The Davis Strait - DCE - Nationalt Center for Miljø og Energi

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and washed sites (Driskell et al. 2001). Use of dispersants in cleaning up oil
spills, as has been practised in earlier years, may increase recovery time of
the treated shores. Recovery lasted from 2-3 years to at least 10 years after
the Torrey Canyon spill off southern England, and up to 15 years on shores
badly affected by dispersants (Hawkins et al. 2002).
How pyrene might affect natural algae and bacteria communities in Arctic
sediment was studied near Sisimiut (West Greenland) using microcosms.
Benthic microalgae were especially sensitive to pyrene and increased toxicity
was found at high levels of UV light already at low pyrene concentrations
(Petersen & Dahllöf 2007, Petersen et al. 2008). The pronounced pyrene effects
caused algal death and organic matter release, which in turn stimulated
bacterial degradation of organic matter.
11.2.3 Oil spill impacts on benthic fauna
Bottom-living organisms (benthos) are generally very sensitive to oil spills
and high hydrocarbon concentrations in the water. The sensitivity of many
benthic species have been studied in the laboratory and a range of sublethal
effects have been demonstrated from exposures not necessarily comparable
to actual oil spill situations (Camus et al. 2002a, Camus et al. 2002b, Camus
et al. 2003, Olsen et al. 2007, Bach et al. 2009, Hannam et al. 2009, Bach et al.
2010, Hannam et al. 2010).
Effects will occur especially in shallow water (< 50 m) where toxic concentrations
can reach the seafloor. In such areas intensive mortality has been recorded
following an oil spill, for example among crustaceans and molluscs
(McCay et al. 2003a, McCay et al. 2003b). Oil may also sink to the seafloor as
tar balls, which happened after the Prestige oil spill off northern Spain in
2002. No effects on the benthos were detected (Serrano et al. 2006), but the
possibility of an impact is apparent. Sinking of oil may also be facilitated by
suspended sediment particles, frequently seen in Greenland waters where
meltwater runoff from glaciers may disperse widely into the open sea.
Effects on benthos have been documented from the Macondo subsea blowout
in the Gulf of Mexico in 2010 where deepwater plumes moved tens of
kilometres away from the blowout site (Diercks et al. 2010, Schrope 2011,
Thibodeaux et al. 2011), but it is too early to draw firm conclusions.
Many benthos species, especially bivalves, accumulate hydrocarbons, which
may cause sublethal effects (e.g. reduced reproduction). Such bivalves may
act as vectors of toxic hydrocarbons to higher trophic levels, particularly
bearded seals, walruses and eider ducks. Knowledge on benthos in the assessment
area is too fragmentary to assess impacts of potential oil spills. The
impact of potential oil spills on benthos in the assessment area has not yet
been assessed in detail.
However, in broad terms, the shallow water (down to 50 m) communities
have high species richness (bivalves, macro algae etc.) and the fauna is
available to higher trophic levels such as eiders and walruses. Another feature
is that individuals of several species have an estimated maximum age of
more than 25 years (the bivalves, Mya spp., Hiatella arctica, Chlamys islandica
and the sea urchin Strongylocentrotus droebachiensis). This indicates that the
benthic communities may be very slow to recover after any type of disturbance
that causes mortality of these old individuals that often constitute the