June 12th, 2021
Today we arrived at the first of our trifecta of sites, Green Canyon (GC-234). GC-234 is a special site for our cruise objectives as it does not actually have any mussels! Instead, we were greeted by a large abundance of tube worm bushes. Tube worms, also known as Lamellabrachia luymesi, are unique to our Gulf of Mexico sites. These tube worms are one of the dominant habitat-forming species found at cold seeps sites in the Gulf, the other habitat-forming species being the mussel species.
Another aspect of this site that’s fascinating is the epibiotic interactions. Epibiotic means things living on other things, like barnacles on a whale. At this site we have a cascading epibiotic relationship with the tubeworms. On top of these tubeworms live a clam called Acesta oophaga, or the egg-eating clam. These clams have a specialized shell that fits over the opening of a tubeworm in order to eat their eggs when they spawn. On top of these clams live another organism, a type of worm called a sabellid worm. These worms bore into the shells of the clams and filter the water flowing around them. One of the graduate students from the University of Oregon on our cruise, Lauren Rice, is interested in these epibiotic interactions. In this picture here, you can see the circular feeding crown of the sabellid worms, on the yellow clams, on the tubeworms with their red heads poking out.
Once ready, Jason began its descent. After passing through nearly 600 meters of deep blue water, with the occasional ctenophore or shrimp floating by, we saw the silty seafloor. A maze of a tubeworm garden appeared before us. The first challenge at every site is locating where our science equipment was deployed on the last cruise. We always save the coordinates of our sites, but they don’t always line up. We scanned the bottom, swerving over and around small and large bushes, searching for our distinctive instruments. Thankfully, we found the target site right next to one of the largest tube worm bushes, larger than Jason. Under the shadow of the worms, we picked up our equipment, placed it within Jason’s basket, and returned to the surface.
Once back on the surface, Sentry was deployed to collect a new plankton sample for us with SyPRID. Tomorrow we will be doing another quick Jason dive to deploy and recover Lauren’s tables and trampolines. Check out this video that Avery Calhoun put together of this site on the last cruise that highlights these crazy tubeworm bushes, but also some beautiful Gorgonian corals with ophiuroids!