Microfossils reveal warm oceans had less oxygen, Syracuse geologists say

Microfossils reveal warm oceans had less oxygen, Syracuse geologists say



"Global warming impacts marine life in complex ways, of which the loss of dissolved oxygen [a condition known as hypoxia] is a growing concern" says Zunli Lu, assistant professor of Earth sciences and a member of Syracuse's Water Science and Engineering Initiative. "Moreover, it's difficult to predict future deoxygenation that is induced by carbon emissions, without a good understanding of our geologic past."

Lu says this type of deoxygenation leads to larger and thicker oxygen minimum zones (OMZs) in the world's oceans. An OMZ is the layer of water in an ocean where is at its lowest.



Fossil skeletons of a group of protists known as foraminiferas have long been used for paleo-environmental reconstructions. Developing an oxygenation proxy for foraminifera is important to Lu because it could enable him study the extent of OMZs "in 3-D," since these popcorn-like organisms have been abundant in ancient and modern oceans.

"By comparing our fossil data with oxygen levels simulated in climate models, we think OMZs were much more prevalent 55 million years ago than they are today," he says, adding that OMZs likely expanded during the PETM. "Deoxygenation, along with warming and acidification, had a dramatic effect on during the PETM, prompting mass extinction on the seafloor."

Lu thinks analytical facilities that combine climate modeling with micropaleontology will help scientists anticipate trends in ocean deoxygenation. Already, it's been reported that modern-day OMZs, such as ones in the Eastern Pacific Ocean, are beginning to expand. "They're natural laboratories for research," he says, regarding the interactions between oceanic and climate changes."

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Geologists confirm oxygen levels of ancient oceans

Journal information: Paleoceanography

Citation: Microfossils reveal warm oceans had less oxygen, Syracuse geologists say (2014, October 16) retrieved 5 April 2020 from https://phys.org/news/2014-10-microfossils-reveal-oceans-oxygen-syracuse.html

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