A tropical cyclone-induced and satellite-detected chlorophyll a elevation accompanied by phytoplankton biomass decrease

Abstract Satellite observations have traditionally associated tropical cyclones (TCs) with phytoplankton blooms through elevated chlorophyll-a (Chla) concentrations, yet this relationship masks complex underlying ecological processes. Through a integration of satellite data and in-situ bio-optical measurements, we reveal a counterintuitive ecological response to TC ‘Chaba’ in 2022 that challenges conventional understanding. While satellite-detected Chla concentrations increased and phytoplankton division rates accelerated following TC passage, we surprisingly documented simultaneous declines in phytoplankton biomass and carbon-to-chlorophyll (C:Chl) ratios. Our analysis demonstrates that physiological regulation, rather than biomass accumulation, dominated high-Chla zones during and after TC disturbance, with C:Chl anomalies contributing over 60% to elevated Chla areas. This research presents a paradigm-shifting scenario: phytoplankton biomass began accumulating initiated pre-TC, yet increased loss rates during/after TC actually reduced phytoplankton biomass despite enhanced division rates. The fundamental decoupling between TC-induced Chla enhancement and phytoplankton biomass dynamics we document has profound implications for oceanic carbon cycling models and climate predictions, necessitating a recalibration of how we interpret satellite Chla signals in storm-affected marine ecosystems.