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Saturday, September 15, 2012

An Abundance of Life in San Juan Channel

Recently I got a newsletter update from the SeaDoc Society that had an interesting article about a sand wave in the middle of San Juan Channel. Underwater sand waves can be created by strong tidal currents, which San Juan Channel has plenty of. Here's a graphic from a paper written by Friday Harbor Lab student Jennifer Blaine showing the location and bathymetry of the sand wave:


Living in the sand wave, they found, are an estimated 44 million immature sand lance, a forage fish that is an essential link between plankton and higher order predators like sea birds, pinnipeds, and cetaceans. That explains why you often see a lot of seabirds in the middle of San Juan Channel! This rhinoceros auklet has a beak full of sand lance - it's a photo I took in San Juan Channel is July:


These thoughts were in my mind as I headed out yesterday to volunteer for a San Juan Channel bird survey. These transect surveys are part of a citizen science effort to get more data on the birds of San Juan Channel and create a year-round dataset to supplement the fall data that has been collected by the Friday Harbor Labs for the last bunch of years. I went on the inaugural volunteer survey in April, and this was my first one since then.

On yesterday's survey I saw 11 different bird species, but hundreds and hundreds of actual birds. The most abundant were the common murres, of which I saw more than 500. Also abundant were rhinoceros auklets and lots of gulls, including glaucous-winged, mew, California, and Heermann's. We also turned up about ten marbled murrelets (an impressive number), a few red-necked phalaropes, and a single Pacific loon still in stunning breeding plumage. Double-crested and pelagic cormorants rounded out my list. Compared to April, we had a lot more marine mammals in our survey zone - both harbor seals and harbor porpoise.

On our way out to do the survey, however, we had another task: an invertebrate release! One of the other volunteers had been doing a marine invertebrate educational unit in local classrooms and was returning some of the collected specimens back into the channel. We were all fascinated to see all the invertebrates up close before we released them! Here's the underside of a sunflower star (Pycnopodia helianthoides), a sea star that usually has between 15 and 25 legs:


I should have taken more pictures, because there were lots of other cool sea stars to look at too. Two that impressed me were the leather star (Dermasterias imbricata), with its intricate red color pattern on olive green skin, and the slime star (Pteraster tesselatus), a fat little sea star that produces a snot-like clear mucous. (Guess who got to release that one? Me!)

I did, however, take some pictures of this umbrella crab (Cryptolithodes sitchensis). This was a female, and was comparatively drab in coloration compared to some others of her species, which can come in brilliant reds and oranges. She was still a marvel to look at though - her carapace is so wide it covers her legs entirely. They really blend into the rocks and can be very hard to see:


Fish, birds, invertebrates - even when the whales aren't around much, there's still a lot to look at and learn about here in the Salish Sea!

1 comment:

Vera said...

Very cool stuff, Monika!