'Formations of water bodies constituted by submerged, rooted, perennial phanerogams with often emerging flower spikes, in particular entirely immersed pondweeds of genus Potamogeton. Some habitats of this unit can be dominated by other species, such as Zannichellia palustris, Elodea canadensis, Elodea nuttallii, Ceratophyllum submersum, Myriophyllum spicatum and Najas marina.
Formations of smaller pondweeds, in particular, Potamogeton crispus, Potamogeton filiformis, Potamogeton pusillus, Potamogeton obtusifolius, Potamogeton berchtoldii, Potamogeton trichoides, Potamogeton acutifolius, Potamogeton pectinatus, Potamogeton nitens, Potamogeton friesii (Potamogeton mucronatus), Groenlandia densa, waterthymes and waterweeds (Elodea spp., Hydrilla spp., Ottelia spp.), horned pondweeds (Zannichellia palustris s.l.), naiads (Najas spp.), tapegrass (Vallisneria spiralis), water crowfoots (Ranunculus circinatus) that colonize shallower, more sheltered Palaearctic waters. Eurasian formations dominated by usually free-floating hornworts of genus Ceratophyllum, in particular by Ceratophyllum demersum, are included because of closer ecological and physiognomic similarity with communities of this unit than with those of unit C1.32.