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

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Besides Greenland halibut and northern shrimp, a subsea blowout may have
consequences for snow crab and sandeel. Sandeel is a key species in the ecosystem
in the assessment area and the potential effects of oil spills on this
species should be further investigated in new background study programmes
prior to an updated version of this report. With respect to Greenland
halibut, snow crab and shrimp, the assessment area is among the most
important fishing grounds in Greenland, implying that consequences for the
fishing industry could be high if larvae concentrations are exposed to a major
subsea oil spill. For Greenland halibut the assessment area is known as
the main spawning ground in the Northwest Atlantic, and fish from important
fishing grounds in the Davis Strait, Baffin Bay, eastern Canada and
inshore waters in Northwest Greenland are recruited from this area. Recent
studies suggest that eggs and larvae drift slowly though the assessment area
at 13-40 m depths (Simonsen et al. 2006).
Copepods, the food chain and important areas
Copepods are very important in the food chain and can be affected by the
toxic oil components (WSF, PAH) in the water below an oil spill. However,
given the usually restricted vertical distribution of these components to the
upper zone during surface oil spills, and the wider depth distribution of the
copepods, a spill at the surface is not likely to cause major population effects.
Ingestion of dispersed oil droplets at greater depth from a subsea blowout or
after a storm may be a problem. Studies of the potential effects of oil spills
on copepods in the Barents Sea (Melle et al. 2001) showed that populations
were distributed over such large areas that a single surface oil spill would
only impact a minor part and not pose a major threat (Anon 2003a). Recent
studies showed negative effects of pyrene (PAH) on reproduction and food
uptake among Calanus species (Jensen et al. 2008b), and on survival of females,
feeding status and nucleic acid content in Microsetella spp. from western
Greenland (Hjorth & Dahllöf 2008). Also negative effects of combined
temperature changes and PAH exposure on pellet production, egg production
and hatching of C. finmarchicus and C. glacialis were demonstrated
(Hjorth & Nielsen 2011).
Again, the experience learned from the Macondo oil spill, where huge subsea
plumes of dispersed oil were found at different depths, may change these
conclusions of relatively mild impacts to more acute and severe impacts
for large subsea spills.
Important areas for plankton including fish and crustacean larvae are often
where hydrodynamic discontinuities occur. Special attention should therefore
be given to the implication of oil spills in connection with such sites,
particularly during the spring bloom. Fronts, upwelling areas and the marginal
ice zone are examples of such hydrodynamic discontinuities where
high surface concentrations of phytoplankton, zooplankton, including
shrimp and fish larvae, can be expected. Except for the shelf banks, however,
very little information is available on such events in the assessment area.
The most sensitive season for primary production and plankton – i.e. where
an oil spill can be expected to have the most severe ecological consequences
– is the spring plankton bloom, when high biological activity of the pelagic
food web from phytoplankton to fish larvae is concentrated in the surface
layers.