Saturday, July 8, 2017

Arts and crafts: part 2

(Former) fouling panel inhabitants
"Ooh, it kind of looks like pasta salad! Maybe like a Mexican salad, you know, with black beans and yellow corn. It doesn't look appetizing though."

My intern was standing over the lab bench, looking at a pile of ascidians and bryozoans I had just pulled off of a fouling panel. I gave her a sideways, confused look. Pasta salad, really?

We had been working all day, pulling invertebrates off of fouling panels, leaving only strategically-chosen individuals behind. We were setting up an experiment in Eel Pond to parallel one we set up at the WHOI pier two weeks ago. For both experiments, we want to find out how the first species to settle on a fouling panel and dominate the community influences other species that might settle. I suspect that the first dominant species inhibits other organisms from recruiting to the panels, either by consuming their larvae, outcompeting them for food, altering the flow of water over the plate, or just taking up space. To figure out if inhibition is happening and if so, which one of the above scenarios is true, we outplanted plates with live animals and with mimics - non-living structures with similar shape and texture. 

The experimental panels, randomly arranged on a PVC
backing and ready for deployment in Eel Pond. The top row is
not part of the experiment. You can see panels with live
Botryllus, some with globs of sealant, some with flat sheets
of sealant, and blank controls. 
The experiments at both sites are the same in principal, but the main difference is which species dominates. At the WHOI pier, hydroids covered the panels, but in Eel Pond, it's all about the ascidians. Botryllus schlosseri, to be more precise. It's a colonial species that forms thick, squishy mats and can easily overgrow other organisms. We removed all species except Botryllus from some fouling panels, and on others, we replaced the living animals with mimics. 

How does one mimic a colonial ascidian species? We used silicon aquarium sealant because it has the same basic texture as ascidians and can be easily smeared on the panels. We used thick globs on some panels to imitate the topography of Botryllus colonies and flat sheets of sealant on others just to take up space. It will be interesting to see if there are any differences among the treatments at the end of the summer!

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