Ulva intestinalis is a green alga in the family Ulvaceae, known by the common names sea lettuce, green bait weed, gutweed, and grass kelp.Grass-kelp, Gutweed Until they were reclassified by genetic work completed in the early 2000s, the tubular members of the sea lettuce genus Ulva were placed in the genus Enteromorpha.Guiry, M.D., John, D.M., Rindi, F. and McCarthy, T.K. (Eds) 2007. New Survey of Clare Island. Volume 6: The Freshwater and Terrestrial Algae. p. 23. Royal Irish Academy.
Distribution This species has a generally world-wide distribution.Burrows, E.M. 1991. Seaweeds of the British Isles. Volume 2 Chlorophyta. British Museum (Natural History). In the Pacific Ocean, it can be found in the Bering Sea near Alaska, the Aleutian Islands, Puget Sound, Japan, Korea, Mexico, the Philippines, and Russia, as well as New Zealand. In the Atlantic Ocean, its range includes the Azores, the Baltic Sea, the Mediterranean Sea, and northern European countries such as Ireland, Belgium, Denmark, Norway, and Poland.
Description The branched fronds are completely tubular and expand in width to mid-thallus, reaching 15 cm long or more. The cells are irregularly arranged and the chloroplast is hood-shaped and placed to one side, generally with only one pyrenoid. The species may be long and wide. The fronds have rounded tips.
This alga may be reproductive at all times of the year, and has a life-cycle with alternation of generations, in which the gametophyte and sporophyte are isomorphic, having identical morphology.
In some references the species (Ulva intestinalis) is treated as two subspecies: ssp. intestinalis (L.) Link and ssp. compressa (L.) Link.Morton, O. 1994. Marine Algae of Northern Ireland. Ulster Museum
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