species.3.Thirty-seven species of benthic macrofauna were identified in the horseshoe crab habitat of Beihai.Among them,13 species belonged to Polychaeta,7 species belonged to Gastropoda,5 species belonged to Bivalvia and 10 species belonged to Crustacean,moreover,6 horseshoe crabs were collected in qualitative sampling.The monthly average density of benthic macrofauna in Beihai research area was 383 ind.·m-2,The density of the polychaetes was dominant,Ceratonereis marmorata is the dominant species of the West Ridge;followed by bivalves,gastropods has the lowest average density.The monthly average biomass of benthic macrofauna was 101.08 g·m-2,followed by Crustaceans,polychaetes has the least density of benthic macrofauna.Phytophagous group was the main benthic macrofaunal functional group in Beihai research area,and Omnivores group has the least number of species,only 3 species.4.The diversity index and evenness index of benthic macrofauna in the sandy intertidal zone of Pingtan Island in summer were higher than those in Tannan Bay,but the spring was opposite.The average diversity index of benthic macrofauna in the intertidal zone of Zhaoan Bay in Autumn 2013 and Spring 2014 was low(0.971).In the summer of 2016,the diversity index of benthic macrofauna in the sandy tidal zone of Xibei Saltern was lower than that in another sandy intertidal zone,but the abundance index(d)was higher than that in another sandy intertidal zone.5.The average of the diversity index indicates that the sandy intertidal zone of Pingtan Island,Chengzhou Island and Beihai are respectively moderate,severe and mildly disturbed.The values of AMBI and M-AMBI indicate that the sandy intertidal zone of Pingtan Island,Chengzhou Island and Beihai are slightly disturbed.It can be seen that the results of AMBI and M-AMBI are consistent in the sandy intertidal zone,while the results of the diversity index are inconsistent with the above results.