This paper presents a timely and significant refinement to the prevailing narrative that global warming universally suppresses marine phytoplankton biomass. By comparing five marginal seas with contrasting hydrodynamic connectivity and anthropogenic nutrient loads, the authors demonstrate that the Chl‑a response to rising SST is not uniform but varies between open basins and enclosed basins, and varies with terrestrial nutrient retention. The study warns that if warming intensifies and nutrient inputs decline further, the suppressive effect of climate change may encroach upon coastal waters.