Seaweeds in the Sand

Below are some images of seaweeds I found exposed on the sand during a recent low tide. Each of these seaweeds, two kelps and two reds, are most at home in the low intertidal and shallow subtidal zones. I described the low intertidal zone, where I took these photos, in Finding Yourself in the Infralittoral Fringe. I’ve tried to correctly identify the marine algae featured here but I’m not an expert so I may have missed a couple, especially the reds. If you can help me out with the identifications, I would appreciate it.

Each of these are attached to rocks that lie beneath the surface and they have become partially buried by accumulating sand. I’ve illustrated fluctuations in sand level and seasonal burying in River of Sand.

Top left image: I’m pretty sure this is Ahnfeltiopsis, probably A. linearis. It’s a red algae that loves surf-swept rocks. Sand scouring isn’t a problem for this red.

Top right image: Winged kelp, Alaria marginata, a large brown algae. Check out the golden midrib.

Middle right image: A red algae I first thought was Ahnfeltiopsis gigartinoides, but now I’m having second thoughts. What about Prionitis linearis? Other ideas? Whatever it is, it’s a lover of surf and swirling sands.

Bottom image: Split kelp, Laminari setchllii, a brown algae. Long blades and short stipes make attractive underwater mini-forests.

Beach sand accumulates during the calm of summer, so if you get out on the the outer shores now, you should find sand levels high. If there are rocks or other structures around, you’ll find some some partially or completely buried organisms. Beach rocks make good markers for seasonal fluctuations in sand level. Find a favorite rock or other marker and follow it through the seasons; you’ll be amazed at how sand level varies.

If you are a lover of marine algae, there are some really nice websites out there. I’ve listed a few below that I enjoy looking at and that have helped me a lot:

The Guide to Seaweeds and Seagrasses: photos and helpful descriptions.

Seaweeds of Alaska: a standard TOS reference.

Seaweeds of the Pacific Northwest: photos and descriptions of 25 common seaweeds of the Washington coast.

Cory Janiak’s Flickr: photosets of marine algae – great photos and captions.

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