Impacts of Sessile Organisms Attached to Artificial Floating Structures on the Surrounding Environment: Review and Update in Tokyo Bay

The surfaces of artificial floating structures such as floating docks, floating solar panels, offshore wind turbines, and very large floating structures provide habitats for sessile organisms. Particularly, very large floating structures, which have the bottom surface, provide a larger habitat for sessile organisms than the other structures. When the artificial structures are constructed in the sea, biofilm appears on their surface, and then animals such as blue mussels and barnacles attach to them. These animals grow by filtering suspended organic particles, consuming oxygen, and releasing waste into the surrounding water. The sessile organisms accumulate as they grow but eventually fall to the seabed due to their own weight and hydrodynamic force. Since these processes affect the surrounding environment, it is indispensable to evaluate the impacts before the construction of artificial floating structures. Moreover, these impacts can vary depending on the specific organisms, the structure, and the location. However, it is not clear to what extent scientific investigations have been carried out for this problem. The purpose of the present study is to investigate the existing scientific papers to elucidate the environmental impacts of sessile organisms attached to artificial floating structures. As a result of the investigation, the impacts of sessile organisms on the surrounding water quality through filtration of particles, consumption of oxygen, and release of waste have been investigated by field measurement and numerical simulation. The impacts of the biodepositions of sessile organisms have been investigated for the environmental impact assessment of aquaculture of bivalves. However, the processes of detachment of sessile organisms from artificial floating structures have not been well examined, particularly the research on the environmental impacts of sessile organisms that fall to the bottom on the benthic ecosystem. Not only dead sessile organisms but live ones fall to the sea bottom, and the live ones continue living on the sea bottom. These phenomena should be elucidated scientifically for the comprehensive environmental impact assessment of artificial floating structures.