Desmarestia viridis (O. F. Müller) J. V. Lamouroux
Type locality: Sinus Dróbachiense (Drøbak, Norway) (Müller 1782: 5).
Etymology: Desmarestia – after A.G. Desmarest, a French phycologist; viridis – Adjective (Latin), green (Stearn 1973).
Desmarestia viridis (Fig 1) is a light golden brown, solitary, erect, lax and fragile alga (Fletcher 1987; Mondragon & Mondragon 2003), that grows up to 120 cm (48 in) tall (Lindeberg & Lindstrom 2010). Thalli have percurrent axis that are subcylindrical, 0.75-1.5 mm wide at the base (Abbott & Hollenberg, 1976). From the central axis, a lot of branches arise oppositely, pinnately branched and occasionally bipinnate (Mondragon & Mondragon 2003). These branches present numerous branchlets that originate from a rarely present hair (Abbott & Hollenberg, 1976). Branchlets become smaller towards the tip and at the apex hair-like and flaccid (Braune & Guiry 2011). The stipe is cylindrical and cartilaginous at the base terminating in a small, bulbous or flattened holdfast (Fletcher 1987; Braune & Guiry 2011). This species exhibits a heteromorphic life history, in which the gametophyte (haploid phase) is small filamentous and the sporophyte (diploid phase) is larger pseudoparenchymatous (Graham & Wilcox 2000).
This species has a wide distribution, with records for Ireland, Europe, Atlantic Islands, North America, Central America, South America, Antarctic and subantarctic islands and Asia (Guiry & Guiry 2013). Occasional to rare from late spring into late summer, Desmarestia viridis occurs in the very low intertidal to subtidal zones (above 45 m) in semi-protected to exposed habitats (Abbott & Hollenberg, 1976; Lindeberg & Lindstrom 2010).
Desmarestia viridis is perennial and can be found growing on rock or epiphyte on larger algae (Braune & Guiry 2011). The regional distribution was assessed through herbarium specimens housed in the FHL Herbarium. Vouchers are commonly labeled as Desmarestia aculeate, Desmarestia intermedia, Desmarestia media and Desmarestia media var. tenuis. The species was firstly reported in the San Juan Islands in 1904, and is reported for the following sites/years:
Minnesota Reef, San Juan Islands, 1904 and 1962;
TurnIsland, FridayHarbor, 1908 / 1915 / 1925 and 1962;
Reid Rock, 1921;
DallasBeach, San Juan Islands, 1951 and 1961;
American Camp, San Juan Islands, 1962;
SmithIsland, IslandCounty, 1964;
Partridge Bank Whidbey Island, 1964;
GoldenGardens, Seattle, 1964;
Dot Rock, CanoeIsland, 1964;
Cattle Point, San JuanIsland, 1966 and 1989;
Cannery Vilage, San Juan Islands, 1974;
MarVistaBeach, San Juan Islands, 1974 and 1989;
FridayHarbor Labs, 1982;
Lime Kiln Point, San Juan Islands, 1989;
RocheHarbor, San Juan Islands, unknown date.
During the development of this page, one herbarium specimen was prepared and deposited on FHL Herbarium. The alga was collected on Friday Harbor Labs Docks, located at San Juan Islands, Washington. The specimen was collected by Brian Wysor, and determined by Brian Wysor and Carolina Azevedo. The date of the record is June 17, 2013.
5. Research Notes
Desmarestia species are able to release sulfuric acid from their cells, which will destroy itself along with other nearby seaweeds if cells are damaged (Lindeberg & Lindstrom 2010). The sulfuric acid is the cause of the rapid disintegration
of these seaweeds, which become discoloured, green and unpleasant-smelling (Braune & Guiry 2011). The sulfuric acid is stored in vacuoles and has a pH of 1 or lower (Graham & Wilcox 2000).
Studies have shown that the sulphuric acid produced by Desmarestia viridis prevents associated algae from herbivory (Molis et al. 2009). In nature, Desmarestia occurs associated to Alaria, and is suggested to protect the kelp from grazing by sea urchins, which suggests that kelp refuges may be chemically defended by associated Desmarestia species (Molis et al. 2009). Therefore, this beneficial effect provides a refuge for associated, more palatable species and contributes to the temporal stability and persistence of macrobenthic communities (Molis et al. 2009).
6. Literature Cited
Abbott, I.A. and Hollenberg, G.J. 1976. Marine algae of California. StanfordUniversity Press, Stanford.
Braune, W. and Guiry, M.D. 2011. Seaweeds. A colour guide to common benthic green, brown and red algae of the world’s oceans. Koeltz Scientific Books, Königstein.
Bunker, F.P.D., Brodie, J.A., Maggs, C.A. and Bunker, A.R. 2010. Seasearch guide to seaweeds of Britain and Ireland. pp.  5-224. Marine Conservation Society, Ross-on-Wye.
Dickinson, C.I. 1963. British Seaweeds. Kew Series No. 3. pp. -232, 92 figs, 12 pls. Eyre & Spottiswoode, London.
Fletcher, R. 1987. Seaweeds of British Isles. BritishMuseum, London.
Graham, L.E. and Wilcox, L.W. 2000. Algae. Prentice-Hall, UpperSaddleRiver.
Guiry, M.D. and Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 02 July 2013.
Lindeberg, M.R. & Lindstrom, S. C. 2010. Field Guide to Seaweeds of Alaska. AlaskaSeaGrantCollege Program, University of AlaskaFairbanks.
Mondragon, J. & Mondragon, J. 2003. Seaweeds of the Pacific Coast. Common Marine Algae from Alaska to Baja California. Sea Challengers, Monterey.
Molis, M., Wessels, H., Hagen, W., Karsten, U. and Wiencke, C. 2009. Do sulphuric acid and the brown alga Desmarestia viridis support community structure in Arctic kelp patches by altering grazing impact, distribution patterns, and behaviour of sea urchins? Polar Biol, 32: 71–82.
Müller, O.F. 1782. Flora danica. Vol. 5, fasc. 15 pp. 6, Plates 841-900. Havniae, Copenhagen.
Stearn, W. T. 1973. Botanical Latin. History, grammar, syntax, terminology and vocabulary. Timber Press, Portland.
7. Links to additional resources
8. Page Authors & Affiliations
Carolina Angélica Araújo de Azevedo.
Universidade de São Paulo, Instituto de Biociências, Departamento de Botânica, Laboratório de Algas Marinhas. São Paulo, Brazil.