Objective The bioremediation effect of sponge-associated microorganisms on marine diesel pollution is to be explored.

Methods Diesel-degrading bacteria strains were screened from sponge-associated microorganism based on diesel degradation rate, and 3 strains were selected for identification and composite analysis.The best combination was selected to carry out the single-factor test and response surface optimization test, and a diesel pollution model was constructed to verify the effect of bioremediation.

Results 38 diesel-degrading bacteria strains were screened.Among them, D1, D7 and D8 with the best hydrocarbon-reducing effect were identified as Halomonas aquamarina, Sphingopyxis terrae and Marinobacter aquaeolei respectively, and their degradation rates were all above 65%.The best combination is D1-D7-D8;and the three factors that affect the hydrocarbon reduction effect were the initial pH value, concentration of diesel oil, and temperature.Based on the response surface methodology, the optimal degradation conditions were identified to be as follow: initial pH value at 7.41, concentration of diesel oil at 32.79 g/L, and the temperature at 30.65℃.The actual degradation rate of the model constructed under the optimal conditions was 84.17%, which was in good agreement with the predicted value of 86.27%.

Conclusions This study can provide theoretical support for the construction of sponge-hydrocarbon-depressing bacteria symbionts, and open up a new way to solve the problem that diesel pollution in seawater is difficult to be centralized.