Food source of the oyster on natural oyster reef and ecological benefit assessment in the tropical intertidal zone of Hainan Island
Land-based large-scale mariculture activities have substantial potential impacts on the ecosystems of near-shore oyster reefs.This study investigates the food sources for oysters on natural oyster reefs in the intertidal zone of Hainan Island using stable isotopes of carbon and nitrogen to determine the assimilation efficiency of oysters to organic particulate matter from coastal aquatic farm effluents.The study focused on three affected natural oyster reefs(effect areas)in Haitou of Danzhou,Changhua of Changjiang,and Longlou of Wenchang,as well as unaffected oyster reefs(control areas)in Haiwei of Danzhou.The food source of oysters was comparatively analyzed in July(summer)and No-vember(winter)in 2022.Results revealed that the main food sources of the oysters were benthic microalgae,phyto-plankton,sediments,organic particles from aquatic farm effluents,and macroalgae debris.Moreover,their average rela-tive contribution rates to oyster diets were 33.8％±16.5％,15.5％±6.9％,24.1％±21.7％,13.0％±3.4％,and 26.6％±16.4％respectively.The relative contribution rates ranged from 12.9％to 61.6％,7.8％to 30.8％,0％to 76.9％,9.3％to 19.2％,and 0％to 45.0％,respectively.Specifically,the highest contribution rate of benthic microalgae was observed in Longlou in November,whereas the lowest was in Haiwei in November.In July,contribution rate of organic matter from Sargassum polycystum to oysters in Haiwei reached 45.0％.The contribution rate of sediment food in November was higher than that in July across all stations.The δ13C values of oysters in the effective areas were-16.48‰,-18.35‰,and-17.06‰ in July,and-15.15‰,-18.05‰,and-15.22‰ in November,which were lower than those in the control area(15.65‰ and 14.48‰)in corresponding seasons.In July,the contribution rates of organic particles from aquatic farm effluents to oyster food in Haitou and Longlou were 15.3％and 12.9％,respectively,which was significantly higher than those in November(9.5％and 9.3％).In Changhua,the contribution rate of organic particles was 11.8％in July,which increased to 19.2％in November.The research shows that oysters can effectively assimilate organic particles from aquatic farm effluents,making these particles an important supplement to the food source of oysters in the effective area.Thus,this study confirms that natural oyster reefs can assimilate and remove a certain proportion of organic particles in aquatic farm effluents of aquaculture,highlighting their role in bioremediation.Therefore,it is suggested that efforts must be made to reduce the discharge of land-based cultured aquatic farm effluents,vigorously protecting and restoring near-shore oyster reefs to help reduce the nutritional load in adjacent waters and protect the marine ecosystem.
万方数据
维普
