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Gulf of California 2015, Leg 2 – Midwater Ecology – Log 1

Gulf of California 2015, Leg 2 – Midwater Ecology – Log 1

ROV Doc Ricketts to the rescue

Upon arrival in La Paz, the midwater scientists were informed that our colleagues on the R/V Rachel Carson needed the help of the remotely operated vehicle (ROV) Doc Ricketts. The autonomous underwater vehicle (AUV), used to map areas of the seafloor to help scientists target interesting features, had gotten caught on something not far from La Paz. The AUV team knew where the AUV was, but it seemed to be stuck at 450 meters below the sea surface. The crew, ROV pilots, and science team mobilized a day early to go investigate with ROV Doc Ricketts.

The ROV quickly descended and came upon the AUV, caught on a line, presumably attached to fishing gear on the seafloor below. The ROV descended and the pilots slowly flew the Ricketts toward the line below the AUV, kitchen knife in mechanical hand, and quickly cut the line. The AUV immediately started floating up to the surface for the AUV team and Rachel Carson crew to recover.


The AUV was buoyant, with the front pointing upward, caught on the line near the tail cone.
The ROV manipulator grips a knife and approaches the line caught on the AUV.
The R/V Rachel Carson waits in the distance while ROV Doc Ricketts worked to free the AUV.

With great relief at the successful recovery of the AUV, we got ready for a science dive! The ship moved further offshore where the seafloor was 1,700 meters below.

This leg of the Western Flyer’s three-month expedition in the Gulf of California will focus on midwater biology, which includes the deep-sea animals that inhabit the oceanic water column. Many midwater species are found in both Monterey Bay and the Gulf of California, despite differences of up to 15 degrees Celsius between two locales. An interesting aspect of the midwater realm in the Gulf of California is that the core of the oxygen minimum zone (OMZ) in the Gulf is five times larger than the OMZ in Monterey Bay.The OMZ is the zone in which oxygen saturation in the ocean is at its lowest. Despite the low oxygen concentration, many midwater animals live in this zone.

Our first ROV dive was exploratory. We had about six hours to look for interesting animals in this oxygen-poor environment. The ROV slowly descended to about 1,100 meters and then slowly ascended, to give us an overview of the animals present. If the first dive is any indication of the ease with which we’ll find animals of interest, we’re in for a great cruise! We saw many familiar faces, as well as ones we rarely see in Monterey Bay. Stay tuned for more as we explore the midwaters of the Gulf of California.

Clockwise from upper left: Carinaria japonica, a heteropod that is abundant in these tropical waters, but rare in Monterey Bay; Serrivomer, a type of deep-sea eel found here and at home; Grimalditeuthis bonplandi, a deep-sea squid that we are seeing for only the second time in MBARI’s 27 years of deep-sea exploration; Japetella diaphana, a species of midwater octopus that is relatively abundant in the Gulf compared to Monterey Bay. A few of the scientists onboard this cruise published research on Grimalditeuthis bonplandi in 2013, speculating that they may use their tentacles to lure prey.