Fróðskaparrit - 01.01.2005, Qupperneq 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.
Literature
Azam, F., Fenchel, T., Field, J.G., Gray, J.S., Meyer-
Reil, L.A. and Thingstad, F. 1983. The ecological
role of water-column microbes in the sea. Mar.
Ecol. Prog. Ser. 10: 257-263.
Baltic Marine Biologists 1979. Recommendation on
methods for marine biological studies in the Baltic
Sea. Phytoplankton and chlorophyll. In Edler, L.
(ed.). The Baltic Marine Publication 5: 1-38.
Bathmann, U.V., Noji, T.T. and von Bodungen, B.
1990. Copepod grazing potential in late winter
in the Norwegian Sea - a factor in the control of
spring phytoplankton growth? Mar. Ecol. Prog.
Ser. 60: 225-233.
Berggreen, U., Hansen, B. and Kiørboe, T. 1988. Food
size spectra, ingestion and growth of the copepod
Acartia tonsa during development: implications for
determination of copepod production. Mar. Biol.
99: 341-352.
Cabal, J., Harris, L.R. and Head, E.J.H. 1997. Egg
production rates of Calanus finmarchicus in the
Northwest Atlantic (Labrador Sea). Can. J. Fish.
Aquat. Sci. 54: 1270-1279.
Dam, H.G. and Peterson, W.T. 1993. Seasonal
contrasts in the diel vertical distribution, feeding
behavior, and grazing impact of the copepod
Temora longicornis in Long Island Sound. J. Mar.
Res. 51: 561-594.
Fenchel, T. 1986. The ecology of Heterotrophic
microflagellates. Adv. Microb. Ecol. 9: 57-95.
Fenchel, T. 1988. Microfauna in the planktonic food
chain. In: Blackburn, T.H., Sørensen, J. (eds).
Nitrogen cycling in coastal marine environments.
SCOPE, John Wiley & Sons Ltd: 59-65.
Gaard, E. 1994. Advection and seasonal development
of Calanus finmarchicus on the Faroe Plateau.
ICES CM 1994/L: 21. 16 pp.
Gaard, E. 1996a. Phytoplankton community structure
on the Faroe shelf. Fróðskaparrit 44: 95-106.
Gaard, E. 1996b. Life cycle, abundance and transport
of Calanus finmarchicus in Faroese waters. Ophelia
44: 59-70.
Gaard, E. 1999. Thc zooplankton community structure
in relation to its biological and physical environment