Satellite observation: an indispensable tool to monitor extreme marine biological events

Abstract

In the last two decades, the East China Sea and its adjacent waters have witnessed radical shifts in the composition of the pelagic plant community which previously comprised of phytoplankton year-round to macroalgae (Ulva prolifera and Sargassum honeri) in a significant part of the year. A large scale U. prolifera outbreaks in the northwestern part of the Yellow Sea in every June-July since 2008. Its floating canopies occupy more than 30,000 km2. S. honeri outbreaks in the wide area of the continental shelf of the East China Sea in April-May since 2012. The landing of these macroalgae at the shore disrupts intensive and extensive enclosure culture of finfish and shellfish, and hanging net macroalgae culture industries in coastal inlets, ship traffic in small harbors, and the shoreline tourism industry. These large-scale abrupt marine biological events will further aggravate already stressed coastal waters with y with recurring harmful dinoflagellate blooms such as Cochlodinium polykrikoides, Gyrodinium moestrupii and marine heatwaves.

A more frequent local and basin-wide observation is increasingly required to address these basin-scale extreme marine biological events for the protection of coastal aquaculture, seashore tourism industry, and small harbor operations. GOCI has an advantage over other ocean color sensors in that it collects images every hour during the day. It enables tracking the temporal evolution of those plant blooms throughout their lifetime. GOCI II has offered 12 narrow bands (380-865 nm) to observe a subtle color change occurring at the sea surface. In situ measured Rrs spectra indicate that dinoflagellate blooms exhibit depressed reflectance in the 412-660nm and enhanced reflectance at 680-709nm. Geostationary ocean color imager (GOCI) sensor was found to distinguish abrupt dinoflagellate bloom from diatom bloom or non-bloom state. We will embark GOCI-IMBeR study group to observe and develop a database over the local area and the full-disk area for the coming decades along with other marine observation platforms (e.g., ESA satellites). The group membership is open-ended to all who have scientific interests.