Reds, Rhodophyta

Below you’ll see examples of intertidal red seaweeds, mainly from the exposed surf-swept shores of the Oregon coast where they live on the rocks or in and around tide pools. You can expect to find many of them, as well as some subtidal forms in sea wrack. Some of these seaweeds are easy to identify with field guides and online resources (see References, below). Others are puzzling. If you find a misidentification, please let me know. There’s nothing new here, just photos of the reds I’ve come across and a natural history note if I can think of something that hasn’t already been said or seems underemphasized. I show examples I can’t identify too. Please drop me a line if you can resolve a mystery red.

Sea sacs

Common names are my choice. I lean on Algaebase for scientific names and other juicy nuggets, and I learn a ton by browsing the pages of Druehl and Clarkston (2016) and Kozloff (1993). 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. All photos are mine, and all are from northern Oregon shores unless noted in the text or captions.

Let’s explore some reds!

Pyropia, nori
There are plenty of species. I can’t sort those out, but I can show examples ranging from the mid to high intertidal. Pyropia leans toward iridescence, but its degree is variable. Kozloff says they appear oiled. You’ll see that in some of the images below. It’s not uncommon to find fragments washed up on the beach.

Bangia
You’ll find Bangia on rounded high intertidal rocks, where it looks and behaves like thinning human hair. To illustrate this, I featured Bangia in A Brief Account (with Video!) of the Bangia-Human Hair Resemblance.

Endocladia muricata, nail brush
Endocladia is one of the high intertidal tufts.

Gloiopeltis furcata
I didn’t notice this unassuming red ’til I took a closer look at the periwinkles that seemed to like it.

You can see why Gloiopeltis furcatais somethimes called red-brown mat weed | Galiano Island

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Cumagloia andersonii, hairy seaweed

Red Crusts
There are enough intertidal red crusts to make identifying them an enjoyable challenge. When it comes to red crusts, the guides listed on this page suggest Hildenbrandia, the crust phase of Mastocarpus, and the basal crusts of a few other reds. Here I feature two seemingly distinct forms: a thin red crust and a thicker darker one. Both are from the low intertidal. If you have ideas about what they are, please let me know.

These images are from April 2018 along a small reach of a rocky shore. The crust is thin and hard to the touch and seems to be associated with red blades.

The images below are from May 2021. The crust seems a little thicker and darker than the crust shown above. The look here is more like a dripping of hard candy or dark caramel. Its surface is hard, and a common theme is the presence of branched corallines.

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.

Neorhodomela
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.

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Plocamium
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.

I believe the images below show Calliarthron, and if they do, it’s probably C. tuberculosum.

Dilsea californica

Farlowia mollis

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.

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Gloiosiphonia
I think this one is G. verticillaris. It’s a beauty.

Callophyllis?
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.

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Turkish towel, Chondracanthus, in the drift line

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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.

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Red sea leaf, Erythrophyllum delesserioidesThis fragment washed ashore in a mass of drift macroalgae.

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Red sea leaf, Erythrophyllum delesserioides

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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 

Odonthalia floccosa f. comosa
Not super common on my home beaches, this shaggy red sure is a beauty.

There are a few delicate fern-like Neoptilota and Ptilota on our low shores. The examples below are among them.

The three images in this set look a lot like Ptilota filicina, common in the low intertidal.

Also in the Neoptilota and Ptilota collection, here’s something a little different. The three images in the set below are of the same drifted mass. There’s a decent superficial resemblance to Ptilota hypnoides, but things are ever so much more complicated than that.

Gastroclonium subarticulatum, sea belly

Osmundea spectabilis

Sarcodiotheca gaudichaudii, succulent seaweed
I’ve seen S. gaudichaudii only at low tide on Salish Sea shores

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Smithora naiadum, red fringe

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Polyneura latissima
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.

Constantinea simplex, cup and saucer
Always a low intertidal treat.

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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.

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Bladder chain, Stephanocystis osmundacea, with a delicate epiphytic red

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A rose red mystery

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Rose-purple frills on a purple blade
Are the frills and the blade the same species?

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References

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 Alaskareds.

Give the Seaweed Sorter App a try!


This page was updated on September 15, 2021.