In a recent paper, Kang et al. (2005), by analyzing T/P data, have shown that average trends of sea level rise were 5.4 0.3 mm yr–1 for all of EJS, which is much larger than the global rates of 3.1 0.4 mm yr–1 by Cabanes et al. . They also showed that the southern EJS shows a non-uniform sea level trend pattern, with larger rates in the Ulleung and Yamato basins. It was hypothesized that the long-term oscillation in the southern EJS may be related to the decadal variability of heat content anomaly in the upper 300 m of the Pacific Ocean, as reported by Levitus et al. , and to the eddy fluctuation in the southern EJS. It is of interest to see if the ecosystem in the EJS responds to the above physical signals. Here we try to test if eddies affect biological productivity. We hypothesized that if eddies become frequent and strong, they could possibly transport nutrients into stratified upper layer in summer. If that is the case, eddy activity would increase surface chlorophyll-a in summer. The effects of eddies would be most evident when nutrient limitation is strongest, probably in August. To test this, we selected two areas, one from the UB and one from the YB. The area in the UB was with higher eddy activities, while the one in the YB was with less eddy activities. In each area, chlorophyll-a from 12 x 12 pixels was extracted for August during 1998~2004 period. The comparison shows that in 2000 and in 2004 when eddy structure was observed in the temperature profiles in the UB, chlorophyll-a was highest. In contrast, chlorophyll-a in the YB showed a much less interannual variability. Another difference was that chlorophyll-a level in the higher eddy activity area was higher and more spatially variable than that in the less eddy-active area.