"Marine ecosystem models predict that anthropogenic warming will likely result in decreased marine fish production in the coming centuries, although the magnitude of this effect is poorly constrained. By contrast, preliminary work on the early Paleogene (62-48 Ma) has suggested that warmer climate periods were associated with long-term increases in open-ocean fish production. The historical response of fish communities to rapid-scale warming events closer in rate to anthropogenic warming remains unknown. The Paleocene-Eocene Thermal Maximum (PETM) was a transient and rapid interval of global warming approximately 56 million years ago (Ma) and is a partial analog to modern climate change. To test how fish populations responded to past rapid ocean warming, we compiled records of fish abundance and diversity across the PETM, using isolated microfossil fish teeth and shark scales (ichthyoliths) preserved in three deep-sea sediment cores: Ocean Drilling Program (ODP) Site 1209 in the North Pacific Ocean, ODP Site 1220 in the Equatorial Pacific, and ODP Site 1260 in the Equatorial North Atlantic Ocean. We find that, in contrast to future projections, ichthyolith accumulation rates (IARs) from all sites show significant increases in fish production coincident with early stages of the PETM, before returning to pre-PETM levels as the hyperthermal conditions waned. Furthermore, the morphological diversity and composition of PETM ichthyolith assemblages remain largely constant across the event, with no evidence of excursion or disaster biotas. These findings suggest that on millennial timescales fishes may be more resilient to rapid global climate change than previously thought. Further, the temperature sensitivity of fish production across the rapid warming of the PETM can be quantitatively compared to the temperature sensitivity of fish production throughout the Early Paleogene, providing a means to interrogate the sensitivity of fish populations to changes in ocean temperature throughout Earth’s past and across different time scales."

https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/934149

Another brick removed from the AGW wall.