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THE NATURALIST
by Dave Evans

Tidepool Discoveries
August 27, 2001

We finished the tidepool excursions for the summer at Fort Abercrombie State Historical Park this past weekend. The fine large group of people included, along with our usual off-island visitors, an Anchorage Girl Scout group that was camping in the park, a Kodiak family with visiting relatives, and just-arrived Coast Guard personnel.

The feeling of regret I have about seeing the last of these sessions must be caused by the fact that tidepooling may be my favorite nature activity at Fort Abercrombie. For me, the last tidepool walks mean that the Park season is winding down. I think that the reason tidepooling appeals to me is that it forces me into a continual discovery mode. I see different things around me every time I take a group out, and tidepooling is one of the most unpredictable Park activities in which I'm involved. We seem to have particularly good fortune when children are along--they're closer to tidepool level, and, since they don't know what they're expected to see, often have the knack of picking up on the completely unexpected.

We sometimes see animals with which we are quite familiar, but there's a sense of newness when they show behavior we've never seen before. Those observations take field biology from the level of locating and identifying organisms, enjoyable enough at the early stages of tidepooling, to newer, and perhaps more exciting levels of seeing how the animals are actually behaving in the natural environment.

We've discovered the large snails called hairy tritons in the midst of a reproductive frenzy. That may not be as dramatic as it sounds--they're snails, after all. But, in an impressively synchronized display of egg-laying, every rock in one area had several individuals that were extruding perfectly spiral series of what looked like pink corn kernels.

The big sunflower stars (slurpies) are common down on the Monashka Bay shore. Last weekend was the first time, though, that I've seen them actually interacting with other sea life. A large slurpie was cruising through a pool faster than I've ever seen a sea star move. It was moving in a fixed direction, too, which can be problematic for a sea star. What was equally spectacular was that the other sealife in the pool was running or swimming away from it just as fast as it could. Dozens of little hermit crabs were frantically ankling for their lives, clued in to the situation by chemical cues given off by the predator.

We often come across sizeable octopi during the good low tides, but our best find last month was a single tiny individual, so small that it was virtually transparent. It had nothing to hide. We could look through it and see the inner workings in action--heart beats (all three hearts!) and respiratory pulsations. I think we all came away with a new appreciation of these animals, when we could see those fundamental physiological processes actually on display.

One of our strangest recent finds was a sea spider, really a rather rare animal up here. It was a bizarre looking crustacean in that it had a front body part bearing mouthparts and legs, but there was just no sign of an abdomen--where all other related animals keep their digestive, circulatory, and reproductive systems. I'm still not quite sure how this organism gets along in life. It apparently eats by sucking juices from slow-moving animals like sea anemones.

There's an Alutiiq saying expressing tidal rhythms in terms of using the plants and animals as food: "When the tide goes out, the table is set. When the tide comes in the dishes are washed." The saying gets to the same rhythmic renewal that makes me appreciate this kind of field activity so much. I know I can go down to an area where I've been dozens of times, and I can be guaranteed of seeing something completely new and wondrous.


http://www.kadiak.org/naturalist/tidepool.html Updated 2001 August 28

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