PARTICULATE ORGANIC MATTER I N SEA WATER
99
rate several times that of their apparent sinking rate, although there is
some question as to what proportion of total carbon will be so affected.
So again there is a considerable range in possible estimates, from
about 109 to 200 mg C.m-2.day-1 in the 300-900 m depth range. The
most likely value is toward the upper end of this range, and a major
proportion of the consumption is believed to occur between 100 and
300 m.
With regard to deep water below the transition zone, physical
oceanographic computation of oxygen consumption (Riley, 195 1 )
indicated that carbon utilization in the bathypelagic zone and on the
bottom totalled 9.4 mg C/m2. A somewhat higher value of 14-16 mg
is indicated for metabolic consumption by bacteria and animals in the
bathypelagic zone and on the bottom.
Again there is some variation in results, but this amount of agreement is reassuring, because the earlier estimate based on oxygen consumption was drastically over-simplified. The problem is simply that
oxygen consumption in deep water is so slight that extensive averaging
is necessary in order to get a body of data that will yield consistent
results. I n this case data were combined into a single north-south
profile of the Atlantic Ocean. Within this profile the deep water showed
an apparent oxygen utilization, as defined by Redfield (1942), which
averaged about 2 ml/litre. If this were due entirely to biological
utilization, the rate of consumption could be calculated in terms of
the age of the sea water. The age probably falls within the general
range of 250-750 years. Calculated carbon utilization in the whole
deepwater column would be about 12-33 mg C.m-2.day- l .
These are maximum values because part of the loss in oxygen is due
to transfer upward toward the oxygen minimum. The analysis utilized
estimates of vertical and horizontal eddy coefficients derived from the
salinity distribution to correct for physical dissipation of oxygen, and
the residual value was the estimate given above. It will be apparent
from the method of calculation that this is a generalized statistic, and
its application to any particular area is questionable. However, it is
the only information of its kind available.
This analysis possibly should be reworked, incorporating new data
and using a finer network of stations. The broad grid that was used
failed to delineate narrow, deep ocean currents, which indeed were
not known to exist at that time, so that total advective circulation
was underestimated. Sverdrup et al. (1942) and Riley (1951) computed
the average age of the deep water as about 1000 years, which now
appears to be an over-estimate, and in both cases this was due to the
assumption that the advective pattern was broader and more diffuse.
99
rate several times that of their apparent sinking rate, although there is
some question as to what proportion of total carbon will be so affected.
So again there is a considerable range in possible estimates, from
about 109 to 200 mg C.m-2.day-1 in the 300-900 m depth range. The
most likely value is toward the upper end of this range, and a major
proportion of the consumption is believed to occur between 100 and
300 m.
With regard to deep water below the transition zone, physical
oceanographic computation of oxygen consumption (Riley, 195 1 )
indicated that carbon utilization in the bathypelagic zone and on the
bottom totalled 9.4 mg C/m2. A somewhat higher value of 14-16 mg
is indicated for metabolic consumption by bacteria and animals in the
bathypelagic zone and on the bottom.
Again there is some variation in results, but this amount of agreement is reassuring, because the earlier estimate based on oxygen consumption was drastically over-simplified. The problem is simply that
oxygen consumption in deep water is so slight that extensive averaging
is necessary in order to get a body of data that will yield consistent
results. I n this case data were combined into a single north-south
profile of the Atlantic Ocean. Within this profile the deep water showed
an apparent oxygen utilization, as defined by Redfield (1942), which
averaged about 2 ml/litre. If this were due entirely to biological
utilization, the rate of consumption could be calculated in terms of
the age of the sea water. The age probably falls within the general
range of 250-750 years. Calculated carbon utilization in the whole
deepwater column would be about 12-33 mg C.m-2.day- l .
These are maximum values because part of the loss in oxygen is due
to transfer upward toward the oxygen minimum. The analysis utilized
estimates of vertical and horizontal eddy coefficients derived from the
salinity distribution to correct for physical dissipation of oxygen, and
the residual value was the estimate given above. It will be apparent
from the method of calculation that this is a generalized statistic, and
its application to any particular area is questionable. However, it is
the only information of its kind available.
This analysis possibly should be reworked, incorporating new data
and using a finer network of stations. The broad grid that was used
failed to delineate narrow, deep ocean currents, which indeed were
not known to exist at that time, so that total advective circulation
was underestimated. Sverdrup et al. (1942) and Riley (1951) computed
the average age of the deep water as about 1000 years, which now
appears to be an over-estimate, and in both cases this was due to the
assumption that the advective pattern was broader and more diffuse.