Desmarestia viridis (Muller) Lamouroux
stringy acid kelp

Introduction to the Algae


© Michael Hawkes     (Photo ID #14789)


E-Flora BC Static Map

Distribution of Desmarestia viridis
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Species Information

Family Description:
This order contains large brown seaweeds with a distinctive pattern of growth. The apex of the sporophyte is a filament with an intercalary meristem, which produces the new cells that form the main axis of the thallus. Similar meristems occur along the length of the thallus so that the entire thallus can be fringed with pigmented hairs terminating the intercalary lateral meristems. These pigmented hairs are most evident during the spring growing season. At maturity, the plant appears parenchymatous, but it is actually pseudoparenchymatous in construction. Members of the Desmarestiales probably originated in the southern hemisphere where the greatest diversity of species occur—some rivaling northern hemisphere kelps in their size and morphological complexity.

Gametophytes are microscopic. They produce eggs and sperm on the same or different thalli. A sperm-releasing and -attracting factor called desmarestene has been identified in this order of seaweeds. Other pheromones, with slight differences in chemical structure, have been found in other orders of brown algae.
Species description:
Stringy Acid Kelp is the most acidic of all the acid kelps, and should be avoided. It is light brown in color, often with greenish areas, more finely branched than Witch's Hair, and usually up to 120 cm (about 4 feet) in length. Most of the side branches come off the central axis in opposite pairs. This is a fragile species that grows only on rocks and is rarely as abundant as Witch's Hair. Look for it especially in areas recently grazed by sea urchins.

When Stringy Acid Kelp is exposed to air (as during a good minus tide) the vacuoles containing the acid break down, releasing large quantities of this acid, turning the individual dull green and damaging nearby organisms. If you must collect it (and there seems little reason for doing so) place it into a container by itself and keep it entirely submerged in sea water
Individuals collected from southern British Columbia/northern Washington survived a week of immersion in water at 23°C (74°F) but died when placed in warmer water.

SourceNorth Pacific Seaweeds

Habitat and Range

Bathymetry: extreme low intertidal and subtidal to 45 meters (148 feet)

World Distribution: Aleutian Islands to Baja California, Mexico; Arctic Ocean; western North Pacific; North Atlantic; North Sea; New Zealand, Chile; Argentina; Antarctic and subantarctic islands

SourceNorth Pacific Seaweeds


Synonyms and Alternate Names:
Desmarestia media var. tenuis
Fucus viridis