The Construction Of The Island Reef Fish-shell IMTA Model And Its Impact On The Ecological Environment Of The Nearby Sea Area

In order to establish and develop a multi-nutrient-level integrated culture model?IMTA?,the fish-shell IMTA culture model was selected in the Sanhengshan Island reef area of Shengsi,Zhejiang Province.The benthic seaweed-fish-shell IMTA culture in the Sanhengshan Island reef area was studied The response mechanism of the pattern.First of all,water quality and sediment eutrophication in the Sparus acrocephlus and Pseudosciaena cage culture areas,Mytilus coruscus culture areas,and non-culture areas in Sanhengshan Island were monitored,evaluated,and compared.Before and after cultivation,the seasonal distribution characteristics of benthic macroalgae in the intertidal zone of Sanhengshan Island were monitored,and on this basis,a fish-shell-algae IMTA culture model was further established,and the fish-shell-algae IMTA culture system sea area was studied.Water quality and sediment microbial distribution characteristics lay a theoretical foundation for the development of a fish-shell-algae IMTA culture model with better ecological and economic benefits.,Make it the detection index of the ecological environment of the breeding sea area.The main findings are summarized below:1?Evaluate the ecological health level of cultured seasIn January?winter?,April?spring?,July?summer?,and October?autumn?,the water quality of the culture area of??the Sanhengshan Island was monitored.The temperature?T?ranged from 10.12 to 24.57?.Annual average temperature 17.82?,and the temperature has obvious seasonal rhythmic changes;the overall range of salinity?PSU?is 25.45?31.12,and the annual average salinity is 28.06;There are no obvious differences in the three quarters;the trend of the change of dissolved oxygen?DO?is obvious,ranging from 4.679 to 25.393 mg/L,with an annual average of 12.985 mg/L,and the range of chemical oxygen demand?COD?is 0.115 to 4.356 mg/L,The annual average value is 1.470 mg/L;throughout 2019,the p H value meets the Class II/III seawater quality standards,and the DO value and the COD value meet the Class I seawater quality standards.The annual average value of its nutrient-soluble inorganic nitrogen?DIN?is 0.338 mg/L.The highest and lowest values??appear in April?spring?and July?summer?,respectively.NO2^--N,NO3^--N,NH4⁺-N accounts for DIN6.94%,91.89%,and 1.17%,respectively;the annual average value of dissolved inorganic phosphorus?DIP?is 0.029 mg/L,with the highest and lowest values??appearing in October?fall?and January?winter?,respectively.The average annual value of active silicate(Si O3^2--Si)is 1.088 mg/L,and the overall water quality is class II-III.The average organic pollution index in the four quarters of the sea area was 4.450,showing a serious pollution state.Compared with 2015,it was found that the breeding behavior of the downhill mountain Hengshan Island had already affected the water quality.The total nitrogen?TN?content in the surface sediments of the culture area of??the Sanhengshan Island ranges from 0.398 to 1.238 g/kg,with an average annual value of1.007 g/kg;the total phosphorus?TP?content ranges from 0.253 to 0.813 g/kg,annual The average value is 0.458 g/kg;the content of organic carbon?OC?ranges from 5.391to 13.263 g/kg,and the average annual value is 9.858 g/kg.According to the calculation based on the single-factor evaluation method,it is known that TN pollution in the sediments of cultured seas is serious,TP has been polluted,and OC has not been polluted.2?Succession changes and evaluation of microbial populations in the culture area of Sanheng Island.In 2016,before the establishment of the fish-shell IMTA culture system,the species and biomass of benthic algae in the intertidal zone of Sanhengshan Island were investigated.Among them,16 species of large algae were collected in winter,including10 species of red algae and green algae.4 species,2 species of brown algae.After the establishment of the fish-shell IMTA culture system in 2019,a survey of benthic algae species and biomass in the intertidal zone of Sanhengshan Island was conducted throughout the year.A total of 36 large seaweeds were collected,of which 24 were red algae and green algae 4 species,8 species of brown algae.Among them,the species and biomass of benthic algae in the intertidal zone of Sanhengshan Island in winter 2019were 14 and 564.084 g/m2,respectively.Compared with the winter of 2016,the different types of seaweed that appeared in winter 2019 are Grateloupia turuturu Yamada,Grateloupia livida?Harv.?Yamada),Grateloupia lanceolata?Okamura?Kawaguchi,amphiroa ephedraea,Chondrus ocellatus Holmes,Gloiopeltis furcata?Postels et Ruprecht?J.Agardh),Sargassum fusiforme?Harvey?Setchell),and Dictyota dichotoma?Hudson?J.V.Lamouroux),the same species are:Gelidium amansii JV Lamouroux,Corallina officinalis Linnaeus,Porphyra haitanensis,Ulva lactuca L.,?Sargassum thunii?And Sargassum horneri?Turner?C.Agardh).By investigating the distribution of large-scale seaweeds before and after breeding,representative economic large-scale seaweeds of Sanhengshan Island have been selected.The main economic algae of Sanhengshan Island are Ulva pertusa,Codium fragile,Sargassum thunbergii,Graloupia livida?Harv.?Yamada,Pyropia haitanensis,Undaria pinnatifida?Harvey?Suringar,etc.The above economic seaweeds can be used as candidate species for establishing a complete IMTA culture model.3?Succession Changes of Microbial Populations in the Aquaculture Area of Xiasanheng IslandUsing high-throughput sequencing,50 planktonic bacteria of 1138 genera and7327 OTU were identified in the study area,among which 50 species of cage culture area were 1120 genera of 7104 OTU,45 species of mussel culture area were 937 genera of 4629 OUT,and 49 species of non-breeding region were 878 is 4264 OUT.The abundance of planktonic bacteria in the three regions showed that the composition of the top three phyla was the same,namely Proteobacteria,Cyanobacteria,and Bacteroidetes,but the abundance ratios were different.Diversity analysis at the class level found that the top 5 bacteria in the three regions were all Gammaproteobacteria,Alphaproteobacteria,Oxyphotobacteria,Bacteroides,Bacteroidia,Alphaproteobacteria and Actinobacteria.According to the RDA analysis of planktonic bacteria and environmental factors,it is known that nitrate?NO3^--N?is the most important environmental factor that affects the planktonic bacteria community in the fish breeding area;temperature is the most important environmental factor that affects the flora in the mussel breeding area.Using high-throughput sequencing,a total of 60 deposits of 1007 genera and 9467OTU were identified,of which 59 were 984 in the cage culture area,8651 OTU,58were in the mussel culture area,857 were in the genus,7059 OUT,and 56 were in the non-breeding area,764,and 5832 OUT,the top 5 most abundant bacteria in the sediments of each culture area are Proteobacteria,Bacteroidetes,Acidobacteria,Planctomycetes,and Chloroflexi;Proteobacteria has the highest abundance in fish farming areas,followed by mussel farming areas and non-farming areas.Diversity analysis of sediments at the ganglia level found that the top 5 bacteria in fish cage culture areas and mussel farming areas were Gammaproteobacteria,Deltaproteobacteria,Bacteroidia,Alphaproteobacteria and Thermoanaerobaculia,while in non-cultivated areas,the top 5 bacteria are Gammaproteobacteria,Deltaproteobacteria,Bacteroidia,Anaerolineae,Alphaproteobacteria.Among sedimentary microorganisms in cultured and non-cultured areas,?-proteobacteria and?-proteobacteria have the highest abundance,that is,proteobacteria are the most abundant microbial populations in the sediments of cultured seas on the lower Sanhengshan Island.