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

species interactions. In the review by Wassmann et al. (2011), 12 examples of
changes in benthic communities are presented. Impacts of climate change
included species-specific changes in growth, abundance and distribution
ranges and community level changes in total species composition. Most of
the examples found were geographically concentrated around Svalbard and
the Bering Sea, where research efforts are highest. Nevertheless, they can be
regarded as examples of changes occurring in many other marine Arctic ecosystems,
including the assessment area.
A future Arctic warming is also likely to result in increased freshwater runoff
from rivers and glaciers. Besides a freshening of surface waters in nearshore
areas, this will also lead to increased turbidity and inorganic sedimentation,
with potential effects on the species composition of benthic communities
(e.g. Wlodarska-Kowalczuk & Pearson 2004, Wlodarska-Kowalczuk et
al. 2005, Pawłowska et al. 2011, Węsławski et al. 2011).
8.4 Fish and shellfish
Fish species form an essential link between lower and higher trophic levels;
the larvae or juveniles of many fish species feed on zooplankton, and fish
represent an important prey for many seabirds and marine mammals.
Changes in temperature and oceanographic conditions will influence fish
populations directly causing them to shift to areas with preferred temperature,
and indirectly through the food supply and the occurrence of predators.
Survival of organisms and populations depends upon the degree to
which they can coincide in time with the occurrence and production of their
prey. Changes in climate can cause changes in the timing of the production
cycles of phytoplankton, zooplankton or fish, in some cases through an influence
on migration times.
Marine fish have complex life histories with eggs, larvae, juveniles and
adults of the same species often occurring in different geographic locations
and at different depths. Changes in temperature may have different effects
on the various life stages of a species (Pörtner & Peck 2010). If a species has
to shift its spawning areas due to an altered temperature regime, its continued
success will depend on factors such as whether ocean current systems in
the new area take the eggs and larvae to suitable nursery areas, and whether
the nursery areas are adequate in terms of temperature, food supply, depth,
etc. Changes in spawning and nursery areas caused by climatic changes
may, therefore, also lead to changes in population or species abundance
(Dommasnes 2010).
Changes in the distribution and abundance of fish populations will have
consequences for the entire food web, also in the assessment area. Some of
the more abundant species are likely to move northward due to the projected
warming, including Atlantic herring (Clupea harengus), Atlantic mackerel
(Scomber scombrus) and Atlantic cod (Gadus morhua), and this may favour
piscivorous birds and mammals. Greenland halibut (Reinhardtius hippoglossoides)
is expected to shift its southern boundary northward or restrict its
distribution more to continental slope regions (ACIA 2005).
The interaction between changing climate and distribution of certain fish
species has been documented for previous warming periods off Greenland
in relation to the abundance of Atlantic cod (Gadus morhua) and Greenland
halibut, Reinhardtius hippoglossoides (Horsted 2000, Drinkwater 2006, Stein
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