Gulf of California 2015, Leg 4 – Seafloor Biology

The oxygen minimum zone is very well-developed in the Gulf of California, particularly in the southern region. Changes in oxygen are correlated with patterns of carbonate chemistry due to the coupling of metabolic oxygen consumption and carbon dioxide release. The accumulation of respiratory carbon dioxide reduces pH levels of seawater and carbon saturation in areas where oxygen is low (e.g., oxygen minimum zones). Benthic animals vary in composition in relation to the tolerances of individual species to hypoxia, but may not also be affected by carbonate chemistry.

The benthic biology group will sample seafloor communities throughout the Gulf of California to:

  • quantify the distribution of benthic fauna
  • determine the condition of individuals (e.g., tissue and skeletal composition)
  • measure metabolic rates of key benthic megafauna, in relation to variation in oxygen and carbonate chemistry


One of the deep-sea cusk eels that the ROV pilots recovered from the core of the oxygen minimum zone in Cerralvo Trough.

A glimpse into a mysterious, oxygen-limited world

As a PhD student in biological oceanography at the Scripps Institution of Oceanography at the University of California, San Diego, I was thrilled to be invited by chief scientist Jim Barry to take part in the MBARI Gulf of California 2015 expedition.
Downtown Cabo Pulmo.  The village has a number of small dive / snorkel shops.

Diving in the canyon off Cabo Pulmo

We are off Cabo Pulmo, a Mexican national park with the most northerly tropical coral reef in the world. Cabo Pulmo was originally colonized by pearl divers.
This montage shows some of the equipment down in the twin hulls of the Western Flyer that helps keep the boat working properly: 1) These massive generators supply power to the ship. 2) The fuel-purification system helps prevent damage to the engines. 3) The hydraulics room provides hydraulic power to many parts of the ship. 4) The oil/water separator reduces the amount of oil to less than 15 parts per million, making the bilge water safe to discharge into the ocean.

A tour of the R/V Western Flyer

Mariah Salisbury writes: Unlike a terrestrial vehicle, which you can just fuel up and drive, it takes a lot more for the Western Flyer to get underway. Lance Wardle, who is sailing as Chief Engineer on this leg of the cruise, gave me a behind-the-scenes tour of the ship’s inner workings.
Isla Tortuga in the Gulf of California.

Observing the seafloor community

We steamed for a day to arrive at Isla Tortuga—a small, rugged, and beautiful little island near the middle of the Gulf. Fortunately, the weather has been great, and everyone aboard seems to be feeling fine and in good spirits.