Abstract: To investigate the influence mechanism of marine organisms on concrete structures, marine organisms were introduced in three categories: marine animals, plants and microorganisms. The corrosion and enhancement mechanisms of marine organisms on concrete structures were analyzed in three categories. Also, the ways of prevention and utilization of the marine organisms were discussed in detail. Through the long term field exposure test of the wharf piles, the distributions of the chloride concentration, concrete resistivity and steel potential in concrete were obtained. The results show that the chloride ion contents at the concrete surface in the splash zone are lower than those of the tidal zone. However, the chloride ion diffusion coefficients of the concrete are fairly close in both of the splash zone and tidal zone. The accumulation of shellfish has both positive and negative effects on the chloride resistance of concrete. On one hand, the chloride ion contents at the surface of concrete covered with shellfish are lower than those without the coverage of shellfish, which indicates that the presence of shellfish might help to reduce the concentration of chloride ions on concrete surface. Shellfish exhibits a physical protection mechanism for the concrete surface, which is beneficial for the prevention of chloride ion ingression into concrete to some extent. On the other hand, the chloride diffusion coefficients of concrete covered by the shellfish are larger than those with the smooth concrete surface. Theoretically speaking, the presence of shellfish may lead to the chemical change of concrete, weaken the chloride resistance of concrete, and eventually accelerate the chloride ion transport in concrete. Additionally, the concrete covered by the shellfish presents the lowest surface resistance, and the reinforcing steel bars embedded in it indicates a relatively negative corrosion potential. Finally, the results demonstrate that the steel reinforcement in the concrete covered by shellfish shows the highest corrosion risk. The existence of shellfish may adversely affect the durability of concrete structures.