| The model of aquaculture was becoming intensive and high-density in China.Because of a large amount of artificial feeding,residual bait and feces accumulated in the bottom of the pond.At the same time,the persistent deterioration of bottom environment limited the sustainable development of aquaculture.Photosynthetic bacteria were a kind of microbial preparations and could specifically play a role in the hypoxia environment in bottom to improve the breeding environment.In this paper,the photosynthetic bacteria adapting to the marine environment were enriched and isolated.The experiment was conducted to study the physiological characteristics,improvement effect of sediment and the effect in aquaculture of isolates,which provided some theoretical basis for the application of photosynthetic bacteria in aquaculture.The photosynthetic bacteria from bacteria liquid of laboratory and sediment of farms in the coast of Weihai were enriched and isolated.Then the isolates were sequenced for their 16 S rDNA to analyze their phylogenetic positions.Two dominant strains were selected to study the utilization of nutrient,growth conditions and the optimization of medium.The sedimentation phenomenon of pond in the natural environment were simulated to analysis the effects of the two strains on the sediment.Finally,the isolate of having highly active strain on sediment were used in the aquaculture of sea cucumber to explore its effect in sea cucumber farming.Five isolates were obtained.What's more,2 isolates were Rhodovulum sp.,2isolates were Rhodopseudomonas sp.,1 isolate was Rhodobacter sp.The results of the use of nutrients showed that PSB1? PSB2 could use most of the carbon source and couldn't use methanol,sodium formate.PSB2 could use sodium propionate.PSB1 and PSB2 could grow well in the condition of 2000 Lx,30 ?.Orthogonal test showed that the impacts of three factors on PSB1 were: carbon source> nitrogen source > sulfide.And the optimal combination was glucose 3 g/L,ammonium chloride 0.5 g/L adn sodium sulfide 2 g/L.The effects of carbon source,nitrogen source and sulfide on PSB2were: carbon source> sulfide> nitrogen source,and the optimal combination was glucose 1 g/L,ammonium chloride 1.5 g/L and sulfide 1 g/L.The results of sediment improvement showed that PSB1,PSB2 could stabilize the pH of the water and degrade the sulfide,ammonia and CODMn in the water.Comparedwith PSB1,PSB2 was less resistant to sulfide and couldn't degrade nitrite.The best results were as follows: when adding 1% PSB1,the pH of water fluctuated in the range of 6.98-7.33 and the rate of degradation CODMn,sulfide,ammonia nitrogen and nitrite nitrogen were 92.91%,79.61%,97.00%,73.56 %,separately.It was studied the effects of photosynthetic bacteria on the growth of sea cucumber and water quality by adding PSB1 into aquaculture water.In this study,the results showed that adding 1‰ PSB1 could promote the growth of sea cucumber and the highest growth rate was 3.12%,which was 1.92% higher than that of the control group.At the same time,PSB1 could improve the water quality of aquaculture water.The concentrations of sulfide,nitrite nitrogen and CODMn in the bottom were lower than those in the control group.Our results suggest that photosynthetic bacteria can promote the growth of animals,improve water quality,maintain the health of lower water bodies,and have a good prospect in aquaculture. |
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