The Study On The Seasonal Characteristics Of Macrfaunal Fouling Community In The Shellfish Aquaculture In The South China Sea

The South China Sea,located in the south of mainland China,is one of the famous natural marine fisheries with rich resources and high biodiversity.Li'an Lagoon is a typical tropical lagoon in the South China Sea,to the south of Hainan Island.The biofouling problem has caused great concern with the recent rapid development of the local aquaculture.In addition,the local environment has been changed by the mariculture activities and may also affect the fouling community.However,few studies have been found in the areas.Therefore we conducted an experiment from July 2014 to July 2015,to study the macrofaunal fouling communities in shellfish aquaculture area in Li'an Lagoon.It was found that:(1)In Li'an Lagoon fouling occurs on aquacultrual facilities throughout the year,the total recorded 32 species,belonging to 9 phylum,are mainly tropical and subtropical.The predominated species was Hydroides elegans,and other dominant species included Styela plicata,Balanus reticulatus,Bugda neritina.The wet weight of fouling assemblages in experiment period ranged from 0.03 kg·m-2 to 0.93 kg m-2,the maximum appeared in e Octomber,and the minimum occurred in March.The structure and biomass of macrofaunal fouling communities varied seasonally;generally the biomass was greater in rainy season than the dry season.(2)The identified tropical 239 plankton species included 118 of phytoplankton species belonging to 53 genera and 121 zooplankton species belonging to 100 genera.,The main phytoplankton species were diatoms and pyrrophyta.The dominant species were Rhizosoleniaceae,Tharassiosira,Cyclotella sp,Leptocylindrus danicus,Tharassionema nitzschioides,Coscinodiscus,Skeletonema cost atum.Zooplankton mainly included copepods,protozoa,tunicate and planktonic larvae,and the dominant species were Favella ehrenbergi,Naupliar Leprotintinnus,Oikopleura,Balanus larva,Helicostomella longa,Globigerinida sp,Oithona sp,Bestiolina sp.(3)The structure of fouling communities was closely correlated with water transparency,salinity and temperature by PRIMER 6.0v analysis.In addition,the abundance of planktonic larvae,water temperature,and food resource may also affect biofouling community.The structure of zooplankton community was mainly related to water temperature and chlorophyll a.Temperature,transparency,DO content and chlorophyll a were significantly correlated with phytoplankton community.The biomass of some macrofaunal species showed a significant positive coorelation with the the abundance of corresponding planktonic larvae,such as Hydroides elegans,mussel(P<0.05),Bugula neritina and,ostrea(P<0.01).(4)Based on the characteristics of the seasonal variation of macrofaunal fouling communities in Li'an Lagoon,We propose to consider taking the following actions to reach an expected antifouling aim.From July to November,the regular physical cleaning actions are supposed to be effective to remove the massive aggragation of Hydroides elegans.The regaular replacement of old cage of shellfish is a better way to avoid the accumulation of hard-shell faunal fouling in other seasons.The other biological control strategies are also suggested to be useful in environment-friendly antifouling tasks in mariculture.