90
GORDON A. RILEY
over-estimate for the relatively poor waters of the Sargasso Sea, but
in view of other possible errors this is a quibble. Results indicated
that total oxygen consumption between 300 m and the bottom averaged
48 mg C.m-2.day-1, a figure in good agreement with the one obtained
in item (2). Most of this utilization occurred in the mid-depth region.
The estimated consumption between 1 000 m and the bottom was only
about 8 mg C/day.
(4) Riley (1951) compiled data on deep water zooplankton from
Leavitt (1938) and estimated what the respiratory requirements might
be if they were similar to experimental results obtained with surface
water forms at low temperatures and surface pressure. I n the absence
of any solid information about respiratory rates of deep water animals
under normal environmental conditions, this is the best that can be
done, and the results seemed more or less realistic. The total for the
depth range between 300 m and the bottom was 38 mg C.m-2.day-1.
An additional 4 mg C/day were estimated as the requirements for benthic bacteria and animals.
Riley et al. (1965) pointed out that although each calculation has
obvious deficiencies or possibilities of error, the four independent
methods yield a range of only 42-70 mg C/day, suggesting that this is
considerably better than an order of magnitude estimate for deep
water consumption.
An obvious deficiency in these estimates is the failure to specify
the respiratory needs of bacteria and other small heterotrophs. Their
inclusion would tend t o lower the estimate in item ( I ) , which is the
highest one, and increase item (4), the lowest one. There was no attempt
to do this in the paper cited, because the results appeared to be adequate
for the purpose that was in mind at that time, namely to attempt to
evaluate the residence time of particulate organic matter in deep water.
However, further examination of the biological system seems desirable at the present time. Some of the published views represent a piecemeal approach to the problem. Menzel and Ryther (1961) concluded
that zooplankton in the Sargasso Sea were capable of consuming
virtually all of the phytoplankton production, whereas Parsons and
Strickland (1962) suggested equal capabilities for small heterotrophs.
A compromise must be chosen between these extremes, for total phytoplankton production must be shared between the two kinds of populations.
Moreover, in the period since Riley et a,Z. (1965) published their
analysis several papers have appeared containing data which are in
marked disagreement with values used in the earlier analysis. The
whole subject needs to be reopened to further discussion. Thus the
GORDON A. RILEY
over-estimate for the relatively poor waters of the Sargasso Sea, but
in view of other possible errors this is a quibble. Results indicated
that total oxygen consumption between 300 m and the bottom averaged
48 mg C.m-2.day-1, a figure in good agreement with the one obtained
in item (2). Most of this utilization occurred in the mid-depth region.
The estimated consumption between 1 000 m and the bottom was only
about 8 mg C/day.
(4) Riley (1951) compiled data on deep water zooplankton from
Leavitt (1938) and estimated what the respiratory requirements might
be if they were similar to experimental results obtained with surface
water forms at low temperatures and surface pressure. I n the absence
of any solid information about respiratory rates of deep water animals
under normal environmental conditions, this is the best that can be
done, and the results seemed more or less realistic. The total for the
depth range between 300 m and the bottom was 38 mg C.m-2.day-1.
An additional 4 mg C/day were estimated as the requirements for benthic bacteria and animals.
Riley et al. (1965) pointed out that although each calculation has
obvious deficiencies or possibilities of error, the four independent
methods yield a range of only 42-70 mg C/day, suggesting that this is
considerably better than an order of magnitude estimate for deep
water consumption.
An obvious deficiency in these estimates is the failure to specify
the respiratory needs of bacteria and other small heterotrophs. Their
inclusion would tend t o lower the estimate in item ( I ) , which is the
highest one, and increase item (4), the lowest one. There was no attempt
to do this in the paper cited, because the results appeared to be adequate
for the purpose that was in mind at that time, namely to attempt to
evaluate the residence time of particulate organic matter in deep water.
However, further examination of the biological system seems desirable at the present time. Some of the published views represent a piecemeal approach to the problem. Menzel and Ryther (1961) concluded
that zooplankton in the Sargasso Sea were capable of consuming
virtually all of the phytoplankton production, whereas Parsons and
Strickland (1962) suggested equal capabilities for small heterotrophs.
A compromise must be chosen between these extremes, for total phytoplankton production must be shared between the two kinds of populations.
Moreover, in the period since Riley et a,Z. (1965) published their
analysis several papers have appeared containing data which are in
marked disagreement with values used in the earlier analysis. The
whole subject needs to be reopened to further discussion. Thus the