Greens, Chlorophyta

Below are examples of intertidal greens from the surf-swept shores of the northern Oregon coast. A fair number of the green seaweeds pose identification challenges for me, so I’m happy with genus-level identifications when I can get there. Please drop me a line if you see a mistake. My organization loosely follows Kozloff (1993) and Lamb and Hanby (2005), showing species you might encounter in the field, from highest to lowest in the intertidal. I lean on Algaebase for nomenclature and taxonomy. Common names are my choice. I learn a ton by browsing the pages of Druehl and Clarkston (2016) and Kozloff (1993). You’ll find a bunch more easy-to-find references at the bottom of the page.

Let’s explore some green seaweeds!

Ulva intestinalis
In the right setting, frequently at freshwater seeps, U. intestinalis can creep to the highest reaches of the splash zone, above the highest barnacles and limpets. It’s also found in high tidepools.

Cladophora, sea moss
Cladophora is frequently found with periwinkles, mussels, thatched barnacles, Fucus, and Endocladia.

Chaetomorpha (probably)
I think the examples below are Chaetomorpha; there are other unbranched filamentous greens with large cells so I do have some uncertainty. These are all from mid to maybe high tide pools. I’ve highlighted the large cells in the lower right panel below.

Sea lettuce
Leafy, bladed Ulva is common on the exposed coast and flourishes, with lush growth, in semi-protected niches. I won’t speculate what species are represented below.

Ulva taeniata, sea spiral
Sea spiral is a distinctive bladed Ulva. It’s at home in and around sand-filled tidepools.

Acrosiphonia coalita, green rope

Codium fragile, sea staghorn

Codium setchellii, spongy cushion


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.

This page was updated on August 19, 2021.

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