A new algorithm based on phytoplankton absorption coefficient for red tide monitoring in the East China Sea

Red tide is an ecological anomaly that phytoplankton in seawater suddenly proliferate or aggregate under certain environmental conditions and within a period of time, resulting in seawater discoloration. Red tide not only harms marine fisheries and aquaculture, deteriorates the marine environment, affects coastal tourist industry, but also causes human health problems. East China Sea (ECS) is a region of high incidence of red tide disasters. Remote sensing has been proven an effective means of monitoring red tides. Phytoplankton-specific light absorption plays a fundamental role in the remote estimation of pigment biomass and red tide. This paper retrieves the phytoplankton absorption coefficient in decade based on MODIS data from July 2002 to June 2012 using quasi-analysis algorithm (QAA), analyzes and compares phytoplankton absorption coefficient spectral curves of red tide events with multiyear monthly averaged ones, as well as phytoplankton absorption coefficient spectral differences at the same location during red tide presence and absence. A new red tide monitoring algorithm based on the phytoplankton absorption coefficient is developed to extract red tide information of the ECS. With the application of the algorithm in the ECS, the results reveal that the developed model can effectively determine the location of red tides, with good correspondence to the results from an official bulletin. This demonstrates that the algorithm can effectively extract red tide information.