BIOGEOCHEMICAL RESPONSES IN THE SOUTHERN EAST CHINA SEA AFTER TYPHOONS

To understand the biogeochemical impact of typhoons in marginal seas, 16 sea-going expeditions were conducted from 2007 to 2009, covering all four seasons and including periods following the passage of several typhoons in the southern least China (SECS). Higher surface nitrate and chlorophylil a (Chl a) concentrations were measured in winter and spring but surface nitrate (<0.1 mu M) and Chl a (0.47 +/- 0.17 mg m(-2)) concentrations were loss in summer under nontyphoon conditions. In comparison, elevated surface nitrate (0.2-2.3 mu M) and Chl a concentration (1.11 +/- 0.40 mg m(-2)) were recorded in the SECS several days after the passage of each of three typhoons in 2008. The results demonstrate that nutrient-rich water are brought to the surface after the passage of typhoons, after which phytoplankton flourish. Most importantly, elevated particulate organic carbon (POC) fluxes (552 +/- 28 mg cm(2) d(-2)) were observed after Typhoon Jangal, about a threefold increase from the monthly mean value (184 +/- 37 mg m(2) d(2)). These field investigations demonstrate that typhoons can have a profound effect on nutrient supply, phytoplankton growth, and POC: fluxes to marginal seas.