Ulva fenestrata vs. Ulvaria blyttii

Ulva fenestrata and Ulvaria blyttii in Maine

These two species of green seaweed have a blade* morphology and are widespread on the coast of Maine: Ulva fenestrata (previously known as Ulva lactuca) and Ulvaria blyttii (previously known as Ulvaria obscura and Ulvaria splendens).

Ulva is a large genus represented by at least six species in Maine. In the absence of molecular data, Ulva pseudocurvata (formerly Ulva gigantea) cannot be reliably distinguished from Ulva fenestrata. Extensive sampling in the Northwest Atlantic indicates that Ulva fenestrata is far more abundant than its uncommon lookalike. Only one species in the Ulvaria genus is found in Maine.

The “green blade” morphology is represented in several other Maine seaweed genera, including Monostroma, Gayralia, Protomonostroma, and Kornmannia. These are delicate, filmy, and membranous compared to Ulva and Ulvaria.