Title Effects of resuspended sediments on the environmental changes in the inner part of Ariake Bay, Japan
Authers Katsuhisa TANAKA and Masashi KODAMA
Keywords Ariake Bay, resuspended sediments, phytoplankton, turbidity, tidal flats, hypoxia
Citation Bull. Fish. Res. Agen. supplement No. 19,9-15, 2007
Turbidity, in situ fluorescence of phytoplankton pigments and dissolved oxygen concentration were monitored and their relationships to tidal variations investigated in the inner part of Ariake Bay. Turbidity during spring tides showed large short-term variations due to the tidal resuspension of bottom sediments. The phytoplankton biomass increased from neap tides to before spring tides, because of the higher nutrient availability in the surface low salinity water caused by the stratification and the higher transparency due to the low turbidity. While during the spring tides, the increase of phytoplankton biomass was restricted by the low light availability due to the turbid water caused by the resuspended sediments, strong mixing with offshore water and possibly flocculation of phytoplankton with the resuspended sediments. During the neap tides in summer, large scale hypoxia was also observed in the offshore area of tidal flats, where resuspended sediments accumulate on the surface sediments. These observations indicate that the recent reduction of tidal currents is one of the contributing factors to the decrease of resuspension of the bottom sediments and increase in hypoxic areas within the bay.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull19/02.pdf