Angiosperms (seagrass) within the EU water framework directive: a UK perspective.

Taxonomic composition, the presence of disturbance-sensitive species and abundance are attributes for monitoring the status of marine angiosperms; a biological quality element required for assessment of environmental condition under the Water Framework Directive (WFD). Their relevance for defining the ecological status of UK water bodies and the establishment of reference conditions for these attributes are described. Founded on quantitative measurements of these attributes, a set of metrics has been developed for monitoring and assessment of the only truly marine angiosperms, seagrass. The proposed metrics are presented and tested against a variety of littoral and sublittoral UK seagrass beds. In combination they express the cumulative response of marine angiosperms to different levels of anthropogenic disturbance.