Below are examples of intertidal green algae from the exposed surf-swept shores of the northern Oregon coast. You have a good chance of encountering all of these greens on the rocks or in and around tide pools. You’ll probably find drifted Ulva on the beaches. The greens are tricky. On this page I’m happy shooting for genus level identifications. Even so, you may find a mistake. If you do, or if you can help me solve an identification mystery, I hope you’ll drop me a line. Mostly, what I want to do is provide some new looks at common greens, and a natural history note, if I have something to say that hasn’t already been said.

The organization loosely follows Kozloff (1993) and Lamb and Hanby (2005), showing species in the order they might be encountered in the field, from highest to lowest in the intertidal. Common names are my choice. I lean on WoRMS for scientific names, and Algaebase when I want to dig deeper. I learn a ton by browsing the pages of Kozloff (1993) and Druehl and Clarkston (2016). All photos are from northern Oregon unless noted in the caption.

Ulva is a diverse group. I’ve found that it can be difficult for us casual beachcombers to say with much certainty what species we are looking at. As if that’s trouble enough, Ulva has similarities to other greens. Sometimes even landing on the right genus is a leap of faith. The examples below are my leaps of faith.

Ulva intestinalis Everybody says it’s ubiquitous around high intertidal and splash zone seeps. The examples in the gallery below are all from vertical rock walls with freshwater seeps, so I’m guessing they’re all U. intestinalis.

Here’s Ulva intestinalis, I think, in a high tide poolrather than a rock wall. This pool gets a variable fresh water flow. Salinity here varies a lot!


Ulva in a high sand-filled tide pool. This pools gets fresh water flow during much of the year. The long narrow blades look a lot like what Kozloff and Oregon’s Rocky Intertidal call U. taeniata, but there are other options.


Below, Ulva carpets a high sand-scoured rock- I’m pretty sure it’s Ulva.

Leafy Ulva is common on the exposed coast, and really flourishes, with lush growth in semi-protected niches. I can’t speculate what species are represented below, but it’s reasonable to refer to the bladed forms as sea lettuce.

For a few other photos see Sea Lettuce, Ulva.


CladophoraSea moss is characteristic of the upper midlittoral, found with mussels, haystack barnacles, Fucus, and Endocladia.


Urospora? – This ID is tentative but you can’t really argue with the common name, green hair.


Spongy cushion, Codium setchellii Codium setchellii, a resident of the low intertidal, appeared in Spongy Cushion, Codium setchellii



Druehl, L. D. and B. E. Clarkston. 2016. Pacific Seaweeds: A Guide To Common Seaweeds of the Pacific Coast. 2nd ed. Harbour Publishing Co.

Harbo, R. M. 2011. Whelks to Whales: Coastal Marine Life of the Pacific Northwest. 2nd ed. Harbour Publishing Co.

Kozloff, E. N. 1993. Seashore Life of the Northern Pacific Coast. 3rd ed. University of Washington Press.

Lamb, A. and B. P. Hanby. 2005. Marine Life of the Pacific Northwest. Harbour Publishing.

Mondragon, J., and J. Mondragon. 2010. Seaweeds of the Pacific Coast. Shoreline Press.

Sept. J. D. 2009. The Beachcomber’s Guide to Seashore Life in the Pacific Northwest. Revised ed. Harbour Publishing.

Web Resources

The green algae page on the Netarts Bay Today website is one of the best references you’ll find for the Pacific Northwest.

Biodiversity of the Central Coast has a great page on greens.

Seaweeds of Alaska is a standard reference for the Pacific northwest. It has a great green algae page.

And, you can, and should, scroll down to the green algae section of Oregon’s Rocky Intertidal by Kate Krieg.


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