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64 | Blades

Pacific Seaweeds

Ulvaria / Kornmannia / Monostroma Dark sea lettuce

Class Ulvophyceae Order Ulvales Family Ulvaceae

Number of Species

Only three species of Ulvaria are known worldwide, and two of these, U. obscura and U. splendens, are found locally.

Description

Ulvaria blades are fan-shaped, usually less than 30 cm (12 in) long and are one cell layer thick. Upon dry-ing, Ulvaria turns dark, because of the presence of polyphenol oxidase, an enzyme that is also found in apples and turns them dark upon exposure to air and is considered a strong antioxidant. This feature distin-guishes Ulvaria from other bladed green seaweeds.

Kornmannia and Monostroma are other one-cell-thick green blades found in our area. A microscope is required to determine the number of cell layers. Together with Ulvaria, these plants occur lower on the beach than most Ulva but otherwise are difficult to distinguish in

Ulvaria sp.

Ulvaria obscura and cross-section (right) showing one cell layer.