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Primary productivity controls on opportunistic bivalves during Early Jurassic oceanic deoxygenation

Caswell, Bryony A. and Coe, Angela L. (2013). Primary productivity controls on opportunistic bivalves during Early Jurassic oceanic deoxygenation. Geology, 41(11) pp. 1163–1166.

URL: http://geology.gsapubs.org/content/early/2013/09/0...
DOI (Digital Object Identifier) Link: https://doi.org/10.1130/G34819.1
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Abstract

Severe paleoclimatic change during the Toarcian (Early Jurassic) oceanic anoxic event (OAE) was characterized by a negative δ13C excursion, increased weathering, higher seawater temperatures, oceanic deoxygenation, and mass extinction. We present abundance and size data (n ≈ 36,000) for the two dominant epifaunal bivalve species from the Toarcian OAE, Yorkshire, UK. We statistically correlate the biotic data with geochemical proxies for environmental change and show that our results are comparable with changes in present-day ecosystems affected by hypoxia. Bositra radiata dominated during declining oxygen levels immediately before the Toarcian OAE sensu stricto, and shell size doubled when δ13Corg was decreasing, indicating a connection with primary productivity. Small Pseudomytiloides dubius dominated during the Toarcian OAE and varied sharply in abundance, indicating that it was highly opportunistic. P. dubius shell size is strongly related to Mo concentration, [Mo]; this indicates a relationship between size and N2-fixing primary productivity via [Mo] limitation. A secondary factor contributing to small shell size was lower oxygen levels. After the Toarcian OAE diversity increased, P. dubius was less abundant and shell size doubled, indicating that bivalve populations were less limited by resources and conditions were more favorable. Size frequency distributions show that both Toarcian species had short life spans, rapid generation times, high recruitment, and high juvenile mortality. The opportunist Mulinia lateralis is a present-day analog for P. dubius. This research provides a case study for the long-term impacts of deoxygenation upon marine ecosystems, including that being observed today.

Item Type: Journal Item
Copyright Holders: 2013 Geological Society of America
ISSN: 0091-7613
Project Funding Details:
Funded Project NameProject IDFunding Body
PhD studentship to B.A.CaswellNot SetNERC (Natural Environment Research Council)
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 38730
Depositing User: Angela Coe
Date Deposited: 15 Oct 2013 08:32
Last Modified: 04 Oct 2016 11:31
URI: http://oro.open.ac.uk/id/eprint/38730
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