PARTICULATE ORGANIC MATTER I N SEA WATER
95
the present case the correction factor recommended by the C14 Laboratory is applied provisionally to the Sargasso Sea data, bringing the
mean value to 290 mg C.m-2.day-1. I n the light of Goldman’s recent
results, the correct figure might be as high as 600 mg C, but the writer
is inclined to doubt this. Even the old light and dark bottle oxygen
techniques, which have been criticized for giving results that are too
high, indicated that the general range of net production in oceanic
waters is of the order of 400-1 000 mg C.m-2.day-l (Riley, 1944), and
the Sargasso Sea should be near the minimum limit of the range.
The total estimate for usable organic production by phytoplankton
also should include extracellular metabolites, which would not be
included in measurements of productivity by routine C14 tests.
Hellebust (1965) reported experimental results on the production of
external metabolites by a large number of algal species. The list included Coccolithus huxleyi, an important species in the Sargasso Sea.
At nominal light intensities of 3-10 x lo3 lux, 1.3-4*4y0 of the photoassimilated carbon was released, and the value increased to 17% in
full sunlight. Dinoflagellates ranged from 4.4-1070. Values of up to
25% were obtained for some of the diatoms, but these algae are not
important constituents in the Sargasso Sea except in winter and spring.
From these data one might suppose that a reasonable estimate for
extracellular release might be of the order of 10% of photoassimilated
carbon. However, (2.1. Choi of this laboratory (personal communication)
has obtained considerably higher values in experiments with natural
populations. These were in situ C14 experiments performed at a series
of depths at stations between the Newfoundland-Nova Scotia shelf
and the Gulf Stream, followed by measurements of organic C14 in the
particulate matter and in the filtrate. At the three southernmost
stations filterable organic C14 averaged 25% of the C14 incorporated
in particulate matter. Even higher values were common at the more
northerly stations.
I n short, extracellular release in the natural environment can be
1 0 - 3 0 ~ 0 or more, and the total organic productivity at the Sargasso
Sea station under present consideration is estimated to be 320-380 mg
C.m-2.day-1, with some possibility that the true value might be
more.
The next step is to attempt to equate organic production in the
surface layer with consumption in the water column as a whole.
The two physical oceanographic computations in items ( 2 ) and (3)
gave closely concordant values of 48-53 mg C.m-2.day-1 for consumption below 300 m, and the others varied around these values. As a
guide to the remainder of the analysis, it will be assumed that these
95
the present case the correction factor recommended by the C14 Laboratory is applied provisionally to the Sargasso Sea data, bringing the
mean value to 290 mg C.m-2.day-1. I n the light of Goldman’s recent
results, the correct figure might be as high as 600 mg C, but the writer
is inclined to doubt this. Even the old light and dark bottle oxygen
techniques, which have been criticized for giving results that are too
high, indicated that the general range of net production in oceanic
waters is of the order of 400-1 000 mg C.m-2.day-l (Riley, 1944), and
the Sargasso Sea should be near the minimum limit of the range.
The total estimate for usable organic production by phytoplankton
also should include extracellular metabolites, which would not be
included in measurements of productivity by routine C14 tests.
Hellebust (1965) reported experimental results on the production of
external metabolites by a large number of algal species. The list included Coccolithus huxleyi, an important species in the Sargasso Sea.
At nominal light intensities of 3-10 x lo3 lux, 1.3-4*4y0 of the photoassimilated carbon was released, and the value increased to 17% in
full sunlight. Dinoflagellates ranged from 4.4-1070. Values of up to
25% were obtained for some of the diatoms, but these algae are not
important constituents in the Sargasso Sea except in winter and spring.
From these data one might suppose that a reasonable estimate for
extracellular release might be of the order of 10% of photoassimilated
carbon. However, (2.1. Choi of this laboratory (personal communication)
has obtained considerably higher values in experiments with natural
populations. These were in situ C14 experiments performed at a series
of depths at stations between the Newfoundland-Nova Scotia shelf
and the Gulf Stream, followed by measurements of organic C14 in the
particulate matter and in the filtrate. At the three southernmost
stations filterable organic C14 averaged 25% of the C14 incorporated
in particulate matter. Even higher values were common at the more
northerly stations.
I n short, extracellular release in the natural environment can be
1 0 - 3 0 ~ 0 or more, and the total organic productivity at the Sargasso
Sea station under present consideration is estimated to be 320-380 mg
C.m-2.day-1, with some possibility that the true value might be
more.
The next step is to attempt to equate organic production in the
surface layer with consumption in the water column as a whole.
The two physical oceanographic computations in items ( 2 ) and (3)
gave closely concordant values of 48-53 mg C.m-2.day-1 for consumption below 300 m, and the others varied around these values. As a
guide to the remainder of the analysis, it will be assumed that these