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

Table 10.1.2. Overview of potential impacts of noise 1 and discharge 2 from a single exploration drilling on VECs in the Davis
Strait assessment area. See section 4.9 for a summary of the VECs. This assessment assumes the application of current
(2011) mitigation guidelines, see text for details (no use of oil based mud).
VEC Typical vulnerable organisms
194
As described in section 4.8 bowhead whales occur in the assessment area in
winter and during spring migration. Their migration corridor seems to be
wide enough to provide alternative routes (Fig. 4.8.7), and displacement of
single animals similar to that described from the Beaufort Sea probably has
no significant effect here, provided that drilling operations are not simultaneous
in multiple sites.
Also narwhals, beluga whales and walruses will only overlap with the season
for exploration drilling for a brief period in winter, and no large effects
are expected.
Rorquals (fin, minke, humpback and blue whale), white beaked dolphins
and harbour porpoises in shelf waters, as well as sperm whales, bottlenose
whales and pilot whales on the continental slope could be displaced by drilling
operations. However, there is no knowledge to date on critical habitats
for these species.
Conclusion on noise from exploration drilling rigs
Exploration activities are temporary and displacement of marine mammals
caused by noise from drilling rigs will also be temporary. The most vulnerable
VECs in the assessment area are the baleen whales such as fin, minke
and humpback whales and toothed whales such as sperm whale and harbour
porpoise. The walruses occurring at the northern edge of the assessment
area are also highly vulnerable. If alternative habitats are available to
the whales no long-term effects are expected (Table 10.1.2), but if several rigs
operate in the same region there is a risk for cumulative effects and displacement
from key habitats.
10.1.2 Drilling mud and cuttings
Population impact* - worst case
Displacement Sublethal effect Direct mortality
Pelagic hotspots 2 plankton, zooplankton - insignificant (L) insignificant (L)
Tidal/subtidal zone none - - -
Demersal fish & Gl. halibut, sandeel short term(L) minor (L) none
offshore benthos 2 filter feeders (e.g. corals) short term(L) minor (L) minor (L)
Seabirds (breeding) none - - -
Seabirds (non-breeding) 2 king eider short term (L) insignificant (R) none
Marine mammals (summer) 1 baleen & toothed whales short term (L) minor (L) none
Marine mammals (winter) 1 bowheads, bearded seal, walrus, short term (L)
narwhal
minor (L) none
* L = local, R = regional and G = global
Drilling creates substantial quantities of drilling waste composed of rock
cuttings and the remnants of drilling mud (see section 2.3). Cuttings and
mud are usually deposited on the sea floor beneath the drill rig, where they
can change the physical and chemical composition of the substrate (e.g. increased
concentrations of certain metals and hydrocarbons) (Breuer et al.
2008). The liquid base of the drilling mud may be water (WBM – water
based mud) or synthetic fluids (SM – synthetic mud; ethers, esters, olefins,
etc). Previously oil was used (OBM – oil based mud), but this has almost