Conclusions
W. SCHRAMM
The preceding chapters provide ample information on the response of
different types of marine benthic vegetation to eutrophication along the
European coasts under a wide range of different climatic and hydrographic conditions, and with different sources and levels of eutrophication. Despite qualitative or quantitative variations in the time course of
the eutrophication process due to such local differences, a common pattern is obvious, as has already repeatedly been described earlier (e.g.
Wallentinus 1981; Kemp et al. 1983; Nienhuis 1983, 1993; Sand-Jensen
and Borum 1991; Vogt and Schramm 1991).
In general, we can observe a sequence of successive phases with
increasing eutrophication as depicted in Fig. 1 in a schematic model
where we have distinguished between four different phases of the eutrophication process.
Un-eutrophicated ("healthy") marine or brackish shallow coastal waters
are characterized by a balanced nutrient regime, i.e. the nutrient load is
low and nutrient concentrations may temporarily become limiting to
primary production (phase I). In shallow nearshore systems, the dominant
primary producer communities usually consist of perennial benthic
macrophytes, such as seagrasses and other phanerogams on soft bottoms,
or long-lived seaweeds on hard substrates, whereas seasonal macro algae or
phytoplankton playa lesser role in terms of biomass and production (see
Fig. 4). Increasing nutrient loading, however, favours these seasonal forms.
A second phase (II) from slight to medium eutrophication is therefore
characterized by increasing blooms of "nutrient opportunists", in
particular fast-growing epiphytic macro algae and bloom-forming
phytoplankton taxa. In contrast, phanerogam and perennnial macro algal
communities gradually decline, usually combined with a change in their
depth distribution limits, and finally disappear. During phase II, parallel
to the blooms or mass development of seasonal fast growing seaweeds,
Institut fUr Meereskunde, Universitat Kiel, Diisternbrooker Weg 20, 24105 Kiel, Germany
Ecological Studies, Vol. 123
Schramm/Nienhuis (eds) Marine Benthic Vegetation
© Springer-Verlag Berlin Heidelberg 1996
W. SCHRAMM
The preceding chapters provide ample information on the response of
different types of marine benthic vegetation to eutrophication along the
European coasts under a wide range of different climatic and hydrographic conditions, and with different sources and levels of eutrophication. Despite qualitative or quantitative variations in the time course of
the eutrophication process due to such local differences, a common pattern is obvious, as has already repeatedly been described earlier (e.g.
Wallentinus 1981; Kemp et al. 1983; Nienhuis 1983, 1993; Sand-Jensen
and Borum 1991; Vogt and Schramm 1991).
In general, we can observe a sequence of successive phases with
increasing eutrophication as depicted in Fig. 1 in a schematic model
where we have distinguished between four different phases of the eutrophication process.
Un-eutrophicated ("healthy") marine or brackish shallow coastal waters
are characterized by a balanced nutrient regime, i.e. the nutrient load is
low and nutrient concentrations may temporarily become limiting to
primary production (phase I). In shallow nearshore systems, the dominant
primary producer communities usually consist of perennial benthic
macrophytes, such as seagrasses and other phanerogams on soft bottoms,
or long-lived seaweeds on hard substrates, whereas seasonal macro algae or
phytoplankton playa lesser role in terms of biomass and production (see
Fig. 4). Increasing nutrient loading, however, favours these seasonal forms.
A second phase (II) from slight to medium eutrophication is therefore
characterized by increasing blooms of "nutrient opportunists", in
particular fast-growing epiphytic macro algae and bloom-forming
phytoplankton taxa. In contrast, phanerogam and perennnial macro algal
communities gradually decline, usually combined with a change in their
depth distribution limits, and finally disappear. During phase II, parallel
to the blooms or mass development of seasonal fast growing seaweeds,
Institut fUr Meereskunde, Universitat Kiel, Diisternbrooker Weg 20, 24105 Kiel, Germany
Ecological Studies, Vol. 123
Schramm/Nienhuis (eds) Marine Benthic Vegetation
© Springer-Verlag Berlin Heidelberg 1996