Geochemistry and micropalaeontology combined to track oxygen levels in Earth's oceans

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Foraminiferas registers iodine ratio to calcium, determining oxygen levels.

Researchers from Syracuse University's College of Arts and Sciences are pairing chemical analyses with micropalaeontology - the study of tiny fossilized organisms - to obtain a better understanding of how global marine life was affected by a rapid warming event over 55 million years ago.

Their findings are the subject of an article published in the journal (John Wiley & Sons, 2014).

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Asst. Professor of Earth Sciences Zunli Lu among those researching oxygen saturation.

"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 results in larger and thicker oxygen minimum zones (OMZs) in the world's oceans. An OMZ is the layer of water in an ocean where oxygen saturation is at its lowest.

Much of Lu's work revolves around the Paleocene-Eocene Thermal Maximum (PETM), a well-studied analogue for modern climate warming. Documenting the expansion of OMZs during the PETM is problematic due to the lack of a sensitive, widely applicable indicator of dissolved oxygen.

In order to address the problem, Lu and his colleagues have started working with iodate, a type of iodine that is apparent in oxygenated waters only. By analysing the iodine-to-calcium ratios in microfossils, they are able to estimate the oxygen levels because of the lack of sensitive widely applicable indicator of dissolved oxygen.

Fossil skeletons of a group of protists known as foraminiferas have long been used for palaeo-environmental reconstructions. Developing an oxygenated proxy for foraminifera is important to Lu because it could allow him to 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 in the PETM, prompting mass extinction on the seafloor."

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

Comment: These little foraminiferas seem to be the hot ticket item in oceanic research of late. They are also being studied for ocean temperature variants (see: http://ift.tt/1u6WT5a )

Even with the iodate application analyzing iodine-to-calcium ratios, the findings are first and foremost still estimates. It is unclear from this article as to whether the foraminiferas are the only defining edge considered in this comparison. It is also unlikely that this research could historically stretch the findings to broad-stroke a human influence on global warming, since this would "theoretically" be the first-of-its-kind "climate alteration" along with the falsely maligned culprit CO2. (Unbiased research shows global warming is happening at this time to all the planets in the solar system.) If the OMZs are present, and have been periodically for eons, it may be due to repeated cycles of a grander nature than the comparatively recent meddling of human activity.

It is more likely that methane released into the oceans (increasingly happening NOW) would overwhelm any influence added CO2 could have to produce a warming effect. Methane is 21 times more potent a greenhouse gas and, by the way, greatly affects the level of oxygenation in both deep and shallow ocean waters since the aerobic oxidation of methane consumes oxygen. Methane-caused oxygen depletion has been proven to create or expand OMZs.