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How the World’s Oceans Recovered from a Global Mass Extinction Event

The University of Gibraltar’s own Dr Sarah Alvarez speaks to us about her research with an international team that provided a unique glimpse into how marine systems were able to ‘reboot’ following the last global mass extinction event.
Around 66 million years ago, a global mass extinction event saw the end of dinosaurs, ammonites and many other species, with major implications for global ocean ecosystems. An international team of scientists have published an unmatched record of the recovery of life in the oceans in the aftermath of the mass extinction event. Dr Alvarez was the lead author of the article published in the highly prestigious academic journal Nature.
The team found that plankton bounced back rapidly after the mass extinction but that the early communities were highly unstable, with cell sizes being abnormally small. It took two million years for the communities to start to approach a stable and resilient ecosystem.
Dr Alvarez said “The marine ecosystem is dependent on plankton as its base. We looked at the best fossil record of ocean plankton we could find – calcareous nannofossils (they still exist today) – and collected 13 million years of information from deep sea sediment cores, taking a sample every 13,000 years. We measured abundance, diversity and cell size from over 700,000 fossils, probably the largest fossil dataset ever produced from one site. This study highlights the risks associated with loss of key species, which will in all likelihood lead to unstable communities that will take and extremely long time to recover
Article: ‘Diversity decoupled from ecosystem function and resilience during mass extinction recovery’ by S. Alvarez, S. Gibbs, P. Bown, H. Kim, R. Sheward and A. Ridgwell in Nature 574, 242–245 (2019)

Images by P. Bown, University College London.