The North Sea Coasts
215
Figure 7.12 shows the increase and decrease in biomass of macrophytes, expressed as percentage coverage, in permanent sample plots in
the Grevelingen and in the Veerse Meer. In the Grevelingen the annual
cycle of changes in biomass of seagrass is not disturbed by macroalgae,
which have only a low presence. In the Veerse Meer the seagrass plot
becomes completely dominated by quickly growing Ulva, suppressing
the growth of Zostera marina.
7.2.4 Belgium
The Belgian North Sea coast south of the Netherlands (Fig. 7.1) consists
of 75 km of sandy beaches with local jetties and harbour constructions as
the only hard substrate. No published information is available on the
distribution of seagrasses or green algae along the Belgian coast
(E. Coppejans, pers. comm., State University, Gent). From my own experience I know that stone piers and jetties are covered with green algae,
showing the 'normal' picture of a semi-exposed sandy beach. I have no
knowledge of recent exceptional green algal growth of floating algal
accumulations on beaches.
Some information is available on the Spuikom of Oostende, an enclosed
eutrophic brackish-water basin connected with the North Sea by sluices.
Mass developments of Ulva scandinavica dominate the basin during summer, accompanied by Enteromorpha linza (Coppejans and Gillis 1983).
7.3 Conclusions
1. Accumulations of green macroalgae appear to be a local management
problem, connected to concentrated loadings of inorganic nutrients
and to the specific hydrographical conditions of enclosed coastal
areas, such as fjords, lagoons, bays and harbours.
2. Eutrophication related macroalgae accumulations increasingly occur
along the coasts of Denmark, Germany and The Netherlands. A conservative attitude towards differences between historic and recent data
sets and data interpretations, however, is needed for the North Sea
coasts.
3. The Baltic habitats of Denmark comprise non-tidal water masses,
sheltered lagoons with long residence time, and hence actual
and potential sites for eutrophication related mass occurrence of
215
Figure 7.12 shows the increase and decrease in biomass of macrophytes, expressed as percentage coverage, in permanent sample plots in
the Grevelingen and in the Veerse Meer. In the Grevelingen the annual
cycle of changes in biomass of seagrass is not disturbed by macroalgae,
which have only a low presence. In the Veerse Meer the seagrass plot
becomes completely dominated by quickly growing Ulva, suppressing
the growth of Zostera marina.
7.2.4 Belgium
The Belgian North Sea coast south of the Netherlands (Fig. 7.1) consists
of 75 km of sandy beaches with local jetties and harbour constructions as
the only hard substrate. No published information is available on the
distribution of seagrasses or green algae along the Belgian coast
(E. Coppejans, pers. comm., State University, Gent). From my own experience I know that stone piers and jetties are covered with green algae,
showing the 'normal' picture of a semi-exposed sandy beach. I have no
knowledge of recent exceptional green algal growth of floating algal
accumulations on beaches.
Some information is available on the Spuikom of Oostende, an enclosed
eutrophic brackish-water basin connected with the North Sea by sluices.
Mass developments of Ulva scandinavica dominate the basin during summer, accompanied by Enteromorpha linza (Coppejans and Gillis 1983).
7.3 Conclusions
1. Accumulations of green macroalgae appear to be a local management
problem, connected to concentrated loadings of inorganic nutrients
and to the specific hydrographical conditions of enclosed coastal
areas, such as fjords, lagoons, bays and harbours.
2. Eutrophication related macroalgae accumulations increasingly occur
along the coasts of Denmark, Germany and The Netherlands. A conservative attitude towards differences between historic and recent data
sets and data interpretations, however, is needed for the North Sea
coasts.
3. The Baltic habitats of Denmark comprise non-tidal water masses,
sheltered lagoons with long residence time, and hence actual
and potential sites for eutrophication related mass occurrence of