Effects Of Cage Culture On Physicochemical Properties And Bioiogical Facies Of Sediment Environment

Cage culture produces lots of biodepositions,which accumulate in sediments and affects the physicochemical property and biological facies of sediments.Thus,there should be one ecotone between cage culture zone and its adjacent waters theoretically.The determination of ecotone is helpful to further understand the environmental impact of cage culture and the interaction between the cage culture zone and its adjacent waters.Nevertheless,there is few data about the ecotone between the two ecosystems.To solve these problems,the spatial-temporal distributions of the content of organic matters,phosphorus with different forms in sediments and macrobenthos are analyzed through field investigation,indoor analysis and identification in Maniao Bay,Hainan.According to the clustering analysis for the non-large-scale cage culture zone by ArcGIS,whether the ecotone can be formed and the location of the ecotone is judged.The results of the present work show:1)The contents of TP in sediments in March,the contents of Ex-P in sediments in July and October,and the content of IP in sediments in July decrease as increased the shortest distance from the sampling site to the cage culture zone,which means that there is significnat spatial gradient of them.2)The sediment environment quality gets worse due to cage culture.Except in March,there is significant spatial gradient of content of organic matters in sediments.Moreover,the content of organic matters decreases as increased the shortest distance from the sampling site to the large cage culture zone.3)Cage culture affects not only the species composition but also the distributionof macrobenthos.There are unique macrobenthic communities in cage culture zone,and the tolerant species occur either in cage culture zone or its adjacent waters.The stability of macrozoobenthos communities in large cage culture zone and its adjacent waters is easily disturbed.However,the biomass and secondary production of macrozoobenthos tend to increase in large scale cage culture zone and its nearest areas.Moreover,the diversity and evenness of macrozoobenthos are higher in large scale cage culture zone and its nearest areas than those in other zones.Nevertheless,there is limitation using macrobenthos to evaluate the carrying capacity for cage culture.4)The contents of Ex-P,IP in sediments are suitable for determining the ecotone during the culture period,however,they don’t work in the non-culture period.5)The content of organic matters in sediments indicates the ecotone between the cage culture zone and its adjacent waters effectively.Moreover,the ecotone has great spatial-temporal stability.6)There is limitation using macrobenthos to indicate the ecotone of cage culture and its adjacent waters.The results of the present work are helpful to further understand the ecological effects of cage culture,and the strengthand mechanisms of interaction between cage culture area and its adjacent waters.Moreover,the work can provide theoretical support for the management and ecological regulation of cage culture area and its adjacent waters.