Ecosystem Succession Mechanism In Mariculture Environment

The paradox between population increment and marine fishery resource accumulate the rapid development of mariculture and the degeneration of marine environment. Therefore, many research aim to sustainable aquaculture.In order to understand the growth and development tendency of mariculture ecosystem, the study conduct to semi-intensive shrimp-crab mixing culture system as a case. On the view of reductionism,we carry on the research basing on the community ecological methods. From October in 2003 to May in 2004, 10 batches of ecosystem sample was collected. The investigation was conducted to the physical and chemical environment factors, microbial community, phytoplankton community, zooplankton community, macrobenthos community and microbenthos community, focused on the quantity or biomass of different community and their predominant species and community structure dynamics. Meanwhile, the correlation analysis, diversity analysis, similarity analysis and cluster analysis was carried out for different community and environment factors.1. Basing on the case study, some dynamic rules of shrimp-crabs mixing culture ecosystem was deduced by the community research:(1)The community structure on water body is influenced greatly by naturally and man-made disturbance which embodies the response of ecosystem to disturbance. The community structure in surface sediment is more stable than water body which is fit for imaging the ecosystem growth and development status. The stable environment gestates the conservative community structure which is reflected on different body size organisms.(2)The environmental physical and chemical factors reflect the prompt metabolic status of ecosystem;The community structure of different body size organisms exhibit the stability at the corresponding generation time scale; (3)The biodiversity is not correlative with the ecosystem stability which is reflected by the reality that the abundant biodiversity exist in dynamic water column while the comparative simple biodiversity take on surface sediment.2. In order to evade the limitation of the community research, in the light of integration methods, this study was conducted to the growth and development of the mariculture ecosystem. Basing on the system ecology research, the following theoretical outcomes was obtained:(1)A new ecosystem tendency theory was proposed that the ecosystem growth and development is not only the increment of matter and energy saving, but also the lag time prolong as a result of the inner saving reorganizing due to the interaction of information and environment. The ecosystem growth and development is always towards minimum energy cost and maximum power.(2)Three ecological model was proposed: 1) Ecosystem ecomass model which define the ecosystem ecomass is the sum of product of different body size organism's biomass and generation time. The ecosystem ecomass describe the extent of ecosystem far from thermodynamic equilibrium which could reflect the stability of ecosystem; 2) The average lag time model which define the average lag time as the ecosystem ecomass/biomass ratio. The model could exhibit the extent of ecosystem growth and development; 3) Ecosystem equilibrium model which define the ecosystem equilibrium parameter as ratio of ecosystem ecomass in the temporal status and in the equilibrium status. The ecosystem equilibrium parameter reflect the equilibrium degree of ecosystem growth and development.3. Combining the quantitative analysis of the community research result and the qualitative analysis of the system ecology research outcome, the following root and evolvement mechanisms was put forward for the unsustainable mariculture ecosystem: (1) The mariculture ecosystem is unsustainable which is originated from the irrational proportion of different body size organisms. The breeding animal feed on the different body size organisms within their different growth and development stage which lead to the redundant matter and energy accumulate into the small body size organisms that the ecosystem oxygen debt increase, the micro-body size algae proliferate explosively in water column and the anaerobic microbes dominate in surface sediment. (2) The root of the oxygen debt and crisis of mariculture ecosystem are also derived from the matter and energy as feed imported from outside which can not be used completely by the breeding animals and pump to the smaller body size organisms to metabolize.(3) The functional origin of unsustainable mariculture ecosystem is the disharmonious niche match which lead to the input matter and energy can not be fixed by different body size organisms efficiently so that the entropy of mariculture ecosystem increase and tend to develop towards the unsustainable orientation.4. Base on the unsustainable mechanisms and ecosystem growth and development tendency, the construction and regulation tendency of mariculture ecosystem was proposed as:(1)The formula feed research must focus on the suitability for the nutrient metabolism requirement of breeding animal.(2) The trophic structure of mariculture ecosystem should confirm according to the regional environment characteristic and economic status. The density or proportion of different body size or trophic level should be adjust according to the general ecological allometric principles of body size, the critical self-organization principle, the equilibrium principle between the positive and negative feedback and the density law of different body size organism. The entropy of the mariculture ecosystem should not go beyond the critical value. There is no redundant matter and energy accumulating at small body size organism which were output as biomass of biggish body size organism. (3)The mariculture ecosystem should prepare the resource species with interdependent niche. The bigger body size and the longer generation time resource species should include not only the goal breeding organism which depend on the feed, but also the match breeding organism which ingest on the smaller body size organism. The moderate match breeding organism will improve the output efficiency and the ecosystem stability. It is suggested that the smaller body size and shorter generation time organisms should be transplanted from other ecosystem to reorganize to make use of their collaborative niche evolved from geological history so as to enhance the recycle efficiency and reduce the humification proportion of the matter and energy.5. In the process of microbial ecology research of shrimp-crabs pond, the following methodology outcome was acquired:(1)In the preliminary research of microbial community structure, the problem was overcome that the humic acids(HAs) coextract with sediment microbial DNA. The specific reagent was screened out to put up the HAs-removing buffer with super performance. The principle of removing HAs was explained reasonably. The simple and convenient method for removing HAs was established successfully.(2)In order to overcome the problem that the heterogenic 16S rRNA gene copies magnify the diversity of microbial community fingerprinting, another house-keeping gene rpoB (RNA polymeraseβsubunit) with single copy was applied to substitute 16S rRNA gene for microbial community fingerprinting research. The primer of rpoB was screened out and the rpoB-PCR method was estabilished.These research result will further the cognition and understanding the influence and response of mariculture ecosystem to natural and man-made disturbance, elucidate the formation mechanisms of unsustainable mariculture ecosystem pattern, retrospect to the profound unsustainable root, make clear the regulate tendency of structure and function of mariculture ecosystem. This study provided the theoretic model and technique tool for sustainable mariculture ecosystem research which would be very significant for the research development.