Autonomous robots expose hurricane-driven hidden ocean bloom

A recent study examining the impact of Hurricane Idalia on the Gulf of Mexico in August 2023 revealed complex changes in ocean biology and chemistry that satellites alone failed to capture. While satellite sensors detected a surface chlorophyll bloom caused by the storm, autonomous ocean robots—including a surface saildrone and a Biogeochemical Argo (BGC-Argo) float operating underwater—uncovered a second, hidden phytoplankton bloom occurring 20 to 50 meters below the surface. This subsurface bloom was driven by intensified upwelling within a cyclonic eddy, which brought nutrient-rich waters upward, a process amplified by the hurricane’s winds. The study combined satellite data with high-frequency profiling from the BGC-Argo float, which increased its sampling rate from every 10 days to every 18 hours to capture rapid biogeochemical changes. The research highlighted how pre-existing ocean features such as the Mississippi River plume, the Loop Current, and the cyclonic eddy shaped the Gulf’s