Calcareous Dinoflagellate Cysts as Paleo-Environmental Tools
149
oxygenated bottom sediments. It is possible that the
preservation of the organic inner wall of calcareous cysts is also sensitive to oxygen availability.
Some species have crystals that are not connected
to each other but grow directly from the organic
layer. Individual calcite crystals might be the only
fossil remnants when this organic layer is degraded.
As a consequence the calcareous cyst association,
recovered from bottom sediments will only represent a part of the cyst production in surface waters. Calculation of the carbonate production by
calcareous dinoflagellates based on such recoveries will therefore always be an underestimation of
the real flux.
Taxonomy
The taxonomy of (fossil) calcareous dinoflagellate
cysts is mainly based on the crystallographic
orientation of the calcite crystals (e.g. Keupp 1987;
Keupp and Versteegh 1989; Kohring 1993; Willems
1995; Janofske 1996). Although some variation in
the morphology ofthe calcite crystals of single species has been observed in culture experiments (e.g.
Lewis 1991; Montresor et al. 1997), the
crystallographic orientation has, thus far, found to
be species specific. To date, two taxonomic systems exist for dinoflagellates. The first system is
based on morphological characteristics of the generally non-fossilizable free-living motile life stage,
whereas the second system is based on the morphological characteristics of (fossil) cysts found in
sediments, which often have not been related to an
equivalent motile form (e.g. F ensome et al. 1993).
As a consequence, two names may appear in the
literature for the same organism; one for the motile stage and one for the cyst stage. Throughout
this paper the motile names are used wherever possible. A list of all presently known dinoflagellate species forming calcareous cysts is given in Table 1.
Material and Methods
In the present paper, the results of the recent global distribution patterns presented in this paper are
based on both literature-derived information and
new material from samples of surface water and
sediments. Furthermore, information on two gravity cores derived from the Equatorial South
Atlantic Ocean are presented. Literature used for
constructing distribution maps of the individual species is given in Fig. 1.
Surface water samples were collected during
the METEOR cruise M23/3 (Wefer et al. 1994;
Table 2, Fig. 1). For qualitative analysis of the calcareous cyst content of the surface waters, about
1401 of water from the upper 4.5 m of the water
column was filtered through cellulose nitrate or
polycarbonate membrane filters (pore size 5 )lll1).
The filters were dried overnight in a stove at 30°C.
The dried filters were fixed on a SEM stub and
sputtered with gold. A CamScan CS44 machine
was used for SEM analysis of the calcareous cyst
content of the filters.
Surface sediment samples were collected during METEOR cruise M20/1 (Wefer et al. 1993;
Kerntopfl997; Table 2, Fig. 1). Samples were obtained by collecting the upper centimeter of sediment from three multicores. For qualitative analysis of the calcareous cyst content, the 5-63 !-Lm
sediment fraction was stored in a 30% alcohol
solution. One part of the homogenized material was
placed on the gelatinous side of a piece of transparent developed film which had been previously
fixed to a SEM stub with double-side adhesive tape.
The stubs were dried overnight. The stubs were
repeatedly washed to remove all particles not embedded in the gelatinous layer of the film. After
drying, the stubs were sputtered with gold and
studied by applying the same SEM technique as for
the water samples.
Two gravity cores, Core GeoB 1105-4 (01°40'
S, 12°26' W, water depth 3225m) and Core GeoB
2204-2(08°31,7' S, 34°01,3' W, water depth 2072m)
were collected during the METEOR cruises M9/4
and M23/3, respectively (Wefer eta\. 1989,1994;
Fig. I). The cores contain sediments deposited
during the last 140 ka. Age-assessment is based on
graphic correlation of the 8 18 0 benthic
formaminifera Cibicidoides wuellerstorfi (Core
GeoB 1105-4) and planktic formaminifera
Globigerinoides sacculifer (Core GeoB 2204-2)
to the SPECMAP oxygen isotope standard record
ofImbrie eta\. (1984) following Prell et a\. (1986;
Bickert 1992; Rlihlemann 1996). Sedimentation
149
oxygenated bottom sediments. It is possible that the
preservation of the organic inner wall of calcareous cysts is also sensitive to oxygen availability.
Some species have crystals that are not connected
to each other but grow directly from the organic
layer. Individual calcite crystals might be the only
fossil remnants when this organic layer is degraded.
As a consequence the calcareous cyst association,
recovered from bottom sediments will only represent a part of the cyst production in surface waters. Calculation of the carbonate production by
calcareous dinoflagellates based on such recoveries will therefore always be an underestimation of
the real flux.
Taxonomy
The taxonomy of (fossil) calcareous dinoflagellate
cysts is mainly based on the crystallographic
orientation of the calcite crystals (e.g. Keupp 1987;
Keupp and Versteegh 1989; Kohring 1993; Willems
1995; Janofske 1996). Although some variation in
the morphology ofthe calcite crystals of single species has been observed in culture experiments (e.g.
Lewis 1991; Montresor et al. 1997), the
crystallographic orientation has, thus far, found to
be species specific. To date, two taxonomic systems exist for dinoflagellates. The first system is
based on morphological characteristics of the generally non-fossilizable free-living motile life stage,
whereas the second system is based on the morphological characteristics of (fossil) cysts found in
sediments, which often have not been related to an
equivalent motile form (e.g. F ensome et al. 1993).
As a consequence, two names may appear in the
literature for the same organism; one for the motile stage and one for the cyst stage. Throughout
this paper the motile names are used wherever possible. A list of all presently known dinoflagellate species forming calcareous cysts is given in Table 1.
Material and Methods
In the present paper, the results of the recent global distribution patterns presented in this paper are
based on both literature-derived information and
new material from samples of surface water and
sediments. Furthermore, information on two gravity cores derived from the Equatorial South
Atlantic Ocean are presented. Literature used for
constructing distribution maps of the individual species is given in Fig. 1.
Surface water samples were collected during
the METEOR cruise M23/3 (Wefer et al. 1994;
Table 2, Fig. 1). For qualitative analysis of the calcareous cyst content of the surface waters, about
1401 of water from the upper 4.5 m of the water
column was filtered through cellulose nitrate or
polycarbonate membrane filters (pore size 5 )lll1).
The filters were dried overnight in a stove at 30°C.
The dried filters were fixed on a SEM stub and
sputtered with gold. A CamScan CS44 machine
was used for SEM analysis of the calcareous cyst
content of the filters.
Surface sediment samples were collected during METEOR cruise M20/1 (Wefer et al. 1993;
Kerntopfl997; Table 2, Fig. 1). Samples were obtained by collecting the upper centimeter of sediment from three multicores. For qualitative analysis of the calcareous cyst content, the 5-63 !-Lm
sediment fraction was stored in a 30% alcohol
solution. One part of the homogenized material was
placed on the gelatinous side of a piece of transparent developed film which had been previously
fixed to a SEM stub with double-side adhesive tape.
The stubs were dried overnight. The stubs were
repeatedly washed to remove all particles not embedded in the gelatinous layer of the film. After
drying, the stubs were sputtered with gold and
studied by applying the same SEM technique as for
the water samples.
Two gravity cores, Core GeoB 1105-4 (01°40'
S, 12°26' W, water depth 3225m) and Core GeoB
2204-2(08°31,7' S, 34°01,3' W, water depth 2072m)
were collected during the METEOR cruises M9/4
and M23/3, respectively (Wefer eta\. 1989,1994;
Fig. I). The cores contain sediments deposited
during the last 140 ka. Age-assessment is based on
graphic correlation of the 8 18 0 benthic
formaminifera Cibicidoides wuellerstorfi (Core
GeoB 1105-4) and planktic formaminifera
Globigerinoides sacculifer (Core GeoB 2204-2)
to the SPECMAP oxygen isotope standard record
ofImbrie eta\. (1984) following Prell et a\. (1986;
Bickert 1992; Rlihlemann 1996). Sedimentation