Friday, June 16, 2017

Squarepants

Friends, I hope one thing you can learn from this blog is how many diverse and fascinating creatures there are in the ocean. Even a habitat as ubiquitous and mundane as a floating dock can be covered by all sorts of captivating fauna. I have told you about the ciliates; I have impressed on you the importance of hydroids. I have shown you barnacles and spirorbids and bryozoans. I have drawn your attention to the ascidians. But there is one organism I have not yet shown you - sponges.

Halichondria panicea on one of my fouling panels, surrounded
by two spirorbids and a bryozoan. Photographed at 50x
magnification.
No, not the kind you use in your bathtub, although bath sponges were harvested from the ocean in centuries past. Marine sponges are sessile animals that filter the water for food.  If you've been reading this blog for a while or clicked on any of the links above, you'll notice that this is lifestyle is a common theme - fouling communities are by definition made up of animals that attach to a surface, and animals that live attached to surfaces tend to filter the water for their food.

There's only one species of sponge showing up on my fouling panels right now, and it only appears in Eel Pond. It's Halichondria panicea, and it's actually a non-native species. It was introduced to New England, presumably a long time ago, though nobody is quite sure when. It's been around long enough to become well-established in the fouling community.

When I first started seeing Halichondria on my panels, I didn't know what it was. It took me a little while to clue in that it was a new organism. Once I recognized its porous texture, though, I could identify it almost immediately!

Sponges are typically slow-growing but are good competitors, so they tend to dominate older communities. I anticipate that Halichondria will come to occupy larger and larger amounts of space on my fouling panels as the summer goes on. We'll see if I'm right!

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