Historic fish thrived throughout excessive international warming from PETM – cotton wool?

Guest contribution by Eric Worrall

The Paleocene-Eocene Thermal Maximum (PETM), a period of extremely rapid global warming that occurred 10 million years after the demise of the dinosaurs, is believed to have been an ocean disaster. Instead, even temperate climate fish treated the heat like a tropical food buffet.

Ancient fish thrived during a period of rapid global warming

Teeth and scales preserved in marine sediments suggest that fish thrived during one of the world’s fastest warming periods.

Through Elyse DeFranco December 14, 2021

About 55 million years ago the earth’s climate went through a rapid and intense period of warming, both on land and at sea. Temperatures rose to over 5 ° C and even the arctic seas became tropical. The reconstruction of this warm era, the Paleocene-Eocene Thermal Maximum (PETM), offers a glimpse into the possible future of the earth. “One of the best tools we have for understanding how that [ocean] System responds is to look at past cases of global change, ”said Elizabeth Sibert, paleoceanographer and paleoecologist at the Yale Institute for Biospheric Studies.

By studying fossil evidence from the PETM stored in marine sediment cores, Sibert and her colleagues sought to understand how fish might respond to ocean warming. Contrary to the predictions of many models, they found that fish actually grew more frequently as temperatures rose. Sibert and her team will present their research on December 14th at the AGU’s autumn meeting 2021.

Sibert and her team examined sediment records in three different cores collected by the Ocean Drilling Program. The drill sites spanned tropical areas of the north-central Pacific, the eastern equatorial Pacific, and the Atlantic Ocean. The researchers filtered microscopic fish scales and teeth from different depths of the sediment core, counted and sorted them for a window into the past ocean life during the PETM.

“This is the first time we’ve had any idea what mid-to-high trophic groups were doing during this warming event,” said team member Richard Norris, a paleobiologist at the Scripps Institution of Oceanography. “So far, almost all studies on PETM have been based on unicellular plankton or microzooplankton.”

The results paint a consistent picture of the past across all three samples: Fish became more abundant as temperatures rose, then gradually decreased again with decreasing warming. Plus, the different fish species hardly changed during this temperature change. “It’s really surprising,” said Norris. “You might think that with increasing warming you get a completely different community of fish.”

Still, Sibert urges caution when comparing results from fish during the PETM and what could happen this century – and beyond. “The rate of warming … can have dramatic and varied effects on marine ecosystems,” she noted.

Read more: https://eos.org/articles/ancient-fish-thrived-during-a-period-of-rapid-global-warming

The abstract of the study;

PP23A-02 – Improved open ocean fish production and community resilience over the Paleocene-Eocene thermal maximum


Elizabeth C. Sibert Yale University
Douglas W. Tomczik Scripps Institution of Oceanography
Daniel Gaskell Yale University
Gregory L. Britten Massachusetts Institute of Technology
Richard D. Norris Scripps Institution of Oceanography

Marine ecosystem models predict that anthropogenic warming will likely lead to decreased marine fish production in the coming centuries, although the magnitude of this effect is hardly limited. In contrast, preliminary work on the early Paleogene (62-48 Ma) suggests that warmer climates were associated with long-term increases in fish production in the open ocean. The historical response of fish communities to rapid warming events closer 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 of modern climate change. To test how fish populations reacted to earlier rapid ocean warming, we compiled records of fish abundance and diversity throughout PETM by using isolated microfossil fish teeth and shark scales (ichthyolites) that have been preserved in three deep sea sediment cores: Ocean Drilling Program (ODP) location 1209 in the North Pacific, ODP location 1220 in the equatorial Pacific and ODP location 1260 in the equatorial North Atlantic. We think, that, Contrary to future projections, ichthyolite accumulation rates (IARs) from all locations show a significant increase in fish production coinciding with the early stages of PETM, before returning to pre-PETM levels as hyperthermal conditions subside. In addition, the morphological diversity and composition of the PETM ichthyolite accumulations remained largely constant throughout the event, with no evidence of excursion or disaster biotas. These results suggest that fish on millennia timescales may be more resilient to rapid global climate change than previously thought. In addition, the temperature sensitivity of fish production during the rapid heating of the PETM can be quantitatively compared to the temperature sensitivity of fish production throughout the early Paleogene, providing a means of studying the sensitivity of fish populations to changes in sea temperature throughout Earth’s past and across different time scales away.

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

Well by the authors for the courage to report and present their results.

I would have loved to be at the AGU meeting where Elizabeth and the other authors presented their study, their proof that all of their carefully crafted alarming models of global warming in the ocean biome could be completely wrong.

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