| For this thesis, a total of 175 water and sedimentary samples was collected from the western (so called "Warm Pool"), eastern (richness of multi-methal nodules) and middle regions of the tropical Pacific Ocean with water depth from 1193 to 5660m in sampling stations. Cruises "DY105-11", "DY105-13" and "DY105-12,14" for the environmental projects supported by China Mineral Resources Association and the "973" project supported by National Ministry of S & T and "WEPAMA" cruise for Sino-France cooperative project, during the time period from May 2001 to November 2003.The sample analyses were carried out in the field or lab as following:1) Bacterial numbers in the water and sediments were counted by Nikon epifluorescence microscopy. And the respiration of microorganisms were detected according to the consumption of dissolved oxygen (DO) with 702 SM solution automatic titrino.2) After microbial strains were isolated, growth patterns of 31 strains (from 110 culturable strains) were tested under a sets of temperatures, salinities and pH values by Multiskan Enzyme-linked Immumosorbent Assay (ELISA) scanner and effects of the tests physical and chemical factors on the growth of target strains were analyzed by SPSS statistic software package; a classification of the selected microbial strains and the profile of their utilizing 95 organic carbons were performed by Biolog Microstation Automatic Identification and Analysis System.3) Cr(VI)-tolerance of some microbial strains was preliminarily reseached as well. According to the measurements mentioned above, the physiological and ecological characteristics of microorganisms in ocean, particularly in deep-sea, and their roles in biogeochemical cycle in deep biosphere were studied. This study will provide some useful parameters for estimating the influences of the Western Pacific "Warm Pool" to the global climate system and the impacts of deep-sea mining on its environments, and will lay a foundation in development of microbial resouces indeep-sea. The main results are summarized below:The geometrical means of bacterial numbers (cells/cm3) was 3.20 104 ranging from 2.19xl03to 1.21xl06 in the investigated water, 6.13xl06 ranging from 3.64xl05 to 2.17xl08 in the sediments, and 6.94xl04 ranging from 3.54xl04 to 1.52xl05 in the sedimentary over-laid water. The average of bacterial biomass (mg/m2) in the surface 200 m of the water column (232) was almost 8 times higher than that in the bottom 200m (29.2). In the surface 1cm of sediments it was 5.98, and 25.2 in 0-18cm. The maxima exhibited in the upper 200m of the water column and the surface (or subsurface) maxima in sediments indicated the ample substantial and energy exchange in air-sea interface and water-sediment interface. In the horizontal direction, bacterial biomass of the western, middle and eastern Pacific Ocean were compared, the higher values of water column and surface sediments were found in west region.Microbial respiration rates [ugO.(dm3 d)"1] in the tropical Pacific Ocean showed: it was 18.45 in 3000m water layer, 10.59 in bottom 200m water column and 40.74 in sediment over-laid water. Presented it in carbon [gC dm d)-1]: 5.314 in 3000m water layer, 3.050 in bottom 200m water column and 11.73 in sediment over-laid water, according to the biomass, sedimentary over-laid water had a quite high mineralization speed.The growth characters of the 31 strains of cultivable microorganisms under different conditions showed: the quantity of exact stenotropic microorganisms was less than 1/3 of the total. And it was a large proportion of eurytropic microorganisms with wide ecological amplitude. These proportion was affected by the sampling, reserving, culturing and other operations. On the other hand, among the 31 microorganisms, there were 25 Psychrotrophs which could grow at 4, 11 moderate halophiles which could grow at a salinity of 100, and 30 individuals preferred growth with certain salinity, and 23 alkalitolerant individuals which could grow at pH 10.2. These occurrences accorded with the nature environment...
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