Biological and hydrographical responses to tropical cyclones (typhoons) inthe continental shelf of the Taiwan Strait

A survey on the changes of chemical and biological parameters in the contin ental shelf of the south East China Sea, northwest of Taiwan was conducted shortly after the passage of tropical cyclone Herb in the summer, 1996. A t ransect with four sampling stations was visited twice to explore temporal a nd spatial variability. Data collected from the same transect in the summer of 1994 and 1997 indicated that the study area was a typical oligotrophic system with lack of typhoon disturbance. The results showed that after the cyclone event, all the values of the measured chemical and biological param eters were much greater than those derived from normal summer periods. The depth (40 m) integrated values of chlorophyll-a, nitrate and particulate or ganic nitrogen concentrations increased 18, 169 and 73%, respectively. More significantly, primary production, particulate organic carbon concentratio ns and bacterial production as well as biomass increased at least two-fold. Wind mixing, re-suspension and terrestrial runoff which resulted from cycl one passage probably were the three major processes resulting in these phen omena, although their relative importance could not be distinguished clearl y in this study. The magnitude of the enhancement of measured parameters va ried with time and space, suggesting that the: study area was at a highly u nsteady status after the passage of the typhoon. This study demonstrated th at the shelf ecosystem became more productive after the cyclone event, but more research is required to explore the fate of these newly formed organic substances. (C) 2000 Elsevier Science Ltd. All rights reserved.