The Eco-environmental Effects Of Marine Ranching In Haizhou Bay

Marine ranching is a new type of aquaculture system,and it is also a large scale system project,involving oceanography,ecology,environmental science,marine engineering,physics and other interdisciplinary cooperation.China's marine ranching is aimed at solving the problem of serious pollution in existing breeding industry and the limit of fishing.It is the combination of marine fishing and aquaculture.In fact,the industrialization level of China's whole marine ranching is low.Reducing the pollution caused by traditional aquaculture,maintaining and improving the role of marine environment have not been paid much attention.Based on the collection and investigation of sediment samples in the marine ranching of Haizhou Bay in October 2016,this paper studied the spatial distribution of heavy metals in sediments,through the correlation analysis with geochemical indicators of sediments,determined that the construction of marine ranching would affect the distribution of heavy metals in sediments and sediments.Based on this conclusion,the data of long-term ecological environment monitoring in the marine pasture of Haizhou Bay in 2008~2015 are analyzed,and the change of the ecological environment of the marine pasture is evaluated by the entropy weight based comprehensive index method and the principal component analysis method.Based on the conclusion,the data of long-term ecological environment monitoring in the marine ranching of Haizhou Bay were analyzed from 2008 to 2015,the comprehensive index method and principal component analysis method were used to evaluate the change of marine ranching ecological environment.The following conclusions were obtained:(1)The sediment of Haizhou Bay Marine ranchingwas neutral and weak alkaline,and belonged to reducing environment.The distribution of Eh was affected by artificial reef.The construction of algal field would increase the content of TOC in sediments.The total contents of heavy metals and secondary phases were smaller in the central and lateral areas of marine pasture than those in the inner and the control areas.The average content in the inner area was generally higher than that in other marine areas.The release of artificial reefs would affect the spatial distribution of heavy metals by blocking transport of terrestrial sediments,adsorption of organic matter on metal ions and resuspension of particles.(2)The retardation effect of artificial reefs on the horizontal transport of sediments and the accumulation of mussels and algae caused the accumulation of TN in the sediments of the Haizhou Bay Marine ranching.The accumulation rate of TN in the marineranching was higher than the control area.DIN in Haizhou Bay marineranchingwas more susceptible by TN,while SRP of the control area was consistent with the change of TP in sediments.(3)The high abundance of phytoplankton maybe accelerate the release of bioavailable phosphorus from sediments,resulting in a decreasing trend of TP.The spatial distribution of TP changed from the marineranching> the control area to the marineranching< the control area.Zoobenthos had low contribution to nutrient exchange fluxes at sediment-water interface of marine ranching,and were not the leading factors affecting the change of TN and TP.(4)Theabundance of phytoplankton is basically determined by Diatom and Dinoflagellate.The total abundances of Diatomwas spring(77.61%)< summer(84.25%)<autumn(90.24%),and Dinoflagellateon the contrary was spring(16.83%)> summer(12.33%)> autumn(10.91%).The seasonal and interannual variations of phytoplankton diversity were controlled by the number and evenness of phytoplankton in the Haizhou Bay Marine marine ranching.Dominant species affected the diversity of phytoplankton communities through interspecific competition.(5)In spring,the zooplankton in the marine ranching showed high productivity and low diversity,wasthe top type of community adapted to climate and environment.In summer,whichwas in the middle productivity level and high biological diversity,wasthe secondary variant of the top community under the stress of environmental conditions.Inautumn thezooplanktonwas at low productivity level and high biodiversity,whichwas in the stage of restoration and succession.(6)The results of comprehensive index method and principal component analysis showed that the ecological environment score of marineranching(CI=0.33,variation coefficient =0.30;CS=0.34,variation coefficient =0.86)was slightly lower than that of the control area(CI=0.34,variation coefficient= 0.41;CS=0.35,variation coefficient=0.66).Spring was the critical period for the construction and maintenance of marine ranching Ecological Environment(CI=0.50,variation coefficient=0.24;CS=0.32,variation coefficient= 0.83).