26
GORDON A. RILEY
by accumulations of Xargassum and floating debris, the configuration
of the cells can be determined visually over a considerable distance,
and the situation is seldom as diagramatically simple as might be implied from the foregoing account. Broad and well-established weed
lines are likely to be interspersed with small and discontinuous ones,
and at wind speeds of about 15 mjsec or more these are in turn interlarded with foam lines and irregular spume patterns which might be
the result either of small-scale convective sinking or turbulent exchange.
Indeed McLeish ( 1968) has presented theoretical and experimental
evidence in support of the hypothesis that turbulence can be responsible
for all of the observed surface phenomena and has expressed doubt as
to the reality of the classical picture of the Langmuir spiral.
For present purposes, the exact form of the circulation pattern is
not particularly important. The existence of downdrafts is well substantiated. Commonly, although not always, the water in the downdrafts is slightly cooler than the surrounding water, and when these
movements occur in an essentially homogeneous mixed layer, they
probably can extend down to the top of the thermocline and can create
a vertical transfer of plankton and particulate matter that is biologically significant and is more important than the question of what the
remainder of the circulation looks like. For convenience the rest of
the discussion will assume the validity of Langmuir circulation, but the
conclusions would not be seriously altered by qualifications about the
character of the motion.
Sutcliffe et ul. (1963) believed that organic particles accumulating
in the surface layer would drift into the convergences, providing curtains of particle rich water which might serve as sources of abundant
food for zooplankton. They found an increase in turbidity and phosphate in the convergence lines. There was evidence that zooplankton
did in fact congregate in such areas, and a paper by Baylor and Sutcliffe
(1963) suggested that particles formed at the surface might provide
useful food, for particles produced experimentally in the laboratory
supported the growth of Artemia.
These results were exciting to biologists on two counts. I n the first
place, although our knowledge of the biochemistry of sea water was
limited, and still is, it was apparent that many substances known to
exist in soluble or colloidal form in sea water would be suitable food
for filter feeding animals if the material could be aggregated into
sufficiently large particles to be retained by their filtering apparatus.
This kind of non-living material appears more promising as food than
semi-decayed detritus.
Secondly, since the evidence is fairly good that there is a physical
GORDON A. RILEY
by accumulations of Xargassum and floating debris, the configuration
of the cells can be determined visually over a considerable distance,
and the situation is seldom as diagramatically simple as might be implied from the foregoing account. Broad and well-established weed
lines are likely to be interspersed with small and discontinuous ones,
and at wind speeds of about 15 mjsec or more these are in turn interlarded with foam lines and irregular spume patterns which might be
the result either of small-scale convective sinking or turbulent exchange.
Indeed McLeish ( 1968) has presented theoretical and experimental
evidence in support of the hypothesis that turbulence can be responsible
for all of the observed surface phenomena and has expressed doubt as
to the reality of the classical picture of the Langmuir spiral.
For present purposes, the exact form of the circulation pattern is
not particularly important. The existence of downdrafts is well substantiated. Commonly, although not always, the water in the downdrafts is slightly cooler than the surrounding water, and when these
movements occur in an essentially homogeneous mixed layer, they
probably can extend down to the top of the thermocline and can create
a vertical transfer of plankton and particulate matter that is biologically significant and is more important than the question of what the
remainder of the circulation looks like. For convenience the rest of
the discussion will assume the validity of Langmuir circulation, but the
conclusions would not be seriously altered by qualifications about the
character of the motion.
Sutcliffe et ul. (1963) believed that organic particles accumulating
in the surface layer would drift into the convergences, providing curtains of particle rich water which might serve as sources of abundant
food for zooplankton. They found an increase in turbidity and phosphate in the convergence lines. There was evidence that zooplankton
did in fact congregate in such areas, and a paper by Baylor and Sutcliffe
(1963) suggested that particles formed at the surface might provide
useful food, for particles produced experimentally in the laboratory
supported the growth of Artemia.
These results were exciting to biologists on two counts. I n the first
place, although our knowledge of the biochemistry of sea water was
limited, and still is, it was apparent that many substances known to
exist in soluble or colloidal form in sea water would be suitable food
for filter feeding animals if the material could be aggregated into
sufficiently large particles to be retained by their filtering apparatus.
This kind of non-living material appears more promising as food than
semi-decayed detritus.
Secondly, since the evidence is fairly good that there is a physical