Artificial reefs

Friends, I want to tell you about something I'm working on now. Back at the beginning of covid, I used my time while stuck at home to go through old video footage from Stellwagen Bank National Marine Sanctuary. Some of the footage was recorded by sanctuary archaeologists years ago (as far back as 2003), and some of it was recorded by my team in 2019-2020. The videos showed shipwrecks throughout the sanctuary, and as I watched, I kept track of the species living on each one. I wasn't sure how the analysis would shape up, but I knew there were bound to be cool patterns in the data. 

I finished going through the footage several months ago, but I never dug into the numerical data to look for those patterns - until now. I decided to focus this particular analysis on the archived footage and look at the distributions of species across the sanctuary. After working the data through my normal analysis procedures, I realized there was actually a very interesting story to be told. Shipwrecks throughout the sanctuary serve as artificial reefs and are colonized by dense communities of invertebrates. The are really distinct patterns in those communities based on where a wreck is located in the sanctuary - north to south and shallow to deep.

Some of you might remember that back in my PhD, I studied invertebrate communities on a set of shipwrecks at the edge of the continental shelf, east of Chesapeake Bay. I compared the patterns I was seeing in their communities to predictions of classic island biogeography theory, and I found a lot of similarities. In that first study, the size of a wreck was really important in determining how many species could live on it. 

A dense invertebrate population on one of the Stellwagen
wrecks, the Paul Palmer.

I'm finding different patterns for the Stellwagen wrecks. The biggest difference is not how many species can live on a wreck, but what those species are. There's a lot more variation in the environment across the sanctuary than there was for my PhD wrecks - some of the Stellwagen wrecks are > 50 km apart, and they range in depth from 30 - 140 m. It seems like the environmental differences are what's driving the variation in invertebrate communities in Stellwagen. The community that one of these artificial reefs supports depends a lot on where it's located within the sanctuary.

I'm pretty excited about this analysis. It's not just an academic exercise - it should help us better manage shipwreck communities. Unintentional shipwrecks serve as analogues for planned artificial reefs. My study shows that if you want to make a new artificial reef, you have to consider very carefully where you put it, because the environmental conditions at that location will control what lives on it. I wrote up the analysis in a manuscript draft and sent it to my co-authors to get their comments. We should be able to submit the paper to a journal for publication soon.