30
productivity between low values typical of oligotrophic waters and high
values characteristic of eutrophic regions. This geographical variability (up to two orders of magnitude) tends to overshadow the expression of seasonal differences.
The two most significant findings resulting from these investigations are: (a) that there is much greater
variability in the productivity parameters studied than had been previously thought, and (b) that the productivity of the Southern Ocean as
a whole, perhaps, is not as high as we were led to believe.
With regard to the former, Fogg (19 7 7) contends that the spatial
variations in primary production in the waters south of the Polar Front
cannot be accounted for by differences in incident radiation, water
temperature, or concentration of nitrate, phosphate, and silicate, as
each of these parameters has similar values over the entire area.
A
similar conclusion was reached by Holm-Hansen et al. (1977) who found
it difficult or impossible to deduce rate-limiting factors by the direct
comparison of anyone parameter (e.g. temperature) as many factors
vary simultaneously, including the species composition of phytoplankton
(where significant floral changes take place at the Polar Front region).
It would seem, however, that the physical structure of the water column
(i.e. stability and the depth of the mixed layer), the near freezing
temperatures of surface waters, and grazing are the most significant
factors controlling phytoplankton pnoduction in the Southern Ocean.
The second significant finding -- namely that recently acquired
data show that the primary productivity of the Southern Ocean is not
as high as originally believed -- has far-reaching implications with
regard to the future exploitation of the living resources of that ocean.
Management decisions regarding the exploitation of these resources must
be based on good estimates of primary productivity and on a better understanding of the flow of energy through the Antarctic marine ecosystem. A review of recent studies of Antarctic bacterioplankton,
dissolved organic matter, nanoplankton and sea ice-algae are forcing us to
to examine the classical description of the simple food chain from diatoms
7krill ~whales.
These studies suggest the presence of other pathways through which a major part of the available energy may be flowing.
This new paradigm (Fig. 4) may contain yet other strands, so that the
classic pathway may constitute only a part of the energy flow within
the Antarctic marine ecosystem.
productivity between low values typical of oligotrophic waters and high
values characteristic of eutrophic regions. This geographical variability (up to two orders of magnitude) tends to overshadow the expression of seasonal differences.
The two most significant findings resulting from these investigations are: (a) that there is much greater
variability in the productivity parameters studied than had been previously thought, and (b) that the productivity of the Southern Ocean as
a whole, perhaps, is not as high as we were led to believe.
With regard to the former, Fogg (19 7 7) contends that the spatial
variations in primary production in the waters south of the Polar Front
cannot be accounted for by differences in incident radiation, water
temperature, or concentration of nitrate, phosphate, and silicate, as
each of these parameters has similar values over the entire area.
A
similar conclusion was reached by Holm-Hansen et al. (1977) who found
it difficult or impossible to deduce rate-limiting factors by the direct
comparison of anyone parameter (e.g. temperature) as many factors
vary simultaneously, including the species composition of phytoplankton
(where significant floral changes take place at the Polar Front region).
It would seem, however, that the physical structure of the water column
(i.e. stability and the depth of the mixed layer), the near freezing
temperatures of surface waters, and grazing are the most significant
factors controlling phytoplankton pnoduction in the Southern Ocean.
The second significant finding -- namely that recently acquired
data show that the primary productivity of the Southern Ocean is not
as high as originally believed -- has far-reaching implications with
regard to the future exploitation of the living resources of that ocean.
Management decisions regarding the exploitation of these resources must
be based on good estimates of primary productivity and on a better understanding of the flow of energy through the Antarctic marine ecosystem. A review of recent studies of Antarctic bacterioplankton,
dissolved organic matter, nanoplankton and sea ice-algae are forcing us to
to examine the classical description of the simple food chain from diatoms
7krill ~whales.
These studies suggest the presence of other pathways through which a major part of the available energy may be flowing.
This new paradigm (Fig. 4) may contain yet other strands, so that the
classic pathway may constitute only a part of the energy flow within
the Antarctic marine ecosystem.