Thursday, August 26, 2010

Tide Pools at Rialto Beach

My wife and I just returned from a trip to Washington state. We visited lots of beautiful places, which have given me plenty of ideas for blog posts!

I couldn't decide which was the best, the wildflowers of Mt. Rainier or the tide pools of Rialto Beach. I flipped a coin and Rialto won, so presented for your enjoyment are some of the creatures lurking in its tide pools.

Rialto Beach is in the northwest corner of Washington, in Olympic National Park near the town of La Push. We hiked to the northern end of the beach, to a spot called "Hole-in-the-Wall". Here is how it gets its name (note the hole at the left end of the wall):


Winning in the bright color category is the Ochre Sea Star:


Although ochre is a sort of orangey-brown color, this sea star also appears in purple:


I was curious as to what caused these different colors in the same species, some of which were right next to each other:


The best answer is "nobody really knows". But another curious blogger has looked into this pretty closely, and their diet seems to be a likely factor. Eating mussels seems to make the sea stars orange, and barnacles seem to make them purple. Hole-in-the-Wall has an abundance of both, in fact there are barnacles growing on mussels:


So the color of each sea star may be determined by what it prefers to eat. Check out this interesting article for more details.

Here is a cool close-up of some Thatched Barnacles. I believe the green part is algae.


And some very weird looking things which I found out are Goose Barnacles:


Here are some Whelks at a barnacle buffet. You can see the empty shells of the ones they have already eaten.


Here is the only type of fish we saw, a Tidepool Sculpin:


Let's finish with some prettier creatures. These are two types of anemone, a Giant Green Anemone (guess which one that is) and an Aggregating Anemone (that's the other one). The Giant Green is pulling a mussel from its shell. The pink stuff across the top is Coralline Algae, with three Limpets munching on it. In the bottom left is some Red Algae.

5 comments:

  1. Makes me long for the west coast again! For more on Pisaster color polymorphism check out http://www.biolbull.org/cgi/content/abstract/211/3/248

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  2. Fantastic day at the beach! Those starfish are so cool - I've never seen a live one. The color differences remind me of hydrangea blooms, and how the bloom color is determined by the pH of the soil. I wonder if barnacles and mussels have notably different pH body chemistry?

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  3. Thanks for the comments.

    @Kevin - thanks for the link. I think that is the article referred to by the blogger I linked to above, although I don't have the entire article.

    @Amber - could be the pH, nobody knows for sure. One theory I saw was that the "base" color was purple, and the orange was caused by carotenoid pigments in the mussels.

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  4. Thank you for this most interesting post! I've lived in Washington state for 40 years now, and sailed all around Puget Sound. Never have made it out to La Push; the colors of the critters are just gorgeous!

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