J. Nannoplankton Res. 30 (2), 2009, pp.83-96 © 2009 International Nannoplankton Association, Inc.
ISSN 1210-8049 Printed by Cambridge University Press, UK

83

Coccolithophore flux in a sediment trap off Cape Blanc (NW
Africa)M.I. Köbrich*, K.-H. Baumann
FB Geowissenschaften, Universität Bremen, Klagenfurter Straße, 28359 Bremen, Germany; *koebrich@uni-bremen.de

Manuscript received 10th May, 2008; revised manuscript accepted 12th December, 2008

Abstract The flux of coccoliths from a one-year-moored sediment trap (March, 1988 to March, 1989) off Cape
Blanc, NW Africa (20˚45’N, 19˚44’W) was studied. Coccolith flux was at a minimum during spring and fall. The
minimum flux (51x107 coccoliths m-2d-1) in fall (September) corresponds to a strong decrease in nutrient content of thesurface-waters. In winter, coccolith flux reached maximum values (384x107 coccoliths m-2d-1). At that time, insolation,wind velocity, and sea-surface temperature had average values, indicating average nutrient content and average light
penetration into surface-waters.
Detailed morphometric measurements were the basis for more precise estimations of the coccolith-derived carbonate content of the settled particles. Numerically significant taxa (Emiliania huxleyi, Florisphaera profunda, Gephyrocapsa oceanica), as well as low flux of large taxa, such as Helicosphaera carteri, Coccolithus pelagicus and Calcidiscus
leptoporus, mainly form the coccolith carbonate contribution, which adds up to 13.32mg m-2d-1 (3.9-22.8mg m-2d-1),
with a relative contribution of coccoliths to the total carbonate flux of 18% (7-35%). The morphometric measurements
further revealed a bimodal distribution of F. profunda allowing separation of two morphotypes, F. profunda var. profunda and F. profunda var. elongata.
The modern sediment-trap assemblage revealed a good correspondence with respect to coccolith flux (accumulation),
species composition and the coccolith-derived carbonate content with the underlying Holocene surface sediment.

Keywords Cape Blanc, NW Africa, sediment trap, coccolithophores, seasonality, succession, morphometry of
species, carbonate flux

1. Introduction
The development of phytoplankton populations, including
coccolithophores, is influenced by the interaction of nutrients and light. Off NW Africa, the speed and direction of
the trade winds determine upwelling intensity, and consequently additional nutrient input, as well as the development and extension of water-mass filaments from the coastto the open ocean. Wind strength has also an impact on thevertical mixing/stratification of the surface-water. Deep
mixing reduces the mean irradiance experienced by phytoplankton, since maintenance in a water-depth with sufficient light may be inhibited for a significant time due toturbulence (Huntsman & Barber, 1977; Blasco et al., 1981;
Dugdale & Wilkerson, 1985).
To examine the export production of living surfacewater communities, sediment trapping is a successful
method. The quantity and composition of the sinking material are functions of variable components within the overlying pelagic system (Peinert et al., 1989; Legendre &Rassoulzadegan, 1996; Delesalle et al., 2001). The settlingof biogenic material is directly related to surface production, and reflects the seasonality of such production(Deuser et al., 1990). The samples provide valuable information on the species composition and seasonal variationsin abundance (Samtleben & Bickert, 1990; Ziveri et al.,
1995; Broerse, 2000).
Off Mauritania, flux of particles into the deep ocean iswell documented (Wefer & Fischer, 1993; Fischer et al.,
1996; Neuer et al., 1997; Ratmeyer et al., 1999a, b, c).

Lithogenic particles, carbonate and organic carbon are themajor components, with foraminifera identified as one
main carbonate producer (Fischer et al., 1996). The coastal
upwelling also influences offshore waters, through the formation of giant water-mass filaments that are characterisedby high pigment concentrations (Estrada, 1974; Gabric etal., 1993; Kostianoy & Zatsepin, 1996; Lange et al., 1998;
Thomas et al., 2004). Information on coccolith export ofthis highly productive region is still not available, however.
In this paper, we present new data concerning the seasonal pattern of coccolith flux in the upwelling area off
Cape Blanc (NW Africa). The settled coccolithophore assemblages from a year-round (1988-1989) moored sediment trap, at 2000m depth, from 176km west of Cape
Blanc, were investigated in order to obtain insight into theseasonal variation of coccolith export and the influence of
abiotic factors on such flux. This study focuses on (1) determination of the seasonal variation of the coccolith flux
and species composition, with an attempt to gain further
insight into influencing factors, (2) the assessment of coccolith-carbonate flux using morphometry, and the relationship of coccolith-derived carbonate to the total carbonate
flux, and (3) the relationship of present-day flux of coccoliths and coccolith-carbonate to long-term Holocene accumulation rates in the underlying sediment.
2. Study area
2.1 Oceanographic setting
The mooring station (20˚45.3’N, 19˚44.5’W) lies within

84

Köbrich, Baumann

the eastern boundary current system of NW Africa, an upwelling region driven by the trade winds. Between 24˚Nand 20˚N, intensity of the year-round upwelling varies interannually and seasonally as a result of the variability andseasonality of the trade winds (van Camp et al., 1991).
The oceanography is dominated by the Canary Current(CC), which is a branch of the subtropical gyre that parallels, and then veers away from, the continental slope in asouth-westerly direction (Figure 1). At the latitude of Cape
Verde (15˚N), all of the flow has turned westward to supply the North Equatorial Current (Barton, 1998). South of
the area where the CC veers away from the continental
slope, a cyclonic gyre exists that persists throughout theyear (between 15˚ and 22˚N). This mesoscale surface-water
cyclonic gyre varies in position and lateral extent with theseasons, being furthest north in fall/winter and at its largest
areal extent in summer (Barton, 1998).
Besides the seasonal surface-water conditions, the deep
water-masses also vary seasonally. In the vicinity of Cape
Blanc, the frontal zone between North Atlantic Central
Water and the more nutrient-rich, less saline South Atlantic
Central Water is located, influencing the circulation
through thermohaline mixing processes, and forming acomplex mesoscale regime of (sub)surface currents (Gabricet al., 1993).
Figure 2: a) Insolation data with running average window width = 3, function of polynomial degree = 10. b) Wind speed (redrawn from Ratmeyer
et al., 1999b) with running average window width = 3, function of polynomial degree = 10 and lithogenic particle flux (Fischer et al., 1996). c)
SST and calculated SST anomaly. Grey shaded area indicates upwelling.
All data were corrected for the settling time of 25 days (for more details,
see Müller & Fischer, 2001)

Figure 1: Mooring/sample location (CB1, GeoB 1121), bathymetry andschematic near-surface circulation at Cape Blanc off NW Africa (CC Canary Current, NEC - North Equatorial Current)

2.2 Insolation, wind and sea-surface
temperature anomaly
Stabilisation of the upwelled nutrient-rich water in the euphotic zone, by solar heating, is a fundamental mechanism
supporting the high biological productivity of coastal upwelling ecosystems (Huntsman & Barber, 1977; Nykjær &van Camp, 1994). Insolation data (from http://eosweb.
larc.nasa.gox/sse/) reveals a steady decrease in insolationfrom April to December, followed by a slight increase inspring; during fall and winter, the lowest insolation values

were observed (Figure 2a).
During the study period, the average wind speed measured at Nouadhibou airport (Cape Blanc, Mauritania)
showed a slight increase in spring, culminating in aJune/July maximum (Figure 2b). Following this, the windspeed decreased steadily, reaching its minimum in December/January. In September/October, this decrease was interrupted by a short-lived, remarkable increase (Fischer etal., 1996). In general, the wind direction was mostly fromthe east and north-east.
The mooring location was not located directly within
the coastal upwelling region, but offshore, influenced by
the coastal upwelling, as well as by the development andmovement of the giant filaments. To determine the upwelling events and strength, the difference between the seasurface temperature (SST) of the characteristically cold
(upwelled) water of the mooring location and the SST of
the open ocean (40˚W) at the same latitude was calculated.
This difference is defined as the SST anomaly (following
Speth & Köhne, 1983; data from http://ingrid.ldeo.columbia.edu/SOURCES/IGOSS/nmc/Reyn_SmithOIv2/). A difference of -3K or lower is interpreted as upwelling (Spethet al., 1978). The SST anomaly for the sampling period displays strong upwelling from April to June, followed by a

Coccolithophore flux...Cape Blanc (NW Africa)

steady decline in upwelling intensity, and with no upwelling signal in September (-1.2K). Between July and December, only a short period of weak upwelling in
October/November was recorded. Upwelling was present
again from December to February, but was not as intense asat the beginning of the study year (Figure 2c).
3. Material and methods
The sediment trap (CB1) was moored off Cape Blanc at a
depth of 2195m (total water-depth 3646m). From March,
1988 to March, 1989, a total of 13 samples were collected,
each sample with a collection time of 27 days. The deployment of the sediment trap, as well as the treatment of
the collected samples, is described in detail by Fischer et al.
(1996). The processing of the samples for scanning electron microscopy (SEM) followed the dilution/filtering
method of Andruleit (1996). Depending on the particle content of the samples, 1/3200, 1/4000 or 1/6400 split of theoriginal were filtered. Qualitative and quantitative analyses of the coccolithophores were performed at x3000 magnification using a Zeiss DSM 940A at 10kV accelerating
voltage. Each coccolith and coccosphere within an arbitrarily chosen transect was counted, until a total number ofat least 500 coccoliths was reached. Species were identified to the lowest taxonomic level as possible, based on thetaxonomical concepts of Cros & Fortuño (2002) and Younget al. (2003). To gain estimates of daily coccolith flux, eachcoccosphere was converted into number of coccoliths,
based on species-specific values (Boeckel & Baumann,2008).
The Holocene surface-sediment sample (GeoB 1121)
was prepared for observation using a similar technique(Andruleit, 1996). From the assumed accumulation rate of
0.08g m-2 d-1, based on Winn et al. (1991), coccolith counts
were converted into numbers per gram of dry sediment.
The coccolith-derived carbonate contribution was calculated using the mass equation of Young & Ziveri (2000)
and the results of size measurements carried out in thisstudy (see Table 1). Size measurements were made directlyon the screen of the SEM at a magnification of x5000 or
x10 000, using an internal Zeiss measuring system. The
resolution was within 0.1-0.2μm. For all species, distal
shield dimensions of at least 20, but often more than 30,
randomly-selected specimens were measured for six of the
13 samples from the sediment trap. In total, morethan 150 coccoliths were measured. The species
measured were Calcidiscus leptoporus, C. leptoporus small morphotype, C. quadriperforatus,
Emiliania huxleyi, Florisphaera profunda,
Gephyrocapsa spp., Umbilicosphaera sibogae
and U. foliosa.
4. Results
4.1 Seasonal species flux
Coccolith flux was high during summer (July toAugust) and winter (January to February), withlow values during spring (March to April) andTaxon
Acanthoica spp.
Algirosphaera spp.
Alisphaera spp.
C. brasiliensis
C. quadriperforatus
C. leptoporus
C. leptoporus (small)C. pelagicus
Calciopappus spp.
Calciosolenia spp.
Coronosphaera spp.
D. tubifera
E. huxleyi
F. profunda
G. ericsonii
G. ﬂabellatus
G. muellerae
G. oceanica
H. hyalina
H. carteri
M. elegans
Ophiaster spp.
P. discopora
Pontosphaera spp.
R. clavigera
R. stylifera
R. xiphos
Rhabdosphaera spp.
S. corona
S. pulchra
S. tumularis
Syracosphaera spp.
U. anulus
U. foliosa
U. irregularis
U. sibogae
U. tenuis
Holococcoliths
Others85
Coccolith-CaCO3 [pg] Mean length [μm]
0.3
+
0.9
2.38
2.6
+
2.6
+
206.6
9.85
70.3
6.88
18.5
4.41
336
12.75
2.6
+
2.6
+
12.1
+
1.5
+
1.9
3.28
3.7
3.25
1
1.98
2.6
+
6.5
3.63
14.6
4.77
35.2
6.39
110
9.34
2.6
+
0.1
+
65.9
+
70
+
41
8.47
40.5
+
2.6
+
8
+
12.1
+
16.6
5.9
12.1
+
0.1
+
8
+
32
5.82
5.8
+
12.7
4.4
8.7
+
2.6
+
2.6
+

Table 1: Species-specific coccolith carbonate weights used and mean coccolith length of selected taxa, based on size measurements carried out forthis study. (+ indicates no size measurements on CB trap samples available, in which case, data from Young & Ziveri (2000) was used)fall (September to December) (Figure 3). The highest
coccolith flux was recorded in January, 1989 (384x107 liths
m-2d-1), and the lowest in September, 1988 (51x107 liths m2 -1d ), coinciding with the maximum SST. In contrast, highcoccolith flux was coincident with low SST. The mean
coccolith flux was 182x107 m-2d-1.

Figure 3: Flux of coccoliths, total carbonate and total mass

86

Köbrich, Baumann

The samples revealed a diverse coccolithophore assemblage. In total, 63 heterococcolith-bearing species, one
species in its hetero-/holococcolith-bearing state (Syracosphaera pulchra – Calyptrosphaera oblonga), and one
species bearing holococcoliths (Syracolithus dalmaticus)
were identified. Coccoliths were excellently preserved,
with no signs of dissolution. The most abundant species arelisted in Table 2. For the following interpretation anddiscussion, only species exceeding 5% relative abundance
at least once during the study period are considered.
Acanthoica spp.
Algirosphaera spp.
Calcidiscus quadriperforatus*
Calcidiscus leptoporus
Calciosolenia brasiliensis
Discosphaera tubifera
Emiliania huxleyi
Florisphaera profunda
Gephyrocapsa ericsonii
Gephyrocapsa muellerae*
Gephyrocapsa oceanica
Gladiolithus ﬂabellatus
Helicosphaera carteri
Helicosphaera hyalina*

Ophiaster spp.
Palusphaera spp.*
Rhabdosphaera spp.
Syracosphaera spp.
Syracosphaera anthos
Syracosphaera pulchra*
Syracosphaera tumularis
Umbellosphaera irregularis
Umbellosphaera tenuis
Umbilicosphaera annulus *Umbilicosphaera hulburtiana
Umbilicosphaera foliosa
Umbilicosphaera sibogae
Holococcoliths

Table 2: Identified coccolithophore taxa found during sampling period in
sediment trap samples off Cape Blanc (CB1). *At maximum, absent fromtwo samples

In general, Emiliania huxleyi, Gladiolithus flabellatus,
Algirosphaera spp., Umbilicosphaera spp., Helicosphaera
spp. and Rhabdosphaera spp. reached their flux maxima in
January (1989) and exhibited additional high flux in August (1988). Gephyrocapsa ericsonii also showed maximum flux in winter, but without a pronounced summer
peak. Gephyrocapsa oceanica, Calcidiscus leptoporus,
Umbellosphaera spp. and Discosphaera tubifera reachedtheir flux maxima between May and August and had an additional high flux period in winter (January or February;
Figure 4). The flux of Coccolithus pelagicus, Syracosphaera spp., Ophiaster spp., Acanthoica spp., Calciosolenia brasiliensis and of the holococcolith-bearing
species varied throughout the year (Figure 4).
The coccolithophore assemblages were dominated by
E. huxleyi (30-45%), Florisphaera profunda (6-19%) andG. oceanica (3-13%; Figure 5). Algirosphaera spp., G. flabellatus, F. profunda and Umbellosphaera spp. made a
constant contribution to the assemblage, with two distinct
maxima (May/June and December/January). G. oceanica
steadily decreased in abundance from summer onward,
with an increase during October/November 1988.
4.2 Morphometric measurements
In general, Emiliania huxleyi is the most abundant living
coccolithophore and dominates the coccolith flux in thisstudy. The morphology of 194 coccoliths of E. huxleyi
shows a unimodal distribution (Figure 6a). Length ranges

from 2.5-4.9μm, with a mean of 3.3μm. Varieties, as given
by Westbroek & Young (1991), were not distinguished during the counting. However, the majority of the measured
specimens are assigned to E. huxleyi type A. A few specimens with more delicate rays indicate that E. huxleyi type
C is also present.
Florisphaera profunda is the main contributor to thelower-photic-zone flora of low to mid latitudes (Okada &Honjo, 1973; Okada & McIntyre, 1977). Overall, lith
lengths in the studied sediment trap samples are 1.4 to
6.4μm (Figure 6b). However, the scatter plot and frequency
distributions clearly document a bimodal pattern, indicating that two varieties of F. profunda are present in the investigated samples, with var. elongata forming larger liths(Reid, 1980). The larger liths are between 4.3μm and6.5μm in length, whereas liths of 1.4μm to 3.9μm may correspond to F. profunda var. profunda. Varieties, as indicatedby the size data, were not distinguished in the counts, andlith-carbonate flux calculations were made using total mean
size (3.4μm).
Placoliths of the heterococcolith-bearing stage of theCalcidiscus leptoporus group into three indistinct clusters,
consistent with C. leptoporus small type, intermediate C.
leptoporus and the large C. quadriperforatus, as introducedby Geisen et al. (2002), with overall lengths of 3.4-5.5μm,
5.1-8.4μm and 6.9-11.4μm, respectively (Figure 7).
The coccoliths of Umbilicosphaera sibogae and U. foliosa show distinct variation in diameter, element numbers,
and diameter of the central area. The distal shield diameterof U. sibogae is 3.1μm to 5.1μm, with a mean of 4.4μm,
with the larger proximal shields having a mean of 4.9μm.
The distal shield of U. foliosa is 5.0-6.8μm in diameter,with a mean of 5.8μm.
In the present study, Gephyrocapsa coccoliths were distinguished by morphological differences (length, width,
structure). Overall, length and width of the placoliths are
extremely well correlated (r2 = 0.97). G. ericsonii coccoliths are 1.6-2.7μm long. Small G. oceanica coccoliths are
medium-sized, 3.1-4.4μm long, whereas the length oflarge-sized G. oceanica generally ranges from 4.2μm to
5.9μm (Figure 8).
4.3 Coccolith-carbonate flux
Calculated coccolith-carbonate flux, based onmorphometric measurements and literature data (Table 1)varied significantly between 3.9 and 22.8mg m-2d-1 in thestudied sediment trap. The mean calculated coccolithcarbonate flux was 13.32mg m-2d-1. On average, coccoliths
contributed 18% to the measured total carbonate flux.
Variation in the relative fraction of coccolith-carbonate to
the total carbonate was high (7%-35%; Figure 9).
Only a few species contributed significantly to the coccolith-carbonate flux, either due to their high specific carbonate mass or due to their high numbers. Thus, the rare
and subordinate species Helicosphaera carteri, Calcidiscus leptoporus and Coccolithus pelagicus were significant
contributors due to their coccolith weight (Young & Ziveri,

Coccolithophore flux...Cape Blanc (NW Africa)

87

Figure 4: Seasonal flux of the most common coccolithophore species of the settling assemblage of CB1

2000). These relatively massive species contributed 3540% to the coccolith-carbonate flux. Due to their highabundance, Emiliania huxleyi, Gephyrocapsa oceanica andFlorisphaera profunda contributed 35-40% to the coccolith-derived carbonate.

88

Köbrich, Baumann

Figure 5: Relative abundance of coccolithophores off Cape Blanc during
1988-89

Figure 7: Scatter plots of diameter vs. pore size and number of elementsin the distal shield of Calcidiscus, and frequency size distribution (0.5μm
intervals)

Figure 8: Length vs. bridge-angle measured in Gephyrocapsa spp.
Figure 6: a) Size variation and frequency distribution (0.25μm intervals)of E. huxleyi. b) Length and width variation, and frequency distribution(0.25μm intervals), of F. profunda

4.4 Coccolith and coccolith-carbonate
accumulation rates
The total coccolith accumulation rate of the Holocene sediment sample (GeoB 1121) was 59x107 liths m-2d-1. In total,
20 heterococcolith-bearing species were identified. Emiliania huxleyi, Florisphaera profunda and Gephyrocapsa
oceanica were the most abundant species, with relative
abundances of 48.5%, 17% and 14.3%, respectively. Umbilicosphaera spp., Calcidiscus leptoporus and Helicosphaera spp. were common (3.6%, 4.0% and 2.6%,
respectively).
The calculated coccolith-carbonate content accounts for

85.7mg g-1 sediment (8.57wt%) and an accumulation rateof 6.52mg m-2d-1 (17.86g m-2y-1), which is 14.9% of thetotal carbonate accumulation rate (measured carbonate content of the sediment is 57.40wt%).
5. Discussion
5.1 Seasonality of the coccolithassemblages
To explain the seasonal flux pattern of coccoliths and their
species composition during 1988-1989, we focused on theinteraction of wind, nutrients and light for the study period
and area, since the dynamics of phytoplankton populations
in upwelling regions are very much controlled by suchforcing factors (Margalef, 1978a). The export of phytoplankton is based, to a great extent, on the productivity inCoccolithophore flux...Cape Blanc (NW Africa)

Figure 9: Comparison of total carbonate flux with calculated coccolithderived carbonate flux at the sample site

89

turbulence and vertical mixing, induced a decrease in light
conditions in the surface-waters (Fischer et al., 1996; Rost
& Riebesell, 2004). Nelson & Conway (1979) concluded
that the light regime is more important than nutrient concentration in controlling the use of inorganic nutrients in
the NW African upwelling system by phytoplankton.
Strong winds limit the effective time period for light-driven
primary production (Dugdale & Wilkerson, 1985). The
wind strength off Cape Blanc often causes the mixed layer
to be deeper than the euphotic zone, thus light limitationof the primary productivity is likely to occur (Blasco et al.,1981). In general, the maximum production rates areachieved only during periods of wind relaxation when vertical mixing is reduced (Gabric et al., 1993).
From April to July, coccolith flux increased up to thefirst seasonal maximum in August, 1988. Diatom flux increased as well, up to their maximum in July (Romero etal., 2002b; Figure 10). Simultaneously, upwelling and windspeed decreased. We deduce that the water movement andthe surface-waters. Comparison of the coccolith flux to theflux of siliceous phytoplankton (Romero et al., 2002b) ishere used to explain the seasonal flux patterns exhibited by
the coccoliths (Table 3).
The mean irradiance experienced by phytoplankton is influenced by the intensity of insolation, upwelling and wind speed, thus by thestrength of turbulence and mixing of the watercolumn. As Margalef (1978a) described, in Margalef’s Mandala, the ecological preferences ofliving coccolithophores are characterised bymedium turbulence and mesotrophic waters,
whereas diatoms dominate in nutrient-rich andturbulent environments. Balch (2004) extended
this profile to include light. Taking this into consideration, the low flux of coccoliths in spring,
1988 (Figure 10) can be explained as follows.
Upwelling determined by SST anomaly is
Figure 10: Total coccolith flux vs. siliceous phytoplankton flux (redrawn fromstrongest, as was the wind strength (Figure 2). Romero et al., 2002b)
The strong influence of the (coastal) upwelling is
also indicated by the dominance of neritic diatoms over oceanic ones at that time (Romero et al., turbulence ebbed allowing light availability in the surface2002b). High wind-speed and strong upwelling, causing water to increase, thus positively influencing primary production, as shown by the peaks in diatom and highcoccolith fluxes (Figure 10). Phytoplankton
differ in their ability to cope with variable
SpringSummerFall
Winterirradiance. Coccolithophores seem to have(Mar-May) (Jun-Aug)(Sep-Nov)(Dec-Feb)a slightly higher light saturation for optimum growth compared to diatoms (Rost &Flux of coccoliths
averagehighminimum
maximum
Riebesell, 2004). As a consequence, diatoms
are commonly the first to bloom when theUpwellingstrongweakeningnoaveragewater-column begins to stabilize early in theseasonal cycle (Rost & Riebesell, 2004).
The coccolith and diatom flux patterns at
Nutrients
high
low
low
average
CB1 seem to agree with these general concepts.
In September, 1988, the overall flux, andIrradiance
low
high
low
average(in water column)
consequently also the coccolithophore flux,
reached a minimum. Upwelling ceased, andTable 3: Summary of the interaction of light, nutrient availability and wind that determine
no additional input of nutrients occurred.
coccolith flux at CB1. The upwelling intensity can be described based on the SST anomaly
After the high flux of diatoms in March andand, consequently, the nutrient input

90

Köbrich, Baumann

July, and the first peak coccolith flux in June/July, the water
was probably depleted in nutrients. Dugdale & Wilkerson(1985) showed that the euphotic zone in that area can temporally be depleted in nutrients.
Later on in fall, the increase in coccolith flux corresponded to the onset of increasing upwelling, most likely
resupplying the surface-water with nutrients. An intense
aeolian input (Romero et al., 2003) represents a further nutrient source for that interval. The light regime for the sampling period seems favourable as well, since upwelling was
not strong and wind speed was at its lowest (Ratmeyer etal., 1999b; Romero et al., 2003).
In January and February, maximum coccolith export
corresponded to average values of the influencing forces,
such as light availability, nutrients, upwelling intensity and
SST. Thus, Margalef’s Mandala is depicted by the seasonal
flux pattern of coccoliths and diatoms in this highly variable environment.
The upwelling region off NW Africa is known to reveal
its highest chlorophyll pigment concentration during spring
and winter (Thomas et al., 2004), and even far offshore,high pigment concentrations have regularly been found(Estrada, 1974; Gabric et al., 1993; Kostianoy & Zatsepin,
1996; Thomas et al., 2004). The seasonal fluxes of coccoliths and diatoms in this region, in 1988-1989 (Figure 10),
imply a change in the dominating phytoplankton group tocause these elevated pigment concentrations. The
spring/summer peak seems to be dominated by diatoms,
whereas the winter peak is dominated by coccolithophores(Figure 10). The change in dominance is supported by themodel calculation of Giraud (2006).

linked to processes of decaying movement associated withthe giant water-mass filaments mentioned above (Margalef,
1978b; Gabric et al., 1993). Thus, finding coccolithophore
species together in one sample, which are associated withdiffering ecological preferences, can be explained by smallscale spatial diversity above the sediment trap.
As described by Young & Westbroek (1991), separation of the different E. huxleyi types, based on biometricanalysis, is difficult, since a great overlap of size exists,
hence the unimodal distribution does not distinguish between type A and type C in our samples (Figure 6a). TypeA was the common morphotype in our study, as documented for the world ocean. The presence of E. huxleyi
type C may indicate the influence of (coastal) upwelled,
cold water, since type C is generally associated with coldwater conditions (McIntyre & Bé, 1967; Hagino et al.,2005).
Species of the lower photic zone, such as F. profunda
and G. flabellatus, increased in relative abundance inwinter (December to January), when insolation was at its
lowest and wind turbulence was low. They may have benefited from low irradiance associated with these environmental factors, due to their apparent adaptation to low light
conditions (Quinn et al., 2005). Furthermore, their habitat
close to the nutricline would provide the requisite nutrientsduring this time of lower nutrient input (fall to early
winter). The simultaneous occurrence of F. profunda var.
profunda and F. profunda var. elongata is well documented(Quinn et al., 2005). However, it is not yet clear whether
the distinct size morphotypes correspond to typologicalvarieties, since further morphological differentiation is
missing.
The (morpho)types of Calcidiscus revealed discrete
flux patterns, with maximum flux of C. quadriperforatus
and C. leptoporus low in summer, but with the small typeincreasing later on. The intermediate-sized C. leptoporus
has a fluctuating seasonal pattern (Figure 11). To assign the
distribution of the different morphotypes of Calcidiscus to
specific environmental parameters during the study period
would be highly speculative. The continuous dominance of
C. leptoporus intermediate morphotype, during signifi-

5.2 Coccolithophore assemblages
Emiliania huxleyi, Florisphaera profunda, Gladiolithus flabellatus, Algirosphaera spp., Umbilicosphaera spp. andSyracosphaera spp. reflect the described general pattern ofcoccolith flux by revealing two seasonal maxima, high flux
in summer and maximum flux in winter. These species do
not generally occupy the same ecological niches, E. huxleyi
being a bloom-forming, placolith-bearing cosmopolitan
species (Westbroek et al., 1993), F. profunda and G. flabellatus living in the lower photic zone, with
F. profunda indicating the vicinity of the nutricline (Winter & Siesser, 1994), and Umbilicosphaera spp. being weakly associatedwith warm, saline, rather oligotrophic water(Okada & McIntyre, 1979; Ziveri et al.,
1995, 2004). However, the sediment trapmaterial is somewhat averaged, with respect
to time and space, thus the entire ecologicalstructure is represented in one sample. The
phytoplankton community may have had apatchy distribution. Margalef (1978b) described the plankton community off NW
Africa as having small-scale fluctuations developed around a trend that showed larger- Figure 11: Flux of Calcidiscus spp. from CB1 plotted against their relative abundances
scale fluctuations. This dynamic pattern is (100% = flux of Calcidiscus spp. only)Coccolithophore flux...Cape Blanc (NW Africa)

cantly changing environmental conditions may indicate its
broad tolerance, as documented by Boeckel et al. (2006).
During spring and summer, Gephyrocapsa muellerae
was present, indicating cold and nutrient-enriched waters,
based on the interpreted strong upwelling (Figure 2). Its
steady decrease in relative abundance (Figure 12) corresponds to the decreasing influence of the cold, upwelledcoastal water. The decline in G. oceanica relative abundance (Figures 4, 12), supports the interpretation of reduced
influence of turbulent and nutrient-enriched waters, induced by the steady decrease in wind speed; Boeckel et al.
(2006) showed that G. oceanica abundance seemed to becorrelated to turbulence, and it has also been shown to havea relationship with the nutrient content of surface-waters(Andruleit et al., 2003; De Bernardi et al., 2005).

91

al. (1999b). Thus, high sinking speeds, as a consequence ofthe high organic matrix loading, may have slowed/stopped
the degradation and disintegration of holococcospheres. In
spring, the time of strong mixing and upwelling, environmental factors may be unfavourable for the settling (and/or
production) of the holococcoliths.

5.3 Upwelling regions – a comparison
For different upwelling regions, the comparison of yearlymean coccolithophore flux shows similar values. The mean
flux off Cape Blanc (CB1 - 65x1010 liths m-2y-1) lies between the range of the Somalian upwelling flux (17x1010
liths m-2y-1 - sediment trap MST-9: Broerse et al., 2000)
and that of the Namibian upwelling (160x1010 liths m-2y-1 sediment trap NU: Romero et al., 2002a). The mooring
stations of CB and MST-9 lay in comparable
oceanographic regions. They were influenced
by upwelling and/or filaments that developed
between the coastal upwelling and the open
ocean, but were not moored in the coastal
upwelling itself. The NU sediment trap wasmoored closer to the coastal upwelling cell.
In oligotrophic sites, a flux of 14x1010 lithsm-2y-1 (sediment trap NABE-48: Ziveri et al.,2000) and 19x1010 liths m-2y-1 (sediment trap
ESTOC: Sprengel et al., 2000) were reported(Figure 14a).
Milliman (1993) estimated the carbonate
Figure 12: Relative abundances of G. oceanica, G. muellerae and G. ericsonii (100% =export production to range between 2-5g mflux of Gephyrocapsa spp. only) plotted against absolute flux of Gephyrocapsa spp. at
2 -1
CB1
y in the central ocean gyres and 30-40g m2 -1
y in the eastern upwelling zones. The
The holococcolith flux corresponded very well to the mooring stations off Somalia (MST-9), Namibia (NU) andflux of lithogenic particles (Figure 13). As holococcoliths Mauritania (CB) have a yearly carbonate export producare composed of numerous minute crystallites, which do tion of 22, 21 and 22g m-2y-1, respectively. All mooring stanot tightly interlock, their morphology is rather fragile and tions lay close to the upwelling, revealing high carbonate
easily disintegrated (Young et al., 2003). In the arid area export, due to the influence of the upwelling. The mooringof the Sahara, strong wind carries great quantities of dust station of NABE 48 (North Atlantic), with a yearly carfar out to sea. These dust loads can be released into the bonate flux of 11g m-2, resembles an oligotrophic site, as do
ocean during times of wind relaxation. From 1988-89, high sediment traps off the Canary Islands (ESTOC), with 8.7g
sinking velocities of particles in the water-column, thus a m-2.
short settling time, were observed (Ratmeyer et al., 1999b).
Comparing the yearly mean carbonate flux derived
The high lithogenic flux during that period may have acted from coccoliths, these trap sites show values in the sameas a carrier system for the fragile holococcoliths. The lith- range: 4.9g m-2y-1 for CB1, 3.8m-2y-1 for the upwelling off
ogenic constituents off Cape Blanc appear to be coupled Namibia (NU), 3.6g m-2y-1 for the Canary Islands (Sprenwith the organic carbon flux documented by Ratmeyer et gel et al., 2000), 3g m-2y-1 for the upwelling off Somalia(MST 9: Broerse et al., 2000), and 2.7g m-2y-1 for the oligotrophic site (NABE-48: Ziveri et al., 2000). However, theproportion of coccolith-carbonate to the total carbonate export differs significantly. In the upwelling region off NW
and SW Africa, the contribution of coccolith-carbonate to
the total carbonate is the same, at 18%, whereas off Somalia, it accounts for 13%, and around the Canary Islands,
41%. With 24% of the total carbonate contribution from
coccoliths, the mooring location of the North Atlantic(NABE-48) lies between these.
Figure 13: Flux of holococcoliths vs. lithogenic material at CB1

92

Köbrich, Baumann

Figure 14: Comparison of average coccolith flux/accumulation (a) and average coccolith-carbonate flux/accumulation (b) recorded in sediment traps
and surface-sediments in the region

cus leptoporus (Figure 16).
5.3 Export production versus surfaceCompared to other upwelling regions (off SW Africa,
sediment accumulation
generally,
the contribution of coccoliths is 23% (Boeckel,
A good correlation between coccolith flux and
2002)
and
in the Canary Islands region 26% (Sprengel etaccumulation in the sediment can be seen (Figure 14),al.,2002)),
the contribution of coccoliths to the total cardespite a slight discrepancy in numbers and species
bonatecontentof the sediment (15%) is relatively low offcomposition (Figure 15). In general, coccolith flux
Cape
Blanc.
recorded in the trap is slightly higher than coccolith accumulation in the underlying sediment. The annual coccolith
flux at 2200m water-depth was about three-fold the coc- 6. Conclusions
colith accumulation rate in the sediment (Figure 14). The Our study of settled coccolithophore assemblages from ahigher coccolith flux in the sediment trap samples is ac- year-round (1988-89) moored sediment trap (CB1) off NW
counted for by higher abundances of more fragile and Africa revealed the following main facts:
small-sized taxa, such as Syracosphaera spp. (Figure 15).
The coccolith flux shows seasonal changes, with highAbsence of these more delicate coccoliths from the sedi- values in summer, a peak in winter and minima in fall andment might be due to enhanced dissolution
at the sediment-water interface, and to destruction due to mechanical impact. Nevertheless, coccolith and coccolithcarbonate flux and accumulation rates(Figure 14), as well as the relative contributions of single species (Figure 16), areof the same order of magnitude. The slight
discrepancies may be a combination oftransport and dissolution processes. Furthermore, the flux derived from the sediment trap displays one seasonal cycle, with
distinct hydrographic and climatic conditions, whereas the sediment sample reveals
an integrated picture of several hundredyears, thus seasonal characteristics arelikely overprinted by interannual variability. The higher coccolith-derived carbonate accumulation of the sedimentcompared to the sediment trap resulted
from the enrichment of the sediment bylarge, massive and carbonate-rich taxa, Figure 15: Comparison of coccolith relative abundance between sediment trap samples (lightsuch as Helicosphaera spp. and Calcidis- grey) and underlying Holocene surface-sediment samples (dark grey)Coccolithophore flux...Cape Blanc (NW Africa)

93

Figure 16: Main species contributing to the coccolith-derived carbonate flux, presented as relative abundances. The mean coccolith-derived carbonate
flux is slightly smaller in the trap

spring. The relatively diverse assemblage consisted of 63
heterococcolith-bearing species, one species in its hetero/holococcolith-bearing state, and one species bearing holococcoliths only.
Minimum coccolith flux corresponds to maximum SST,
and high flux occurs with low SST. Maximum coccolithexport reflects an oceanic setting, in which influencing factors, such as wind strength, upwelling intensity, nutrient
content and light availability in the surface-waters were attheir respective medium values.
Respective maximum fluxes of diatoms, coccolithophores and silicoflagellates occurred in different seasons, starting with diatoms in fall, followed bycoccolithophores in winter, and finally silicoflagellates inlater winter. It is concluded that diatoms reacted first to additional nutrients, whereas coccolithophores dominatedafter some depletion of these, when neither high nor lowhydrographical and climatic conditions prevailed. The
complex setting of the NW African upwelling, nevertheless, represents an example of Margalef’s (1978a) Mandalaand its extension by Balch (2004).
Emiliania huxleyi was the dominant species. Morphometric measurements revealed a unimodal distribution of
E. huxleyi coccoliths. The majority of the specimens belong to E. huxleyi type A and only a few specimens to typeC.
Species of the lower photic zone, Florisphaera profunda and Gladiolithus flabellatus, increased in winter andwere most abundant during conditions of minimum insolation and minimum water turbulence. The sizes of the nannoliths of F. profunda have a bimodal distribution pattern,indicating two varieties of F. profunda, with var. elongata
forming larger coccoliths.

Calcidiscus leptoporus, C. leptoporus small morphotype and C. quadriperforatus reveal different seasonal
abundance patterns, with C. leptoporus dominating andstrongly fluctuating in abundance during the year, indicating a broader tolerance to the changing environmental conditions. C. quadriperforatus and C. leptoporus small
morphotype show similar seasonal patterns, with high flux
in summer and low in fall/winter. However, C. quadriperforatus reaches its maximum flux earlier in summer. The
assumed addition of nutrients seems to favour their occurrence.
Decreased relative abundances of Gephyrocapsa
oceanica and G. muellerae indicate the reduced influenceof cold, nutrient-enriched and turbulent waters. The documented decrease in wind strength supports this assumption.
The flux of holococcoliths parallels the measured lithogenic flux. Off Cape Blanc, the lithogenic material appears
to be coupled with the organic carbon flux. The high sinking speeds, as a consequence of the high organic matrix
loading, may slow or stop the degradation and disintegration of holococcoliths.
The mean coccolith-derived carbonate, based on broad
morphometric measurements, adds up to 4.9g m-2y-1. Compared to other oceanic regions, the mooring location represents a meso-eutrophic environment. The proportion of
coccolith carbonate to the total carbonate production accounts for 18% in the upwelling region of NW Africa. Thisis within the range of the upwelling region of SW Africa,
but is less than that of the Canary Island region (41%).
A good correlation between the coccolith flux and theaccumulation in the underlying Holocene surface-sedimentcan be seen. Nevertheless, with respect to species composition, relative and absolute abundances, small discrepan-

94

Köbrich, Baumanncies were observed, with a slightly higher abundance ofmore fragile and small-sized coccoliths in the sedimenttrap samples. In the underlying surface-sediment, coccolith-derived carbonate accounts for 15% of the total
carbonate flux. This is less than that of the upwelling region
off SW Africa (23%) and of the Canary Island region(26%).
Acknowledgements
We are grateful to Dr. B. Boeckel for the intensive discussions
and valuable suggestions on the manuscript. The comments of
Drs M. Geisen, B. De Bernardi, J. Lees, and a further anonymous
reviewer of an early version of the manuscript, were thankfully
considered. M. Krysta is thanked for technical support inpreparation of the samples. This research was funded by theDeutsche Forschungsgesellschaft as part of the European
Graduate College ‘Proxies in Earth History’ EUROPROX,
Bremen Universität.

References
Andruleit, H. 1996. A filtration technique for quantitative studies
of coccoliths. Micropaleontology, 42(4): 403-406.
Andruleit, H., Stager, S., Rogalla, U. & Cepek, P. 2003. Living
coccolithophores in the northern Arabian Sea: ecologicaltolerancesandenvironmental
control.
MarineMicropaleontology, 49(1-2): 157-181.
Balch, W.M. 2004. Re-evaluation of the physiological ecology of
coccolithophores. In: H.R. Thierstein & J.R. Young (Eds).
Coccolithophores - From molecular processes to global
impact. Springer-Verlag, Berlin: 165-190.
Barton, E.D. 1998. Eastern boundary of the North Atlantic:
Northwest Africa and Iberia. In: A.R. Robinson & K.H. Brink(Eds). The Sea. The global coastal ocean - regional studies
and synthesis. John Wiley, London: 633-657.
Blasco, D., Estrada, M. & Jones, B.J. 1981. Short time variabilityof phytoplankton populations in upwelling regions - theexample of Northwest Africa. In: F.E. Richards (Ed.). Coastal
Upwelling, Coastal and Estuarine Sciences, 1. American
Geophysical Union, Washington: 339-347.
Boeckel, B. 2002. Present and past coccolith assemblages in theSouth Atlantic: implications for species ecology, carbonate
contribution and palaeoceanographic applicability. Berichte
aus dem Fachbereich Geowissenschaften der Universität
Bremen, Bremen: 157pp.
Boeckel, B. & Baumann, K.-H. 2008. Vertical and lateral variations in coccolithophore community structure across the subtropical frontal zone in the South Atlantic Ocean. Marine
Micropaleontology, 67(3-4): 255-273.
Boeckel, B., Baumann, K.-H., Henrich, R. & Kinkel, H. 2006.
Coccolith distribution patterns in South Atlantic and Southern
Ocean surface sediments in relation to environmental
gradients. Deep-Sea Research I, 53(6): 1073.
Broerse, A.T.C. 2000. Coccolithophore export production in
selected ocean environments: seasonality, biogeography,
carbonate production. Phd thesis, Vrije Universiteit te
Amsterdam, Amsterdam: 185pp.
Broerse, A.T.C., Brummer, G.-J. & van Hinte, J.E. 2000.
Coccolithophore export production in response to monsoonal
upwelling off Somalia (northwestern Indian Ocean). DeepSea Research II, 47(9-11): 2179-2205.
van Camp, L., Nykjær, L., Mittelstaedt, E. & Schlittenhardt, P.
1991. Upwelling and boundary circulation off Northwest

Africa as depicted by infrared and visible satellite
observations. Progress In Oceanography, 26(4): 357-402.
Cros, L. & Fortuño, J.-M. 2002. Atlas of Northwestern
Mediterranean Coccolithophores. Scientia Marina, 66(Supplement 1): 186pp.
De Bernardi, B., Ziveri, P., Erba, E. & Thunell, R.C. 2005.
Coccolithophore export production during the 1997–1998 El
Niño event in Santa Barbara Basin (California). Marine
Micropaleontology, 55(1-2): 107-125.
Delesalle, B., Sakka, A., Legendre, L., Pages, J., Charpy, L. &Loret, P. 2001. The phytoplankton of Takapoto Atoll(Tuamotu Archipelago, French Polynesia): time and spacevariability of biomass, primary production and composition
over 24 years. Aquatic Living Resources, 14(3): 175-182.
Deuser, W.G., Muller-Karger, F.E., Evans, R.H., Brown, O.B.,
Esias, W.E. & Feldman, G.C. 1990. Surface ocean colour anddeep-ocean carbon flux: How close is the connection? DeepSea Research I, 37: 1331-1343.
Dugdale, R.C. & Wilkerson, F.P. 1985. Primary production in theCape Blanc region. In: C. Bas, R. Margalef & P. Rubies (Eds).
Simposion internacional sobre las areas de afloramiento mas
importantes del oeste Africano (Cabo Blanco y Benguela).
Instituto de Investigaciones Pesqueras, Barcelona: 233-243.
Estrada, M. 1974. Photosynthetic pigments and productivity inthe upwelling region of NW Africa. Téthys, 6(1-2): 247-260.
Fischer, G., Donner, B., Ratmeyer, V., Davenport, R. & Wefer, G.
1996. Distinct year-to-year particle flux variations off Cape
Blanc during 1988-1991: Relation to δ18O-deduced seasurface temperatures and tradewinds. Journal of Marine
Research, 54: 73-98.
Gabric, A.J., Garcia, L., Van Camp, L., Nykjær, L., Eifler, W. &Schrimpf, W. 1993. Offshore export of shelf production in theCape Blanc (Mauritania) filament as described from coastalzone color scanner imagery. Journal of GeophysicalResearch, 98(C3): 4697-4712.
Geisen, M., Probert, I. & Young, J.R. 2002. Coccolithophores for
exhibition: a note. Journal of Nannoplankton Research, 24(1):3-7.
Giraud, X. 2006. Modelling an alkenone-like proxy record in the
NW African upwelling. Biogeosciences Discussions, 3: 71121.
Hagino, K., Okada, H. & Matsuoka, H. 2005. Coccolithophore
assemblages and morphotypes of Emiliania huxleyi in theboundary zone between the cold Oyashio and warm Kuroshio
currents off the coast of Japan. Marine Micropaleontology,
55: 19-47.
Huntsman, S.A. & Barber, R.T. 1977. Primary production off
northwest Africa: the relationship to wind and nutrient
conditions. Deep-Sea Research I, 24: 25-34.
Kostianoy, A.G. & Zatsepin, A.G. 1996. The West African coastal
upwelling filaments and cross-frontal water exchange
conditioned by them. Journal of Marine Systems, 7(2-4): 349359.
Lange, C.B., Romero, O.E., Wefer, G. & Gabric, A.J. 1998.
Offshore influence of coastal upwelling off Mauritania, NW
Africa, as recorded by diatoms in sediment traps at 2195m
water depth. Deep-Sea Research I, 45: 985-1013.
Legendre, L. & Rassoulzadegan, F. 1996. Food-web mediatedexport of biogenic carbon in oceans: hydrodynamic control.
Marine Ecology Progress Series, 145: 179-193.
Margalef, R. 1978a. Life-forms of phytoplankton as survival
alternatives in an unstable environment. Oceanologica Acta,
1(4): 493-509.

Coccolithophore flux...Cape Blanc (NW Africa)
Margalef, R. 1978b. Phytoplankton communities in upwellingareas. The example of NW Africa. Oecologia aquatica, 3: 97132.
McIntyre, A. & Bé, A.W.H. 1967. Modern Coccolithophoridae of
the Atlantic Ocean - I. Placoliths and Cyrtoliths. Deep-Sea
Research and Oceanographic Abstracts, 14(5): 561-597.
Milliman, J.D. 1993. Production and accumulation of calcium
carbonate in the ocean: budget of a nonsteady state. Global
Biogeochemical Cycles, 7(4): 927-957.
Nelson, D.M. & Conway, H.L. 1979. Effects of light regime on
nutrient assimilation by phytoplankton in the Baja California
and northwest Africa upwelling systems. Journal of Marine
Research, 37: 304-318.
Neuer, S., Ratmeyer, V., Davenport, R., Fischer, G. & Wefer, G.
1997. Deep water particle flux in the Canary Island region:seasonal trends in relation to long-term satellite derived
pigment data and lateral sources. Deep-Sea Research I, 44(8):1451-1466.
Nykjær, L. & Van Camp, L. 1994. Seasonal and interannual
variability of the coastal upwelling along northwest Africa
and Portugal from 1981 to 1991. Journal of GeophysicalResearch, 99: 14197-14207.
Okada, H. & Honjo, S. 1973. The distribution of oceanic
coccolithophorids in the Pacific. Deep-Sea Research andOceanographic Abstracts, 20(4): 355-364.
Okada, H. & McIntyre, A. 1977. Modern coccolithophores in thewestern North Atlantic Ocean. Micropaleontology, 23(1): 155.
Okada, H. & Mcintyre, A. 1979. Seasonal distribution of modern
coccolithophores in the western North Atlantic Ocean. Marine
Biology, 54: 319-328.
Peinert, R., Bodungen, B.V. & Smetacek, V. 1989. Food web
structure and loss rate. In: W.-H. Berger, V. Smetacek & G.
Wefer (Eds). Productivity of the Ocean: Present and Past.
John Wiley, London: 35-48.
Quinn, P.S., Cortez, M. & Bollmann, J. 2005. Morphologicalvariation in the deep ocean-dwelling coccolithophore
Florisphaera profunda (Haptophyta). European Journal of
Phycology, 40(1): 123-133.
Ratmeyer, V., Balzer, W., Bergametti, G., Chiapello, I., Fischer, G.
& Wyputta, U. 1999a. Seasonal impact of mineral dust on
deep-ocean particle flux in the eastern subtropical Atlantic
Ocean. Marine Geology, 159: 241-252.
Ratmeyer, V., Fischer, G. & Wefer, G. 1999b. Lithogenic particle
fluxes and grain size distributions in the deep ocean off
northwest Africa: Implications for seasonal changes of aeolian
dust input and downward transport. Deep-Sea Research I, 46:
1289-1337.
Reid, F.M.H. 1980. Coccolithophorids of the North PacificCentral Gyre with notes on their vertical and seasonal
distribution. Micropaleontology, 26(2): 151-176.
Romero, O.E., Boeckel, B., Donner, B., Lavik, G., Fischer, G. &Wefer, G. 2002a. Seasonal productivity dynamics in the
pelagic central Benguela System inferred from the flux ofcarbonate and silicate organisms. Journal of Marine Systems,
37(4): 229-307.
Romero, O.E., Dupont, L., Wyputta, U., Jahns, S. & Wefer, G.
2003. Temporal variability of fluxes of eolian-transported
freshwater diatoms, phytoliths, and pollen grains off Cape
Blanc as a reflection of land-atmosphere-ocean interactions
in northwest Africa. Journal of Geophysical Research,
108(C5).
Romero, O.E., Lange, C.B. & Wefer, G. 2002b. Interannual

95

variability (1988-1991) of siliceous phytoplankton fluxes off
northwest Africa. Journal of Plankton Research, 24(10):1035-1046.
Rost, B. & Riebesell, U. 2004. Coccolithophores and thebiological pump reponses to environmental changes. In: H.R.
Thierstein & J.R. Young (Eds). Coccolithophores - From
molecular processes to global impact. Springer-Verlag,
Berlin: 99-126.
Samtleben, C. & Bickert, T. 1990. Coccoliths in sediment traps
from the Norwegian Sea. Marine Micropaleontology, 16(12): 39-64.
Speth, P., Detlefsen, H. & Sierts, H.-W. 1978. Meteorologicalinfluences on upwelling off northwest Africa. Deutsche Hydrographische Zeitschrift, 31(3): 95-104.
Speth, P. & Köhne, A. 1983. The relationship between sea surface temperatures and wind off Northwest Africa and Portugal. Oceanogr. Trop., 18: 69-80.
Sprengel, C., Baumann, K.-H. & Neuer, S. 2000. Seasonal andinterannual variation of coccolithophore fluxes and species
composition in sediment traps north of Gran Canaria (29˚N
15˚W). Marine Micropaleontology, 39(1-4): 157-178.
Sprengel, C., Baumann, K.-H., Henderiks, J., Henrich, R. &Neuer, S. 2002. Modern coccolithophore and carbonate sedimentation along a productivity gradient in the Canary Islands
region: seasonal export production and surface accumulation
rates: Deep-Sea Research II, 49(19): 3577-3598.
Thomas, A., Strub, P., Carr, M.-E. & Weatherbee, R. 2004.
Comparisons of chlorophyll variability between the four
major global eastern boundary currents. International Journalof Remote Sensing, 25(7-8): 1443-1447.
Wefer, G. & Fischer, G. 1993. Seasonal patterns of verticalparticle flux in equatorial and coastal upwelling areas of theeastern Atlantic. Deep-Sea Research I, 40(2): 1613-1645.
Westbroek, P., Brown, C.W., Bleijswijk, J.V., Brownlee, C.,
Brummer, G.J., Conte, M., Egge, J., Fernandesz, E., Jordan,R., Knappertsbusch, M., Stefels, J., Veldhuis, M., Van Der
Wal, P. & Young, J. 1993. A model approach to biologicalclimate forcing: the example of Emiliania huxleyi. Global
and Planetary Change, 8: 27-46.
Winn, K., Sarnthein, M. & Erlenkeuser, H. 1991. δ18O stratigraphy and chronology of Kiel sediment cores from the East Atlantic, 45. Geologisch-Paläontologisches Institut undMuseum Chrisitan-Albrecht-Universität, Kiel: 156pp.
Winter, A. & Siesser, W.G. 1994. Coccolithophores. Cambridge
University Press, Cambridge: 242pp.
Young, J.R., Geisen, M., Cros, L., Kleijne, A., Sprengel, C.,
Probert, I. & Østergaard, J. 2003. A guide to extant
coccolithophore taxonomy. Journal of Nannoplankton
Research, Special Issue, 1: 125pp.
Young, J.R. & Westbroek, P. 1991. Genotypic variation in the
coccolithophorid
Emiliania
huxleyi.
MarineMicropaleontology, 18: 5-23.
Young, J. & Ziveri, P. 2000. Calculation of coccolith volume andits use in calibration of carbonate flux estimates. Deep-Sea
Research II, 47: 1679-1700.
Ziveri, P., Baumann, K.-H., Böckel, B., Bollmann, J. & Young,
J.R. 2004. Biogeography of selected Holocene coccoliths in
the Atlantic Ocean. In: H.R. Thierstein & J.R. Young (Eds).
Coccolithophores - From molecular processes to global
impact. Springer-Verlag, Berlin: 403-428.
Ziveri, P., Broerse, A., van Hinte, J.E., Westbroek, P. & Honjo, S.
2000. The fate of coccoliths at 48˚N, 21˚W, northeastern
Atlantic. Deep-Sea Research II, 47(9-11): 1853-1875.

96

Köbrich, Baumann

Ziveri, P., Thunell, R.C. & Rio, D. 1995. Export production of
coccolithophores in an upwelling region: Results from a San
Pedro Basin, Southern California Bight. Marine
Micropaleontology, 24(3-4): 335-358.