is it edible?
Yes, the blades are sometimes used in certain dishes
Postelsia
The blades (and less often, the stipes) of "Postelsia" are sometimes used in certain dishes, usually in California. 
what is postelsia? The sea palm from where does it get its name? From geologist Alexander Philipov Postels and artist who worked with Ruprecht, while the specific name, "palmaeformis", describes the alga's superficial similarity in appearance to true palms. where is it found? In California are any fossils available? Yes, from Monte Bolca, a lagerstätte near Verona
wiki:15430627
Postelsia [SEP] Edibility
The blades (and less often, the stipes) of "Postelsia" are sometimes used in certain dishes, usually in California. "Postelsia" is a protected species, however, and harvesting it is illegal throughout much of its range, as clipping the blades too low, below the meristem, prevents reproduction. "Postelsia" can regenerate blades cut above the meristem, but removing the blades can limit a sporophyte's ability to produce spores and contribute to subsequent populations. "Postelsia" has also been in danger of overharvesting at some points. It is illegal to harvest "Postelsia" in British Columbia, Washington and Oregon. In California, "Postelsia" is a partially protected species: recreational harvesting is illegal, but commercial harvesting is legal.