Leibniz-Institut für Ostseeforschung, Warnemünde
(IOW) (Baltic Sea Research Institute, Warnemünde)
Bundesamtes für Seeschifffahrt und Hydrographie, Hamburg, Rostock
(Federal Maritime and Hydrographic Agency of Germany, Hamburg, Rostock)
In general the 2005 results of heavy metal concentrations in the Baltic Sea revealed no pronounced changes
compared to previous years. Regional and temporal limited variations of trace metal concentrations, which have been observed
periodically in the western Baltic, have been attributed to the changing enrichment of suspended matter in the water column,
released by wind induced mixing up to the ground level. During sample filtration only particles
<0.4 µm were restrained, while particles
>0.4 µm passed the filter.
Changes induced during the main saltwater inflow event in February 2003 were observed in the vertical trace metal
distribution in the Bornholm- and Gotland Basin with nearly homogeneous concentrations for
and Zndiss in surface waters. Stagnant conditions with anoxia and decreasing dissolved
trace metal conditions below the oxic-anoxic interface were noticed in the near bottom layer of the
Bornholm Basin at 80 m depth, below 200 m in the Gotland Deep and below
100 m in the Landsort Deep.
For the contents of CdSPM, CuSPM and
ZnSPM a slight increase was observed with depth in the central Baltic,
a possible hint for the beginning of a new stagnation period. Altogether the saltwater inflow event in 2003 had
influenced the trace metal long term trends in the deepwater of the central Baltic Sea. Now there is another chance to
study changes in trace metal concentrations during the stabilisation of an anoxic deep water body as well as the
"feedback mechanism” on the trace metal concentrations in the surface water body.
Heavy metal concentrations in surface sediments of the western Baltic Sea
still not show a significant temporal trend (1998 to 2005). In the western Arkona-Basin (Station K7), a sediment
core was taken, dated, and analyzed for temporal reconstruction of heavy metal pollution history. The results show
that especially for Hg, at the end of the 50th of the past century, an exceptional
contamination was found which causes still remain unknown.