21
bloom (entirely dominated by the colonial flagellate Phaeocystis
pouchetti (Hariot) Langerheim was widespread over the southern Ross
Sea region (nearly 620 km), and extended from the Ross Ice Shelf offshore to about 185 km.
At some stations, ~ pouchetti reached depths
of 100 to 150 m. Another large bloom of ~ pouchetti was encountered
during the German Antarctic Expedition (November-December, 1980) in the
vicinity of the South Shetland Islands in the Bransfield Strait; the
average concentration of chlorophyll was between 5-11 mg/m 3 (von
Bodungen, et al., 1982).
The vertical distribution of chlorophyll ~ shows that maximum
values were found at subsurface depths. Following these maxima, there
is a gradual decrease in the chlorophyll values to the depth of 200 m,
below which chlorophyll concentration is greatly reduced (EI-Sayed,
1970; El-Sayed and Turner, 1977; El-Sayed and Weber, 1982). At several
stations in the Pacific and Indian sectors of the Antarctic, substantial
amounts of chlorophyll were found below the euphotic zone.
Primary productivity data from the Southern Ocean, in general,
showed good correlation with the distribution of the phytoplankton
standing crop.
For instance, low values were reported in the Drake
Passage, the Bellingshausen Sea, and in the oceanic waters in general.
The open-ocean system recorded rates of production typical of oligotrophic regions ~ 0.1 gc/m 2 /day). On the other hand, high values were
found in coastal regions and in the vicinity of Antarctic and subAntarctic islands. For example, EI-Sayed (1967) recorded 3.2 gc/m 2 /day
in the Gerlache Strait; Mandelli and Burkholder (1966) reported 3.62
gC/m 2 /day near Deception Island. Horne et al. (1969) found a peak of
2
productivity of 2.8 gC/m /day in the inshore waters of Signy Island
in the South Orkney Islands. These values which are comparable to the
upwelling systems off Peru, southeast Arabia, Somalia and southwest
Africa no doubt have perpetuated the belief in the proverbial richness
of the Antarctic waters.
They may also have contributed to the high
productivity estimates of the Antarctic waters published in the midsixties.
As to the vertical distribution of primary productivity in the
circum-Antarctic waters, maximum photosynthetic activity occurred at
depths corresponding to between 25 and 50% of surface light intensity.
At most of the stations where primary production measurements were
14
carried out,
C uptake extended well below the depth of 1% surface
illumination (i.e. the euphotic zonel. The contribution of primary
production below the euphotic zone in the Ross and Weddell Seas was
bloom (entirely dominated by the colonial flagellate Phaeocystis
pouchetti (Hariot) Langerheim was widespread over the southern Ross
Sea region (nearly 620 km), and extended from the Ross Ice Shelf offshore to about 185 km.
At some stations, ~ pouchetti reached depths
of 100 to 150 m. Another large bloom of ~ pouchetti was encountered
during the German Antarctic Expedition (November-December, 1980) in the
vicinity of the South Shetland Islands in the Bransfield Strait; the
average concentration of chlorophyll was between 5-11 mg/m 3 (von
Bodungen, et al., 1982).
The vertical distribution of chlorophyll ~ shows that maximum
values were found at subsurface depths. Following these maxima, there
is a gradual decrease in the chlorophyll values to the depth of 200 m,
below which chlorophyll concentration is greatly reduced (EI-Sayed,
1970; El-Sayed and Turner, 1977; El-Sayed and Weber, 1982). At several
stations in the Pacific and Indian sectors of the Antarctic, substantial
amounts of chlorophyll were found below the euphotic zone.
Primary productivity data from the Southern Ocean, in general,
showed good correlation with the distribution of the phytoplankton
standing crop.
For instance, low values were reported in the Drake
Passage, the Bellingshausen Sea, and in the oceanic waters in general.
The open-ocean system recorded rates of production typical of oligotrophic regions ~ 0.1 gc/m 2 /day). On the other hand, high values were
found in coastal regions and in the vicinity of Antarctic and subAntarctic islands. For example, EI-Sayed (1967) recorded 3.2 gc/m 2 /day
in the Gerlache Strait; Mandelli and Burkholder (1966) reported 3.62
gC/m 2 /day near Deception Island. Horne et al. (1969) found a peak of
2
productivity of 2.8 gC/m /day in the inshore waters of Signy Island
in the South Orkney Islands. These values which are comparable to the
upwelling systems off Peru, southeast Arabia, Somalia and southwest
Africa no doubt have perpetuated the belief in the proverbial richness
of the Antarctic waters.
They may also have contributed to the high
productivity estimates of the Antarctic waters published in the midsixties.
As to the vertical distribution of primary productivity in the
circum-Antarctic waters, maximum photosynthetic activity occurred at
depths corresponding to between 25 and 50% of surface light intensity.
At most of the stations where primary production measurements were
14
carried out,
C uptake extended well below the depth of 1% surface
illumination (i.e. the euphotic zonel. The contribution of primary
production below the euphotic zone in the Ross and Weddell Seas was