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.
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.
This patch of Pyropia is rarely submerged, but it gets a lot of splash 
Blades tend to be translucent and lean toward iridescence 
Pyropia can completely cover intertidal rocks 
Pyropia will share its space 
Some forms have long narrow blades 
Pale yellow Pyropia 
Dark Pyropia draped over the foreground 
Broad reddish blades | Galiano Island 
Broad olive-colored blades 
Where sand burial is prevalent, you’ll sometimes see Pyropia poking out of the sand
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.
Bangia, showing off its true red 
Bangia looks like a limp mop of thinning hair
Endocladia muricata, nail brush
Endocladia is one of the high intertidal tufts.
Endocladia loves the tops of rocks 
Endocladia on the Mytilus bed 
Tiny spines and a wiry hand feel, even when wet, help identify Endocladia 
Endocladia is at home in the barnacle zone 
Endocladia is one of the common tufts of the higher zones
Gloiopeltis furcata
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
A band of Cumagloia andersonii (red) just above Ulva (green); a little Pyropia (blackish) 
Cumagloia andersonii shares upper intertidal space with B. glandula | Good looking June stalks 
You can see why they call it hairy seaweed 
The strands look rubbery, and they are! 
Hairy seaweed seems to love draping over a vertical surface 
You might pass right by Cumagloia andersonii without giving it much notice
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.
April is a good month to find Mazzaella parksii 
The base of the blades is deep purplish-red 
M. parksii is sometimes called frilly turf 
M. parksii playing its part in the high intertidal
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.
Crust phase; erect phase in the upper left | Galiano Island 
Mastocarpus, sharing high intertidal space with Fucus | Galiano Island 
Papillate and smooth blades | Seaweed Sorter says female Mastocarpus have papillae and males are smooth. 
Wide Y-shaped blade; lower arm curled behind 
Lovely Mastocarpus blades among acorn barnacles
Neorhodomela
This is Neorhodomela larix, black pine
Black pine can form good-sized patches 
Towards the lower intertidal, Neorhodomela can see seasonal sand burial 
Neorhodomela larix loves nothing more than draping down over its rock
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.
Cryptosiphonia woodii 
Splendid hanging tufts of C. woodii | Central Oregon 
C. woodii tufts often have a dark, matted appearance 
Southern Oregon sunrise illuminates a tuft of Cryptosiphonia woodii 
Floated branches in a finger bowl
Microcladia borealis, sea lace
Dark tufts are nondescript from a distance 
Branchlets on one side of the main branch 
Lovely detail in morning light 
Microcladia borealis showing off one-sided branching in a finger bowl
Halosaccion, sea sacs
The examples below are Halosaccion glandiforme.
A brown, a red, and a green | Orcas Island, WA 
Sea sacs also go by old man’s fingers | Orcas Island, Wa 
Memories of high tide, exposed sea sacs are filled with seawater | Orcas Island, WA 
Halosaccion, with some fellow reds | Central Oregon 
Halosaccion, with sea cabbage in the background | Central Oregon 
Finding Halosaccion on the beach as sea wrack isn’t too common, but it happens
Good chance this filamentous tuft is Polysiphonia.
A softball-size tuft of Polysiphonia (identification tentative) | Central Oregon 
A closer look at the filaments (note the tiny photobombing fish) | Central Oregon
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.
Look for beauty bush in the high and mid-intertidal 
Beauty bush is pure reddish-brown fuzziness 
Callithamnion pikeanum is at home in the mussel beds, and higher
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.
***
Plocamium
I’m not sure what species is/are shown here.
A bit of a mat 
Such a lovely seaweed 
In a finger bowl
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.
Tinge of Melobesia colors the foreground 
Melobesia mediocris on surfgrass 
Pits indicate a mature patch
I believe the images below show Calliarthron, and if they do, it’s probably C. tuberculosum.
Calliarthron in a clear pool | Central Oregon 
Look for white reproductive conceptacles on segment margins | Central Oregon
Dilsea californica
Dilsea diorama | The lighter red blades are Schizymenia 
Dilsea californica in a typical setting 
I’ve seen Dilsea referred to as leathery strap 
Longer Dilsea californica blades tend to take on a sickle shape 
Dilsea californica is at home is surf exposed settings
Farlowia mollis
Farlowia mollis, a low tide beauty 
Farlowia laid out to better expose structure (an attempt) 
Farlowia in a small tidepool 
I’ve read Farlowia is sometimes called tattered red seaweed
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.
***
Gloiosiphonia
I think this one is G. verticillaris. It’s a beauty.
Gloiosiphonia can handle sand scouring 
Gloiosiphonia verticillaris in a finger bowl 
This site experiences annual sand burial
Callophyllis?
A beautiful puzzler, small and erect. Drifted in on the tide
Callophyllis is a starting point here, not a certainty | Galiano Island 
Lovely fan-shaped blades | Galiano Island
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.
Mazzaella splendens lives up to all its common names 
M. splendens, sharing space on a rock wall 
M. splendens sports a short stipe 
M. splendens | Central Oregon coast
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 delesserioidesThis 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.
A disturbed clump, showing the base 
You can see the sand-filled bottom of the pool below 
Peering through surface ripples 
Disturbed strands show the branching pattern
Odonthalia floccosa
Odonthalia floccosa accompanied by Neorhodomela larix (background) | Central Oregon 
A bushy branch O. floccosa floated in a finger bowl | Central Oregon
Odonthalia floccosa f. comosa
Not super common on my home beaches, this shaggy red sure is a beauty.
Odonthalia floccosa f. comosa, facing the surf, just below the mussel bed | Central Oregon 
O. floccosa f. comosa doesn’t mind draping down a rock face | Central Oregon 
A tuft of O. floccosa f. comosa, off to the right, Endocladia | Central Oregon 
O. floccosa f. comosa‘s lovely locks | Central Oregon
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.
Ptilota, always a low tide treat 
Who could tire of Ptilota? 
There is a lot of detail in the branches and branchlets
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.
Found in a tangle of sea wrack 
Lovely branches and branchlets 
Floating in a finger bowl
Gastroclonium subarticulatum, sea belly
The blades (upper center) are a mystery to me | Orcas Island 
Neogastroclonium subarticulatum, Leathesia, and a kelp blade too
Osmundea spectabilis
Osmundea has a pungent odor and a pepper taste; so says Kozloff | Central Oregon 
O. spectabilis goes by red sea fern and sea laurel |Central Oregon 
Morning sun lights up Osmundea‘s blades | Central Oregon 
Wet blades are reflective and maybe a little iridescent | Central Oregon 
Osmundea on an anemone backdrop | Central Oregon
Sarcodiotheca gaudichaudii, succulent seaweed
I’ve seen S. gaudichaudii only at low tide on Salish Sea shores
***
Smithora naiadum, red fringe
***
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.
Polyneura, exposed at low tide 
Crisscross veins is a characteristic of Polyneura latissima 
Polyneura latissima is the only species of Polyneura in our area
Constantinea simplex, cup and saucer
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.
Delicate epiphytes on a bull kelp stipe 
An eye-catching red adorns a drift timber 
Drift bull kelp is aways worth a closer look
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
Are the frills and the blade the same species?
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 Alaska – reds.
Give the Seaweed Sorter App a try!
This page was updated on September 15, 2021.
