That Green Slime or Sea Goo on Oregon / Washington Coast: What Is It?

Published 04/02/21 at 10:05 PM PDT
By Oregon Coast Beach Connection staff

(Oceanside, Oregon) – It’s kind of intriguing, sometimes smelly, and it is truly slippery and fairly dangerous. It’s easy to slip on this dark green stuff covering rocky areas of the Oregon or Washington coastline and crack your head. (Above: sea lettuce in Oceanside)

You can find it just about anywhere there are rocky slabs or terrain close to the ocean, but they are cause for caution.

What is it?

On Oregon and Washington beaches, it’s sea moss, sea lettuce, rockweed and sea cabbage. Mostly it’s two forms of sea lettuce.

One common kind of Sea lettuce, according to Tiffany Boothe of Seaside Aquarium, has the technical name of Ulva fenestrata, and Boothe said it is a green macroalgae that's distributed by the ocean from the Bearing Sea to Chile. It's actually found around the world and is composed of eight individual species. There is also the Sea Lettuce called Ulva intestinalis. Also called gutweed or hollow green weeds, it is a green algae with flattened green tubes.

Ulva fenestrata at Depoe Bay

Fenestra is more leaf-like. Intenstinalis is longer and grassier, but in some ways resembles green cotton candy.

You’ll also find Then there are the dead man's fingers (Codium fragile), which are dark green with fingerlike blades.

Various algae and a ghost forest at Sunset Bay, Coos Bay (photo courtesy Brent Lerwill)

There are other types of seaweed as well, but both kinds of sea lettuce are mostly what you’re looking at.

Boothe said sea lettuce is a very important food source as it feeds a myriad of sea critters. Sea urchins, crabs, nudibranchs and even fish feed on this delicious plant.

But the surprise is you could – technically – munch on it while on the beach.

“It is also consumed by humans in soups, salads, and as a substitute for nori (the popular seaweed used in preparing sushi rolls) in sushi,” Boothe said. “Nutritionally, it is very healthy. Not only is it high in iron and protein, it is also packed full of vitamins and minerals. In Scotland, Ulva has become quite popular.”

Boothe said sea lettuce can be found attached to hard substrates, such as pebbles, shells, or rocks, or they are free floating in calm bays and estuaries.

Both kinds of sea lettuce at Oceanside

You'll typically all this on low-lying intertidal areas at mostly rocky regions, like those at Sunset Bay in Coos Bay, Harris Beach near Brookings, Haystack Rock at Cannon Beach, Bandon, Yachats, Washington’s Rialto Beach or Waikiki, Oceanside, Depoe Bay and more. You won't find it on sandy beaches like Seaside, Waldport, Gold Beach, Newport or Lincoln City, unless there are patches of rocks around the tideline.

Still, there's more going on in these photos.

“I think you may be looking at two or three different species of seaweed, each with their own distinct characteristic and story.” Boothe said of some the photos provided.

Whatever you find, they’re the things that make you slip and fall on rocky areas, which is extremely painful as you hit the stones or slabs. However, if you’re lingering near an ocean edge, that’s where these things become life-threatening. If you slip on a place like that on the Washington coast or Oregon coast you’ll likely be gone.

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MORE PHOTOS BELOW

Sea cabbage

Sea cabbage, next to Devil's Punchbowl, near Depoe Bay

Sea cabbage are the darker olive-brown, blade-looking things that are often quite large. Hedophyllum sessile can’t resist wave action too much, and you’ll find them up to two feet long.

Sea moss is also common. Endocladia muricata looks more like a browning old bush, and they’re not very big.

Marine gardens at Devil's Punchbowl: here it really lives up to its name with all sorts of algae

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