INFLUENCES OF CYCLONES ON CHLOROPHYLL-A CONCENTRATION AND SYNECHOCOCCUS ABUNDANCE IN A SUBTROPICAL WESTERN PACIFIC COASTAL ECOSYSTEM

The effects of tropical cyclones on seasonal variations in phytoplankt on biomass were studied at a station on the northern coast of Taiwan. Water temperature at the study site varied between 17 and 30 degrees C in 1994. Both chlorophyll a concentration and Synechococcus abundance were low in the winter and started to increase when surface water bec ame warmer than 25 degrees C. Tn July and August, 4 cyclones struck th e study site. All cyclones dramatically reduced phytoplankton biomass in the water column, and caused significant increases in nitrate, nitr ite, phosphate, and silicate concentrations. Blooms of phytoplankton w ith total chlorophyll a concentration as high as 4.2 mu g l(-1) were o bserved after cyclonic disturbances, and were mainly composed of speci es greater than 5 mu n in size. Our results suggest that cyclones dist urb coastal marine ecosystems in a consistent way, and induce ordered and predictable changes in a phytoplankton community.