96
GORDON A. RILEY
numbers are approximately correct, and for convenience a value of
50 mg will be chosen arbitrarily, although the later discussion will
indicate that this may be an underestimate.
An additional simplification arises from the fact that the analyses
were not quite comparable as to depth ranges that were selected.
Zooplankton data by Menzel and Ryther (1962) were based on tows
made from 500 m to the surface, so that their calculation of zooplankton
consumption was lumped into a single estimate for this depth range. I n
item (4), deep water estimates of zooplankton Consumption were calculated from 300 m to the bottom, of which about 20 mg can be assigned
to the depth range of 300-500 m. To avoid counting part of the zooplankton twice, this number will be subtracted from the estimate based
on the data of Menzel and Ryther. The estimates for consumption by
zooplankton will then be 110 mg C in the upper 300 m, and the remainder of vertical column will remain the same.
Data for estimating heterotrophic consumption are scanty, as was
evident in the last section. Observations by Vaccaro and Jannasch
(1966) yield the following averages: 1-10 m, 0.045 pg C.litre-l.hr-l;
35-50 m, 0.061 ; 100 m, 0.004 (excepting one anomalously high value
of 0.062). Further, assuming that consumption from 100-300 m is
about 0.001, their lowest value for 100 m, the daily carbon requirement
for the upper 300 m would be 120 mg C/m2. A similar treatment of
the observations of Parsons and Strickland (1962) gives a value of 45
mg C/day. The agreement is not particularly close, and of course
neither estimate is directly applicable to the area in question. There
is the further question of whether experimental results of this type are
indicative of the natural rate of absorption of the more complicated
array of substances available in nature. Nevertheless, for what it may
be worth, the combined estimate for consumption by zooplankton and
heterotrophs in the upper 300 m plus the assumed deep water value
of 50 mg comes to 205-280 mg C, which is about two-thirds to threequarters of the postulated surface production.
Direct measurements of consumption by heterotrophs would be
desirable, but there are grave dangers of introducing experimental
artifacts into such determinations. Ordinary dark bottle incubation
is useless because of the well known problem of extensive bacterial
growth in bottles of stored sea water. Pomeroy and Johannes (1968)
have attempted to get around this problem by developing a method
for gentle filtration of large volumes of sea water, permitting short
term measurements of oxygen consumption in the concentrate. Their
paper contains an interesting descriptive account of the collections,
which has been mentioned earlier, in addition to the experimental
GORDON A. RILEY
numbers are approximately correct, and for convenience a value of
50 mg will be chosen arbitrarily, although the later discussion will
indicate that this may be an underestimate.
An additional simplification arises from the fact that the analyses
were not quite comparable as to depth ranges that were selected.
Zooplankton data by Menzel and Ryther (1962) were based on tows
made from 500 m to the surface, so that their calculation of zooplankton
consumption was lumped into a single estimate for this depth range. I n
item (4), deep water estimates of zooplankton Consumption were calculated from 300 m to the bottom, of which about 20 mg can be assigned
to the depth range of 300-500 m. To avoid counting part of the zooplankton twice, this number will be subtracted from the estimate based
on the data of Menzel and Ryther. The estimates for consumption by
zooplankton will then be 110 mg C in the upper 300 m, and the remainder of vertical column will remain the same.
Data for estimating heterotrophic consumption are scanty, as was
evident in the last section. Observations by Vaccaro and Jannasch
(1966) yield the following averages: 1-10 m, 0.045 pg C.litre-l.hr-l;
35-50 m, 0.061 ; 100 m, 0.004 (excepting one anomalously high value
of 0.062). Further, assuming that consumption from 100-300 m is
about 0.001, their lowest value for 100 m, the daily carbon requirement
for the upper 300 m would be 120 mg C/m2. A similar treatment of
the observations of Parsons and Strickland (1962) gives a value of 45
mg C/day. The agreement is not particularly close, and of course
neither estimate is directly applicable to the area in question. There
is the further question of whether experimental results of this type are
indicative of the natural rate of absorption of the more complicated
array of substances available in nature. Nevertheless, for what it may
be worth, the combined estimate for consumption by zooplankton and
heterotrophs in the upper 300 m plus the assumed deep water value
of 50 mg comes to 205-280 mg C, which is about two-thirds to threequarters of the postulated surface production.
Direct measurements of consumption by heterotrophs would be
desirable, but there are grave dangers of introducing experimental
artifacts into such determinations. Ordinary dark bottle incubation
is useless because of the well known problem of extensive bacterial
growth in bottles of stored sea water. Pomeroy and Johannes (1968)
have attempted to get around this problem by developing a method
for gentle filtration of large volumes of sea water, permitting short
term measurements of oxygen consumption in the concentrate. Their
paper contains an interesting descriptive account of the collections,
which has been mentioned earlier, in addition to the experimental