Study On Total Organic Carbon Budgets And Bacterial Productivity And Metabolism Of Polyculture System Of Portunus Trituberculatus, Litopenaeus Vannamei And Ruditapes Philippinarum

In this thesis, total organic carbon budgets and bacterial productivity andmetabolism of polyculture system of Portunus trituberculatus, Litopenaeus vannameiand Ruditapes philippinarum were studied with land-based enclosures, including totalorganic carbon budgets, organic carbon storage, sediment organic carbon storage andvertical distribution, bacterial productivity and functional diversity of microbialcommunities of polyculture system of Portunus trituberculatus, Litopenaeusvannamei and Ruditapes philippinarum. There were8culture systems, monocultureof Portunus trituberculatus (C), polyculture of Portunus trituberculatus andLitopenaeus vannamei (CS), polyculture of Portunus trituberculatus and Ruditapesphilippinarum (CB2), polyculture of Portunus trituberculatus, Litopenaeus vannameiand Ruditapes philippinarum (CSB1, CSB2, CSB3and CSB4), polyculture ofLitopenaeus vannamei and Ruditapes philippinarum (SB2). The main results aredetailed as follows:1Total organic carbon budgets of polyculture system of Portunus trituberculatus,Litopenaeus vannamei and Ruditapes philippinarumThe budget of total organic carbon (TOC) was studied with land-basedenclosures with different polyculture systems of Portunus trituberculatus,Litopenaeus vannamei and Ruditapes philippinarum. The results showed that thebenefit of Portunus trituberculatus was significantly improved in the polyculturesystem of Portunus trituberculatus, Litopenaeus vannamei and Ruditapesphilippinarum. Primary production of phytoplankton was the main TOC (accountingfor46.13%~79.14%) inputs in the enclosures while the feed provided 18.07%~51.37%of TOC inputs. Among the output items, the major output of TOCwas the biological and sediment respiration, which accounted for50.84%~77.30%ofTOC outputs. The accumulation in sediment compromised15.84%~25.39%of TOCoutputs. The highest utilization efficiency of TOC of polyculture systems was CSB3system, which improved1.80%~6.14%than the other systems. The treatment givingthe best culturing benefit was crabs at6ind/m2, shrimps at45ind/m2and clams at30~60ind/m2.2Storage of the organic carbon of polyculture system of Portunus trituberculatus,Litopenaeus vannamei and Ruditapes philippinarumThe storage of organic carbon was studied with land-based enclosures withdifferent polyculture systems of Portunus trituberculatus, Litopenaeus vannamei andRuditapes philippinarum. The results showed that the storage of dissolved organiccarbon(DOC) and particulate organic carbon(POC) pools(mgC/L) ranged from(1.71±0.05) to (4.68±0.46) and (5.60±0.58) to (18.44±1.81), respectively. Organiccarbon storage of phytoplankton, zooplankton and bacteria ranged from (0.08±0.02)to (1.53±0.10)mg C/L,(10.58±1.71) to (173.70±13.68)μgC/L and (0.10±0.04) to(1.46±0.05)mg C/L, respectively. The ratios of DOC and POC to total organiccarbon(TOC) were77.95%~81.89%and18.11%~22.05%, respectively. The ratios ofdetritus organic carbon(DC), phytoplankton organic carbon(PBC), bacterial organiccarbon(BC) and zooplankton organic carbon(ZBC) were6.92%~13.85%,3.67%~7.33%,2.53%~4.59%and0.25%~0.61%, respectively.3Sediment organic carbon storage and vertical distribution of polyculturesystem of Portunus trituberculatus, Litopenaeus vannamei and RuditapesphilippinarumThe sediment organic carbon storage and vertical distribution was studied withland-based enclosures with different polyculture systems of Portunus trituberculatus,Litopenaeus vannamei and Ruditapes philippinarum. The results showed thatSediment Organic Carbon(SOC), Microbial Biomass Carbon(MBC) and ReadilyOxidizable Carbon (ROC) decreased with the depth of sediment layers. The contentsof SOC, MBC and ROC changed with the range of0.85~2.91mg/g, 2.75×10-4~7.40×10-2mg/g and0.23~1.14mg/g, respectively. The proportion of MBCand ROC changed with the range of0.78%~1.33%and35.70%~40.39%respectively.SOC of C and SB2treatments got lower stability while the polyculture of Portunustrituberculatus, Litopenaeus vannamei and Ruditapes philippinarum could improvemicrobial communities activity in sediment.4Variation of functional diversity of microbial communities in the polyculturesystem of Portunus trituberculatus, Litopenaeus vannamei and RuditapesphilippinarumFunctional diversity of water microbial communities were examined usingthe Biolog method in land-based enclosures with different polyculture systems ofPortunus trituberculatus, Litopenaeus vannamei and Ruditapes philippinarum.The results, including the carbon utilization, diversity indexes (Shannon, Simpson,McIntosh, S-E), and principal component analysis (PCA) with carbon sources,showed that microbial community functional diversity were significantlydifferent among8systems throughout the experiment, especially in Septemberwhen compared with in July.(1) In the later stage of the experiment, metabolicactivity of the microbial communities in CSB3were significantly higher than theother treatments while C was the lowest treatment (P<0.05).(2) The microbialcommunities in the water and sediment of different treatments of changedsignificantly on the use of carbon sources over time. In the later stage of theexperiment, the microbial communities in the water of CSB1, CSB3and CSB4treatments and sediment of CSB3treatment had significantly higher intensity thanC treatment on the using of carbon source (P<0.05).(3) PCA analysis showedthat microbial community functional diversity of CSB1, CSB2, CSB3and CSB4treatments were significantly different with the other treatments throughout theexperiment.(4) In the later stage of the experiment, the microbial communityfunctional diversity of microbial communities in the water of CSB3and CSB4treatments and sediment of CSB3treatment was significantly higher than Ctreatment. Our results indicated that the microbial communities in CSB3hadsignificantly higher functional diversity (P<0.05) than any other treatments. This study may provide a novel strategy for the culture of Portunus trituberculatus.5Bacterial Productivity of polyculture system of Portunus trituberculatus,Litopenaeus vannamei and Ruditapes philippinarumBacterial productivity (BP) was studied in situ with land-based enclosureswith different polyculture systems of Portunus trituberculatus, Litopenaeusvannamei and Ruditapes philippinarum. The results showed that BP ranged from(157.02±21.19) to (766.94±30.45)μgC/(L·d) with an average of377.57μgC/(L·d).The BP showed the same trend in general, increasing atbeginning and then decreasing. At the early stage of the study, BP of differenttreatments showed the similar trend. While at the middle and later stage, BP ofCSB3and CSB4were significantly higher than the other treatments(P<0.05).Redundancy analysis showed that was BP and bacterial number(BN) were closelyrelevant to environmental factors. The most significant environmental variableswere dissolved organic carbon(DOC), particulate organic carbon(POC),chlorophyll a and phytoplankton productivity(PP) with BP while NH4-N, NO2-N,NO3-N and PO4-P with BN, respectively.