Fróðskaparrit - 01.01.2005, Page 99

LUTFALSLIGA ÁVIRKANIN AV PROTOZOOPLANKTON OG KOPEPODUM Á VÁRBLÓMING 97
AV PLANTUPLANKTON Á LANDGRUNNINUM í 1999
trophic dinoflagellates, yields an average
ingestion rate of 0.6 mgC m 3 d'1 during
mid-bloom (Table 2 and Fig. 5) and corre-
sponds to only 0.4% of the phytoplankton
standing stock. The ingestion rate of the
naked heterotrophic dinoflagellates and
the ciliates is unknown, but it is unlikely
to be of any significant importance due
to their low standing stock and apparently
low growth rates, as they did not increase
in numbers.
Thus during mid-bloom the grazing im-
pact of both the copepods and the pro-
tozooplankton on the phytoplankton seem
to have been of minor importance. Hence
the bulk part of the phytoplankton biomass
was most likely settling out of the euphotic
zone.
Conclusion
On the Faroe Shelf the importance of
protozooplankton as grazers on the phy-
toplankton during the pre-bloom period
seems to be negligible. The copepods on
the other hand seem to have a large graz-
ing potential. However, to what degree the
copepods are able to suppress or postpone
the phytoplankton spring bloom is un-
known. During mid-bloom the estimated
grazing impact on the phytoplankton by
the protozooplankton and the copepods
was negligible.
Acknowledgements
This research was supported by the Na-
tional Danish Scientifíc Research Board to
Benni W. Hansen project no. 21-01-0549.
We would like to acknowledge the crew on
RV Magnus Heinason, especially Olavur
Jákup Sørensen, for their help during the
field-work, and Eilif Gaard for his help,
both in the laboratory and for his com-
ments while writing the paper.
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