20
GORDON A. EILEY
While regional coverage of deep water is still fragmentary, there
are enough observations for some generalities to emerge. The total
variation is large, but a major proportion of the observations fall
between 15 and 100 pg C/litre. I n general there appears to be about
a three-fold to five-fold variation between poor areas and rich ones.
Markedly high values have been found underlying the upwelling zone
off the west coast of Africa, and the averages decrease to low and
relatively constant values through most of the tropical and subtropical
regions of the western North Atlantic. Dal Pont and Newel1 (1963)
obtained fairly large values in the South Pacific, particularly in waters
of Antarctic origin, which presumably are productive. Thus to some
extent, a t least, the magnitude of deep water carbon concentrations is
associated with high levels of surface productivity. Temperate waters
of the North Atlantic and North Pacific presumably have a level of
primary productivity that is above average, and in those areas carbon
values tend to be moderately large, although some low ones have also
been obtained.
Low values were obtained by Gordon (1970b) in the Irminger Sea,
which probably is not highly productive on an annual basis, despite
good phytoplankton flowerings during the short subarctic summer.
More recently he has obtained extremely low values in tropical Pacific
waters off Hawaii (personal communication).
Menzel (1964) obtained intermediate values in the Arabian Sea, an
area that is subject to seasonal upwelling but probably is not as productive on an annual basis as the west African coast. The west coasts
of the Americas should be productive, and moderately high values were
recorded by Holm-Hansen et al. (1966) in the California offing.
I n summary, there are substantial regional variations in deep
water particulate organic matter, which appear to be related at least
in part to primary productivity in the surface waters above. This
presupposes that vertical transport of materials down through the
water column is more rapid than horizontal displacement by deep
water currents and diffusion. McGill ( 1964) obtained essentially similar
results in studies of deep water distribution of organic phosphate,
despite the fact that the latter was primarily in dissolved rather than
particulate form.
However, this is a broad generality, which is subject to exceptions.
Deep water transport probably is not negligible, for variations have
been reported in carbon concentrations which hardly can be explained
in any way other than water mass transport. This will be discussed
in the next section.
GORDON A. EILEY
While regional coverage of deep water is still fragmentary, there
are enough observations for some generalities to emerge. The total
variation is large, but a major proportion of the observations fall
between 15 and 100 pg C/litre. I n general there appears to be about
a three-fold to five-fold variation between poor areas and rich ones.
Markedly high values have been found underlying the upwelling zone
off the west coast of Africa, and the averages decrease to low and
relatively constant values through most of the tropical and subtropical
regions of the western North Atlantic. Dal Pont and Newel1 (1963)
obtained fairly large values in the South Pacific, particularly in waters
of Antarctic origin, which presumably are productive. Thus to some
extent, a t least, the magnitude of deep water carbon concentrations is
associated with high levels of surface productivity. Temperate waters
of the North Atlantic and North Pacific presumably have a level of
primary productivity that is above average, and in those areas carbon
values tend to be moderately large, although some low ones have also
been obtained.
Low values were obtained by Gordon (1970b) in the Irminger Sea,
which probably is not highly productive on an annual basis, despite
good phytoplankton flowerings during the short subarctic summer.
More recently he has obtained extremely low values in tropical Pacific
waters off Hawaii (personal communication).
Menzel (1964) obtained intermediate values in the Arabian Sea, an
area that is subject to seasonal upwelling but probably is not as productive on an annual basis as the west African coast. The west coasts
of the Americas should be productive, and moderately high values were
recorded by Holm-Hansen et al. (1966) in the California offing.
I n summary, there are substantial regional variations in deep
water particulate organic matter, which appear to be related at least
in part to primary productivity in the surface waters above. This
presupposes that vertical transport of materials down through the
water column is more rapid than horizontal displacement by deep
water currents and diffusion. McGill ( 1964) obtained essentially similar
results in studies of deep water distribution of organic phosphate,
despite the fact that the latter was primarily in dissolved rather than
particulate form.
However, this is a broad generality, which is subject to exceptions.
Deep water transport probably is not negligible, for variations have
been reported in carbon concentrations which hardly can be explained
in any way other than water mass transport. This will be discussed
in the next section.