Wednesday, August 12, 2015

Barnacle cake

Squatting next to a cement block on the deck, Caitlin looked up at me with a goofy grin on her face.

"Hey Kirstin!" she called, "I'm already bleeding in two places! That's how you know it's good field work!"

I rolled my eyes. Yes, we give blood, sweat, and tears for our science, but I'm not sure that bleeding should ever be considered a good thing. I looked at Caitlin's hands, then examined my own. Both of us had countless little cuts and scrapes, the inevitable result of getting friendly with barnacles. Because today, we had lots of barnacles.

R/V Pluteus at OIMB's dock
We were offshore on OIMB's 42' research boat, R/V Pluteus, recovering the settlement plates I outplanted earlier this summer. The original plan was actually to go out every three weeks to recover the settlement plates, but that just didn't happen. I already told you how bad the weather was on deployment day, and it only got worse after that. Then the boat needed some repairs. Then the boat needed more repairs. Then the boat captain retired. Then I went on a cruise in the Atlantic. Then I got back, and the boat captain was still retired.

So I got creative. It turns out there's one other OIMB employee capable of driving the boat, and after a little convincing (read: bribery with baked goods), he was willing to spend a day offshore. By this point, my blocks have been underwater for 12 weeks, so I had no idea if they would even still be there. I grabbed some volunteers, took 2 Dramamine, and headed out to find them.

Glassy and perfect.
We actually did pretty well. For starters, the weather today was fantastic. The sea surface was flat, glassy, and calm, which kept me from being too queasy and also made it easy to spot the orange floats at the surface. We found 4 out of the 10 cement blocks I had outplanted, which I think is pretty good, considering how long they've been out there. It's possible that the floats for the other 6 blocks were run over by fishing boats, tangled and dragged underwater, or any number of catastrophic fates. Whatever happened, they just simply weren't there.

Even so, we were able to retrieve four of the cement blocks and remove the settlement plates from them. Everything was covered in barnacles. The plates, the blocks - even the rope and the zip ties. It was one solid barnacle cake. You know, when this experiment first started last year, I naïvely expected a variety of organisms, with clean, distinct patterns in abundance and diversity among stations. Not so. I guess if I owned a boat, I would have known better. I mean, barnacles are ubiquitous fouling organisms. My blocks were outplanted at 65 m depth, not actually that far offshore. I should have expected them to take over, right?

One of my cement blocks (settlement plates already removed)
covered in barnacles. The brown dots on the front side are
juvenile whelks, or barnacle-eating snails.
Well, fortunately for my future publication prospects, it's not quite that simple. Barnacles may have been expected on my settlement plates, but the particular species of barnacle that showed up was not. I identified the species as Hesperibalanus hesperius, and if that name sounds unfamiliar to you, you're not alone. I had never heard of it either. The only information I was able to find on this particular barnacle species is (1) that it exists, and (2) that it lives on the North American west coast north of San Francisco. That's not very specific information. 

After seeing the dense barnacle recruitment today, I started to think it would actually make a pretty interesting story. After all, I observed high larval recruitment of a species that isn't very well-known, and the cement blocks with the highest recruitment were essentially located in the middle of a sand flat. That's weird. There are a number of ecological concepts I could draw on for a discussion of my findings, including the Desperate Larva Hypothesis (look it up!). Maybe all the barnacles settled on my cement block and the attached settlement plates because they just wanted to settle on something, anything, and it was the only solid object in the area. 

In short, it feels good to finally have my settlement plates back, and I'm actually getting pretty excited about my findings. I doubted for a long time whether the data from my experiment would actually be useful, but I'm convinced now that they are. I'll end up answering a different question than I set out asking, but it's good data all the same.  

Long live barnacles.

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