Monostroma fuscum, Ulva blyttii, Ulvaria obscura var. blyttii, Ulvaria fusca, Ulvaria splendens; misidentified as Ulvaria obscura

Description: A young thallus starts out as a sac and then splits into a blade expanding to least 30 cm (12 in) in diameter. The blade is a bright green, one cell layer thick (up to 72 μm), and almost opaque. When dried, the thallus can turn dark brown to almost black due to the presence of dopamine in cells. Habitat: The species is found in the low intertidal and subtidal on protected and semi-protected coasts and is frequently found on pebble or cobble substrates. Similar taxa: Monostroma, Ulva.