Encrustation

While we were at the Bureau of Cultural Heritage (BUCH), I finally got an answer to a question I have had for a long time. First, I need to give you some background. 

The anchor encrustation

A few years ago, Calvin used the term "encrustation" in my presence. My ears perked up. There are so many terms in archaeology - like, established jargon in the field - that sounds funny or even made-up to my ears: historiography, ecofacts, lifeways. Those terms regularly drive me nuts. But "encrustation" was something I could immediately grasp - a crust on an artifact, mostly made from calcium carbonate. 

"Hey Calvin," I asked. "Is encrustation a biological or chemical phenomenon? As an artifact gets covered in calcium carbonate, is that because there's a purely chemical process like precipitation going on, or is the encrustation from the shells and skeletons of organisms?"

He couldn't answer me. In fact, none of the dozen or so archaeologists I have asked over the past few years could give me a straight answer either. But I have to know. 

There is an anchor in the conservation lab at the BUCH that's covered in calcium carbonate. I can clearly see coral skeletons and impressions from clam shells in the mass. The crust is clearly biological in origin - it is the remnant of calcifying marine animals. I saw my opportunity to get a straight answer, and I took it. Instead of asking an archaeologist whether an encrustation was biological in origin, I would point to something that I knew was biological and ask if it was an encrustation. 

Another "encrustation" example: coral on a
bottle at BUCH. I think the coral is Porites!

I started with one archaeologist in the crowd. Not everyone's English skills extend to field-specific jargon, so it took a second for me to explain what I was asking. Our interpreter stepped up to help, and after about 90 seconds of back-and-forth in English and Mandarin and me pointing vehemently at the anchor saying "This!" I got my answer.

Yes, that is an encrustation. 

Alright, people, we have an answer! An encrustation can be biological in origin. I was incredibly excited. Why does this matter? I'm so glad you asked. 

The central tenet of Maritime Heritage Ecology is that structural changes to a shipwreck over time (called "site formation") are coupled with changes in the biological community (called "succession"). I have had the opportunity to study how structural changes to a shipwreck drive change in the biological community, but we also need to understand the reverse process. How does biological colonization help or hinder the integrity of a shipwreck? 

Friends, enter "encrustation." Now that I have a clear answer, I get to write all sorts of proposals highlighting that corals and tube worms and mussels and other calcifying organisms create a protective crust around underwater cultural heritage. By understanding the recruitment of those organisms and assembly of those communities, we can better protect our history. Maybe we'll even be able to predict rates of structural change just by looking at what lives on a shipwreck. The sky is the limit. 

Brace yourselves, friends, because I have been given carte blanche. Encrustations can be biological. Now here come the proposals.