From: University of Maryland Center for Environmental Science
Published May 17, 2017 04:53 PM

Scientists Begin to Unlock Secrets of Deep Ocean Color from Organic Matter

About half of atmospheric carbon dioxide is fixed by ocean's phytoplankton, mainly picocyanobacteria, through a process called photosynthesis. Picocyanobacteria are tiny, unicellular microorganisms that are abundant and widely distributed in freshwater and marine environments. A large portion of biologically fixed carbon is formed by picocyanobacteria at the sea surface and then transported to the deep ocean. But what remains a mystery is how colored dissolved organic matter which originates from plant detritus (either on land or at sea) makes it into the deep ocean. A team of scientists from the University of Maryland Center for Environmental Science and around the world potentially found a viable marine source of this colored material.

“We are still at the beginning of understanding the marine carbon cycle,” said Michael Gonsior, a chemist at the University of Maryland Center for Environmental Science. “So far the sources of specific chemicals in the ocean are not well defined because it is such a vast and complex system. So any step forward to take apart the complexity makes this a valuable contribution.”

In the deep ocean, dissolved organic matter displays a fluorescence signal that looks like what you’d see in a river or stream. It has been traditionally named humic-like fluorescence, assuming it comes from degrading trees and other terrestrial organic matter. Many scientists have hypothesized that this material found in the deep ocean is the remnants from rivers and streams around the world that carry it off the land and into the ocean. However, evidence is growing that there are marine sources of this material, which may well explain the majority of this colored material found in the deep ocean.

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