Ecosystem Resilience to Ocean Deoxygenation and Acidification: Lessons from Contrasting Mass Extinction Events
Abstract
Mass extinction events (MEEs) are among the few readily identifiable turning points in the evolution of life, and could serve as potential analogues for understanding ecosystem responses to projected trends in climate change. This study addresses marine ecosystem resilience by examining the biomarker signature of planktonic communities across two contrasting MEEs: (a) the end-Triassic, characterized by intense volcanism, high pCO2 and ocean anoxia; (b) the Cretaceous-Paleogene (K-Pg) boundary, characterized by a bolide impact, reduced photosynthesis and ocean acidification. Results from Kennecott Point in western Canada, provide the first evidence for the occurrence of reducing conditions and photic zone euxinia across the end-Triassic and early Jurassic in the Panthalassic Ocean. The latter was accompanied by abrupt turnovers in plankton ecology favoring prasinophytes, chrysophytes, cyanobacteria, and methanotrophs, which advocates for large perturbations in nutrient inventories. The length of our record suggests that such changes might have persisted for at least 500 ky into the early Jurassic. On the other hand, biomarker and isotopic results from the clay layer of the stratotype section of El Kef in northern Africa indicate that, in stark contrast to calcareous organisms, primary production by non-calcifying organisms was not significantly affected across the K-Pg boundary, whereas no important ecological turnovers were observed. Taking into account the short duration of the boundary clay layer (~10 ky), these results indicate that non-calcifying organisms might have been responsible for sustaining benthic communities in the immediate aftermath of the K-Pg, and probably longer until calcifying organisms resurged again. Our results suggest that environmental changes stemming from elevated CO2, oxygen-deficiency, acidification, and nutrient limitation (end-Triassic scenario) have more negative consequences on marine ecosystems (calcifying and non-calcifying organisms) than transient events of acidification and productivity change (K-Pg scenario). Since ocean deoxygenation and acidification are projected to increase in the near future, our work provides information for predicting potential changes in marine ecosystems.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP31A2000S
- Keywords:
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- 0473 BIOGEOSCIENCES / Paleoclimatology and paleoceanography;
- 1605 GLOBAL CHANGE / Abrupt/rapid climate change;
- 4900 PALEOCEANOGRAPHY;
- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change