Problems associated with the 'one-out, all-out' principle, when using multiple ecosystem components in assessing the ecological status of marine waters

摘要

Recent legislation worldwide (i.e. Oceans Act in USA, Australia or Canada; Water Framework Directive (WFD) or Marine Strategy in Europe, and National Water Act in South Africa) has been developed to address ecological quality or integrity within estuarine and coastal systems (Borja et al., 2008a). The main objective of these legislative measures and policies is to maintain a good environmental or ecological status for marine waters, habitats and resources. When such good status is not achieved, the restoration of degraded aquatic habitats and ecosystems must be addressed (Apitz et al., 2006; Borja et al., 2008a). Most such legislation seeks to define quality in an integrative way by using several biological elements (i.e. phytoplankton, macroalgae, angiosperms, benthic invertebrates and fishes), together with physico-chemical and pollution elements. Such an approach permits the assessment of ecological status at the ecosystem level ('ecosystem approach' or 'holistic approach' methodologies) (Borja et al., 2008a).