British distribution: Round the whole coast, commonly in estuaries.
A common green alga near the top of the shore, on rocks or other algae, on open coasts or in estuaries and harbours, where it may grow mixed with U. intestinalis or other species of the genus. It is better known as Enteromorpha prolifera, but Enteromorpha is now considered to be part of the genus Ulva (Maggs et al., in Brodie et al, 2007).
The fronds are tubular, though often more or less flattened, little to much-branched. The arrangement of the cells, in longitudinal and transverse rows in the central part of the frond, is characteristic of this species, as are the cylindrical chloroplasts seeming to fill the cell and the usually single, central pyrenoids. Critical identification details are provided by Burrows (1991) (as Enteromorpha prolifera) and updated and clarified by Maggs et al., in Brodie et al (2007).
The life history is an isomorphic alternation of generations. Gametes (biflagellate) and zoospores (quadriflagellate) are released from the tips of the fronds, which have a slightly darker appearance when fertile.
Predictably, the fronds are colonised by epiphytic diatoms, particularly, it seems, on some of the smaller, more rigidly tubular branches: