2
GORDON A. RILEY
production, but the range that has been given establishes a reasonable
order of magnitude.
Benthic algae and rooted aquatic vegetation of the shore zone can
have a level of production that is an order of magnitude higher than
the values given for phytoplankton, and the output from rivers and
salt marshes can be very important locally. However, the area where
such factors are important is less than 1% of the world oceans, and
there is little doubt that phytoplankton provides 90% or more of the
basic stock of oceanic organic matter.
Although much of the organic matter is used quickly, the accumulated remains of non-living organic matter, particulate and dissolved,
are larger than the annual production and much larger than the
quantity of living organisms that is present at any one time.
Most of the published data for particulate organic carbon, as
determined by passing the water through a filter with a pore size of 1 p
or less and analysing the collected material for its carbon content, fall
in the general range of 5-50 pg C/litre in deepwater samples and are
somewhat higher in the surface layer. A reasonable average for total
filterable carbon, summed from surface to bottom in an average water
column of 4 000 m would be 100 g/m2. Filter-passing organic substances, commonly denoted as the dissolved fraction but obviously
including colloids and any particles small enough to escape the filter,
commonly have a carbon content of the order of 0.5 mg/litre as determined by wet oxidation, so that the total quantity in a water column
of 1 m2 is about 2 kg. This is roughly two orders of magnitude higher
than the amount present at any one time in living organisms, and this
may be a minimum estimate, for there are indications (Skopintsev,
1966) that dry combustion methods yield somewhat larger values.
The fact that these organic remains have accumulated in such large
quantities, even though most of the products of photosynthesis are
consumed quickly by living organisms, is sufficient evidence that they
have a slow rate of degradation. The reasons for this are not altogether
clear, for biochemical characterization of the material has not proceeded
far enough to give us a detailed picture of composition. We know that
some of the dissolved substances are highly refractory and have little
biological utility. We also know that there are simple sugars, amino
acids, and other substances which are potentially usable ; however,
except in near surface waters the concentration of such substances
appears to be too low to provide anything more than bare subsistence
for a scanty population of heterotrophs.
The situation is similar with respect to non-living particulate matter.
The total stock is large, and some of it is assimilable; however, the
GORDON A. RILEY
production, but the range that has been given establishes a reasonable
order of magnitude.
Benthic algae and rooted aquatic vegetation of the shore zone can
have a level of production that is an order of magnitude higher than
the values given for phytoplankton, and the output from rivers and
salt marshes can be very important locally. However, the area where
such factors are important is less than 1% of the world oceans, and
there is little doubt that phytoplankton provides 90% or more of the
basic stock of oceanic organic matter.
Although much of the organic matter is used quickly, the accumulated remains of non-living organic matter, particulate and dissolved,
are larger than the annual production and much larger than the
quantity of living organisms that is present at any one time.
Most of the published data for particulate organic carbon, as
determined by passing the water through a filter with a pore size of 1 p
or less and analysing the collected material for its carbon content, fall
in the general range of 5-50 pg C/litre in deepwater samples and are
somewhat higher in the surface layer. A reasonable average for total
filterable carbon, summed from surface to bottom in an average water
column of 4 000 m would be 100 g/m2. Filter-passing organic substances, commonly denoted as the dissolved fraction but obviously
including colloids and any particles small enough to escape the filter,
commonly have a carbon content of the order of 0.5 mg/litre as determined by wet oxidation, so that the total quantity in a water column
of 1 m2 is about 2 kg. This is roughly two orders of magnitude higher
than the amount present at any one time in living organisms, and this
may be a minimum estimate, for there are indications (Skopintsev,
1966) that dry combustion methods yield somewhat larger values.
The fact that these organic remains have accumulated in such large
quantities, even though most of the products of photosynthesis are
consumed quickly by living organisms, is sufficient evidence that they
have a slow rate of degradation. The reasons for this are not altogether
clear, for biochemical characterization of the material has not proceeded
far enough to give us a detailed picture of composition. We know that
some of the dissolved substances are highly refractory and have little
biological utility. We also know that there are simple sugars, amino
acids, and other substances which are potentially usable ; however,
except in near surface waters the concentration of such substances
appears to be too low to provide anything more than bare subsistence
for a scanty population of heterotrophs.
The situation is similar with respect to non-living particulate matter.
The total stock is large, and some of it is assimilable; however, the