PARTICULATE ORGANIC MATTER IN SEA WATER
19
corrections were made. However, in all three papers the values reported for particulate organic carbon were considerably lower than
most analyses previously reported. As indicated earlier, preliminary
work by P. J. Wangersky (personal communication) has shown no
evidence that dissolved organic materials with molecular weights of
less than 10 000 are adsorbed to an appreciable extent on silver filters.
Thus a correction factor probably is improper, and in either case these
analyses are not comparable with older data and cannot be included
in the general regional analysis.
(b) Regional variations in organic carbon. As far as the surface layer
is concerned, present data are insufficient to draw conclusions about
seasonal cycles or regional variations. I n areas where data are available for more than one season, large variations have been observed,
and in most cases the highest values have been obtained in spring.
This is to be expected. A spring diatom flowering in the open sea
commonly has a chlorophyll concentration of the order of 2-10 pgllitre,
and the carbon content of a phytoplankton crop of this size probably
is about 60-300 pgllitre. Thus a large proportion of the total carbon
reported during the spring season may be derived from living cells.
However, the particle counts described earlier suggest that non-living
organic matter also may increase at this season.
At other seasons the quantity of phytoplankton carbon is likely to
be at least an order of magnitude lower than at the height of the spring
flowering. Referring again to particle counts, the non-living fraction
may then be somewhat larger than the quantity of phytoplankton
carbon.
No great improvement in our knowledge of particulate organic
matter in the surface layer will be obtained until more information is
available on seasonal cycles of organic carbon and on fractionation into
its different components. A semiquantitative estimate of phytoplankton
carbon can be made on the basis of chlorophyll analyses; however,
chlorophyll : carbon ratios are variable, and there is lack of agreement
as to limits of variability. ATP analyses (Holm-Hansen and Booth,
1966) and DNA analyses (Holm-Hansen et al., 1968) possibly will
supply a more precise separation of living and non-living fractions.
Modern techniques seem more or less adequate for the task, but
accumulation of data will be slow. After many years of phytoplankton
investigation there are still only a few open ocean areas where we have
a satisfactory knowledge of seasonal cycles and average abundance.
The larger task of determining total organic matter and its components
will also require years to accomplish.
19
corrections were made. However, in all three papers the values reported for particulate organic carbon were considerably lower than
most analyses previously reported. As indicated earlier, preliminary
work by P. J. Wangersky (personal communication) has shown no
evidence that dissolved organic materials with molecular weights of
less than 10 000 are adsorbed to an appreciable extent on silver filters.
Thus a correction factor probably is improper, and in either case these
analyses are not comparable with older data and cannot be included
in the general regional analysis.
(b) Regional variations in organic carbon. As far as the surface layer
is concerned, present data are insufficient to draw conclusions about
seasonal cycles or regional variations. I n areas where data are available for more than one season, large variations have been observed,
and in most cases the highest values have been obtained in spring.
This is to be expected. A spring diatom flowering in the open sea
commonly has a chlorophyll concentration of the order of 2-10 pgllitre,
and the carbon content of a phytoplankton crop of this size probably
is about 60-300 pgllitre. Thus a large proportion of the total carbon
reported during the spring season may be derived from living cells.
However, the particle counts described earlier suggest that non-living
organic matter also may increase at this season.
At other seasons the quantity of phytoplankton carbon is likely to
be at least an order of magnitude lower than at the height of the spring
flowering. Referring again to particle counts, the non-living fraction
may then be somewhat larger than the quantity of phytoplankton
carbon.
No great improvement in our knowledge of particulate organic
matter in the surface layer will be obtained until more information is
available on seasonal cycles of organic carbon and on fractionation into
its different components. A semiquantitative estimate of phytoplankton
carbon can be made on the basis of chlorophyll analyses; however,
chlorophyll : carbon ratios are variable, and there is lack of agreement
as to limits of variability. ATP analyses (Holm-Hansen and Booth,
1966) and DNA analyses (Holm-Hansen et al., 1968) possibly will
supply a more precise separation of living and non-living fractions.
Modern techniques seem more or less adequate for the task, but
accumulation of data will be slow. After many years of phytoplankton
investigation there are still only a few open ocean areas where we have
a satisfactory knowledge of seasonal cycles and average abundance.
The larger task of determining total organic matter and its components
will also require years to accomplish.