Toxic Ocean Conditions During Mass Extinction Reveals Insight into Today's Climate

It turns out that it doesn't take much to turn our planet's ocean waters into something that's toxic to life. Scientists have taken a closer look at a massive extinction event that occurred 93.9 million years ago and have found that it didn't take as much sulfide as previously thought in the ocean waters to cause this major climatic perturbation.

In order to examine this particular extinction, the scientists examined the chemistry of rocks deposited during that time period. This revealed that oxygen-free and hydrogen sulfide-rich waters extended across roughly five percent of the global ocean. That's far more than today modern ocean's at .1 percent, but far less than previously thought.

"These conditions must have impacted nutrient availability in the ocean and ultimately the spatial and temporal distribution of marine life," said Jeremy Owens, one of the researchers, in a news release. "Under low-oxygen environments, many biologically important metals and other nutrients are removed from seawater and deposited in the sediments on the seafloor, making them less available for life to flourish."

That's not all the researchers discovered, though. This particular biological extinction that occurred 93.9 million years ago was also associated with high levels of carbon dioxide in the atmosphere. These gas levels were probably linked to an elevation in ocean and atmospheric temperatures. In fact, these particular conditions highlight the importance of curtailing the warming occurring today.

"Today, we are facing rising carbon dioxide contents in the atmosphere through human activities, and the amount of oxygen in the ocean many drop correspondingly in the face of rising seawater temperatures," said Timothy Lyons, one of the researchers, in a news release. "Oxygen is less soluble in warmer water, and there are already suggestions of such decreases. In the face of these concerns, our findings from the warm, oxygen-poor ancient ocean may be a warning shot about yet another possible perturbation to marine ecology in the future."

The findings are published in the Proceedings of the National Academy of Sciences.