Out to sea
July 10, 2013
Today we set sail at 11:00 a.m. The timing of the departure and return of each cruise on the research vessel Western Flyer depends on the tides. The slip where the ship docks has relatively shallow water, so we need to wait until the tide is high enough to safely maneuver out of the harbor. Despite this late start, we had a very successful day at sea!
We steamed to a site in the Monterey Bay that is about 2,000 meters deep. The ship’s crew and science team participated in a safety drill, to ensure that everyone knows what to do in the event of an emergency. As we approached the site, the remotely operated vehicle (ROV) pilots were getting ready to deploy ROV Doc Ricketts, to get it in the water as soon as possible. We had a very successful ROV dive, sending the vehicle quickly down to 1,250 meters and working its way up, collecting target organisms as it ascends. As the ROV was diving, Lynne Christianson and Alexander Jaffe deployed a plankton net to collect plankton for a colleague at MBARI. They also collected water with a bucket and filtered it for analysis of phytoplankton.
The seas were flat calm and winds were down, so as the ROV worked in the deep midwater, our blue-water divers got ready for a SCUBA dive. There are many animals that are interesting to the scientists on board within SCUBA depths. Because of the tether it drags behind, ROV Doc Ricketts is not allowed to operate in shallow water (above 200 meters). There are also many shallow animals that are too small to observe with the ROV, so to collect shallow animals, the science team sends out SCUBA divers. A blue-water dive is one where the divers launch a rigid-hulled inflatable boat (RHIB) from the back deck of the Western Flyer. A crew member drives the RHIB and up to four divers can go on the dive. The divers hook onto a line that is attached to the RHIB, so they drift together as the divers collect animals.
Yesterday, a few of the divers did a “check out” dive in MBARI’s test tank. The MBARI dive safety officer, Kim Reisenbichler needed to make sure the divers from other institutions understood and were capable of following MBARI’s blue-water dive safety procedures. The divers attach to these lines, one diver staying near the central “down line” as the safety diver. The other divers are tethered to this main line like spokes on a wheel, and they swim away from the line to collect animals. When the dive is over, they all return to the main line and ascend together. On today’s SCUBA dive the divers collected 50 specimens of one of the high-priority jellies — an efficient use of 30 minutes!
Below are some frame grabs from the ROV video taken on today’s dive. Clockwise from top left: Phronima sedentaria is clear amphipod that eats the inside out of a salp and lays its eggs in the left-over barrel. This cydippid comb jelly with red tentacles is yet to be described by scientists. Three of the scientists on board the cruise have submitted a paper describing this long Apolemiasiphonophore. Bargmannia amoena is a beautiful orange/red siphonophore.
This is just the beginning of the cruise, yet we have already collected many species of interest. With each dive, we will get closer to understanding and enumerating the diversity of gelatinous animals in the deep midwater. Documenting the diverse assemblage of animals in the deep ocean will help answer questions about their evolution and will help us understand large-scale changes to the deep-ocean ecosystem.
—Susan von Thun