Wreck and boulder patch

We have done it! We had a successful dive yesterday and were able to collect data from both a shipwreck and its nearest natural hard-bottom habitat. 

Sonar image of the shipwreck and the hard-bottom site.

I was the scientist in charge for the hard-bottom site. I sat beside the ROV pilot in the shipping container that serves as their control van on the deck. Radio in hand, I communicated with the navigator up in the lab, the captain on the bridge, and the pilot beside me. We surveyed the site by flying over it with the ROV and collecting video. We really weren't sure from our preliminary sonar data what we were going to find at the hard-bottom site. It just looked rough - it could have been mussels, rocks, or just clumps of mud. It turned out to be basalt boulders that had probably ended up on the seafloor through a geological uplift. 

There wasn't a ton of stuff living on the boulders, but then again, we were pretty deep - about 80 m. I noted crustose coralline algae, some orange encrusting thing that might be a sponge, and a few hydroids. There were wire corals and feather stars, which I was very excited to see. The boulder patch overall seemed like what I expected for a deep hard-bottom site in the Gulf. 

The shipwreck was so close, we didn't even have to recover the ROV to get there. We just transited along the bottom. I have been hypothesizing for several years that the distance that a shipwreck is from its nearest source population (natural hard-bottom habitat) determines what can live there. The closer you are, the more species can arrive. This shipwreck, though, was barren. I saw one little reef fish and absolutely nothing else. Eventually, I handed over control to the archaeologists because there was no biology for me to survey. 

A partial 3D model of the hard-bottom site made from ROV
footage by Scott Sorset.

It's really interesting to have data already from our first site that flies in the face of one of my long-standing ideas. Now I'm thinking that maybe the animals don't need the shipwreck if there's a rock pile right there. I'm really curious what we'll find for our other sites that are farther away from their nearest hard-bottom. 

It was a great day on the Sea Scout, and I'm excited that we have data!