Assessment of environmental variations caused by a very large floating structure in a semi-closed bay.

To assess the environmental impacts of large floating structures, various physical, chemical, and biological parameters were measured. The current and water quality were monitored around a prototype floating structure called the Phase-II Mega-Float model (MF-II model), which was moored off Yokosuka in Tokyo Bay during the period 1999-2000. The effects of the MF-II model on the condition of the physical environment, e.g., the direction and flow rate of water currents and the stratification structure, were negligible. Analysis of water quality showed that the concentrations of chlorophyll a and nutrients only varied just below the MF-II model. However, such variations were localized to within 5 m below the MF-II model since the waters were exchanged because of the tidal current. The minor changes in water quality are attributable to the impedance of photosynthesis due to the sea-covering effect and the activities of sessile organisms fouling the bottom surface of the MF-II model.