This environmental impact assessment for Kriegers flak ... - Vattenfall

Research was carried out as a compliment to the
very extensive examination of the invertebrate benthic
fauna, commissioned by the Group and carried out
over the entire Kriegers Flak area during 2002 and
2003. These examinations were carried out in accordance
with German norms for inventory of sea areas for
wind power construction.
The selected area at Kriegers Flak has a heterogeneous
biotopical composition. During tests of makrozoobentos
a total of 90 species proved to be of a superior
nature. The richest in species were polychaeters,
crustaceans and molluscs.
The epifauna in the area was sparse of species and
completely dominated by blue mussels, Mytilusedulis,
Other species present were sand prawn, Crangon cran-
Seabed examination with side viewing sonar at Kriegers Flak
gon and shore crab, Carcinus maenas.
Characteristically for the infauna was a high degree
of small, short-lived species. The most common were
polychaeters and molluscs. The biomass was dominated
by different species of mussels. Three different
habitations were detected. The decisive criterion is the
water depth (which inß uebces the parameters salt and
PRESENTATION OF THE AREA 79
oxygen content). The parameters from the analyses
of the sediments (grain size) seemed to inß uence the
composition of the fauna, but a direct connection with
the certiÞ ed fauna habitations could not be established
with available data.
Two of the species found within this area, the two
mussel species Astarte borealis and Astarte ellipicta,
are entered in the list of endangered species in Sweden
(category ”v. vulnerable”, Gärdenfors 2000). The presence
of the species was, however, low.
A. borealis is an arctic boreal species. Populations
in the Baltic are practically isolated remains. The move
to increased water depth which can be observed in
the Baltic does not derive, as with other species, from
salinity but from the temperature of the water. (Jagnow
& Gosselck 1987). In accordance therewith, this species
can be found Þ rst at a depth of 35m. This species
can reach an age of maximum ten years and belongs
therefore to the long-living mussels in the Baltic.
The species Astarte elliptica exists in a nearly sympatric
relationship (development of species happens
between populations without a physical barrier that
keeps them apart) with the closely related A. borealis.
This species has been found within the survey area in
the same habitat, but less frequently.
In conclusion, it can be established that the area is
characterized by a great variety of and small proportion
of threatened species.
A difference was observed depending on weather
the survey stations with seabed catchers were situated
above or below the halocline). The area has therefore
been divided into three communities with reference to
the benthic fauna, ”A”, ”B1”, and ”B2”.
Station group A contained all stations above the
halocline. These areas were characterized by the
great variety of the seabed (sand, gravel and stone). In
accordance with this, only two species with high ecological
potency were present at all stations, namely
the polychaet Pygospio elegans and the common Baltic
mussel Macoma baltica. Also the polychaet Hediste
diversicolor, the sand mussel Mya arenaria, the blue
mussel Mytilus edulis and the water snail Hydrobia
ulvae were present at nearly all stations. Occurrence of
both the polychaet Travisia forbesii and the amphipods
Bathporeia pilosa were plentiful, (a precence of >50%).
Both are typical sand seabed inhabitants within the eufotic
zone. A further 28 species were registered only ir-