Below you’ll see examples of intertidal red seaweeds, mostly from the exposed surf-swept shores of the Oregon coast. You are likely to encounter these reds on the rocks or in and around tide pools, and you’ll see a few of them as drift on the beaches. Some are easy to identify with field guides and online resources (see References, below). Others are tricky. I try to get the IDs right, but I’m far from an expert. I apologize for any misidentifications; if you find one, please let me know. There’s nothing new here, just my photos of common reds and a natural history note if I can think of something that hasn’t already been said or seems underemphasized. I show some reds I can’t identify too. Please drop me a line if you can resolve a mystery red.
I more or less follow Lamb and Hanby (2005), showing species in the order they might be encountered on the rocky shore, from highest to lowest in the intertidal. Common names are my choice. I lean on Algaebase for scientific names, and I learn a ton by browsing the pages of Druehl and Clarkston (2016) and Kozloff (1993). All photos are mine, and all are from exposed northern Oregon shores unless noted in the text or captions.
Let’s explore some reds!
There are plenty of species. You’ll see the ones shown here as Porphyra in some of the guides. According to Druehl and Clarkston (2016), most of the Porphyra we encounter in Oregon have been reassigned to Pyropia. Those featured here are common on the high intertidal rocks. Pyropia is rubbery to the touch and somewhat iridescent. A heavy growth can obscure rocky details, making for treacherous footing.
You’ll find Bangia on rounded high intertidal rocks, where it looks and behaves like thinning human hair. Bangia is featured in A Brief Account (with Video!) of the Bangia-Human Hair Resemblance.
Endocladia muricata, nail brush
Endocladia is one of the common high intertidal tufts.
I didn’t notice this unassuming red ’til I took a closer look at the periwinkles that seemed to like it.
Cumagloia andersonii, hairy seaweed
Hildenbrandia, red rock crust, rusty rock
Rich reddish hard brown crusts are a bit of a mystery to me. I think these images feature Hidebrandia. They’re all from fairly low intertidal settings, and they’re hard, resisting indentation by my fingernail.
Mazzaella parksii, horn-of-plenty
A fun one to know; it’s another one of those reds that aren’t very red. Look for it on surf-exposed high intertidal rocks. On my home beaches, March through May is a good time to find nice-looking patches.
Mastocarpus, Turkish washcloth
One of the common bladed reds in the mid to upper intertidal. I used to confidently call the bladed form shown below Mastocarpus papillatus. But Druehl and Clarkston (2016) explain the genus is a complex of variable species. To make things more interesting, Mastocarpus also has a black crust life history phase.
This is Neorhodomela larix, black pine
Cryptosiphonia woodii, bleached brunette
Cryptosiphonia woodii can be dense and turfy or show up as isolated tufts, as shown here. It is delicate when exposed and can become limp and matted. The branch tips supposedly bleach to a blondish color in the summer, accounting for the common name. I haven’t seen much of that.
Microcladia borealis, sea lace
Halosaccion, Sea sacs
The examples below are Halosaccion glandiforme.
Good chance this filamentous tuft is Polysiphonia.
Callithamnion, beauty bush
The images below probably show Callithamnion pikeanum. Some references mention the branches are often covered with diatoms. I don’t know if the distinctive fuzzy look in the images below is due to a covering of diatoms or an inherent fuzziness.
Bleach weed, Prionitis
With several species of Prionitis in our area, I’m hesitant to make a specific identification call on this one. When conditions are right it can produce dense growth and a thick somewhat treacherous mat of blades at low tide.
I’m not sure what species is/are shown here.
Melobesia, seagrass crust
Easy to find whenever the tide is low enough to expose surfgrass beds. Melobesia can also be found in drifted surfgrass among sea wrack.
Flat-tipped forked seaweed, Ahnfeltiopsis linearis
I’m pretty sure about the ID here, but like all of these reds, my IDs are open to interpretation. Attractive and photogenic, A. linearis is at home with periodic sand burial. Ahnfeltiopsis was featured in Seaweeds in the Sand.
A beautiful puzzler, small and erect. Drifted in on the tide
Turkish towel, Chondracanthus exasperatus
When I see Chondracanthus, it’s usually as drift on the sandy beaches. Chondracanthus was featured in a brief older post, Turkish Towel.
Mazzaella splendens, rainbow leaf
With its splendid scientific name, common names don’t seem particularly warranted, but besides rainbow leaf, you’ll see splendid iridescent seaweed and iridescent seaweed. Its big blades will give you a lot of looks. Here are a few. Note: M. splendens is variable enough that I’m not going to claim I’m certain these are all M. splendens, but I think they are.
Cryptopleura or Hymenena
Or maybe both! These reds washed ashore in a diverse mass of drift macroalgae. The irridescence stands out pleasingly in the drift line. My identification is tentative and general; please drop me a line if you have identification ideas.
Red sea leaf, Erythrophyllum delesserioides
This fragment washed ashore in a mass of drift macroalgae.
I’m pretty sure the examples below are in that Gracilaria/Gracilariopsis crowd
These are all from semi-protected sand-filled pools on the central Oregon coast
Odonthalia floccosa f. comosa
Not common on my home beaches, this shaggy red threw me for a while. It’s sure a beauty.
Red wing, Ptilota filicina
There are a few species of delicate fern-like reds in the lower intertidal. The coverage of these in the references cited below is variable and kind of confusing. Thus, identifying most of these with certainty isn’t possible for me. I like the treatment of P. fillicina in Mondragon and Mondragon (2010) and Oregon’s Rocky Intertidal by Kate Krieg.
Succulent seaweed, Sarcodiotheca gaudichaudii
I’ve seen S. gaudichaudii only at low tide on Salish Sea shores.
Red fringe, Smithora naiadum
Simplicity is rare among the reds, but we’ll take it where we can get it. Any Polyneura encountered on Pacific northwest shores is P. latissima.
Cup and Saucer, Constantinea simplex
Always a low intertidal treat.
Something approximating Antithamnionella, red sea skein
If indeed it is Antithamnionella, you’ll see it as Irtugovia in some of the guides. It also goes by hooked or red skein. There are several filamentous reds which are hard to tell apart from photos alone. Antithamnionella a common epiphyte on bull kelp stipes, so I’m trusting that’s what at least two of these images show. They all seem to have the same look so I’ve lumped in the reds on the drifted timber too.
Mysteries From the Drift Line
A lacy epiphyte that gives a much different impression than Antithamnionella (above). There’s a decent chance it’s Pterochondria woodii.
A rose red mystery
Rose-purple frills on a purple blade
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.
Online Resources for Reds
Netarts Bay Today – reds.
Biodiversity of the Central Coast – reds.
Seaweeds of Alaska – reds.
Give the Seaweed Sorter App a try!
Note: This page was updated on Feb 13, 2020.