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Recovery of benthic communities following the Toarcian oceanic anoxic event in the Cleveland Basin, UK

Caswell, Bryony A.; Dawn, Stephanie J.


Stephanie J. Dawn


During the Toarcian oceanic anoxic event (OAE) considerable environmental changes occurred that were associated with global warming, perturbations to the C-cycle and ocean deoxygenation which resulted in a mass extinction of marine fauna. Recovery of the biota after the event was protracted and has to date undergone limited study. However, understanding the patterns and processes of recovery are critical to anticipating ecosystem responses to the environmental changes predicted for the near future. Results showed that increases in benthic diversity, and the re-establishment of the Toarcian infauna was gradual and followed the changing redox conditions. Pioneering infauna, such as Dacryomya ovum that dominated the seafloor after the event in the Cleveland Basin, Yorkshire, UK, can modify the physico-chemical environment and thus facilitate ecological succession after disturbance. The length of D. ovum increased >8 mm throughout the bifrons Zone and these body-size changes were linked with total organic carbon (TOC) content suggesting a link to primary productivity, although only at intermediate levels of deoxygenation. Major changes in the phytoplankton, and so food supply, seem to have driven changes in bivalve body size, across trophic guilds, both during and after the event in Yorkshire, and on the mid to lower shelf in Spain and France, respectively. Primary productivity collapse seems then to have been a major driver of biotic change throughout the Toarcian event, as it was during the Permian–Triassic, Triassic/Jurassic and Cretaceous/Tertiary mass extinctions. Further investigation of both the palaeontological and geochemical changes that occurred within early successional Toarcian infaunal communities are required to more fully understand the pattern of recovery after the OAE.


Caswell, B. A., & Dawn, S. J. (2019). Recovery of benthic communities following the Toarcian oceanic anoxic event in the Cleveland Basin, UK. Palaeogeography, palaeoclimatology, palaeoecology, 521, 114-126.

Journal Article Type Article
Acceptance Date Feb 18, 2019
Online Publication Date Feb 21, 2019
Publication Date May 1, 2019
Deposit Date Mar 13, 2019
Publicly Available Date Feb 22, 2020
Journal Palaeogeography, Palaeoclimatology, Palaeoecology
Print ISSN 0031-0182
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 521
Pages 114-126
Keywords Jurassic; Lilliput effect; Shell morphology; Population structure; Dysoxia; Alum shale member
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