The Midwater Ecology Group is out here studying a layer in the water column called the oxygen minimum zone, or OMZ. The OMZ is a layer where the oxygen levels are lower than the waters above. In the Monterey Bay area the OMZ is typically 600 to 900 meters below the surface. OMZs form where large amounts of organic material (marine snow) sink down from the sea surface. When bacteria break down this organic material, they remove oxygen from the water. Above the OMZ, this oxygen is replaced by oxygen-rich seawater that mixes down from the sea surface. Below the OMZ, oxygen is replaced to a lesser extent by deep-ocean currents. But seawater within the OMZ doesn’t mix very much with the waters above or below it, so oxygen concentrations are often very low. Many animals cannot live in or even swim through the OMZ, but a few species have adapted to survive in this challenging environment.

MBARI researchers are very interested in knowing more about how sensitive deep-sea organisms are to changing oxygen levels which requires knowing how much oxygen they use to survive. While the deep Midwater Respirometry System collects data (this last deployment was a 48-hour deployment at 2,900 meters), Kim Reisenbichler is hard at work in the lab measuring the respiration of other animals collected on earlier dives. He also is the person with the most experience with net deployment, thus he also assisted in the deployment of the midwater trawl last night.

And, while all of this is going on, you never forget that the deep-sea is full of amazing organisms like this incredible whalefish that gathered the attention of the everyone aboard as it slowly posed for us before swimming away into the darkness.