Ocean flakes surprise researchers

Carbon transport in the ocean: it depends on the size of the floc

This is what the porous flakes look like: Aquatic aggregate from Lake Constance, one centimeter in diameter. © Hans-Peter Grossart / IGB / Leibniz Institute of Freshwater Ecology and Inland Fisheries
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Researchers have investigated seaborne transport processes and discovered surprising behavior of porous flakes of dead organic matter that could significantly affect carbon accounting.

Because these flakes are colonized by microorganisms that decompose some of the material to carbon dioxide during descent, the rate of descent determines the amount of carbon that reaches the deep sea and is stored over long periods of time.

The scientists of the Max Planck Institute for Marine Microbiology in Bremen are now presenting their results together with a US colleague from the Massachusetts Institute of Technology in the "Proceedings of the National Academy of Science" (PNAS).

Flakes as sponge double

Similar to sponges, the flocs in the ocean contain only a very small proportion of solids and often consist of more than 95 percent of their volume of water. In addition, the water masses of the oceans are layered as a function of temperature and salinity. The water depth therefore increases with the depth of the water.

Due to their high porosity, that is, the high level of light surface water, flakes can be held up in these stratifications until their density, by exchanging the liquids stored in the pores, becomes large enough to continue to sink. display

Kolja Kindler of the Max Planck Institute emphasizes that this effect has so far been largely neglected, although for some years he has been discussing this as an explanation for unusually sharply defined accumulations of flakes that can be observed in nature.

Laboratory experiments and mathematical modeling

As the scientists in this study have now shown for the first time through a combination of laboratory experiments and mathematical modeling, the effect is probably far more important than previously thought. Since the flakes are not flowed through and the adaptation of the stored water to the surrounding liquid essentially takes place by diffusion, the following applies: the larger the flake, the longer it is held up at the intermediate layer.

"Accordingly, large flakes are likely to have a much longer residence time in areas where they can be degraded by microorganisms than previously thought. In the future, these new findings must be taken into account in order to realistically describe, or model, carbon transport in the ocean, "explains Max Planck researcher Professor Arzhang Khalili.

Sustainable use of the oceans

IntensThe more intensively we deal with small-scale phenomena, the more we discover that they control the crucial processes in the ocean. The chances of a sustainable use of the oceans depend on how well we understand these processes, "says Professor Roman Stocker of the Massachusetts Institute of Technology.

(Doi: 10.1073 / pnas.1012319108)

(Max Planck Institute for Marine Microbiology, 08.12.2010 - DLO)