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

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and unpredictable production of diatoms (rich in polyunsaturated fatty acids)
with consequences for higher trophic levels (Kattner et al. 2007).
In Southwest Greenland, including the assessment area, C. finmarchicus is already
the dominant Calanus species, outnumbering both C. glacialis and C.
hyperboreus by a factor of three throughout the year, depending on food
availability (Pedersen et al. 2005, and references therein). With increasing
temperature the predominance of C. finmarchicus will further increase, as also
shown experimentally by Kjellerup (2011). Such a scenario will presumably
cause a trophic cascade due to less energy content per individual
(Hansen et al. 2003, Falk-Petersen et al. 2007). In addition, the share in biomass
accounted for by C. finmarchicus will further increase (Hirche &
Kosobokova 2007) due to its higher growth rate and short life cycle (Scott et
al. 2000). A regime shift towards C. finmarchicus will without doubt influence
important seabirds such as the little auk negatively (Karnovsky et al. 2003)
and favour certain intermediate species like herring (Falk-Petersen et al.
2007).
C. finmarchicus also plays an important role as prey for larval stages of the
Atlantic cod Gadus morhua. In West Greenland waters C. finmarchicus is the
most important food source for cod larvae (Drinkwater 2005). Changes in its
abundance and distribution will likely have a direct effect on the distribution
of Atlantic cod, and other species as well.
Since C. finmarchicus grazes on phytoplankton, its spatial distribution and
life cycle are not only influenced by temperature but also by algal food
abundance measured as chlorophyll a concentrations. Based on satellite data
collected from 1997-2009 (Kahru et al. 2011) there is already some evidence
that Chl maxima occur earlier in the year off Greenland, indicating changes
in the development of phytoplankton blooms and thereby primary production.
A change or increase in the primary production season in the assessment area
could not only influence C. finmarchicus but also favour certain other zooplankton
species, with consequences at community level.
Phytoplankton is also a conduit for the uptake, processing and transformation
of carbon dioxide. Changes in the amount of carbon that flows and
cycles through this food web will change the amount of carbon retained in
the ocean or respired back into the atmosphere. These changes may fundamentally
alter the structure of marine Arctic ecosystems, including the assessment
area.
8.3 Benthic fauna
Climate variability can also modify interactions between the pelagic and the
benthic realm within the assessment area. Future fluctuations in zoobenthic
communities will depend on the temperature tolerance of the present species
and their adaptability. If further warming occurs, those species tolerating
a wide temperature range will become more frequent, causing changes
in the zoobenthic community structure and probably in its functional characteristics,
especially in coastal areas, with consequences for the higher
trophic levels. At the time being our knowledge about temperature tolerance
and adaptability of macrobenthic species in the assessment area is limited
and it is not possible to make predictions for changes in biogeography and