???? Melting glaciers serving the Southern Ocean?

2023-07-07 04:00:35

The low availability of iron limits the absorption of atmospheric CO2 by the biological pump of the Southern Ocean. However, the combined contributions of organic matter and minerals from the melting waters of the glaciers are sources of highly bioavailable iron for the phytoplankton of this region. This is demonstrated by the study conducted by a researcher from a CNRS-Insu laboratory (see box), using samples collected during the Antarctic circumnavigation (Antarctica (pronounced [ɑ̃.taʁk.tik] Listen) is the continent most…).
Balleny Islands.
© Noé Sardet / Parafilms / EPFL.

The article reveals that the fate of this iron can quickly evolve once released into the ocean (An ocean is often defined, in geography, as a vast expanse of water…). For example, in the polynya of the glacier (A glacier is a more or less extensive mass of ice formed by the settling of layers…) Mertz, iron is particularly bioavailable for phytoplankton in the direct vicinity of the glacier but a few not far from there, it becomes almost inaccessible. However, the dissolved iron concentration is similar at both locations. Quantification of bioavailable forms of iron, established on profiles up to 500 m deep, confirms a weak link between dissolved iron concentration and its absorption (In optics, absorption refers to the process by which the energy of ‘a photon is taken by…) by the model organism used (Phaeocystis antarctica) by the study. These results call into question the consensus on the sole use of dissolved iron concentrations to predict primary production in the Southern Ocean (The Southern Ocean or Antarctic Ocean or glacial Antarctic Ocean is the body of water that…).

On the other hand, the authors describe a still unexplained relationship between iron isotopes, iron ligands and its bioavailability, and open up new research perspectives to better understand the biogeochemistry of this element. Finally, the authors conclude that after 30 years of research, the complexity (Complexity is a notion used in philosophy, epistemology (for…) of the bioavailability of iron in the marine environment remains a mystery to be solved.

This reality contrasts starkly with the simplicity with which bioengineering studies tout iron seeding as an effective solution to capture CO2 by ocean phytoplankton.