Study On Carrying Capacity Of Cultured Shrimp In Shrimp Pond Of Integrated Bioremediation

A number of the excretion and baits in the cultur process of shrimp deposited to affect the quality of the bottom sediments, and its accumulation and decomposition was the major source of self-pollution in the cultured water. In the seriously polluted shrimp ponds, because of the decomposition of organic matter, ammonia increased significantly to cause disease resistance of shrimp to decrease and be more susceptible to disease. Combined-cycle culture is one of eco-culture model to overcome self-pollution of shrimp ponds and reasonablely make use of water, but how to get reasonable density of shrimp and other farmed species, and realize the economic benefits and maximum efficiency of energy use become necessary in the environment-friendly premise may be resolved by carrying capacity model, so the study on carrying capacity of cultured shrimp is necessary.For a valid evaluation for carrying capacity of an ecosystem for cultured shrimp in pond of integrated bioremediation, it is necessary to include processes relating to uptake and excretion of inorganic nitrogen. A dynamic model for carrying capacity of cultured shrimp in pond of integrated bioremediation was established according to the principles of Inorganic nitrogen in the water and the main processes involved in evaluation for carrying capacity through historical data, field surveys, in situ simulated experiments and simulated natural condition experiments. In the model,9 state variables (shrimp, shellfish, zooplankton, Sediment-water interface, the remains of new bait, phytoplankton, macroalgae, bio-filter and the nitrification and denitrification) were included. The results showed that this model could simulate the seasonal variations of Inorganic nitrogen in the water properly. Not only the logical structure but model parameters were feasible. Then the model was used to estimate carrying capacity of cultured shrimp in pond in different integrated bioremediation ecosystem. The main conclusions are as follows:1. An indoor study of integrated bioremediation was carried out from October 2007 to November. The results showed that circulation group with the composite shell, asparagus and bio-filter was the best group of bioremediation, because its water quality was close to or better than a single intensive model with 10% of its water change.2. An in situ study of integrated bioremediation was carried out from May 2009 to October. The results showed that there was no significant change with pH in shrimp pond, the dissolved oxygen content maintained at 5 mg·1-1 above, and nutrients, COD and SS remain in the permitted range.3. Nine main processes were studied and their trend between rate and time was discussed, according to the measured data and formula, from 2008 to 2009. These processes included nitrogen excretion of shrimp, inorganic nitrogen dissolution of the remains of newborn bait, inorganic nitrogen releasing in sediment, ammonia excretion of oyster, microzooplankton herbivory on phytoplankton, primary production, nitrogen fixation of asparagus, removing inorganic nitrogen of bio-filter and nitrification and denitrification in shrimp pond.4. On the base of above process research, a dynamic model for carrying capacity of cultured shrimp in shrimp pond of integrated bioremediation was established and used to set up the calculation method of its carrying capacity, and also used to simulate the seasonal changes of IN in shrimp pond. The result shows that when the oyster stocking was 0-1500 kg·mu-1, asparagus 0-430 kg·mu-1, the capacity of shrimp culture in shrimp pond is 100-600 kg·mu-1, at a fixed organization and structure of other species of the integrated bioremediation system.