This past June, a vessel called the Okeanos Explorer set off to map and observe the southeast continental margin of the United States, sending remotely operated vehicles (ROVs) to the poorly understood deepwater areas off Florida, Georgia, South Carolina and North Carolina.
The mission, part of the National Oceanic and Atmospheric Administration’s (NOAA) Windows to the Deep 2018 expedition, aimed to collect baseline information. Some sites had never even been explored before. What the team discovered ended up challenging fundamental assumptions they had about the region’s deep-sea organisms and landscapes.
Kasey Cantwell, the expedition’s coordinator with the NOAA Office of Ocean Exploration and Research, took Oceans Deeply on a photographic tour of the newly explored area.
Most of our expedition is targeted on areas that end up changing what we know. In 2014, the Okeanos Explorer mapped an area that we refer to as the “Million Mounds.” This is within the Deepwater Coral Habitat Area of Particular Concern that’s protected by the South Atlantic Fishery Management Council. We knew at the beginning of this expedition that we wanted to collect additional mapping data there, as well as take a look at what these mounding features are. We had a pretty good idea that they were going to be corals, but our hesitation was that there were thousands of mounds. If these truly were corals, we are way, way underestimating the coral population in this area – it’s a massive habitat that we’re not aware of.
The Gulf Stream runs basically on top of this mounding area, so we ended up diving on three of the less impressive mounds. Sure enough, they were all coral. And if every other mound in that area is either the same or on the more impressive scale, there are thousands of coral mounds out there, which we just didn’t know about before.
One of my personal favorite highlights was identifying deep-sea coral habitats in areas where they weren’t known to exist before. Along the edge of the Blake Escarpment, just offshore of Georgia and South Carolina, there’s an area that we’d anticipated to be a low slope-featured.
We used a 2014 model, which uses satellite data to predict what the seafloor will look like in any given place. While extremely helpful, this model does not have the same level of detail that we are able to get using multibeam echo sounders like we have onboard the Okeanos Explorer.
It turned out that when we mapped the area, there were actually these terrace features. Not only were they very different from what the satellite altimetry had suggested, but when we did an ROV dive, we found they hosted a very diverse and very dense deep-sea coral and sponge community.
This one is a Chaunacops, a type of anglerfish. These are sometimes referred to as sea toads. This is one of my favorite animals because they always look so grumpy – although this one looks a little happy. And yes, I anthropomorphize all of the fish.
You can see that the anglerfish is on soft sediment. If you look at this bobtail squid, you can see coral rubble in the area. As we were climbing the terrace, that was a repeated pattern that we saw. Finding those terraces was probably one of the bigger discoveries of that cruise. It kind of changes the way that we think about that continental margin.
This is a type of king crab. When they’re small, their spiky features look very, very awkward compared to the rest of the size of their body. There are so few observations in the deep sea as a whole that anytime we see juvenile species, or even predation events or the deterioration of organisms as they get older and are no longer fulfilling their individual role, we learn more about the life histories of these organisms.
Here is an ophiuroid, or brittle star, holding on to a coral. One of the things that we’re just learning about in the deep sea is how organisms find their habitats and how they establish that association. When we collect organisms for study, and to go to the public archives, we’ll also collect the associated coral. So little is known about the deep sea in general that we’re still trying to figure out how these organisms are both finding and living on these corals.
If you look very closely at all of those dots, those are this squid’s chromatophores, which are essentially sacs that expand and contract as it wants to change its color. What was really cool about this picture is that we actually caught the animal changing from a dark brown color – where the sacs are expanded – to this light color.
It’s really hard to determine what the animals think of us. Sometimes they completely ignore us, sometimes they try to hide, which is probably what this guy was doing. But sometimes, like with some of the crabs, they’ll actually go into a very defensive pose and try to attack the vehicles.
There were certainly a large number of predation events that we observed during this expedition. We would highlight the prey, and a predator would come and snatch it right in front of us, which made for amazing video and which really helped us understand how the organisms interact with each other. But it always brings up the question of how much our presence there was altering that behavior. Predation events are another one of those things that in the deep sea are so infrequently recorded, we have little information about what is abnormal and what is normal.
If you can believe it, what those urchins are eating is one of these jellyfish:
This type of jellyfish is typically known from shallow waters, but we saw it very close to the seafloor, in the canyons just offshore North Carolina. Just seeing this jellyfish – and we saw dozens of them – brings up interesting questions about benthic-pelagic coupling, which refers to interactions between the water column and the seafloor. But in addition to that, seeing these urchins go after a jellyfish is very unusual. Or at least, we thought it was unusual. It shows that there is some sort of carbon exchange, at a minimum, between the water column and the seafloor.
This is probably one of my favorite moments from the expedition. There’s also a video. We saw this crab as he was walking up and approaching an area with brittle stars and we thought, “That’s interesting, he’s probably looking for lunch.” Then he picks up a brittle star and starts to eat it. You hear our team on the line go, “Wait, I didn’t know that crabs eat brittle stars.”
We reasoned, “It’s probably not eating the flesh of the brittle star. It’s probably eating something on its arm.”
We stay a little bit longer, and it is very clearly eating the actual arm of the brittle star. So then our scientists go on to say, “It’s very odd that it would eat an arm, but at least it won’t eat the center disc of that brittle star.”
Later, the crab picks up the central disc, cracks it in half, and starts eating it. To which everyone just responded, “Well, that just goes to show we know nothing about the deep sea.”
This interview has been condensed and edited for clarity.