Overview
- Researchers compiled ~14 years of observations from about 90 Pacific research cruises, counting over 800 billion Prochlorococcus cells from 3 to 8 meters depth.
- Division rates rose with temperature up to roughly 28 °C, then fell steeply, dropping to about one third of the maximum by around 31 °C.
- Model runs under RCP4.5 and RCP8.5 project regional tropical declines of 17–51 percent and global productivity reductions of roughly 17 percent (moderate warming) to 38 percent (strong warming), with a near‑collapse signaled for the West Pacific Warm Pool.
- Shifts toward cooler latitudes are expected, and increases in Synechococcus could partially offset losses, but its larger size and higher nutrient needs limit full compensation in nutrient‑poor waters.
- Experts emphasize caveats including sampling confined to near‑surface waters, potential heat‑tolerant strains or deeper recolonization, and note that reduced division does not necessarily mean immediate loss of function or a near‑term drop in atmospheric oxygen.