148
W. Schramm
A drastic decline of benthic vegetation was observed in some areas
along the Polish coasts, especially in Gdansk Bay (Plinski and Tarasiuk
1992). In the Puck Lagoon (northwestern Gdansk Bay), the formerly rich
vegetation of Fucus vesiculosus beds, seagrass meadows, and Furcellaria
lumbricalis-dominated red algal communities, inhabited by abundant
and diverse fauna, deteriorated rapidly from 1970. In 1987, Fucus vesiculosus, Furcellaria lumbricalis and Coccothylus truncatus (formerly
Phyllophora brodiaei) had disappeared and the Zostera meadows had
declined, whereas Zanichellia palustris and filamentous brown algae,
such as Pilayella littoralis, spread out (Plinski and Florszyk 1984; KrukDowgiallo 1991; Zmudzinski and Osowiecki 1991; Ciszewski et al. 1992;
Fig. 5.8).
Distinct changes occurred also in the brackish, semi-enclosed inlets
(Bodden) of the eastern German coasts. In the Greifswalder Bodden
(Island of Rugen), fringing Potamogeton and Zostera meadows, and red
algal communities, dominated by Furcellaria lumbricalis extending down
to 8 m depth, covered approximately 50% of the area in the 1930s. In
1988, the red algae had nearly disappeared. The remaining communities
of green algae (0 -1.5 m), Potamogeton pectinatus (I - 3 m), Zostera marina (2-4 m), and red algae (3-4 m) occupied only 3% of the bottom
(Messner and von Oertzen 1991; Fig. 5.9).
A comprehensive, large-scale quantitative study on the phytobenthos
in the Kiel Bay (western Baltic) employing SCUBA diving and underwater television was undertaken during 1985-1988 (Breuer and
Schramm 1988; Schramm 1988; Vogt and Schramm 1991). The distribution and biomass of Fucus along the German coasts of Kiel Bay was
investigated in 1987/1988 (Vogt and Schramm 1991). Comparison with
earlier investigations in the 1950s and 1960s (Hoffmann 1952; Schwenke
1965) revealed a drastic decline in Fucus biomass from nearly 45 000 t
wet weight down to only 2400 t within 35 years (Fig. 5.10). While Fucus
vesiculosus as well as Fucus serratus were still frequent at depths below
2 m down to 10 m in the 1970s (Black 1978), no Fucus was found below
2 m depth during the investigation in 198711988.
A model including the major potential causes or their combination,
and considering the particular conditions in Kiel Bight, is proposed to
explain the observed decline (Fig. 5.11). Vogt and Schramm come to the
conclusion that in Kiel Bay diseases, ice scoring (Ronnberg and Haathela
1988) or pollution seem to be of minor importance. Among the major
factors is the loss of substrate suitable for settlement of Fucus through
deposition of eroded cliff material, and to a certain extent as a result of
commercial stone collection. The primary factor, however, seems to be
eutrophication, enhancing growth of "opportunistic" annual seaweeds,
W. Schramm
A drastic decline of benthic vegetation was observed in some areas
along the Polish coasts, especially in Gdansk Bay (Plinski and Tarasiuk
1992). In the Puck Lagoon (northwestern Gdansk Bay), the formerly rich
vegetation of Fucus vesiculosus beds, seagrass meadows, and Furcellaria
lumbricalis-dominated red algal communities, inhabited by abundant
and diverse fauna, deteriorated rapidly from 1970. In 1987, Fucus vesiculosus, Furcellaria lumbricalis and Coccothylus truncatus (formerly
Phyllophora brodiaei) had disappeared and the Zostera meadows had
declined, whereas Zanichellia palustris and filamentous brown algae,
such as Pilayella littoralis, spread out (Plinski and Florszyk 1984; KrukDowgiallo 1991; Zmudzinski and Osowiecki 1991; Ciszewski et al. 1992;
Fig. 5.8).
Distinct changes occurred also in the brackish, semi-enclosed inlets
(Bodden) of the eastern German coasts. In the Greifswalder Bodden
(Island of Rugen), fringing Potamogeton and Zostera meadows, and red
algal communities, dominated by Furcellaria lumbricalis extending down
to 8 m depth, covered approximately 50% of the area in the 1930s. In
1988, the red algae had nearly disappeared. The remaining communities
of green algae (0 -1.5 m), Potamogeton pectinatus (I - 3 m), Zostera marina (2-4 m), and red algae (3-4 m) occupied only 3% of the bottom
(Messner and von Oertzen 1991; Fig. 5.9).
A comprehensive, large-scale quantitative study on the phytobenthos
in the Kiel Bay (western Baltic) employing SCUBA diving and underwater television was undertaken during 1985-1988 (Breuer and
Schramm 1988; Schramm 1988; Vogt and Schramm 1991). The distribution and biomass of Fucus along the German coasts of Kiel Bay was
investigated in 1987/1988 (Vogt and Schramm 1991). Comparison with
earlier investigations in the 1950s and 1960s (Hoffmann 1952; Schwenke
1965) revealed a drastic decline in Fucus biomass from nearly 45 000 t
wet weight down to only 2400 t within 35 years (Fig. 5.10). While Fucus
vesiculosus as well as Fucus serratus were still frequent at depths below
2 m down to 10 m in the 1970s (Black 1978), no Fucus was found below
2 m depth during the investigation in 198711988.
A model including the major potential causes or their combination,
and considering the particular conditions in Kiel Bight, is proposed to
explain the observed decline (Fig. 5.11). Vogt and Schramm come to the
conclusion that in Kiel Bay diseases, ice scoring (Ronnberg and Haathela
1988) or pollution seem to be of minor importance. Among the major
factors is the loss of substrate suitable for settlement of Fucus through
deposition of eroded cliff material, and to a certain extent as a result of
commercial stone collection. The primary factor, however, seems to be
eutrophication, enhancing growth of "opportunistic" annual seaweeds,