BSEP116B Biodiversity in the Baltic Sea - Helcom

Guidelines (adopted in 2007), to report on the
amount and contaminant levels of dredged spoil
disposed at sea. Currently, there is information
available only from Sweden (153 000 tonnes in
2006), Germany (450 000 and 50 000 tonnes in
2006 and 2007, respectively), and Lithuania (1.39
million tonnes in 2007). Obviously, the volume of
disposed spoils varies annually depending on large
construction projects, such as port enlargements.
HELCOM Contracting Parties have agreed to use
the Best Environmental Practice (BEP) approach to
minimize both the quantity of material that has to
be dredged and the impact of the dredging and
disposal activities in the maritime area. Moreover,
when evaluating disposal sites, comprehensive
information on natural features and human activities
should be obtained for environmental impact
assessments (EIAs).
Ecosystem impacts of sand and gravel extraction,
small-scale dredging and dumping of
dredged spoils
The harmful impacts of sand and gravel extraction,
dumping of dredged spoils, and dredging on
the marine ecosystem are mainly caused by direct
killing of benthic infauna and epifauna, increased
turbidity, siltation, and resuspension of nutrients
and hazardous substances (reviewed by HELCOM
1999). For example, the spill of sand from the
dredging operation in the Århus harbour enlargement
was estimated to be 3.7% and the resuspension
of inorganic nitrogen and phosphorus was
estimated to increase the nutrient concentrations in
the water phase 3–100 fold (ICES 2003).
cally change the species composition of the benthic
fauna. At an extraction site in the English Channel,
this effect reduced the species diversity by half,
and decreased the density and biomass down to
10% of that in nearby areas (Harlay et al. 2003).
Small-scale dredging in marinas, boat routes, and
private shores have potentially a large local negative
impact on biodiversity because they are often
located in sheltered bays, coastal lagoons and estuaries,
which support rich submerged vegetation
and associated fauna (Dahlgren & Kautsky 2004;
see also Chapter 6.4, Recreational activities). Some
sensitive species, such as Chara spp., have disappeared
from areas exposed to small-scale dredging
(Appelgren & Mattila 2005).
An additional problem with dredging old ports is
that the sediments often contain substances toxic
to marine organisms (Smith et al. 1995).
6.3.2 Technical installations
There is a growing number of construction works
and different types of installations on the Baltic
coasts but also in offshore areas and on the
seabed: traffic links, high voltage power cables
(HVPC), oil platforms, oil and gas terminals, pipelines,
wind farms, marinas and ports, and numerous
coastal protection barriers. This section provides
an overview of existing large installations and
their known impact on the Baltic biodiversity.
Extraction activities destroy, at least temporarily,
the vegetation and benthic fauna of the dredged
area. After minor sand extractions, benthic invertebrate
communities are usually restored after 2–4
years, but after major sand extraction the recovery
phase lasts much longer (e.g., Boyd et al. 2005).
In the Baltic Sea, benthic species richness has been
found to recover within a year after finishing the
activities, whereas biomass and density remain low
for several years (HELCOM 1999). However, water
currents have been shown to spread the plume of
fine sand up to 4 km away from the site of activity.
Although the observed negative impact on
benthos at that distance may be minor and shortlasting
(Lisberg et al. 2002, Vatanen & Haikonen
2008), siltation and overflowing sand may drasti-
Sediment extraction
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