Synonymy

Ceratophyllum submersum societie den Hartog 1963.

Constant species

Ceratophyllum submersum, Potamogeton pectinatus, Ranunculus baudotii.

Rare species

Ceratophyllum submersum, Ranunculus baudotii.

Physiognomy

Ceratophyllum submersum is a softer and fresher green plant than the more widely distributed C. demersum, with its finely segmented leaves 3^4- times forked, rather than once or twice divided (Tutin et al. 1964). And, although it can form similar dense masses of submerged, unanchored shoots, it seems generally to be found in this distinctive Ceratophylletum submersi, with amounts of Potamogeton pectinatus and Ranunculus baudotti, a rare water-crowfoot with considerable variation in the degree of development of its floating laminate leaves and the finely divided submerged ones (Holmes 1979). Myriophyllum spicatum is also frequent, though often quite hard to make out among the C. submersum, and there is occasionally some Zannichellia palustris, Callitriche obtusangula and Ranunculus trichophyllus.

Habitat

The Ceratophylletum submersi is characteristic of standing or sluggish, eutrophic and generally brackish waters, and is almost entirely confined to the extreme south-east of England where it is a locally common vegetation type of pools and dykes in coastal and estuarine marshes.

C. submersum has a fairly wide distribution throughout Europe, except towards the extreme north (Tutin et al. 1964), but in Britain its range is very restricted. It has sometimes been confused with C. demersum but, though there are old inland records scattered across the southeastern part of the country, recently confirmed stations lie mostly on or near the coast and, apart from a few localities in the west, the plant appears to be largely confined to the submaritime fringe from Sussex round to Essex (Perring & Walters 1962). Here, it is typically found in the dykes, usually shallow and fairly narrow, that drain the reclaimed marshes, where it can extend into waters that are quite saline: along the north Kent coast, the community has been found in brackish dykes with a mean conductivity of over 5000 /zmho, or a salinity of 2.7% (Charman 1981). Generally, however, there is no tidal movement, the waters being stagnant or very sluggishly draining the surrounding ground.