Ontwikkelen van een score of index voor fytoplankton, macrozoöbenthos, macro-algen en angiospermen voor de Vlaamse overgangswateren volgens de Europese Kaderrichtlijn Water

On October 23th 2000, the EU Water Framework Directive was finally adopted. The Directive was published in the Official Journal on December 22th 2000 and entered into force the same day. The Water Framework Directive expands the scope of water protection of all waters and sets clear objectives that a 'good status' must be achieved for all European waters by 2015 and that water use must be sustainable throughout Europe. According to the Directive, the individual member states are obligated to describe ecological objectives orgoals for different waters.The aim of this project was to define ecological objectives for different biological quality elements for the Flemish transitional waters. In this document quality indices for benthos and phytoplankton have been presented. This document includes a study about the different approaches and methods used in Europe to define these ecological objectives. None of the existing indices was satisfactory and applicable on the Flemish transitional waters, neither forbenthos nor for phytoplankton. This has to do with the complexity of transitional water systems. For the Flemish transitional waters no temporal or spatial reference is available. The reference is therefore based on the available knowledge about the ecological functioning of estuaries.Concerning phytoplankton, separate indices have been established for the salt and fresh water zones of an estuary. For brackish water, a natural mortality zone for plankton, indices would be pointless. The scoring system for phytoplankton takes into account the trophic status (including the important element silica), the photic status and the danger of flushing. This scoring system has a simple design and determination of the coefficients requires minimal effort. After evaluation by specialists and comparison with other scoring systems, we can state that the proposed phytoplankton index is promising. Nevertheless the index needs testing, because the available data of the Flemish transitional waters were used for its compilation.For benthos indices have been established for fresh water and for salt and brackish water together. These indices are derived from the marine index of Borja et al. (2000), which takes into account the response of species to organic load. For salt and brackish water the 'Borja'- index was combined with an index based on sensitivity/tolerance for current velocity. The 'Borja'-index and the proposed index were tested on the sediments of the Scheldt estuary. Although the proposed indices showed improvement in comparison with application of 'Borja', they, still are not fully satisfying. The lack of any score for absolute density - or biomass values proved to be a shortcoming. The sensitivity/tolerance of species to organic pollution needs to be further examined, especially for estuarine fresh water species.For macro-algae and angiosperms no indices have been established. At present the role of macro algae in the Flemish transitional waters is nihil, and most probably this will not change in the future, so indices would be pointless. The only angiosperms occurring in the Flemish transitional waters are tidal flat vegetation, the discussion whether tidal flat vegetation must be incorporated in the quality index still exists