PARTICULATE ORGANIC MATTER I N SEA WATER
101
a considerable oxygen deficit during the slow northward movement of
the water.
The difficulty with the core method is that it is incapable of detecting this biological deficit except under certain special circumstances.
The observed oxygen concentrations a t the two ends of the profile are
arbitrarily chosen to compute intermediate values. These concentrations show an apparent oxygen utilization, but whether it has taken
place locally or at the point of origin or how rapidly it has occurred
are unknown. Menzel and Ryther begin with values that do not deny
their hypothesis but do not support it either. And if local utilization
has occurred, the use of arbitrary reference values will hide any utilization that has taken place at intermediate points, provided this utilization proceeds at a reasonably constant rate with respect to time and
mixing rates along the path of flow. Only pronounced anomalies and
non-linearities can be detected.
There is, unfortunately, no solution to this problem except the
treatment developed by Sverdrup et al. (1942), requiring evaluation of
advection and diffusivity in terms of conservative properties and
application to non-conservative distributions to derive a residual rate
of biological change. Ideally this is done as a three-dimensional problem, although a two-dimensional profile can serve the purpose. This
type of analysis, developed by Riley (1952), is not a very dependable
solution, because there are so many complexities and uncertainties in
the application. However, vertical and horizontal diffusion are both
important enough so that one-dimensional analysis of deep water is
seldom effective, even aside from pitfalls of the kind described.
Returning to a consideration of biological problems in waters below
300 m, total consumption was postulated to be of the order of 50 mg
C.m-2.day-1, and earlier estimates indicated that 38 mg are consumed
by pelagic animals and 4 mg on the bottom. However, no real confidence can be placed in these figures. They are largely derived by
extrapolation of experiments on surface water forms. Little is known
about effects of pressure and nutritional state on the respiratory rates
of these organisms.
Some speculation is necessary in order to try to fit the pieces of the
puzzle together. One can suppose that animal respiration might consume as much as 38 mg C/day, or perhaps it might be only half that
much. This would leave 8-27 mg/day for heterotrophs. Converting
to more familiar terms, this is 1-4 x 10-4pgC.litre-l.hr-l as an
average for the deep water mass as a whole, a range that is one order
of magnitude less than observed uptake at depths of 100-175 m, two
orders less than in near-surface waters, and essentially similar to the
101
a considerable oxygen deficit during the slow northward movement of
the water.
The difficulty with the core method is that it is incapable of detecting this biological deficit except under certain special circumstances.
The observed oxygen concentrations a t the two ends of the profile are
arbitrarily chosen to compute intermediate values. These concentrations show an apparent oxygen utilization, but whether it has taken
place locally or at the point of origin or how rapidly it has occurred
are unknown. Menzel and Ryther begin with values that do not deny
their hypothesis but do not support it either. And if local utilization
has occurred, the use of arbitrary reference values will hide any utilization that has taken place at intermediate points, provided this utilization proceeds at a reasonably constant rate with respect to time and
mixing rates along the path of flow. Only pronounced anomalies and
non-linearities can be detected.
There is, unfortunately, no solution to this problem except the
treatment developed by Sverdrup et al. (1942), requiring evaluation of
advection and diffusivity in terms of conservative properties and
application to non-conservative distributions to derive a residual rate
of biological change. Ideally this is done as a three-dimensional problem, although a two-dimensional profile can serve the purpose. This
type of analysis, developed by Riley (1952), is not a very dependable
solution, because there are so many complexities and uncertainties in
the application. However, vertical and horizontal diffusion are both
important enough so that one-dimensional analysis of deep water is
seldom effective, even aside from pitfalls of the kind described.
Returning to a consideration of biological problems in waters below
300 m, total consumption was postulated to be of the order of 50 mg
C.m-2.day-1, and earlier estimates indicated that 38 mg are consumed
by pelagic animals and 4 mg on the bottom. However, no real confidence can be placed in these figures. They are largely derived by
extrapolation of experiments on surface water forms. Little is known
about effects of pressure and nutritional state on the respiratory rates
of these organisms.
Some speculation is necessary in order to try to fit the pieces of the
puzzle together. One can suppose that animal respiration might consume as much as 38 mg C/day, or perhaps it might be only half that
much. This would leave 8-27 mg/day for heterotrophs. Converting
to more familiar terms, this is 1-4 x 10-4pgC.litre-l.hr-l as an
average for the deep water mass as a whole, a range that is one order
of magnitude less than observed uptake at depths of 100-175 m, two
orders less than in near-surface waters, and essentially similar to the