The fucoid zone is the characteristic hard bottom vegetation of the upper sublitoral along the open coastline. In the western Baltic Sea this zone is built up by two native species Fucus vesiculosus (bladder wrack) and Fucus serratus (toothed or serrated wrack). The species Fucus evanescens is regarded being a neophyte based on its first observation in 1990 in the Flensburg Fjord. This species is not regarded as a natural component of the Fucus biotope. Its occurrence is regarded as being neutral causing neither an improvement nor degradation in the assessment as it is not an invasive species. The classification metrics for the fucoid zone are
- depth limit of Fucus spp. (F. serratus and/or F. vesiculosus) and
- dominance (percentage cover) of Fucus spp.
By this the normative definitions “occurrence of sensitive species”, “abundance”, and “species composition” of the WFD have been covered for hard bottom vegetation in the upper sublitoral.