SPATIO-TEMPORAL VARIATION OF WATER QUALITY ON A TIDAL FLAT

In order to investigate the spatio-temporal variations of water quality on a tidal flat, field observations of water quality have been made on Wajiro tidal flat in summer. In both daytime and nighttime, the concentration of materials varies spatially in the on-offshore direction. The budget of chlorophyll-a in the water column also varies spatially owing to the balance between the feeding rate of consumer and production rate of phytoplankton. The dissolved oxygen is produced largely by the benthic microalgal in the shallow region and phytoplankton is dominant for the primary production in the offshore region. Although the variations of dissolved inorganic nitrogen (DIN) and phosphate (DIP) are similar in daytime, they are different in the nighttime because of the oxygen deficiency in the shallow region.