Temporal and Spatial Changes of ChlorophyII in the KEEP Study Waters off Northern Taiwan


The distribution data of chlorophyll a collected from 11 cruises between 1990-1993 in the KEEP study area was analyzed to demonstrate its temporal and spatial changes. Chlorophyll a concentration in the euphotic layer was generally low in March (0.02-0.67 mg.m-3) and high in November (0.02-3.79 mg.m-3). Sampling stations showed the highest chlorophyll a concentration during each cruise was mostly in the water along the brim of the East China Sea continental shelf, thus, indicating an association between the upwelling and bottom topography. Surface chlorophyll a concentration was negatively related to surface water temperature on all cruises. The distribution of the low surface water temperature was mostly caused by the upwelling. In winter, however, the shelf was flooded with cold water from the north, and the chlorophyll a concentration was low. The strength and the position of the center of the upwelling affected the dynamics of the chlorophyll a concentration. When the upwelling strength was not strong enough to reach water surface, the surface chlorophyll a concentration at the upwelling stations remained low. A significant negative relationship between the surface water temperature and the chlorophyll a concentration in all stations still existed because the chlorophyll a concentration in the warm Kuroshio water was even lower than in other regions. Dynamic temporal and spatial variations in chlorophyll a distribution were observed at the upwelling center surveyed repeatedly at one-week intervals. The vertical distribution of chlorophyll a showed a shallow subsurface maximum between 0 and 25 m in the upwelling region in contrast to between 50 and 75 m in the Kuroshio water. Surface chlorophyll a and the 0-100 m integrated chlorophyll a concentrations showed significantly positive correlations during nine out of the eleven cruises.

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