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Abstract The TEX86proxy, based on the distribution of isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) from planktonic Thaumarchaeota, is widely used to reconstruct sea surface temperature (SST). Recent observations of species‐specific and regionally dependent TEX86‐SST relationships in cultures and the modern ocean raise the question of whether nonthermal factors may have impacted TEX86paleorecords. Here we evaluate the effects of ecological changes on TEX86using one Pliocene and two Pleistocene sapropels from the Mediterranean Sea. We find that TEX86‐derived SSTs deviate from‐derived SSTs before, during, and after each sapropel event.‐derived SSTs vary by less than 6 °C, while TEX86‐derived SSTs vary by up to 15 °C within a single record. Compound‐specific carbon isotope compositions indicate minimal confounding influence on TEX86from exogenous sources. Some of the variation can be accounted for by changes in nitrogen cycling intensity affecting thaumarchaeal iGDGT biosynthesis, as demonstrated by an inverse relationship between TEX86and δ15NTN. TEX86‐derived SSTs also consistently show warm anomalies in the Pleistocene, while the Pliocene samples exhibit both warmer and cooler relative offsets. These anomalies result from systematic differences between Plio‐Pleistocene iGDGT distributions and both modern Mediterranean and modern, globally distributed core top samples. Through characteristic GDGT distributions, we suggest the existence of three distinct endemic populations of Thaumarchaeota in the Pliocene, Pleistocene, and modern Mediterranean Sea, respectively. Importantly, these communities prevailed during both sapropel and oligotrophic conditions. Our results demonstrate that ecological and community‐specific effects must be considered when applying the TEX86proxy to paleorecords.
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Summer Surface CO 2 Dynamics on the Bering Sea and Eastern Chukchi Sea Shelves From 1989 to 2019
- Award ID(s):
- 1733564
- PAR ID:
- 10312718
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 127
- Issue:
- 1
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1029/2021JC017424
