Ecological And Functional Characteristics Of Macrobenthos In The Intertidal Zone Of Daya Bay

Daya Bay is located between Honghai Bay and Dapeng Bay in the western part of Guangdong,and is an important semienclosed bay in the South China Sea.The coastline is dominated by rocky reefs,sandy,gravelly,muddy and mangrove coasts,inhabited by a variety of microbenthic animals.However,under the interaction of human activities and natural evolution,the shoreline of Daya Bay has been eroded,the habitat of macrobenthos has been reduced,and the community structure has been significantly changed.In order to understand the patterns and trends of the ecosystem in Daya Bay,this study analyse the community structure、ecological functions of macrobenthos and the influencing factors based on the data obtained from the intertidal zone of Daya Bay in August（summer）and November（autumn）2021 in different substrate types.The main findings are as follows:Ⅰ.Structural characteristics of the macrobenthic community1.A total of 118 species of macrobenthic animals were identified in both seasons.In summer,82 species were identified,with the largest number of mollusc species（35）,followed by arthropods（30）,and 13 and 3 species of annelids and chordates respectively.In autumn,the 64 species are still the most abundant（28）,followed by arthropods（22）,followed by nine annelids,three chordates,and one each of echinoderms and nematodes.The dominant species are different in three substrate types.2.The mean biomass and habitat density of the intertidal macrobenthos in the six sections were 589.36 g·m^-2、356.39 ind·m^-2 in summer and 188.22 g·m^-2、1010.3 ind·m^-2respectively;in terms of quantitative percentage composition,The biomass and abundance of Molluscs、Arthropods and Annelids were higher Horizontally,biomass and abundance were highest in the DYW06 in both seasons;vertically,biomass and abundance were low tide zone>middle tide zone>high tide zone.3.The Shannon-Wiener diversity index of the six intertidal sections ranged from0.35～3.12 in both seasons,with an average of 1.78 in summer and 2.05 in autumn;The Pielou evenness index of the six intertidal sections ranged from 0.11～0.93 in both seasons,with an average of 0.53 in summer and 0.68 in autumn;the Shannon-Wiener diversity index were highest in DYW06 in summer and DYW01 in autumn,and lowest in DYW03in summer and DYW05 in autumn;the distribution of Pielou evenness index were highest iny DYW01 in two seasons,and lowest in DYW02 in summer and DYW06 in autumn;st and section.In terms of vertical distribution,the Shannon-Wiener diversity index and Pielou evenness index of macrobenthos in Daya Bay showed that the middle tide zone>low-tide zone>high-tide zone.4.Both Cluster and MDS results showed that there were significant differences in intertidal macrobenthic communities of different substrate types in Daya Bay waters,which can be divided into three communities:sand,mud and artificialrock.5.The ABC curve results showed that the artificial shoreline and sand（autumn）communities had the best stability.The sand（summer）and mud section（summer）sections were moderately disturbed,and the mud（autumn）section had poor stability being severely disturbed.The results of the relationship between community structure and environmental factors based on db RDA analyseshowed that substrate type and anthropogenic disturbance were the main factors influencing the community structure of the intertidal macrobenthos in Daya Bay.Ⅱ.Ecological and functional characteristics of macrobenthos1.Fuzzy correspondence analysis,FCA showed that different sediments had different trait patterns,and mobility,maximum adult size or body size、habitat、reproduction frequency and feeding mode were the main factors for the differences;artificial rocky section had higher Shannon-Wiener index and functional diversity and lower the functional redundancy;functional diversity and functional redundancy fluctuated in sandy beaches between seasons.2.Analysis of macrobenthic biological traits and environmental factors by the distance-based linear model Dist LM showed that the environmental factors measured together explained 80.8%of the variation in db RDA1（99.2%）and db RDA2（0.8%）,with substrate type and anthropogenic disturbance reaching significant levels（P<0.05）.