Warming Crosses Phytoplankton Threshold

Updated: 2025.10.13 8D ago 3 sources
A decade-long Pacific survey finds Prochlorococcus—Earth’s most abundant phytoplankton—drops sharply once sea surface temperatures exceed ~82°F (27.8°C). The study projects up to a 50% decline in tropical regions over 75 years, contradicting lab-based expectations that warming would boost these microbes. Other phytoplankton may partly fill in, but they are not perfect substitutes for this keystone species. — If a warming threshold collapses a foundational ocean microbe, climate risk assessments, fisheries, and biogeochemical models must adjust from generic 'productivity' assumptions to species‑specific thermal limits with cascading ecological effects.

Sources

Earth's Climate Has Passed Its First Irreversible Tipping Point and Entered a 'New Reality'
msmash 2025.10.13 60% relevant
Both pieces identify ecosystem-scale thermal thresholds; this report’s claim about coral reefs complements evidence that key oceanic biota (e.g., phytoplankton) hit temperature limits, reinforcing a broader threshold narrative.
Shark Teeth Are Crumbling
Sara Kiley Watson 2025.09.11 55% relevant
Both pieces highlight species‑specific physiological thresholds from climate change: the earlier work showed tropical Prochlorococcus collapse beyond ~82°F SST, while this article reports shark teeth crumbling under lower pH, together reframing climate impacts as concrete, mechanism‑level limits across the food web.
Warming Seas Threaten Key Phytoplankton Species That Fuels the Food Web
BeauHD 2025.09.09 100% relevant
Nature Microbiology paper (Ribalet et al., University of Washington): 'populations could shrink by as much as half' when SSTs exceed ~82°F, with many tropical waters projected to surpass 86°F.
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