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Tropical Atlantic climate and ecosystem regime shifts during the Paleocene–Eocene Thermal Maximum
Frieling, J.; Reichart, G.-J.; Middelburg, J.J.; Röhl, U.; Westerhold, T.; Bohaty, S.M.; Sluijs, A. (2018). Tropical Atlantic climate and ecosystem regime shifts during the Paleocene–Eocene Thermal Maximum. Clim. Past 14(1): 39-55. https://dx.doi.org/10.5194/cp-14-39-2018
In: Climate of the Past. Copernicus: Göttingen. ISSN 1814-9324; e-ISSN 1814-9332, meer
Peer reviewed article  

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  • Frieling, J.
  • Reichart, G.-J., meer
  • Middelburg, J.J., meer
  • Röhl, U.
  • Westerhold, T.
  • Bohaty, S.M.
  • Sluijs, A.

Abstract
    The Paleocene–Eocene Thermal Maximum(PETM, 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean–atmosphere system from a 13C-depleted reservoir. Many midlatitude and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation,biotic overturning, and migrations, but detailed records from tropical regions are lacking. Here, we study the PETM at Ocean Drilling Program (ODP) Site 959 in the equatorial Atlantic using a range of organic and inorganic proxies and couple these with dinoflagellate cyst (dinocyst)assemblage analysis. The PETM at Site 959 was previously found to be marked by a 3.8 percent negative carbon isotope excursion(CIE) and a 4C surface ocean warming from theuppermost Paleocene to peak PETM, of which 1 C occurs before the onset of the CIE. We record upper Paleocenedinocyst assemblages that are similar to PETM assemblagesas found in extratropical regions, confirming poleward migrationsof ecosystems during the PETM. The early stagesof the PETM are marked by a typical acme of the tropical genus Apectodinium, which reaches abundances of up to 95 percent. Subsequently, dinocyst abundances diminish greatly,as do carbonate and pyritized silicate micro fossils. The combined paleoenvironmental information from Site 959 and aclose-by shelf site in Nigeria implies the general absence of eukaryotic surface-dwelling microplankton during peak PETM warmth in the eastern equatorial Atlantic, most likely caused by heat stress. We hypothesize, based on a literature survey, that heat stress might have reduced calcification in more tropical regions, potentially contributing to reduced deep sea carbonate accumulation rates, and, by buffering acidification, also to biological carbonate compensation of the injected carbon during the PETM. Crucially, abundant organic benthic foraminiferal linings imply sustained export production, likely driven by prokaryotes. In sharp contrast,the recovery of the CIE yields rapid (10 kyr) fluctuations in the abundance of several dinocyst groups, suggesting extreme ecosystem and environmental variability.

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