16 If You Could Turn Back Time: An Open Session on Paleoclimatology of Any Sort (Posters)

Thursday, 4 May 2023
1:30 PM - 5:30 PM
EC 215

BIOLOGICALLY DRIVEN ISOTOPIC FRACTIONATIONS IN BIVALVE GENERA DOSINIA AND MACTRA BETWEEN 43°S AND 53°N

Paper number: 16-3
Program: Theme Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

The δ18O, δ13C, Δ47, and recently Δ48 composition of mollusk shells has been widely used to reconstruct past climate. The outer shell layers (OSL) of fossil bivalves are especially useful for paleoenvironment, as the isotopic values tend to reflect water temperature and δ18O of water at the time of shell growth. However, recent work has shown that the composition of the inner shell layer (ISL) can be different from the OSL in any or all of these isotopic parameters. These differences can be attributed to different biologically-controlled precipitation mechanisms governing formation of each layer. These biologically driven isotopic fractionations (BioDIFs), or “vital effects,” are typically avoided in paleoclimate studies, but new tools (paired δ18O-Δ47 and Δ47-Δ48 measurements) and an integrated understanding of biology and geochemistry can help illuminate the mechanisms driving these fractionations. Preliminary data suggests that these BioDIFs may be characteristic of particular genera, however there are few systematic measurements of BioDIFs that control for phylogeny and location/environment. We measured δ18O, δ13C, Δ47, and Δ48 in modern bivalves of two different genera (Dosinia spp. and Mactra spp.) to characterize BioDIFs. We sampled 10 species of genus Mactra and 13 species of genus Dosinia (total n = 48) over a latitudinal range of 43°S to 53°N. This can test whether BioDIFs are the same among species of a certain genus. Considering latitude and growth environment may reveal how or whether certain external factors influence BioDIFs in bivalves. This could give insight into how bivalve shells record environmental information, which can strengthen paleoclimate interpretation. Differences in BioDIFs may reveal information about how the organism regulates its internal environment during the biomineralization process in response to environmental conditions. Characterizing these relationships in modern bivalves can help us interpret BioDIFs in fossil bivalves as a paleophysiological proxy. This can help address questions of evolutionary relationships, responses to environmental stress, and survivorship during episodes of climate change.

Geological Society of America Abstracts with Programs. Vol. 55, No. 3

doi: 10.1130/abs/2023NC-386954

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