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

focus should improve our understanding and allow the distribution and recruitment
for fish and shellfish to be predicted.
Vulnerability of plankton to anthropogenic impacts should be linked even
more to local environmental conditions that influence the pelagic food web,
such as temperature, water circulation and ice occurrence in order for the
ecological impact of future environmental disturbances associated with climate
change and increased human activities (e.g. oil exploration) to be understood.
4.2.7 Zooplankton sensitivity to oil
In connection with hydrodynamic discontinuities, i.e. spring blooms, fronts,
upwelling areas or the marginal ice zone, high biological activity in the surface
waters can be expected. Anthropogenic impacts, e.g. oil pollution, might
also influence productivity.
Exposure experiments performed on natural plankton communities (Hjorth
et al. 2007, Hjorth et al. 2008) and copepods (Hjorth & Dahllöf 2008, Jensen et
al. 2008b, Hjorth & Nielsen 2011) with pyrene (as a proxy for crude oil) have
shown reductions in primary production, copepod grazing and production
and an indirect positive effect on bacterial growth due to substrate release.
Effects of pyrene have been studied in relation to a wide range of variables
and life stages of the calanoid copepods Calanus finmarchicus and C. glacialis
held under three different temperatures (0, 5 and 10º C) (Hjorth & Nielsen
2011, Grenvald et al. in prep.).
Adult C. finmarchicus were affected the most by pyrene exposure and
sensitivity increased in warmer water in contrast to C. Glacialis, which may
be partly due to buffering from lipid stores. Pyrene had no effect on development
time for the two first non-feeding nauplii stages but clearly prolonged
development time from nauplii stage III onwards when they begin to
graze on phytoplankton. This was most pronounced at the lowest temperature
(0º C), which suggests that the effects of pyrene exposure would be
more severe during a spring phytoplankton bloom (~0º C in the upper 50m),
since reduced grazing on phytoplankton would potentially lead to lower incorporation
of phytoplankton into lipids with more being left ungrazed to
sedimentate to the benthic community. The different responses to pyrene
exposure in relation to food uptake, production and development time of
the two species and higher water temperatures will not only affect them on a
species level but will affect the Arctic food chain through a regime-shift to a
less lipid-rich energy flux. Temperature stimulates C. finmarchicus more than
C. glacialis, but the former is also more sensitive to oil. Vulnerability of
plankton to anthropogenic impacts should be linked even more to local environmental
conditions that influence the pelagic food web, such as temperature,
water circulation and ice occurrence. The impacts of human activity
are likely to vary according to season, location and biological activity. High
biological activity in surface waters can be expected in connection with hydrodynamic
discontinuities, i.e. spring blooms, fronts, upwelling areas and
the marginal ice zone. In Arctic marine habitats, the most severe ecological
consequences of massive anthropogenic impacts (such as oil spills) are to be
expected in seasons with high biological activity within the pelagic food web
in the upper 50m. In late summer after Calanus have migrated down to
where they overwinter above the seabed biomass of grazers in surface waters
is low (Dünweber et al. 2010) and biological activity is lower or concen-
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