88
GORDON A. RILEY
tends t o facilitate the maintenance of a fairly uniform vertical distribution and to accentuate regional differences in particulate organic
matter and other properties. However, evidence has been presented
of the existence of thermal discontinuities in the deep ocean. These
could lead to the development of layers of particle rich water, although
the somewhat inadequate data now available suggest that the distribution is only slightly non-random (Gordon, 1970b). Vertical turbulence can have some effect in dispersing any local concentrations that
develop, but it cannot produce a systematic downward flux, for the
mean vertical gradient of particulate carbon is essentially nil in most
areas that have been examined.
Thus particulate matter sinks passively from the main thermocline
to the ocean floor and seems to be influenced very little by any of the
physical oceanographic processes of the deep ocean except in a few
local situations that have been described.
2. Biological relationships
Having brought together available information on physical movements of particulate organic matter in the sea, we come now to questions
of the character and magnitude of the biological processes which can be
expected to affect the concentration and distribution of the non-living
matter. This involves a consideration of the degree of balance between
production and consumption at various depths in the sea.
Theoretically, of course, total carbon fixation by photosynthetic
plants is expected t.0 equal total respiratory utilization of ca,rbon by
animals and heterotrophic plants, neglecting the residue that remains
unoxidized in sediments or in the water column. This residue is large
in its total accumulation, but it has accrued during a long period of
time and is believed to be a small percentage of total carbon production.
For practical purposes we can assume a balance over a period of a year
or several years. During shorter periods there are seasonal imbalances
in the surface layer, so that the discussion must be limited to areas
where the information is available on mean annual production and
consumption.
This balance between total production and consumption is of course
realized only by considering the total vertical column from surface to
bottom. At any particular depth there is an imbalance. All photosynthesis occurs in a thin surface stratum which seldom exceeds 125 m in
depth and generally is less. Much of the consumption also occurs here,
and the remainder of the surface production, once it has been delivered
to deep water by one means or another, provides minimal sustenance
for the sparse deep water fauna and flora.
GORDON A. RILEY
tends t o facilitate the maintenance of a fairly uniform vertical distribution and to accentuate regional differences in particulate organic
matter and other properties. However, evidence has been presented
of the existence of thermal discontinuities in the deep ocean. These
could lead to the development of layers of particle rich water, although
the somewhat inadequate data now available suggest that the distribution is only slightly non-random (Gordon, 1970b). Vertical turbulence can have some effect in dispersing any local concentrations that
develop, but it cannot produce a systematic downward flux, for the
mean vertical gradient of particulate carbon is essentially nil in most
areas that have been examined.
Thus particulate matter sinks passively from the main thermocline
to the ocean floor and seems to be influenced very little by any of the
physical oceanographic processes of the deep ocean except in a few
local situations that have been described.
2. Biological relationships
Having brought together available information on physical movements of particulate organic matter in the sea, we come now to questions
of the character and magnitude of the biological processes which can be
expected to affect the concentration and distribution of the non-living
matter. This involves a consideration of the degree of balance between
production and consumption at various depths in the sea.
Theoretically, of course, total carbon fixation by photosynthetic
plants is expected t.0 equal total respiratory utilization of ca,rbon by
animals and heterotrophic plants, neglecting the residue that remains
unoxidized in sediments or in the water column. This residue is large
in its total accumulation, but it has accrued during a long period of
time and is believed to be a small percentage of total carbon production.
For practical purposes we can assume a balance over a period of a year
or several years. During shorter periods there are seasonal imbalances
in the surface layer, so that the discussion must be limited to areas
where the information is available on mean annual production and
consumption.
This balance between total production and consumption is of course
realized only by considering the total vertical column from surface to
bottom. At any particular depth there is an imbalance. All photosynthesis occurs in a thin surface stratum which seldom exceeds 125 m in
depth and generally is less. Much of the consumption also occurs here,
and the remainder of the surface production, once it has been delivered
to deep water by one means or another, provides minimal sustenance
for the sparse deep water fauna and flora.