PARTICULATE ORGANIC MATTER I N SEA WATER
97
measurements. The latter were obtained from collections off Peru and
in subtropical latitudes of the western North Atlantic, an area well to
the west of the Bermuda station that is under present consideration and
which probably is somewhat richer biologically.
The results that they obtained were considerably higher than the
present writer’s estimates of in situ oxygen consumption in the central
Atlantic basin as determined by physical oceanographic calculations,
and the question is not fully resolved as to whether this represents real
regional differences or is due to errors in one method or the other.
Pomeroy and Johannes determined changes in rate of oxygen consumption with varying concentrations of their material and found that the
curves extrapolated to the origin. Thus there were no obvious indications of density dependence in the results.
Even their minimum values are equivalent to a carbon consumption
of about 300 mg.m-2.day-l in the upper 300 m and 500-600 mg in the
whole of the surface and mid-depth column. These figures do not fit
comfortably into the carbon balance sheet for the Sargasso Sea, but as
indicated earlier, they were dealing with more productive regions.
There is another way to look at the situation which might be more
informative. Their measurements in the Peru offing were accompanied
by experiments on C14 uptake and they obtained a mean P / R ratio of
1-5:1, where P is uncorrected C14 uptake, and R is total carbon consumption in the upper 500 m as determined by measurements of oxygen
consumption. Their experiments in the Atlantic did not include C14
measurements, but they reported that there was about a 1 : l ratio
between earlier C14 estimates in the area and their determinations of
respiratory requirements.
If the same sort of ratio is applicable to the Bermuda region, the
carbon consumption by ultraplankton in the upper 500 m would be
about 133-200 mg.m-2.day-1. Total utilization in the water column
would then be 290-360 mg, a range that is essentially in agreement
with production figures, although the indirect methods used to derive
it leave much to be desired.
Below 300 m there are three major oceanographic regimes, biologically speaking. There is a mid-depth zone which includes the
oxygen minimum layer and a mid-depth assemblage of animals which
comes up close to the surface at night, and migrates downward some
hundreds of metres to a daytime position that more or less corresponds
with the depth of the oxygen minimum layer.
Below the main thermocline the species composition changes and
the total quantity of animals is much reduced. The deep water animal
population will be referred to here simply as bathypelagic animals
97
measurements. The latter were obtained from collections off Peru and
in subtropical latitudes of the western North Atlantic, an area well to
the west of the Bermuda station that is under present consideration and
which probably is somewhat richer biologically.
The results that they obtained were considerably higher than the
present writer’s estimates of in situ oxygen consumption in the central
Atlantic basin as determined by physical oceanographic calculations,
and the question is not fully resolved as to whether this represents real
regional differences or is due to errors in one method or the other.
Pomeroy and Johannes determined changes in rate of oxygen consumption with varying concentrations of their material and found that the
curves extrapolated to the origin. Thus there were no obvious indications of density dependence in the results.
Even their minimum values are equivalent to a carbon consumption
of about 300 mg.m-2.day-l in the upper 300 m and 500-600 mg in the
whole of the surface and mid-depth column. These figures do not fit
comfortably into the carbon balance sheet for the Sargasso Sea, but as
indicated earlier, they were dealing with more productive regions.
There is another way to look at the situation which might be more
informative. Their measurements in the Peru offing were accompanied
by experiments on C14 uptake and they obtained a mean P / R ratio of
1-5:1, where P is uncorrected C14 uptake, and R is total carbon consumption in the upper 500 m as determined by measurements of oxygen
consumption. Their experiments in the Atlantic did not include C14
measurements, but they reported that there was about a 1 : l ratio
between earlier C14 estimates in the area and their determinations of
respiratory requirements.
If the same sort of ratio is applicable to the Bermuda region, the
carbon consumption by ultraplankton in the upper 500 m would be
about 133-200 mg.m-2.day-1. Total utilization in the water column
would then be 290-360 mg, a range that is essentially in agreement
with production figures, although the indirect methods used to derive
it leave much to be desired.
Below 300 m there are three major oceanographic regimes, biologically speaking. There is a mid-depth zone which includes the
oxygen minimum layer and a mid-depth assemblage of animals which
comes up close to the surface at night, and migrates downward some
hundreds of metres to a daytime position that more or less corresponds
with the depth of the oxygen minimum layer.
Below the main thermocline the species composition changes and
the total quantity of animals is much reduced. The deep water animal
population will be referred to here simply as bathypelagic animals