PARTICULATE ORGANIC MATTER I N SEA WATER
31
ratios are real, but more investigation will be needed in order to
determine limits of variation and regional aspects if any. Handa’s
evidence of a systematic increase in C : N ratios with depth cannot be
accepted as a general phenomenon without more thorough examination
in other regions. Data from the North Pacific by Parsons and Strickland (1962a) and from the south-eastern Indian Ocean (Newell, 1966)
show no such evidence.
There is some possibility that these variations can be ascribed to
differences in the relative proportions of amorphous aggregates and
flakes, the former consisting mostly of carbohydrate, while the latter
are also rich in protein. Counts now available do not reveal marked
differences in the proportion of these components ; however, counts
are somewhat deficient in their assessment of large aggregates, which
are few in number but might have sufficient mass to influence bulk
chemical analyses.
Holm-Hansen et al. (1966) found that the ratio of particulate
carbon to phosphorus in thc surface layer was about 33 :1 by weight.
A considerable fraction of this particulate matter presumably consisted
of living phytoplankton, and they regarded the observed ratio as being
fairly typical of phytoplankton growing in a nitrogen deficient medium.
The C : P ratio declined to a minimum at mid-depths and increased in
near-bottom waters. The average C : P ratio for the vertical column
was about 50 : l . The average ratio for the dissolved fraction was about
9 0 : l .
Menzel and Ryther (1964) found essentially no phosphorus in deep
water particulate matter. McGill ( 1964) was particularly concerned
with total organic phosphorus, particulate and dissolved, in his monographic treatment of phosphorus distribution in the Atlantic Ocean.
The concentrations were of the order of 0-0.15 pg at P/litre and averaging about 0.05 pg, suggesting that the C : P ratio by weight might be
several times higher than that obtained by Holm-Hansen et al. (1966)
for the dissolved fraction.
These observations, admittedly scanty, suggest that deep water
particulate matter is poor in phosphorus as compared with plankton
and the general assemblage of particulate matter in the surface layer.
Much of the phosphorus in living organisms is regenerated quickly
after their death, and apparently only a few components are resistant
to biological utilization. Holm-Hansen et al. (1966) suggested that most
of this deep water phosphorus is in nucleic acids, and thought that the
increase in C : P ratios which they observed in near-bottom waters was
due to the fact that nucleic acids were more resistant to decomposition
than protein.
31
ratios are real, but more investigation will be needed in order to
determine limits of variation and regional aspects if any. Handa’s
evidence of a systematic increase in C : N ratios with depth cannot be
accepted as a general phenomenon without more thorough examination
in other regions. Data from the North Pacific by Parsons and Strickland (1962a) and from the south-eastern Indian Ocean (Newell, 1966)
show no such evidence.
There is some possibility that these variations can be ascribed to
differences in the relative proportions of amorphous aggregates and
flakes, the former consisting mostly of carbohydrate, while the latter
are also rich in protein. Counts now available do not reveal marked
differences in the proportion of these components ; however, counts
are somewhat deficient in their assessment of large aggregates, which
are few in number but might have sufficient mass to influence bulk
chemical analyses.
Holm-Hansen et al. (1966) found that the ratio of particulate
carbon to phosphorus in thc surface layer was about 33 :1 by weight.
A considerable fraction of this particulate matter presumably consisted
of living phytoplankton, and they regarded the observed ratio as being
fairly typical of phytoplankton growing in a nitrogen deficient medium.
The C : P ratio declined to a minimum at mid-depths and increased in
near-bottom waters. The average C : P ratio for the vertical column
was about 50 : l . The average ratio for the dissolved fraction was about
9 0 : l .
Menzel and Ryther (1964) found essentially no phosphorus in deep
water particulate matter. McGill ( 1964) was particularly concerned
with total organic phosphorus, particulate and dissolved, in his monographic treatment of phosphorus distribution in the Atlantic Ocean.
The concentrations were of the order of 0-0.15 pg at P/litre and averaging about 0.05 pg, suggesting that the C : P ratio by weight might be
several times higher than that obtained by Holm-Hansen et al. (1966)
for the dissolved fraction.
These observations, admittedly scanty, suggest that deep water
particulate matter is poor in phosphorus as compared with plankton
and the general assemblage of particulate matter in the surface layer.
Much of the phosphorus in living organisms is regenerated quickly
after their death, and apparently only a few components are resistant
to biological utilization. Holm-Hansen et al. (1966) suggested that most
of this deep water phosphorus is in nucleic acids, and thought that the
increase in C : P ratios which they observed in near-bottom waters was
due to the fact that nucleic acids were more resistant to decomposition
than protein.