Atlantic Polar Biome
135
complex where lateral interleaving of water masses occurs along a convoluted ice front.
Embayments along the receding ice edge correspond to the flow of warm water associated
with topographic troughs on the Chukchi shelf and elsewhere.
Little eddy activity occurs below the permanent ice cover of the Arctic Ocean, and
mesoscale features there are thought to be very long-lived (Muench, 1990), but ice-edge
fronts and shelf-edge fronts are significant elsewhere. The position of the ice edge of the
Beaufort and Chukchi Seas during the summer is constrained by the position of the shelf
break. Warm, northward currents are steered by deep troughs on the Chukchi shelf, and
the ice-edge frontal system therefore follows this topography (Muench, 1990).
You will perhaps have noted that I have not commented on the concern now widely
expressed that the permanent ice-cover of the Arctic ocean is yielding to atmospheric CO 2 -
induced climate change; throughout this work, such issues are avoided: it is enough here
to try to characterize the pristine regional ecosystem. But, if the breakup is progressing
as is currently reported, then much of the foregoing account will require modification
rather soon.
Response of the Pelagic Ecosystems
The general ecology and physiology of arctic organisms is now reasonably well explored,
perhaps especially because their diversity is as low as anywhere in the oceans, so that
relationships between them are simpler to understand than in warm seas. Arctic heterotrophic bacteria, for example, act as a uniform psychrophilic assemblage and actively
metabolize glucose and amino acids down to subzero temperatures, ensuring turnover
rates for glucose and amino acids of 1–50% daily in the upper 100 m of the North Water
(Li and Dickie, 1984).
While recognizing that they represent a continuum, it may help us to understand the
ecology of the BPLR province if we recognize three different ecological zones: (i) those
areas that are permanently ice covered, (ii) the marginal ice zone during retreat in spring
or formation in autumn, which may or may not have “polynya” status, and (iii) the more
extensive open-water areas of summer. As noted earlier, each of these zones has been
extensively investigated in the Canadian archipelago and northern Baffin Bay.
Permanently Ice-covered Regions The Arctic Ocean will serve as a model for all parts
of BPLR that remain ice-fast in summer, with the caution that in ice-covered passages
within the archipelago strong currents must advect biota from adjacent open-water areas.
Biota found below the ice may not have developed there. In fact, it has been calculated
that during their larval period of < 90 days, boreal cod may drift as far as 2500 km
through the Canadian archipelago from their point of origin.
The strong nitracline at the halocline of the Arctic Ocean is not mediated by local
biology. Rather, it is due to the fact that the halocline water originates on the surrounding
continental shelves and carries from there the nutrient signatures of Pacific and Atlantic
Ocean water. Though some biological uptake of nitrogen does occur in the surface water,
levels remain relatively high compared with those of other oceans; 4 or 5 M is normal in
the central Arctic Ocean (Jones et al., 1990). For silicate and phosphate, concentrations
above and below the halocline are similar.
In computing both the sub-ice irradiance field and the total plant production in the
Arctic Ocean in summer, it will be necessary to recognize the existence of a subaerial algal
community, the so-called nivalis cryobionts dominated by Chlamydomonas nivalis, on
the surface of the snowpack. These cells form highly visible patches ranging in color from
green to red in which the cells occur either singly or as mucilaginous aggregates associated
with wind-blown dust particles: cell concentrations may reach 15 × 10
5 cells ml
−1 in
melted snow from such patches. The 1991 Polastern voyage across the central basin of
135
complex where lateral interleaving of water masses occurs along a convoluted ice front.
Embayments along the receding ice edge correspond to the flow of warm water associated
with topographic troughs on the Chukchi shelf and elsewhere.
Little eddy activity occurs below the permanent ice cover of the Arctic Ocean, and
mesoscale features there are thought to be very long-lived (Muench, 1990), but ice-edge
fronts and shelf-edge fronts are significant elsewhere. The position of the ice edge of the
Beaufort and Chukchi Seas during the summer is constrained by the position of the shelf
break. Warm, northward currents are steered by deep troughs on the Chukchi shelf, and
the ice-edge frontal system therefore follows this topography (Muench, 1990).
You will perhaps have noted that I have not commented on the concern now widely
expressed that the permanent ice-cover of the Arctic ocean is yielding to atmospheric CO 2 -
induced climate change; throughout this work, such issues are avoided: it is enough here
to try to characterize the pristine regional ecosystem. But, if the breakup is progressing
as is currently reported, then much of the foregoing account will require modification
rather soon.
Response of the Pelagic Ecosystems
The general ecology and physiology of arctic organisms is now reasonably well explored,
perhaps especially because their diversity is as low as anywhere in the oceans, so that
relationships between them are simpler to understand than in warm seas. Arctic heterotrophic bacteria, for example, act as a uniform psychrophilic assemblage and actively
metabolize glucose and amino acids down to subzero temperatures, ensuring turnover
rates for glucose and amino acids of 1–50% daily in the upper 100 m of the North Water
(Li and Dickie, 1984).
While recognizing that they represent a continuum, it may help us to understand the
ecology of the BPLR province if we recognize three different ecological zones: (i) those
areas that are permanently ice covered, (ii) the marginal ice zone during retreat in spring
or formation in autumn, which may or may not have “polynya” status, and (iii) the more
extensive open-water areas of summer. As noted earlier, each of these zones has been
extensively investigated in the Canadian archipelago and northern Baffin Bay.
Permanently Ice-covered Regions The Arctic Ocean will serve as a model for all parts
of BPLR that remain ice-fast in summer, with the caution that in ice-covered passages
within the archipelago strong currents must advect biota from adjacent open-water areas.
Biota found below the ice may not have developed there. In fact, it has been calculated
that during their larval period of < 90 days, boreal cod may drift as far as 2500 km
through the Canadian archipelago from their point of origin.
The strong nitracline at the halocline of the Arctic Ocean is not mediated by local
biology. Rather, it is due to the fact that the halocline water originates on the surrounding
continental shelves and carries from there the nutrient signatures of Pacific and Atlantic
Ocean water. Though some biological uptake of nitrogen does occur in the surface water,
levels remain relatively high compared with those of other oceans; 4 or 5 M is normal in
the central Arctic Ocean (Jones et al., 1990). For silicate and phosphate, concentrations
above and below the halocline are similar.
In computing both the sub-ice irradiance field and the total plant production in the
Arctic Ocean in summer, it will be necessary to recognize the existence of a subaerial algal
community, the so-called nivalis cryobionts dominated by Chlamydomonas nivalis, on
the surface of the snowpack. These cells form highly visible patches ranging in color from
green to red in which the cells occur either singly or as mucilaginous aggregates associated
with wind-blown dust particles: cell concentrations may reach 15 × 10
5 cells ml
−1 in
melted snow from such patches. The 1991 Polastern voyage across the central basin of