PARTICULATE ORGdNIC MATTER IN SEA WATER
13
Wangersky and Gordon demonstrated that there was a major
concentration of particulate carbon in the immediate surface layer, at
least under the calm conditions prevailing during most of their cruise.
Surface bucket samples taken in the Guinea Current had concentrations
ranging from 300 to 800pgC/litre, in contrast to about 55-2OOpg
C/litre in water bottle samples from depths of 13-15 m. I n less productive areas most of the bucket samples had values of 20-120 pg
C/litre. Slightly deeper collections, some with the bottles barely submerged or at most at a depth of 10 m, were of the order of 14-58 pg.
Williams (1967) developed methods for collecting a thin layer of
water near the surface and compared organic carbon and various other
determinations in these samples with subsurface concentrations. His
work confirmed and extended previous conclusions as to the existence
of a large vertical gradient in near surface waters. There is of course
a tendency for bacteria, nanoplankton and non-living particulate
matter to become adsorbed at the surface film, although pronounced
vertical turbulence tends to disrupt the film and drive some of this
material into deeper water. A certain balance between these processes
presumably is responsible for the observed vertical gradient. The
observations that have been described were obtained mainly in calm
weather, because surface film collection becomes increasingly difficult
in rough water. Hence such observations represent an extreme development of near surface gradients. However, later evidence will indicate
that there is a measurable and biologically important accumulation of
particulate matter at the sea surface at higher sea states.
Most of the investigations of organic carbon in the surface layer of
the sea have employed serial casts of various kinds of collecting bottles,
with the uppermost bottle at a depth of a metre or more, so that
surface film effects were slight or negligible. These investigations have
not been extensive enough yet to provide a clear picture of either
regional or seasonal variations ; however, the available information
should be summarized in order to give a general idea of areal coverage
and degree of variation.
Menzel and Ryther (1964) described some observations obtained in
January 1962 between 41" and 37"N Latitude in the western Atlantic,
which thus included both temperate and subtropical waters. Another
cruise in April of the same year obtained a line of stations between
42'30"
and 20"N along the 65"W Meridian. Their Fig. 1, which
apparently includes only observations north of the Gulf Straam and
includes all data taken in the upper loom, shows a total range in
January of about 25-200 pg C/litre, with a large majority of observations between 35 and 95 pg. I n April the general range was of the
13
Wangersky and Gordon demonstrated that there was a major
concentration of particulate carbon in the immediate surface layer, at
least under the calm conditions prevailing during most of their cruise.
Surface bucket samples taken in the Guinea Current had concentrations
ranging from 300 to 800pgC/litre, in contrast to about 55-2OOpg
C/litre in water bottle samples from depths of 13-15 m. I n less productive areas most of the bucket samples had values of 20-120 pg
C/litre. Slightly deeper collections, some with the bottles barely submerged or at most at a depth of 10 m, were of the order of 14-58 pg.
Williams (1967) developed methods for collecting a thin layer of
water near the surface and compared organic carbon and various other
determinations in these samples with subsurface concentrations. His
work confirmed and extended previous conclusions as to the existence
of a large vertical gradient in near surface waters. There is of course
a tendency for bacteria, nanoplankton and non-living particulate
matter to become adsorbed at the surface film, although pronounced
vertical turbulence tends to disrupt the film and drive some of this
material into deeper water. A certain balance between these processes
presumably is responsible for the observed vertical gradient. The
observations that have been described were obtained mainly in calm
weather, because surface film collection becomes increasingly difficult
in rough water. Hence such observations represent an extreme development of near surface gradients. However, later evidence will indicate
that there is a measurable and biologically important accumulation of
particulate matter at the sea surface at higher sea states.
Most of the investigations of organic carbon in the surface layer of
the sea have employed serial casts of various kinds of collecting bottles,
with the uppermost bottle at a depth of a metre or more, so that
surface film effects were slight or negligible. These investigations have
not been extensive enough yet to provide a clear picture of either
regional or seasonal variations ; however, the available information
should be summarized in order to give a general idea of areal coverage
and degree of variation.
Menzel and Ryther (1964) described some observations obtained in
January 1962 between 41" and 37"N Latitude in the western Atlantic,
which thus included both temperate and subtropical waters. Another
cruise in April of the same year obtained a line of stations between
42'30"
and 20"N along the 65"W Meridian. Their Fig. 1, which
apparently includes only observations north of the Gulf Straam and
includes all data taken in the upper loom, shows a total range in
January of about 25-200 pg C/litre, with a large majority of observations between 35 and 95 pg. I n April the general range was of the