Gulf of California 2015, Leg 2 – Midwater Ecology

February 22-March 3, 2015

The second leg of this expedition will be concentrated in the Gulf of California’s central and southern basins to better understand the oxygen minimum zone in this area and its influence on the ecology and physiology of midwater animals.

Researchers on this leg hypothesize that the unusual composition, vertical distribution, and migration patterns of the Gulf of California’s midwater fauna are driven chiefly by the characteristics of the oxygen minimum zone (OMZ), which vary from basin to basin within the Gulf. The effects of hypoxic (low oxygen) water include physiological and behavioral adaptations that allow some species to inhabit the OMZ during daylight hours, vertical distribution patters for some species that are compressed above the OMZ, and unusual diel vertical migration cycles.

To investigate these issues researchers will determine the vertical distribution, migration and abundance patterns of the principal midwater species, measure their oxygen consumption rates, observe their behavior and activity levels in situ, and study their trophic linkages.

Quantifying the relative abundance and distribution of species in the Gulf and their adapations to their extreme environment will provide important data which can be used to anticipate how other seas will be affected by ongoing changes that lead to similar conditions such as warming and acidification.

Logbook

Wrapping up a productive cruise

Today we completed our leg of the Gulf of California expedition with a half-day ROV dive close to the port where the Western Flyer docks near La Paz. It was an incredibly productive cruise with ROV Doc Ricketts dives every day, MiniROV dives most days, midwater trawls most nights, and even a few nights of jigging for squid!

Food web ecology

As we near the end of the midwater ecology leg, scientists onboard are beginning to piece together a unique collection of observations and data gathered from ROV dives and midwater trawls.

Unique organisms in the deep sea

In addition to documenting the ecological zonation of the water column in the Gulf of California, we are venturing into parts of the ocean that have likely not been explored by humans before, in particular, not with the deep-sea observational tools we are using during this cruise.

MiniROV and ROV Doc Ricketts

Today was another very successful day aboard the Western Flyer, with nearly six-hour dives with both the MiniROV and ROV Doc Ricketts.

Oxygen minimum zones

Henk-Jan Hoving's collaborative work with Bruce Robison and the Midwater Ecology Group will eventually allow a comparison of the distribution of pelagic animals between areas with oxygen minimum zones of different intensity in different ocean basins.

Coping with low oxygen levels

Today we observed quite a few deep-sea fish that seem to be coping with the low oxygen level of the deep midwaters here in the Gulf.

MiniROV deployment

We began the day bright and early, ready to deploy the MiniROV. This small ROV was designed as a fly-away system that could be shipped anywhere in the world and used on any ship. It has been used to explore Arctic seafloors multiple times. Now it’s getting the chance to explore the warm midwater here in the Gulf of California.

ROV Doc Ricketts to the rescue

Upon arrival in La Paz, the midwater scientists were asked to mobilize a day early so the ROV Doc Ricketts could be used to help rescue MBARI's autonomous underwater vehicle which was operating nearby, off the R/V Rachel Carson.