What is Sea Lettuce?

Sea lettuce belongs to the green seaweed family. It is characterized by flat, green blades that are typically less than 30cm but can grow up to 60 cm in height. The blades are two cells in thickness and have small perforations throughout. The colour can range from very pale to bright emerald green, resembling leaves of green lettuce. The holdfasts of Sea Lettuce are very small and hardly noticeable in the initial stages of growth. When in its reproductive phase, cells at the margins of the blades appear white. This white colour indicates that the cells have released their spores or gametes and only a cell wall remains.  

Names:

Scientific Name: Ulva lactuca (formerly Ulva fenestrata)

Family: Ulvaceae

Common Name: Sea Lettuce

First Nations Names:

Straits Salish (Saanich): kw’eqəәq

Comox: kw’ámkw’əәm

Haisla: tixtxàais (also other green algae)

Heiltsuk: tíxis ‘green or yellow colour’ (algae in the water near the beach)

Habitat:

Sea lettuce occurs in the mid to low intertidal zone and in tide pools. It grows attached to cobbles, boulders and bedrock in semi-protected habitats. 

Green tides or algae blooms occur when sea lettuce and other algaes proliferate in growth due to an increase of pollution. Sea lettuce uses nitrogen and phosphorus as fertilizer to grow, therefore when there is a surplus of these nutrients due to increased pollution the seaweeds can grow in excess. Nitrogen and phosphorus runoff into marine environments usually from agricultural runoff or inadequate treatment of human waste. 

Distribution: 

Occurs along the Pacific Coast from Alaska to California; Japan; Russia (Bering Sea, Commander Islands, southeast Kamchatka; Okhotsk Sea, Kurile Islands, Saghalien, Japan Sea).

Indigenous Knowledge and Uses:

Sea lettuce was eaten by the Nuu-Chah-Nulth with seal or whale oil and dried into seaweed cakes. 

Nutritional Content

Sea lettuce has a variety of nutrients. It contains high amounts of Vitamin B12, iron, calcium, sodium, potassium, magnesium, iodine, aluminium, manganese, and nickel and contains Vitamin A, Vitamin B1, Vitamin C, calcium, soluble nitrogen, phosphorous, and numerous trace elements. In a 100 gram serving, it has 87 mg of iron and 700 mg of calcium. Ulva’s protein content can represent up to 33% of the plant’s dry mass. It has also been shown to be a source of dietary fiber, better than that of fruits and vegetables. 

In the wild!

After writing this article I headed out to a beach in West Vancouver and found lots of Sea Lettuce :)