Hi all! Since my last post, we saw the end of science for this cruise, a brief stop in Cabo Verde, and now we are heading back across the Atlantic. When I wrote my last post, things were just starting to look up for this cruise. As I mentioned, coring is notoriously difficult and this cruise was actually the repeat of one that happened about ten years ago in which they only had success getting cores at one site. So there was a lot of pressure this time around to do it right. We had a much larger corer than the last cruise and the Soutar as backup and that, along with the camera and some other tools were our efforts to see what was happening and get it right.
One of the things that makes coring so much harder than operating the CTD is that our communication with it is very limited. The CTD wire has electrical cables in it running all the way up to a deck box. During deployments, we are able to watch the data from the sensors appear on a computer screen real time and decide exactly when we want to trigger each Niskin bottle to capture water samples. So, we put it in the water then run inside and watch the data plots all the way down and back up. Occasionally, a Niskin bottle doesn’t seal right and we lose the sample, but most of the time there is very little tension when it comes back up, we already have the data. Operating the multicorer is completely different. There is no computer aboard the multicorer and we use a dumb wire, so once we lower it into the water, communication is extremely limited. All that we generally have is a pinger that we put on the wire 10m above the corer. The pinger pings each second at a specific frequency and we use our echosounder in a listening only mode to watch the time delay of each ping increase as the multicorer moves away from us. As we get close to the bottom, we also track the reflection of the pinger off the seafloor and the convergence of this and the original ping marks the corer reaching the bottom. That and change in tension are all that we have to judge what happens on the seafloor and after that we have to wait another two hours to see if we got any mud.
Tension runs high as we peer in to catch sight of the corer. Casts were at all hours of the day; this one came up around 2am [Photo by Sam Katz]
Relief as we catch sight of mud, two casts later and during the day this time, but same idea [Photo by Ben Geyman]
Last time I talked about the camera system that I worked on for the corer. That was very useful in seeing what went wrong, but every time the corer fails, we lose about 5 hours of time, so real time data is really what we need. To this end, I also worked on rigging up a pre-trip pinger system – a way to mount a second pinger onto the multicorer that only turns on once the multicorer trips. We didn’t finalize a good configuration for the second pinger on this trip, but have some methods and new ideas to test on future cruises with the multicorer.
Sometimes when the CTD or multicorer comes back up, it brings us additional presents from the deep. The other day, when the CTD appeared at the surface I caught sight of this strange thing tangled at the bottom of the cable.
Reminiscent of a jellyfish or sea cucumber, it turns out that this is a pyrosome, and only related to each of those as far as kingdom, which is to say not at all. In fact, they’re closely related to the tunicates that live on the underside of docks. In contrast to those, pyrosomes are free-floating and can grow to be many meters long. The pyrosome is actually a large colony with each little bump its own zooid. They’re also bioluminescent and in high enough numbers, can be seen glowing in the sea.
One other cool thing that we found in a mud sample is the following:
The photograph doesn’t do it justice, but this is nature’s fiber optic. It’s a spicule, or structural element, from a deep-ocean silica based sponge species, sometimes called a glass sponge. It has some amazing optical properties. It conducts light just as well as the fiber optic cables that our communications depend on and, in fact, possibly a little bit better due to the sodium content. Besides that, it’s extremely strong and flexible thanks to an inner protein layer. All that we have are the spicules, so we don’t know exactly what species they’re from but one similar species, Venus’ Flower Basket may use these optical properties to its advantage. The depths of the ocean are not exactly where you’d think that organisms would have adaptations to use light, but it turns out that Venus’ Flower Basket serve as the home to bioluminescent bacteria. They also house small shrimp and it seems that the optical properties of the sponge funnel light in such a way to attract small organisms that the shrimp eat. It’s a crazy adaptation for a crazy symbiotic relationship and a great example of the cool things that live deep in the ocean that we still know little or nothing about.
It has been scary watching the extremely fast progression of COVID-19 separated as we are on our ship. Since I last wrote, we watched as the various schools we come from – URI, Case Western, and Harvard – announced transitions to virtual learning, first for a few weeks and now for the whole semester. While we are safe on the ship, stopping in ports and getting scientists from places all over the world are now more dangerous things. Due to the risks, nearly the entire academic fleet will hold off on their operations until the situation improves. This decision was made near the end of our cruise and so we still had to go to port in Praia, Cabo Verde in order to get fuel and stores for the trip back. However, we stayed in quarantine in Praia to protect the ship and made an extremely quick turnaround of about 21 hours.
Praia looks like a beautiful place. I’d love to visit sometime.
One of the last planes before Cabo Verde shut its borders.
Now we are headed directly back to the Endeavor’s homeport at GSO instead of to Florida, where the next cruise would have begun. Those of you who have been following my blog from the beginning know that after my time on the Endeavor, the plan was to head to Bermuda. That is now on hold until the situation improves so just a couple more blogs for now and I’ll make sure to post an update if that changes.
These are strange times, stay safe and healthy out there.
