General Features of Dinoflagellate Material Collected by the "Anton Bruun"
167
trations. The data for the theory was derived from the "Valdivia Expedition" material,
presented by KARSTEN (1907).
Although the data did not support this theory very well, the idea was taken up by
several later authors, particularly those studying tropical and subtropical dinoflagellates
(e.g. STEEMANN NIELSEN, 1934, 1939; GRAHAM, 1941). This later work has largely
confirmed the tendency of certain dinoflagellate (and some diatom) species to occur
consistently at depths below 50 or 100 m except in regions of upwelling (HALIM, 1967).
GRAHAM (1941) has stressed that in many speCIes of Ceratium thought to inhabit deeptl
waters the theca is pften greatly flattened and extended, either in the epitheca (subgenus
Archaeceratium, e.g.' Ceratium gravidum, Fig. 4£.) or in the antapical horns. The latter
may have paddle- or wing-like shapes (C platycorne) or the ends may be extended in a
resemblance to the fingers of a hand (C ranipes). The extensions are packed with
chloroplasts. GRAHAM considered that the thin walls provided a "window" effect allowing
greater penetration of weak light into the cell.
The shade flora phenomenon, if it exists other than under ice, appears to be limited to
tropical and subtropical waters. STEEMANN NIELSEN (1934) was unable to observe it in
waters south of New Zealand, and HASLE (personal communication) was not able to
recognize shade species in her study of cold southern Pacific waters (HASLE, 1969). However, she was also not able to find supporting evidence in her quantitative study of the
distribution of equatorial Pacific phytoplankton (HASLE, 1959). It is possible that the
small volumes of sample used (an unfortunate but unavoidable consequence of sedimentation counting techniques) were not sufficient to observe the patterns of species in low
numbers.
There is also a possibility of physiological adaptation in cells of species also found
near the surface. Although deep (below 50 m) chlorophyll a maxima have been commonly
reported in tropical waters (SAI]O, 1973), there is no conclusive evidence that this is a
product of dark adaptation or of the presence of a shade flora.
By sampling from 200 m to the surface on the "Anton Bruun" cruises the material
was effectively integrated throughout the depths used by these earlier authors. The
depths used by them were usually 200 -100 m, 100 - 50 m, and 50 - 0 m. The species
from these depths were unfortunately termed oligophotic, mesophotic and euphotic by
STEEMANN NIELSEN (1939), unfortunate because of the use of the same terms today
to designate much greater depths defined by light parameters. In view of the 200 - 0 m
sampling by the "Anton Bruun", it might be expected that the horizontal distribution
patterns would reflect the distributions of all three components, completely obscuring
the effects of vertical distribution.
In fact, the only reason for raising the question of depth distribution in this otherwise
inappropriate context was the picture which emerged from the horizontal plotting of the
distributions of several of the so-called oligo- and mesophotic species (determined
from the tables of GRAHAM, 1941 and the observations of KAESLER, 1938). For example,
in Fig. 1 the distribution of members of the genus Histioneis (all considered meso- or
oligophotic) and Ceratium subgenus Archaeceratium (excluding C praelongum which
has not been found as selectively deep as the other members of the subgenus) has bet;n
plotted. The species concerned are quite noticeably distributed in the western sectors of
both the Bay of Bengal and the Andaman Sea. With the exception of the letter stations,
they are also in water where the surface salinity is greater than 33%0. At this season the
surface and near surface water near the western shore of the Bay of Bengal is derived
167
trations. The data for the theory was derived from the "Valdivia Expedition" material,
presented by KARSTEN (1907).
Although the data did not support this theory very well, the idea was taken up by
several later authors, particularly those studying tropical and subtropical dinoflagellates
(e.g. STEEMANN NIELSEN, 1934, 1939; GRAHAM, 1941). This later work has largely
confirmed the tendency of certain dinoflagellate (and some diatom) species to occur
consistently at depths below 50 or 100 m except in regions of upwelling (HALIM, 1967).
GRAHAM (1941) has stressed that in many speCIes of Ceratium thought to inhabit deeptl
waters the theca is pften greatly flattened and extended, either in the epitheca (subgenus
Archaeceratium, e.g.' Ceratium gravidum, Fig. 4£.) or in the antapical horns. The latter
may have paddle- or wing-like shapes (C platycorne) or the ends may be extended in a
resemblance to the fingers of a hand (C ranipes). The extensions are packed with
chloroplasts. GRAHAM considered that the thin walls provided a "window" effect allowing
greater penetration of weak light into the cell.
The shade flora phenomenon, if it exists other than under ice, appears to be limited to
tropical and subtropical waters. STEEMANN NIELSEN (1934) was unable to observe it in
waters south of New Zealand, and HASLE (personal communication) was not able to
recognize shade species in her study of cold southern Pacific waters (HASLE, 1969). However, she was also not able to find supporting evidence in her quantitative study of the
distribution of equatorial Pacific phytoplankton (HASLE, 1959). It is possible that the
small volumes of sample used (an unfortunate but unavoidable consequence of sedimentation counting techniques) were not sufficient to observe the patterns of species in low
numbers.
There is also a possibility of physiological adaptation in cells of species also found
near the surface. Although deep (below 50 m) chlorophyll a maxima have been commonly
reported in tropical waters (SAI]O, 1973), there is no conclusive evidence that this is a
product of dark adaptation or of the presence of a shade flora.
By sampling from 200 m to the surface on the "Anton Bruun" cruises the material
was effectively integrated throughout the depths used by these earlier authors. The
depths used by them were usually 200 -100 m, 100 - 50 m, and 50 - 0 m. The species
from these depths were unfortunately termed oligophotic, mesophotic and euphotic by
STEEMANN NIELSEN (1939), unfortunate because of the use of the same terms today
to designate much greater depths defined by light parameters. In view of the 200 - 0 m
sampling by the "Anton Bruun", it might be expected that the horizontal distribution
patterns would reflect the distributions of all three components, completely obscuring
the effects of vertical distribution.
In fact, the only reason for raising the question of depth distribution in this otherwise
inappropriate context was the picture which emerged from the horizontal plotting of the
distributions of several of the so-called oligo- and mesophotic species (determined
from the tables of GRAHAM, 1941 and the observations of KAESLER, 1938). For example,
in Fig. 1 the distribution of members of the genus Histioneis (all considered meso- or
oligophotic) and Ceratium subgenus Archaeceratium (excluding C praelongum which
has not been found as selectively deep as the other members of the subgenus) has bet;n
plotted. The species concerned are quite noticeably distributed in the western sectors of
both the Bay of Bengal and the Andaman Sea. With the exception of the letter stations,
they are also in water where the surface salinity is greater than 33%0. At this season the
surface and near surface water near the western shore of the Bay of Bengal is derived