PARTICULATE ORGANIC MATTER I N SEA WATER
75
In looking over the results as a whole, a good many ambiguities
remain. The complete spectrum of sizes and sinking speeds has not
been examined. Most of the particle counts described in earlier parts
of the paper were based on samples of not more than 250 ml of sea
water. These commonly contain a few particles of the order of 100200 p in diameter, which could have sinking rates of as much as 5-10 m/
day, The " marine snow ') which has been reported by direct observation probably is still larger and can have a correspondingly faster
sinking rate, but the concentration is too small for them to appear in
small samples except on rare occasions. However, in certain circumstances they may be important. Aggregates predominate in the surface
layer, and the larger sizes are volumetrically the most important. They
are presumably delivered into deep water in the same proportions as
they exist in the surface layer, and the apparent decrease in abundance
is due in large part to the fact that they have a rapid sinking rate and
a relatively short residence time in the deep water column. The rate
of delivery t o animals in deep water or to the deep ocean bottom will
be proportional to the product of the sinking rate and the concentration
in the water. Dynamic considerations of this sort will seriously underrate the importance of large particles if one considers them only in
terms of observed concentrations in the water.
The relationship between temperature and sinking rate has not been
examined experimentally. This would be desirable, but temperature
effects are minor compared with some of the other variables that have
been discussed above. I n the case of small particles with a specific
gravity of 1.1 or more, the effect of increased density of the water
would be less than the differences recorded in individual experiments.
The most important temperature dependent variable would be the
increase in the viscosity of the water, which could reduce sinking
rates nearly 50% in deep ocean waters.
Since the reduction in specific gravity of large particles is believed
to be due mainly to water inclusions, temperature equilibration as
particles sink would tend to maintain a constant difference between
the specific gravity of particles and water except in strong temperature
gradients. Again the main variable is expected to be increased viscosity.
V. GENERAL DISCUSSION
A. Re-examination of the aggregation process
The original aggregation process as described by Baylor et al. (1962)
and Sutcliffe et al. (1963) involved migration of surface active substance
toward the surface via bubbles and the formation of particles containing
75
In looking over the results as a whole, a good many ambiguities
remain. The complete spectrum of sizes and sinking speeds has not
been examined. Most of the particle counts described in earlier parts
of the paper were based on samples of not more than 250 ml of sea
water. These commonly contain a few particles of the order of 100200 p in diameter, which could have sinking rates of as much as 5-10 m/
day, The " marine snow ') which has been reported by direct observation probably is still larger and can have a correspondingly faster
sinking rate, but the concentration is too small for them to appear in
small samples except on rare occasions. However, in certain circumstances they may be important. Aggregates predominate in the surface
layer, and the larger sizes are volumetrically the most important. They
are presumably delivered into deep water in the same proportions as
they exist in the surface layer, and the apparent decrease in abundance
is due in large part to the fact that they have a rapid sinking rate and
a relatively short residence time in the deep water column. The rate
of delivery t o animals in deep water or to the deep ocean bottom will
be proportional to the product of the sinking rate and the concentration
in the water. Dynamic considerations of this sort will seriously underrate the importance of large particles if one considers them only in
terms of observed concentrations in the water.
The relationship between temperature and sinking rate has not been
examined experimentally. This would be desirable, but temperature
effects are minor compared with some of the other variables that have
been discussed above. I n the case of small particles with a specific
gravity of 1.1 or more, the effect of increased density of the water
would be less than the differences recorded in individual experiments.
The most important temperature dependent variable would be the
increase in the viscosity of the water, which could reduce sinking
rates nearly 50% in deep ocean waters.
Since the reduction in specific gravity of large particles is believed
to be due mainly to water inclusions, temperature equilibration as
particles sink would tend to maintain a constant difference between
the specific gravity of particles and water except in strong temperature
gradients. Again the main variable is expected to be increased viscosity.
V. GENERAL DISCUSSION
A. Re-examination of the aggregation process
The original aggregation process as described by Baylor et al. (1962)
and Sutcliffe et al. (1963) involved migration of surface active substance
toward the surface via bubbles and the formation of particles containing