| The importance of shellfish industry for fisheries is self-evident in China. Recent years, datas show that marine shellfish aquaculture production accounted for more than 70% of the total output of marine aquaculture, and the output is also increasing year by year. There have been some problems behind the shellfish industrial prosperity.Fishermen actively expand the aquaculture area and the number of raft frame in order to improve aquaculture production and maximum profit. The large-scale, high density style not only changes the biological and physicochemical environment in natural sea area, different niche composition and causes a negligible impact on aquaculture itself and aquaculture water environment.This article has studied the apparent vertical flux of settling particulate matter deposition in shellfish culture area and the structure of the mytilus edulis and crassostrea gigas community, nutrient release rate, feeding physiology and metabolism,the sources of organic matter deposited in biological material, nutrient budget, energy budget based on the community level. The biogeochemistry progress of mytilus edulis farming in particle organic carbon （POC） and the theoretical model of filter feeding bivalve -apostichopus japonicus-siganus canaliculatus were established. We also have studied the bioturbation effect of musculus senhousei to the sediment. The main results are as follows:1. The apparent vertical flux of settling particulate matter in large-scale aquaculture area and energy and nutrient budget of community levelThe survey found that the deposition flux of bivalve area is always higher than the control area and there is a seasonal difference that the flux in summer and autumn was significantly higher than that in spring and winter （P<0.05）; The content of organic matter in particle deposition in control area was always higher than bivalve area. The content of organic matter between two areas in the month of Sep-Oct in 2015 andMar-Apr in 2016 was significant （P<0.05）, no significant in other months （P>0.05）; The apparent vertical flux of POC （particulate organic carbon） and TN （total nitrogen） in bivalve area and control area in the summer and autumn was significantly higher than that in spring and winter （P<0.05） and bivalve areas were all higher than those of control area in other months except March, the two area were significantly different except June （P<0.05）.Experiments showed that the number of large fouling organisms can be identified by eyes in mytilus edulis community was 18 in Apr and 21 in Jun. The dominant species of fouling organisms in April were crassostrea gigas, bugula neritina, sphaerozius nitidus, each dry weight respectively accounted for 20.24±2.53%, 30.09±3.10%,15.28±0.34% of the total dry weight; The dominant species of fouling organisms in July were crassostrea gigas, bugula neritina, cliona sponge, each dry weight respectively accounted for 11.47±1.26%, 8.38±1.29%, 48.28±2.07% of the total dry weight. The number of large fouling organisms can be identified by eyes in crassostrea gigas community was 9 in Sep. The dominant species of fouling organisms in July were Codium fragile （Sur.） Hariot, bugula neritina, Ciona intestinalis, each dry weight respectively accounted for 4.77±3.13%,79.74±1.75%, 7.41±1.11% of the total dry weight. （Bivalves use soft dry weight, total dry weight for all other creatures）.The energy and nutrient budget of mytilus edulis community and the energy budget of crassostrea gigas community were as follows:Apr（16℃）Energy budget: 100C=6.38P+30.94F+4.34U+58.34R Carbon budget: 100C=5.10P+15.60F+4.39U+74.91RJul （20℃）Energy budget: 100C=2.29P+22.34F+10.16U+65.21R Carbon budget: 100C=1.36P+12.83F+9.38U+76.43R Sep （25℃）Energy budget: 100C=26.93P+29.88F+1.06U+42.13RAccording to the annual apparent vertical flux of POC in bivalve area and control area and sediment mineralization rate and burial rate in bivalve area and the means of mytilus edulis community carbon budget, we construct a POC biogeochemical processes per unit mytilus edulis area （0.62 r/m2, the length of a mussel rope is 2 m, the average shell length is 68.33 mm, the number is about 567 individual）. The results show that the deposit POC of the mytilus edulis accounted for 14.22% of the total intake of POC,which accounted for 41.07% of the total settlement of POC. Most of deposit POC mineralized to CO2, accounting for 55.58%, the buried part accounting for 33.19%.2. The construction of the integrated model of filter feeding bivalves-apostichopus japonicus-siganus canaliculatusUsing large cage for apostichopus japonicus seedling protection is an important part before bottom sowing. But the food cost and attachment of fouling organisms in the net is the key problem to restrict the further development of the seedling method.Aiming at the problem of high cost of food, we use organic sediments of bivalve area as natural food of apostichopus japonicas. The growth rate of apostichopus japonicus with different sediment feeds were observed in natural areas, the results indicated that the growth situation of bivalve area is better than other areas.A series of laboratory experiments and field observations was carried out in cage culture area of Chu Dao,Sanggou Bay to understand the monthly variations of fouling macroalgae biomass and diversity in different layers, the feeding ability of Siganus oramin to dominant specie of fouling macroalgae, the biological control ability of Siganus oramin on the fouling macroalgae .The results showed that the growth rate of fouling macroalgae in the same month and different layer was different, the growth rate of fouling macroalgae in the period of 7th August to 14th September was significantly higher than other months in different layers （P<0.01）. Plocamium telfairiae were the dominant specie among different months in this area. A carbon budget equation for the Siganus oramin feeding with Plocamiun telfairiae was built under the appropriate seawater temperature（100C=11.69G+10.82F+6.06U+71.43R）. The average wet weight of Siganus oramin reached 45.38 ± 4.22g after 152d cultural period beginning with initial weight of 1.44 ±0.61g and the growth rate was 0.26 g per day. The removal rate for fouling macroalgae was from 80.28% to 90.15%. The results will be very helpful to build environment-friendly model of marine cage culture and enhance the sustainable development of cage aquaculture industry.3. The effect of musculus senhousei bioturbation on the mineralization of biodepositionMusculus senhousei is a top quality food organism of shrimps and crabs and has great potential. The bioturbation of musculus senhousei has different effects on the fluxes of five nutrients （N4+-N, NO3--N,NO2--N, SiO32-, PO43-）. Compared to the undisturbed groups, the change rates of NH4+-N, NO3--N, NO2--N, SiO32-, PO43- were 18.55%, -41.56%, 135.42%, 0.00%, -46.11%, the mineralization rate increased by 13.08% in 7℃; Compared to the undisturbed groups, the change rates of NH4+-N,N03--N, N02--N, Si032-, PO43- were 42.99%, 226.35%, -85.12%, -5.19%, 67.86%, the mineralization rate increased by 36.36% in 15℃; Compared to the undisturbed groups,the change rates of NH4+-N, N03--N, N02--N, Si032-, P043- were 8.90%, -153.51%,-18.32%, 8.91%, 1798.17%, the mineralization rate increased by 102.31% in 23℃.The energy budget equation at different temperatures:7℃ 100C=58.12F+46.74R+2.54U-7.40P15℃ 100C=44.28F+29.14R+1.85U+24.73P23℃ 100C=17.18F+41.81R+6.64U+34.37P31℃ 100C=53.35F+28.26R+14.66U+3.73P... |
