Monday, May 25, 2009

Searching for Bivalves

Hmm . . . so much for twice per week! But I do have an excuse - the winds finally died down enough for us to go out starting Thursday and the waves were actually quite calm the last few days, so we could actually get work done! It's still cold though - and it hasn't been all that sunny either.

We finished deployed temperature loggers and checking my bivalve recruitment spat collectors (although that begins again very soon, since we try to do it every 2 weeks) and have moved on to a new project: random surveys around the atoll for bivalves. So far, we've done 10 sites in the SW patches and sand, N backreef, and NW patches. The first two were dictated by weather, since we can only work in the NW area (Welles Harbor) when winds are pretty low since it's not protected by the island or raised rim.

For those who don't know, a bivalve is, broadly, a mollusk with two shells, like a clam, mussel, or oyster. The main point of these surveys is to estimate the population size and distribution of black-lipped pearl oysters Pinctada margaritifera (above), since I'm working on the population dynamics and restoration of this species. However, we've expanded it to include other large bivalves, such as the Chama to the right.

We've been surprised to find very few bivalves for the amount of time we spend looking, but we've seen some other cool things, like branching coralline algae, nudibranches (first two below), sea stars, another huge marine debris net that Kate managed to bring back to the island, and a big channel marker buoy with a solar panel, light, and huge chain. The branching coralline algae (last photo below) was interesting to me because I've seen sediment samples from Midway with lots of branching coralline algae, but hadn't noticed it alive before so I took some photos of that. We also found one site with an extraordinary diversity of algae - seemed like at least 10 species fairly common.

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