A sharply decreasing DSi flux and quickly increasing DIN and DIP fluxes into the sea have enhanced eutrophication and caused frequent harmful algal blooms in coastal waters. On average, red-tide frequency was from 0.04 during 1933e1979
to 7.0 during 2000e2002. TheSkeletonema costatum(siliceous alga), the red-tide-predominant species that is in positive proportion to DSi
flux, decreased from 33% during the 1980s to 24% during 2000e2002. The present data evidence the increase ofProrocentrum dentatum
(non-siliceous alga) from 12.5% in the 1980s to 36% in 2000e2002, which tends to be dominant species of the red tides off the Yangtze
estuary. The number of big dams in the Yangtze River basin will double in the next 30e50 years. This will significantly influence the
variations of nutrient fluxes in the river basin and estuary, in relation to health management of river-coast ecosystem.
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