Fossilized oysters are helping to understand the mysteries of a second great mass extinction. This mass extinction took place roughly 201 million years ago, defining the border between the Triassic and Jurassic periods. A recent study, co-authored by Dr. James Rae, a Reader in the School of Earth and Environmental Studies, highlights the role of ocean acidification driven by a drastic rise in atmospheric carbon dioxide as a primary factor behind this extinction.
Researchers from the University of St Andrews and the University of Birmingham worked together to analyze fossilized oysters. In doing so, they honed their research on this decisive moment. The second part of the study looked at chemically ‘fingerprinting’ the sources of that carbon to figure out where it was coming from. Their results revealed that the primary source of this carbon was solid Earth. Consequently, ocean pH levels dramatically dropped.
Prior to the extinction event, ocean pH was at 8.2. The researchers found an extraordinary decrease, by a minimum of 0.3 and probably more than 0.4 pH units. This downward trend coincides with a double in the amount of atmospheric CO2, putting extreme and disorienting pressure on our marine ecosystems. Research also indicates that acidification was responsible for coral reefs recovering from the mass extinction. This led to a global “reef gap” which the planet took several hundred thousand years to start to recover from.
Dr. Rae emphasized the implications of their findings for present-day climate concerns. “The geological record tells us that major CO2 release transforms the face of our planet, acidifying the ocean, and causing mass extinction. We have to act fast to avoid these outcomes in our future.”
Ocean acidification has now been associated with three of the five largest mass extinction events in Earth’s history. Unlike the gradual process observed during the Triassic-Jurassic extinction, modern ocean acidification is occurring at an accelerated rate due to anthropogenic greenhouse gas emissions.
Dr. Sarah Greene, another researcher involved in the study, remarked on the urgency of addressing contemporary climate issues: “The mass extinction event during the Triassic-Jurassic period was over a much longer timeframe, whereas modern ocean acidification is happening at a much quicker rate. This warning from the past should give us fresh cause to step up efforts to reduce human greenhouse gas emissions that could otherwise see acidification reach or exceed levels seen during these mass extinction events.”
The study’s implications were published in the journal Nature Communications. Through stunning graphics, the authors illustrate the time and place relationship between high carbon levels and ocean devastation throughout geologic time. Rather, scientists are still actively probing ancient events. Fighting to defend these dynamic systems, they hope to use lessons from historic trends to ensure vibrant marine habitats for their children and grandchildren.