Seaweeds of the Pacific Northwest

Desmarestia aculeata

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Color: Brown
Shape: Branched, Bushy
Texture: Smooth
Size: Up to 3’+
Zone: Low Intertidal to Subtidal
Range: Alaska to Oregon

Description: This highly branching seaweed is connected to a small, disc-shaped holdfast. The many thin, round branches give it a busy appearance. 

Edibility: Do not eat. 

Distinctive characteristics: Releases sulfuric acid when damaged. 

Collection notes: Best to avoid. The acid released by this seaweed will destroy other seaweeds collected if left in the same container.

Phylum: Phaeophyta (Brown Algae)
Previous names: Fucus aculeatus, Desmarestia intermedia
Similar species: Desmarestia viridis

Alaria marginata

Color: Brown (Carmel to Olive Green)
Shape: Blade
Texture: Smooth
Size: 2’–6’+
Zone: Low intertidal to subtidal
Range: Alaska, British Columbia, Washington, Oregon, California

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Description: Large, thin blade with flat midrib, May be torn on edges or ends or appear ruffly. Stipe up to 24” long, often with groups of leaf-like sophorophls on each side (“wings”). Branched, root-like holdfast. 

Edibility: Delicious! Great in miso and other soups. Use as a vegetable. High in calcium and other vitamins and minerals. 

Distinctive characteristics: Center rib. “Wings” (groups of leaf-like sophorophls on each side of the stipe.) One of many Alaria species that look similar. All are edible.

Collection notes: Use scissors to cut off upper part of blade. Leave the leafy “wings” as these are the reproductive parts of the seaweed that will produce next years’ seaweed.

Phylum: Phaeophyta (Brown Algae)
Previous names:
Similar species: Other Alaria species, Laminaria species

Mastocarpus papillatus

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Color: Brown (Yellowish, Reddish, Black when Dry)
Shape: Irregular Blade
Texture: Bumpy
Size: Up to 6”
Zone: Intertidal
Range: Alaska to Mexico

Description: Short, upright irregular blades that are rubbery and covered with small bumps. The ruffly blades taper to a small stipe and holdfast.

Edibility: Used to make carrageenan. Can be boiled to make a gel-like thickener at home as well. 

Distinctive characteristics: Forms a black tar-like “crust” on rocks during one phase of its lifecycle. 

Collection notes:

Phylum: Rhodophyta (Red Algae)
Previous names: Gigartina papillata, Gigartina sitchensis, Petrocelis franciscana, Petrocelis middendorffii, Gigartina mamillosa, Gigartina dichomta, Gigartina cristata
Similar species: Chondracanthus exasperatus (Turkish Towel)

Chondracanthus exasperatus

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Color: Red (Dark red to purple when young, red to yellow when older, can be iridescent when wet.)
Shape: Irregular Blade 
Texture: Bumpy
Size: 12–32”
Zone: Low intertidal and subtidal
Range: Alaska to Mexico

Description: Broad blade, irregular edges. Small discoid holdfast, one or more blades per hold fast. Covered with small bumps (papillae). 

Edibility: Used to make carrageenan

Distinctive characteristics: 

Collection notes: Can be used like a loofah

Phylum: Rhodophyta (Red Algae)
Previous names: Gigartina exasperata, Gigartina californica, Gigartina radula  
Similar species: Mastocarpus papillatus

Soranthera ulvoidea

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Color: Brown 
Shape: Pod-like, hollow or filled with liquid
Texture: Bumpy
Size: 2–6”
Zone: Intertidal
Range: Alaska to California

Description: Branching stipe connected to a small holdfast. Bushy or shaggy-looking branches alternating with bumpy brown to olive balloon-like sacs of 1–2”. 

Edibility: 

Distinctive characteristics: An epiphyte — grows on species of red algae. 

Collection notes:

Phylum: Phaeophta (Brown Algae)
Previous names:
Similar species: Can be confused with Sea Cauliflower, Leathesia difformis, when young

Laminaria saccharina

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Color: Brown
Shape: Blade
Texture: Smooth with Puckers
Size: Up to 6′
Zone: Lower intertidal to subtidal, semi-protected areas, rocky areas  
Range: Alaska, British Columbia, Oregon, California

Description: Wide blade with a 5–20” round stipe connected to root-like, branching holdfast. Blade may be smooth in the center and on the edges. Indentations tend to look like two rows. Blade may be torn or studded with blotchy coral encrustations. 

Edibility: Delicious! Can be eaten many ways. Rich in iodine, vitamin C, calcium, potassium, and other vitamins and minerals.

Distinctive characteristics: 

Collection notes: Use scissors to cut the upper blade and leave the rest to keep growing.

Phylum: Phaeophyta (Brown Algae)
Previous names: Fucus saccharinus
Similar species: Other Laminaria species

Scytosiphon simplicissimus

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Color: Brown
Shape: Tube-like
Texture: Segmented
Size: Up to 2’
Zone: Intertidal
Range: Alaska to South America

Description: Long narrow tubes, less than .5” in diameter, in clusters but not branched. Small disc-like holdfast. Simplicissimus is segmented, reminiscent of sausage links; other species of Scytosiphon are not.

Edibility: Edible

Distinctive characteristics:

Collection notes:

Phylum: Phaeophyta (Brown Algae)
Previous names: Chorda lomentaria, Scytosiphon lomentaria 
Similar species: Melanosiphon intestinalis and other Melanosiphon (Twisted Soda Straws). Can also be confused with Ralfsia in its crustose phase, when it looks like a brown coating on rocks.

Ulva fenestrata, Ulva lactuca

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Color: Green (Bright)
Shape: Sheet
Texture: Smooth, often with holes like Swiss-cheese
Size: 4–12”+
Zone: Intertidal
Range: Alaska to California (Ulva fenestrata), World-wide (Ulva lactuca and other species)

Description: Bright green thin, lettuce-like “leaves” attached in tufts to a small holdfast. May be white at the edges. Several similar species. Some have holes like Swiss-cheese. Can be long or round. Prefers calm areas.

Edibility: Makes a tasty fresh salad.

Distinctive characteristics:

Collection notes: If sea lettuce populations are particularly profuse or dominant, check to be sure the area is free of sewage drainage or other pollution before collecting as sea lettuce grows particularly well in these conditions. Rinse with water to remove small sea creatures such as snails hiding in the blades.

Phylum: Chlorophyta (Green Algae)
Previous names:
Similar species: Easy to confused with Monostroma. Monostroma is only one cell layer thick while Sea Lettuce is two cell layers thick. Monostroma grows in a circle around a disc-shaped holdfast; Sea Lettuce has a short stipe growing up out of the holdfast. Also similar to other Ulva species. All are edible.

Lethesia difformis

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Color: Brown (Golden)
Shape: Pod-like
Texture: Bumpy
Size: Up to 6”
Zone: Intertidal
Range: Alaska to Mexico

Description: This seaweed looks like small yellow-brown brains growing on the rocks or on other seaweeds. The interior is hollow. Sea Cauliflower tends to grow in clusters.

Edibility:

Distinctive characteristics: Disentegrates into filaments when squeezed.

Collection notes:

Phylum: Phaeophyta (Brown Algae)
Previous names: Tremella difformis 
Similar species: Soranthera ulvoidea and Colpomenia bullosus when young.