Biodegradation In Mangrove Planting-aquaculture Coupling System In Pearl River Intertidal Area

This researching program is one part of the project "Researching and demonstrating of maricultural technology in mangrove planting-aquaculture system in Pearl River intertidal area"(National "863"program (2001AA627030)).It focused on bioremediation. Mariculture is reputed as "blue agriculture"to exploit ocean resource, which is an important factor of ocean economy. But the maricultural environment was seriously polluted because of land pollution source. The pollution limited development of "Blue Agriculture"and sustainable mariculture. The planting -aquaculture ecosystem, coupling mangrove with mariculture, can remove part of pollutants in a different sysytem. Microorganism plays an important role to clear and purify environmental pollutants. In the program to explore the new system, one of the objectives was enrich some effective microorganisms to remediate aquacultural water quality and to apply them in the experiment plot. Based on the characteristics of aquacultural water, removing of nitrogen,phosphorus and organic matter were determined as the main objective in the research of bioremediation of aquaculture wastewater By adding enriched microorganisms to the planting-aquaculture system bioremediation in situ were performed. It revealed there are some difficulties to set a dominant population or community even though the adding microorganisms were enriched from this system. Their ecological requirement in the system to be set should be important to control pollution of aquaculture water. Dynamics of bacteria community in the mangrove planting –aquaculture system were performed at the first stage of our research. Some bacteria strains to be enriched and domesticated from the planting-aquaculture system were applied to simulate their adaptability and the degradation of organic matter,nitrogen and phosphorus and in lab and field. The result showed the following achievements and problems. (1)By exchanging water periodically of the system, the dynamics of bacteria community in mangrove planting-aquaculture system, was affected by water quality. Population dynamic of bacteria were positively relative to concentration of N,P. The number of bacteria could be maintained in a range when water quality was stable. Water quality was monitored at the same time to sample bacteria population dynamics in the system. Bacteria community to excrete enzyme were important microorganisms in cycling of nitrogen and phosphorus in the system. Positive correlation was significant between enzyme bacteria number and N,P concentration in water body in the period of exchanging water in mangrove planting-aquaculture system, the correlation coefficients were 0.65-0.78(TN),0.53-0.80(P) at p<0.05. The mangrove planting-aquaculture system showed strong purification for aquacultural wastewater and contaminant marine water to be imported from near estuary. Concentration of N,P and the number of bacteria in the imported contaminant marine water can be decreased by the mangrove complex system. (2) It was easier to get objective bacterium strains to enrich and domesticate bacteria samples from the mangrove planting –aquaculture system. It was a better way for domesticating degradation microorganisms to add objective matter with escalating concentration in the medium. Taking account removal rates of CODcr,NH4-N,NO2-N,NO3-N and PO4-P in the system and their adaptability in the system, 12 bacterium strains to degrade objective mater high effectively were obtained . The rates of degradation ofmixed culture were higher than pure culture. By selective special medium, microscopic observation and of physiological and biochemistry testings, these strains were identified to be Rhodopseudomonas sp., Nitrobacter sp., Vibrio sp., Bacillus sp. and Pseudomonas sp.. The bacteria stains to decrease nitrate and phosphate effectively under domesticating could be adaptive to intertidal aquaculture environment, grow well and set reproductively better in the condition of pH 7.5～8.5, temperature 20～30 ℃and salinity 3～8‰. (3)Water quality was influenced greatly by N,P concentration produced by breeding action. Ammonia nitrogen was released into water body in 3 days from baits of the simulative experiment, and in 5 days for dissolved phosphorus (DP); breeding density had greatly affected on water quality during simulative aquaculture experiment; and interacting of fish and bait will increase the concentration of DIN and DP by 10-25%. (4)Bioremediation simulation showed the method of biomembrane with the enriched bacteria strains could greatly decrease NH4-N,NO2-N,BOD5,CODcr from 52.50% to 99.83%. It is obvious to improve aquaculture water quality. A new materials for the base of bacteria growing—AquaMats was applied in the simulation experiment. According to the results of the experiment , AquaMats biofilm technology could be the best process in remediation of aquaculture wastewater environment, AquaMats carrier had large specific surface area(at=200 m2/m3) which could supply a very good habitat for degrading bacteria to make remarkable bioremediation, and support aerobic and anaerobic bacteria to grow on the same place. Therefore, AquaMats biofilm technology was considered as demonstrating technology in mangrove planting –aquaculture system. AquaMats process is easy to use and no additional demand in equipment and no influence or decontaminates in application. (5)AquaMats biofilm technology was extraordinary effective to improve aquaculture water environment in intertidal area. Within 1 month or so, the degradation rate of ammonia nitrogen (NH4-N), TN of water body and TN of sediment was 70.98%, 34.96% and 17.07%, respectively; at the same time, degradation bacteria reduced the...