7
Figure 4.8: Carbon mesopelagic remineralization fluxes (in mmol C.m
-2
.d
-1
) at all stations sampled with
Niskin bottles, between 100 - 1000 m. Provinces are indicated below the x-axis. .............................. 163
Figure 4.9: Comparison of POC remineralization fluxes from this study (circles lined in black) to
remineralization fluxes from literature in the North Atlantic. Note that these studies used different
methods for determining remineralization fluxes: moored sediment traps (# symbols, Honjo et al., 2008),
onboard incubations (° symbols, Giering et al., 2014; Collins et al., 2015); excess barium proxy (*
symbols, Brewer et al., unpublished results). ...................................................................................... 168
Figure 4.10: Time averaged map of Chlorophyll-a concentrations (mg.m-3) over January – June 2014
(monthly 4 km MODIS Aqua model; http://giovanni.sci.gsfc.nasa.gov/). ............................................ 169
Figure 4.11: Mesopelagic remineralization fluxes (mmol.m-2.d-1) plotted as a function of the
corresponding fractions of micro-, nano- and pico-phytoplankton. The black line corresponds to the
linear regression between both parameters for all stations except Station 51 (pink triangle). ............ 171
Figure 4.12: Bubble plot showing the mesopelagic remineralization flux (mmol.m-2.d-1) and the
abundance of the two main phytoplankton communities (diatoms and coccolithophorids, in %) along the
GEOVIDE transect. The size of the bubble is proportional to the magnitude of the flux. ................... 173
Figure 4.13: Potential temperature θ - salinity S plots and isopycnals for the Stations a) #44 and #69
and b) #32 and #38 of the GEOVIDE cruise focus on the 50-2000 m depth interval. The
concentrations
of Baxs are shown by the colored points. LSW: Labrador Sea water; SAIW: Subarctic Intermediate
water. ................................................................................................................................................... 174
Figure 4.14: Global schematic of the biological carbon pump during GEOVIDE in the NAST, NADR and
ARCT provinces. Primary production (PP) data from A. Roukaerts and D. Fonseca Batista; particulate
organic carbon (POC) export fluxes from Lemaitre et al., in prep.; and POC remineralization fluxes from
this study. The dominating phytoplanplankton communities and the stage of the bloom are also
indicated. The red numbers are the ratio between PP and mesopelagic remineralization fluxes and
indicate the proportion of PP remineralized through the mesopelagic layer. ...................................... 177
Chapter 5:
Figure 5.1: Map of the GEOVIDE section in the North Atlantic with the stations (stars) investigated
within the North Atlantic Subtropical gyre (NAST) province, the North Atlantic Drift (NADR) province and
the Arctic (ARCT) province (Longhurst, 1995). ................................................................................... 187
Figure 5.2: Particulate aluminum (pAl) (a); particulate iron (pFe) (b); particulate phosphorus (pP) (c);
particulate manganese (pMn) (d); particulate zinc (pZn) (e); particulate cobalt (pCo) (f); particulate
cadmium (pCd) (g); particulate cupper (pCu) (h); and particulate nickel (pNi) (i) to
234
Th ratios (nmol.dpm
-
1
) in the large size fraction (LSF; > 53 µm) along the GEOVIDE transect. ......................................... 195
Figure 5.3: Particulate trace element export fluxes in µmol.m
-2
.L
-1
estimated in the large size fraction at
the Eq depth (black bars) and at 400 m (grey line). Note the different y-axis scales.......................... 199
Figure 5.4: Variance of thirteen elemental fluxes determined at Eq at all stations (Test 1), at all stations
except Station 1 (Test 2). The description of the components is provided in the text. ....................... 202
Figure 5.5: Molar ratios of the trace element over Al fluxes along the GEOVIDE transect determined at
Eq. The brown horizontal dashed line represents the ratios determined in the upper continental crust
(UCC) by Taylor and Mclennan (1985). Note that the y axis represents the values of the ratios in a
logarithmic scale (mol.mol
-1
). ............................................................................................................... 204
Figure 5.6: Export fluxes of lithogenic materials (Litho in mg.m
-2
.d
-1
), Mn oxides (MnO
2
in mg.m
-2
.d
-1
)
and Fe oxides (Fe(OH)
3
in mg.m
-2
.d
-1
) determined at a) Eq and b) 400 m. Negative values have been
set to zero. ........................................................................................................................................... 206
Figure 5.7: Beam attenuation (%; in blue) and fluorescence (µg/L; in green) profiles of Stations 1 and
64, located near the
Iberian and Greenland margins, respectively. .................................................... 207
Figure 5.8: (left)
Relationships between pCo, pNi,and pCu fluxes versus pMn oxides fluxes (µmol.m
-
2
.d
-1
), and (right) relationships between pCo, pNi and pZn fluxes versus pFe oxides fluxes.The grey
circles and the black diamonds represent respectively the fluxes estimated at Eq and 400 m. ......... 210
Figure 5.9: Carbon normalized Fe, Mn, Zn, Co, Cu, Cd and Ni molar ratios for export fluxes determined
at Eq, from Station 1 (Iberian Margin; right) to Station 77 (Newfoundland Margin; left). The green
rectangles indicate the range of intracellular metal stoichiometries presented by Twining et al. (2015),
Muggli et al. (1996), Muggli and Harrison (1996) and Sunda and Huntsman (1995 a and b). ........... 213
Figure 5.10: Phosphorus normalized Fe, Mn, Zn, Co, Cu, Cd and Ni molar ratios for export fluxes
determined at Eq, from Station 1 (Iberian Margin; right) to Station 77 (Newfoundland Margin; left). The
green rectangles indicate the range of intracellular metal stoichiometries presented by Twining and
Baines (2013). ..................................................................................................................................... 214