Ocean surface responses to super typhoon in coastal zone based on biogeochemical buoys data: A case study of "Lekima"

Situ observations were conducted by biogeochemical buoys (BGC buoys) to discover the physicochemical processes during super typhoon Lekima's passage in Zhejiang coastline, helping us gain deep insights into the responses of the sea surface on the coastal zones throughout the whole typhoon's lifetime, especially during typhoon's landing. The results show that precipitation and terrestrial inputs induced by Lekima led to the hyposalinity, demonstrated by the sharp reduction of surface seawater salinity in estuary. Phosphate concentration reached its highest point 2-4 days after the typhoon's passage, with the concentrations increasing two folds to values between 20 mu g L-1 and 91 mu g L-1. High chlorophyll a (Chl-a) value (4.9 mu g L-1) appeared shortly after the Lekima's arrival, accompanied by algal bloom. Chl-a correlation with other physicochemical parameters showed significant variation in the typhoon's different stages of development, which have unique factors of influence. The lower N/P ratio in the coastal zones play roles in Chl-a concentration and phytoplankton bloom and the optimal N/P ratio for Prorocentrum donghaiense and Skeletonema costatum is 25 and 15 respectively.