Blades light to grass green, irregular in outline, perforations are rare (Image A) to common (Image B) and the overall shape can be highly variable. In some sheltered habitats blades can reach a few meters in size, but are more typically 10-40 cm. This species is bistromatic in section, 40-100 µm wide, with parietal chloroplasts that contains 1(2-3) pyrenoids (Image C).
This species can be difficult to distinguish from species of Ulvaria obscura (Kützing) P.Gayral ex C.Bliding in the field, however, the latter is monostromatic rather than bistromatic in section, which can only be verified with microscopy. In the field, individuals with a dark blackish-green hue at the margins are likely Ulvaria obscura. There are a number of other species of Ulva in our waters that form blades (exclusively or only in certain environments being tubes in other habitats) and confident identification requires molecular data.
We have genetically verified records from throughout BC, AK, Kamchatka, the Canadian Arctic, throughout Atlantic Canada extending south of Cape Cod to CN. Individuals range from the mid intertidal pools to subtidal (10 m) growing on rock, as well as on wood piers and a wide variety of inverts and other algae.
Image A. Fresh specimen from the subtidal (1 m) on rock displaying the irregular blade shape with rare perforations (Davis Ln. Beach, NB; GWS041734).
Image B. Specimen with a highly perforated blade (low intertidal pool, Maces Bay, NB; GWS036992).
Image C. Section displaying the bistromatic habit of the blade with parietal chloroplasts typically with a single prominent pyrenoid (Letete exposed biodiversity site, NB; EGWS000689).