It’s not fish we’re looking for, but tonight we found them anyway. As soon as we saw the bottom at about 300 meters, there were halibut, a sea skate, and a dogfish. Then, before long, we saw the first of 3 giant Pacific octopi, curled up on the side of a rock and apparently unbothered by the ROV and its bright lights.
The halibut especially would prove plentiful as we made our way up and down the cliffs on either side of Barkley Canyon. The mission for the current series of dives is to run straight lines across at a set depth. But at 300 meters and some other depths, the canyon isn’t wide enough for a full 1 kilometer transect, so we end up going down one rocky canyon side and back up the other.
The halibut were everywhere here, probably because the canyon offers something of a hideout. At that depth, and with so many rocky obstructions for nets, it would prove quite a difficult place to fish.
Dining Options
The real focus of the dive was food. The team is hoping to figure out some of the key food sources that drive life in places like Barkley Canyon, particularly the portions lower in oxygen. One idea has been that kelp coming from inshore could be important. And it may be, but early on in tonight’s dive there was something quite different at play.
We’ve seen places where kelp pieces are covered in sea urchins. And a few days ago, after just a few hours on the bottom, one of the frames for Neus’s experiments had a piece of kelp on it. So the stuff is clearly out here. But what we saw tonight was a huge concentration of sea urchins with no kelp in sight.
A closer look with the downward facing ROPOS camera revealed that a film of dead phytoplankton material from surface waters covered the area, and plenty of animals were making a meal of it. Besides the urchins, there was a variety of small crustaceans.
There at 300 meters, oxygen levels are lower than most ocean waters, but a good bit higher than at greater depth in Barkley. Later in the night during work at 400 meters, there was no such film of phytoplankton detritus, but ROPOS revealed some kelp blades absolutely covered with sea urchins.
There are all kinds of factors that might affect the flow of these different potential food sources to deep waters. For instance, sea otters eat sea urchins, which in turn eat kelp. Changes to otter populations might change how much kelp is available for transport offshore. That’s just one tiny piece of an extremely complex web of interactions. Better understanding which foods are most important in the deep might help to unravel the puzzle of which pieces of that web could be changing in ways that affect where low oxygen levels develop.
Whale Tails
On the surface, there was a pretty good show running as well. Whale sightings have been surprisingly few this trip, but we spotted a number of humpbacks off the stern at midday. And a fur seal came alongside Falkor and put on a few shows. But one of the most unusual sightings was an ocean sunfish, or mola mola. These huge fish have a strange shape that makes it seem like they couldn’t even swim. But they grow to be up to 1,000 kilogram. Sightings are so rare that many aboard, despite having logged months or even years at sea, had never seen one before.
Unusually calm seas have made such sightings a little easier, and more comfortable for everybody. The forecasts say it should stay this calm for most of the days we have left, so we should finish out our final days with dives going in at full speed. We’re streaming all the dives live so be sure to follow along.
