Suppressed biological production in the coastal waters off Visakhapatnam, India under the impact of the very severe cyclonic storm Hudhud
Tropical cyclones generally enhance biological production due to the increase in nutrients input due to vertical mixing. In contrast, the very severe cyclonic storm (VSCS)Hudhud decreased primary production due to the strong stratification associated with torrential rainfall and high suspended load from the major city where the cyclone made landfall. The study region received nutrients from the cold core eddy and coastal upwelling in the offshore and inshore regions, respectively, during pre-cyclone period and the same was suppressed under the influence of cyclonic winds led to convergence by shoreward Ekman transport. The land run-off brought nutrients to the coast during cyclone Hudhud; however, their concentrations were less than that during other cyclones (Orissa supercyclone, Sidr and Phailin). Such low nutrient levels resulted from the VSCS Hudhud crossing the urban region (Visakhapatnam city) whereas other cyclones crossed the coast over fertile agricultural lands which led to high nutrients input associated with phytoplankton blooms. Therefore, the biological response to a cyclone not only depends on the intensity of the cyclone but also on the region of the land it crosses.
Volume 129, 2020
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