Ulva fasciata
Chlorophyta, Ulvaceae
Authority: Delile
Hawaiian name: limu palahalaha ('spread out, flattened, broad')
Characteristic feature: Thin green divided blades.
Description: Plants to several decimeters tall; characteristically deeply lobed or divided with clefts often extending to near holdfast; divisions somewhat digitately arranged from broadened basal region; blades plane, margins simple, crisped, or slightly undulate, bright gold when reproductive, margins then eroding; blades mostly (25-)45-110 µm thick in central part, thinner toward margins. Cells tending taller than broad (10-25 µm) in many specimens, or more quadrate and of equal dimensions; near base of blades, extracellular material between two cell layers thickens blade; margins relatively smooth, but irregular from erosion of spent reproductive cells; with occasional coarse spines on basal portions.
Habitat: Brackish water to marine sites; abundant in most habitats where groundwater or streams enter the ocean; ponds, upper intertidal to 5 m; on a variety of substrates (rock, coral, human-made structures, epiphytic, unattached, in drift material) and from numerous quiet water and open coast localities. Subtidal to 100 m.
Hawaiian distribution: All main Hawaiian Islands, including the Northwestern Hawaiian Islands.
Other: Indigenous to Hawai‘i. Another common name is sea lettuce. It is a popular seaweed for consumption, often eaten with other limu. Its abundance is an indicator of excessive nutrients in the water.
Ulva reticulata is reticulate or netlike, mostly unattached, and entangled with other algae. U. expansa, also common in Hawaiian waters, has broad, undivided blades with strongly ruffled margins.