6
commonly are over 5 ~g chl. per liter.
Considering the high nutrient levels. in Antarctia waters, the peak
density of phytoplankton blooms do not appear impressive (Table 3) as
they range far below the expected level at nutrient depletion.
In sheltered waters, such as Gerlache Strait, 18-25 ~g chl. 1- 1 ha~ been observed (EI-Sayed 1968, Burkholder and Mandelli 1965). This level is not
much higher than that in the Arctic Ocean and adjacent seas.
Table 3. Typical ranges for chlorophyll a and primary production in Arctic and
Antarctic waters which are openor seasonally ice-covered.
Based on data from El-Sayed (1970b), Holm-Hansen et al. (1977) and Nemoto and Harrison (1981)
chlorophyll maximum, ~g 1- 1
expected at nutrient depletion
primary prod., 9 C m-2yr- l
primary prod., 9 C m-2 day-l
Antarctic
deep
inshore/shelf
8-10
18-25
40-80
16
25-130
0.05-4.7
Arctic
deep
inshore/shelf
10-15
10-15
15-20
25-55
50-250
0.2-2.5
Primary production in the Antarctic (Table 3) generally reflects
the variation in phytoplankton biomass (Holm-Hansen et al. 1977), implying that the variation in growth rate is small in comparison to biomass variation. Both the daily and the annual primary production vary
within wide limits with the higher values pertaining to inshore and
shelf areas (Table 3). On the average higher values have been reported
for the Arctic than for the Antarctic (Table 3). The seasonality of
polar phytoplankton is, however, inadequately known, so it may suffice
to say that the Arctic and the Antarctic are not notably different with
respect to annual primary production per unit area of open or seasonally
open water.
In spite of fewer investigations a general pattern for phytoplankton distribution can also be generated for the Arctic Ocean and its adjacent seas. The adjacent Norwegian Sea and the southern Barents Sea
where surface water of Atlantic origin prevails, and which are permanently ice free, develop a spring bloom in early to late May (Halldal
1953, Paasche 1969, Rey 1981, Sakshaug et al. 1981) when thermal stratification sets in. Along the Norwegian Coastal Current and the fjords
where stability is salinity dependent, the spring bloom occurs as early
as March-April. This difference in spite of identical light regimes
made Braarud and Klem (1931) postulate the importance of water column
stability for spring blooms, an idea which was brought forth further
by studies in the Denmark Strait and in the Greenland Sea (Braarud 1935,
Steeman Nielsen 1935). On this basis Sverdrup (1953) introduced a
simple mathematical model for the onset of spring blooms as well as the
commonly are over 5 ~g chl. per liter.
Considering the high nutrient levels. in Antarctia waters, the peak
density of phytoplankton blooms do not appear impressive (Table 3) as
they range far below the expected level at nutrient depletion.
In sheltered waters, such as Gerlache Strait, 18-25 ~g chl. 1- 1 ha~ been observed (EI-Sayed 1968, Burkholder and Mandelli 1965). This level is not
much higher than that in the Arctic Ocean and adjacent seas.
Table 3. Typical ranges for chlorophyll a and primary production in Arctic and
Antarctic waters which are openor seasonally ice-covered.
Based on data from El-Sayed (1970b), Holm-Hansen et al. (1977) and Nemoto and Harrison (1981)
chlorophyll maximum, ~g 1- 1
expected at nutrient depletion
primary prod., 9 C m-2yr- l
primary prod., 9 C m-2 day-l
Antarctic
deep
inshore/shelf
8-10
18-25
40-80
16
25-130
0.05-4.7
Arctic
deep
inshore/shelf
10-15
10-15
15-20
25-55
50-250
0.2-2.5
Primary production in the Antarctic (Table 3) generally reflects
the variation in phytoplankton biomass (Holm-Hansen et al. 1977), implying that the variation in growth rate is small in comparison to biomass variation. Both the daily and the annual primary production vary
within wide limits with the higher values pertaining to inshore and
shelf areas (Table 3). On the average higher values have been reported
for the Arctic than for the Antarctic (Table 3). The seasonality of
polar phytoplankton is, however, inadequately known, so it may suffice
to say that the Arctic and the Antarctic are not notably different with
respect to annual primary production per unit area of open or seasonally
open water.
In spite of fewer investigations a general pattern for phytoplankton distribution can also be generated for the Arctic Ocean and its adjacent seas. The adjacent Norwegian Sea and the southern Barents Sea
where surface water of Atlantic origin prevails, and which are permanently ice free, develop a spring bloom in early to late May (Halldal
1953, Paasche 1969, Rey 1981, Sakshaug et al. 1981) when thermal stratification sets in. Along the Norwegian Coastal Current and the fjords
where stability is salinity dependent, the spring bloom occurs as early
as March-April. This difference in spite of identical light regimes
made Braarud and Klem (1931) postulate the importance of water column
stability for spring blooms, an idea which was brought forth further
by studies in the Denmark Strait and in the Greenland Sea (Braarud 1935,
Steeman Nielsen 1935). On this basis Sverdrup (1953) introduced a
simple mathematical model for the onset of spring blooms as well as the