Dynamic resuspension behaviors of microphytobenthos and cohesive sediment in shallow tidal channel

Using a long-term mooring system, dynamic resuspension behaviors of microphytobenthos (MPB) and sediment were investigated in shallow tidal channel, west coast of Korea. Under several forcing conditions with different time scales (daily to fortnightly), the responses of MPB and sediment were uncovered by time series of tidal current, chlorophyll a (chl-a), and suspended sediment concentration (SSC). During the daytime, the chl-awas varied primarily with tidal cycles. During the nighttime, in contrast, it remained constant or gradually decreased regardless of tidal cycles. Over flood and ebb cycles, there was a good correlation between SSC and Reynolds stress (τ_R) measured in the tidal channel, but the correlation between chl-a and τ_R was not clear, suggesting that the chl-a transport from the shallow tidal flat to the channel might be newly provided. During spring tide when high tide coincides with midday, decrease of chl-awas observed during daytime flood tide. During neap tide when low tide coincides with midday, in contrast, chl-aincreased during early to mid-flood tide. The onshore flux of suspended sediment was approximately balanced by the offshore flux, whereas the chl-a flux was unbalanced due to the excessive transport toward the onshore domain. These outcomes suggest, therefore, that the dynamic behaviors of sediment and chl-aalong the tidal channel could differently respond due to the migration of MPB decoupled from sediment dynamic processes.