Abstract
Calanus finmarchicus and Calanus glacialis are
keystone zooplankton species in North Atlantic and Arctic
marine ecosystems because they form a link in the trophic
transfer of nutritious lipids from phytoplankton to predators
on higher trophic levels. These calanoid copepods spend several
months of the year in deep waters in a dormant state
called diapause, after which they emerge in surface waters
to feed and reproduce during the spring phytoplankton bloom.
Disruption of diapause timing could have dramatic consequences
for marine ecosystems. In the present study, Calanus
C5 copepodites were collected in a Norwegian fjord during
diapause and were subsequently experimentally exposed to
the water-soluble fraction of a naphthenic North Sea crude
oil during diapause termination. The copepods were sampled
repeatedly while progressing toward adulthood and were analyzed
for utilization of lipid stores and for differential expression
of genes involved in lipid metabolism. Our results
indicate that water-soluble fraction exposure led to a temporary
pause in lipid catabolism, suggested by (i) slower utilization
of lipid stores in water-soluble fraction-exposed C5 copepodites
and (ii) more genes in the b-oxidation pathway being
downregulated in water-soluble fraction-exposed C5 copepodites
than in the control C5 copepodites. Because lipid content
and/or composition may be an important trigger for termination
of diapause, our results imply that the timing of
diapause termination and subsequent migration to the surface
may be delayed if copepods are exposed to oil pollution during
diapause or diapause termination. This delay could have
detrimental effects on ecosystem dynamics.
keystone zooplankton species in North Atlantic and Arctic
marine ecosystems because they form a link in the trophic
transfer of nutritious lipids from phytoplankton to predators
on higher trophic levels. These calanoid copepods spend several
months of the year in deep waters in a dormant state
called diapause, after which they emerge in surface waters
to feed and reproduce during the spring phytoplankton bloom.
Disruption of diapause timing could have dramatic consequences
for marine ecosystems. In the present study, Calanus
C5 copepodites were collected in a Norwegian fjord during
diapause and were subsequently experimentally exposed to
the water-soluble fraction of a naphthenic North Sea crude
oil during diapause termination. The copepods were sampled
repeatedly while progressing toward adulthood and were analyzed
for utilization of lipid stores and for differential expression
of genes involved in lipid metabolism. Our results
indicate that water-soluble fraction exposure led to a temporary
pause in lipid catabolism, suggested by (i) slower utilization
of lipid stores in water-soluble fraction-exposed C5 copepodites
and (ii) more genes in the b-oxidation pathway being
downregulated in water-soluble fraction-exposed C5 copepodites
than in the control C5 copepodites. Because lipid content
and/or composition may be an important trigger for termination
of diapause, our results imply that the timing of
diapause termination and subsequent migration to the surface
may be delayed if copepods are exposed to oil pollution during
diapause or diapause termination. This delay could have
detrimental effects on ecosystem dynamics.