Eelgrass beds represent the characteristic soft bottom vegetation along the open coastline. In the western Baltic Sea those beds are built up by only one species, Zostera marina (common eelgrass). Other angiosperms like Zostera noltei (dwarf eelgrass, formerly known as Z. noltii), Ruppia spp. (tasselweed), pondweed Stuckenia (formerly known as Potamogeton) pectinatus or Zannichellia palustris (horned pondweed) occur only in low abundance in open coastal waters and are therefore not regarded for BALCOSIS. The classification metrics for eelgrass beds are
- depth limit of Zostera marina and
- the biomass proportion of opportunistic algae.
By this the normative definitions “occurrence of sensitive species”, “abundance” and “species composition” of the WFD have been covered for soft bottom vegetation.