FACTORS GOVERNING PELAGIC PRODUCTION IN POLAR OCEANS
E.SAKSHAUG 1 and O.HOLM-HANSEN 2
luniversity of Trondheim, Biological Station,
N-7000 Trondheim, Norway
2 Polar Research Program, Scripps Institution of
Oceanography, University of California, La Jolla,
California 92093, USA.
INTRODUCTION
The standing stock of pelagic primary producers is conveniently
eXPressed as the difference between growth and reduction of the standing stock by grazing or by sinking out of the euphotic zone. The rate
of growth is determined largely by environmental variables such as the
light regime, temperature, and nutrient supply. In polar regions these
variables are generally quite different than those in lower latitudes.
The atmospheric light regime, for instance fluctuates extremely through
the season at high latitudes. Sea ice affects the submarine light
regime profoundly, and the formation and melting of ice affect the stability of the water column.
The Arctic and Antarctic Oceans do, however, also differ in
certain respects : size, topographical features, large-scale water
transport patterns, and the magnitude of nutrient supply to the euphotic zone. Therefore we cannot assume a priori that the primary production in the two areas are governed by environmental variables in an
identical fashion even if the seasonal variation in phytoplankton standing stocks may not be notably different.
In this paper we attempt to review existing knowledge regarding
phytoplankton growth V8. environmental variables in polar seas in relation to geographical and seasonal distribution of standing stock. We
shall deal only with pelagic primary producers, which account for most
primary production in polar regions. Ice biota, of which the ecology
has been reviewed elsewhere (Horner 1976, 1977), often attain a high
standing stock but shows low production due to light limitation (HolmHansen and Huntley 1984). Benthic algae, although of much ecological
importance in- specific habitats, also contribute but a small percentage
of the total primary production at high latitudes. As a "background"
to viewing primary production in the polar regions, it is of interest
to note that fisheries experts predict that the Antarctic seas can sustain a krill harvest of over 100 million metric tons a year, as compared
to the present total world harvest of about 75 million tons per year
of fish and shellfish (Gulland 1970). Does this reflect very high primary production in the Antarctic, or does it merely reflect a short
and efficient food chain ?
PHYSICAL AND CHEMICAL FEATURES
The major difference_ between the Arctic and the Antarctic involves
E.SAKSHAUG 1 and O.HOLM-HANSEN 2
luniversity of Trondheim, Biological Station,
N-7000 Trondheim, Norway
2 Polar Research Program, Scripps Institution of
Oceanography, University of California, La Jolla,
California 92093, USA.
INTRODUCTION
The standing stock of pelagic primary producers is conveniently
eXPressed as the difference between growth and reduction of the standing stock by grazing or by sinking out of the euphotic zone. The rate
of growth is determined largely by environmental variables such as the
light regime, temperature, and nutrient supply. In polar regions these
variables are generally quite different than those in lower latitudes.
The atmospheric light regime, for instance fluctuates extremely through
the season at high latitudes. Sea ice affects the submarine light
regime profoundly, and the formation and melting of ice affect the stability of the water column.
The Arctic and Antarctic Oceans do, however, also differ in
certain respects : size, topographical features, large-scale water
transport patterns, and the magnitude of nutrient supply to the euphotic zone. Therefore we cannot assume a priori that the primary production in the two areas are governed by environmental variables in an
identical fashion even if the seasonal variation in phytoplankton standing stocks may not be notably different.
In this paper we attempt to review existing knowledge regarding
phytoplankton growth V8. environmental variables in polar seas in relation to geographical and seasonal distribution of standing stock. We
shall deal only with pelagic primary producers, which account for most
primary production in polar regions. Ice biota, of which the ecology
has been reviewed elsewhere (Horner 1976, 1977), often attain a high
standing stock but shows low production due to light limitation (HolmHansen and Huntley 1984). Benthic algae, although of much ecological
importance in- specific habitats, also contribute but a small percentage
of the total primary production at high latitudes. As a "background"
to viewing primary production in the polar regions, it is of interest
to note that fisheries experts predict that the Antarctic seas can sustain a krill harvest of over 100 million metric tons a year, as compared
to the present total world harvest of about 75 million tons per year
of fish and shellfish (Gulland 1970). Does this reflect very high primary production in the Antarctic, or does it merely reflect a short
and efficient food chain ?
PHYSICAL AND CHEMICAL FEATURES
The major difference_ between the Arctic and the Antarctic involves