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Order Ulvales

Family Ulvaceae

Ulva intestinalis Linnaeus 1753: 1163

Thallus grass green to dark green or yellowish green in sheltered pools or lagoons. Plants up to 50 cm tall, tubular or with compressed apical part, narrowly to broadly cuneate in outline, surface often wrinkled. In surface view cells in no definite order, rounded, 6-12 µm in diameter; chloroplast situated against the distal radial cell wall, with one pyrenoid. Thallus membrane (one cell layer) varying in thickness from 17 µm near the apex to 30 µm in upper basal region. Rhizoidal cells larger and darker than the normal vegetative cells, the two types of cells mixed in the upper basal region.

Collections, ecology and regional distribution

Common along the whole South African coast in the lower eulittoral and in supralittoral pools; also in lagoons and estuaries and even in freshwater bodies where it often indicates nutrient pollution.

World distribution: virtually cosmopolitan (Guiry & Guiry, 2012).

Type locality: Woolwich, London, England? (Hayden et al. 2003).

Note: Stegenga et al. (1997) report that west coast lower eulittoral specimens tend to be broadly cuneate, whereas those found in quieter water have the typical “intestine” shape. This species was known as Enteromorpha intestinalis.


Ulva intestinalis Kini Bay near East London (BOL 147292).

Ulva intestinalis showing cells in surface view

Ulva intestinalis, XS showing single cell layer

Ulva intestinalis. 1, Habit. 2, Cross section of basal thallus. 3, Detail of cross-sectional anatomy of basal thallus. 4, Surface view of basal part. 5, Cross section of upper thallus. 6. Surface view of upper thallus. 6. Surface view of upper thallus showing chloroplasts in vegetative cells and formation of sporangia. Reproduced from Stegenga et al. (1997).


References Ulva intestinalis

Guiry, M.D. & Guiry, G.M. 2012. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched September 2012.

Hayden, H.S., Blomster, J., Maggs, C.A., Silva, P.C., Stanhope, M.J. & Waaland, J.R. (2003). Linnaeus was right all along: Ulva and Enteromorpha are not distinct genera. European Journal of Phycology 38: 277-294

Linnaeus, C. (1753). Species plantarum, exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas. Vol. 2 pp. [i], 561-1200, [1-30, index], [i, err.]. Holmiae [Stockholm]: Impensis Laurentii Salvii.

Stegenga, H., Bolton, J.J. and R. J. Anderson. 1997. Seaweeds of the South African west coast. Contributions from the Bolus Herbarium 18: 655 pp.


Cite this record as:

Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town,; Accessed on 02 March 2024.