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A bacteria strain for efficiently removing nitrite nitrogen was isolated and purified from sediment in shrimp pond, and the morphology of bacteria was observed using scanning electron microscopy, and the homology analysisof 16SrDNA sequence of the strain was conducted. The results showed that the strain was identified as Acinetobacter baumanii according to the morphological characteristics, physiological and biochemical characteristics and 16SrDNA sequence analysis. The isolated strain had a high heterotrophic nitrification function, the removal rate of nitrite nitrogen reached 97.17% after 12 h.

Under laboratory conditions, the absorption law of three kinds of nutrients by three species of algae was investigated, the results showed that: the concentration of nitrate nitrogen, ammonium nitrogen and activated phosphate in the culture medium reduced with the extension of time. Enteromorpha intestinalis,Sargassum fusiforme and Sargassum thunbergii showed the highest uptake for nitrate nitrogen, ammonium nitrogen and activated phosphate, respectively;S. fusiforme, E. intestinalis and S. fusiforme showed the lowest uptake for nitrate nitrogen,ammonium nitrogen and activated phosphate, respectively. It illustrated that macroalgae could effectively reduce nutrients from the surrounding water.

The effect of salinity (10,20,30,40,50) on the growth and biochemical composition of Sargassum thunbergii and Gracilaria verrucosa were investigated under the laboratory conditions, the results showed that: specific growth rate and chlorophyll a of Sargassum thunbergii and Gracilaria verrucosa were first increased and then decreased with the increase of salinity, the carotenoids content of Sargassum thunbergii in 10 salinity group and Gracilaria verrucosa in 40 salinity group were the maximum respectively. After comprehensive analysis, in the 10-50 salinity range, The optimal salinity for the growth of G.verrucosa and S. thunbergii were 20 and 30 respectively.

Allelopathic effect of Sargassum fusiforme on growth of Karenia mikimotoi was studied, the results showed that: fresh tissue and dry powder of S. fusiforme had a good inhibitory effect on the K. mikimotoi growth, and enhanced with the increase of mass concentration.The concentration dependence relationship was existed between S. fusiforme and K. mikimotoi. Aqueous extract of S. fusiforme had a promoting effect on K. mikimotoi at low concentration, and showed obvious inhibition at high concentration, in the 1.6 g/L of extract group, K. mikimotoi died on day 8. It illustrated that the inhibition of S. fusiforme on K. mikimotoi was implemented mainly by its soluble components.