Carbonate counter pump stimulated by natural · 2014-11-27 · Salter et al. SI Methods Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone SIMethodsPage

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NGEO2285

NATURE GEOSCIENCE | www.nature.com/naturegeoscience

Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone

Supplementary Information -‐ Summary

Supplementary Methods – Additional details of the analytical methods.

Supplementary Information 1 – Map of study area.

Supplementary Information 2 – Summary of CaCO3 determinations from published

Southern Ocean sediment trap data sets.

Supplementary Information 3 – Raw data tables on CaCO3 particle analysis and

fluxes determined in the Crozet sediment trap deployments.

Supplementary Information 4 – Calculation of Ψ and the reduction of carbon

dioxide drawdown.

Supplementary Information 5 – Calcite and aragonite saturation depth and

dissolution.

Supplementary Information 6 – Size distribution and size normalised weights of

planktonic foraminifera tests.

Supplementary Information 7 – Si:POC ratios of deep-ocean particle flux in

relation to the Subantarctic front.

Supplementary Information 8 – Summary of published sediment trap estimates

used in Southern Ocean synthesis.

Supplementary References – Additional references used in Supplementary

Information.

Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone

Ian Salter, Ralf Schiebel, Patrizia Ziveri, Aurore Movellan, Richard Lampitt and George Wolff

© 2014 Macmillan Publishers Limited. All rights reserved.

http://dx.doi.org/10.1038/ngeo2285

Salter et al. SI Methods Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone

SI Methods Page 1 of 11

Supplementary Methods

Total CaCO3 content was determined in all sediment trap-sampling cups from

deployments M5[+Fe]-NE and M6[HNLC]-S. Foraminifer, pteropod and fine-fraction

coccolithophore fluxes were determined in the sediment trap sampling cups that

contained adequate particulate material, which accounted for 98.3-99.6% of the annual

total CaCO3 flux budget (Table S3.1).

(i) Total CaCO3

TOC was determined using a Carlo-Erba NA-1500 elemental analyzer following

standardization with acetanilide. Freeze-dried samples (2–4 mg) were weighed into

precombusted (12 h at 450ºC) silver cups that were formed into small capsules with

metal spatulas. POC was determined using the same procedure on acidified samples

(Nieuwenhuize et al. 1994). Fifteen microliter aliquots of 20% HCl were added to the

sample in order to remove calcium carbonate. After each aliquot was added, the acid

was evaporated by gently heating on a hot plate (<60ºC). The procedure was repeated

until all carbonates were removed, as evidenced by the absence of any effervescence

on addition of the acid, and then two more additions of acid were performed to ensure

complete removal of inorganic carbon. Samples were subsequently rinsed with 5 x 40

µL aliquots of ultrapure water and dried on a hot plate at <60ºC, and then at 50ºC

overnight. Care was taken to note any sample loss from silver cups, and samples were

discarded if this was the case (Salter et al. 2012). Selected samples were analyzed

independently at the University of Liverpool, UK. Excellent data correlations were

observed for both total carbon (r=0.96, p<0.001, n=15) and organic carbon (r=0.97, p <

0.001, n=15). The average analytical precision (relative error) from 106 sets of




triplicate measurements was 4.3% for organic carbon and 2.1% for total carbon

analyses (Salter et al. 2010).

(ii) Foraminifer and pteropod analyses

One-eighth wet aliquots were used for the foraminifer and pteropod analysis. Samples

were rinsed through a 63µm mesh using the overlying preservative solution from the

same sampling bottle, followed by a tap-water rinse. The samples were then dried

overnight at room temperature. Samples were further dry-split according to the

number of particles present (1/1 to 1/32, but generally 1/8 splits) with the exception of

larger particles (>400µm), which were removed and weighed separately to avoid

splitting uncertainty.

Particle analyses were carried out with a fully automated incident light microscope

system. Images were acquired and particles were analysed with analySIS FIVE

(SIS/Olympus©) software supported by a software add-in developed by MAS©.

Samples were prepared on up to six glass trays, and automatically moved under a

Leica© Z16APO monocular microscope (plan-apochromatic objective) using a

motorized xy-stage and Lstep-PCI controller manufactured by Märzhäuser©. Images

were captured with a CC12 colour camera (SIS©). Constant illumination of samples is

provided by a Leica© CLS100X light source and a Leica© ring-light (cf Bollmann et al.

2004)

Particles were manually classified and counted from the digital images and verified

directly from the samples if necessary. Particle analyses were carried out separately on

the 63-100 µm and the >100 µm fraction. Classification and test weight of foraminifers




of the 63-100 µm size fraction was done to the systematic level of the sub-order.

Planktic foraminifers and the shells of pelagic gastropods (Thecosomata, from now

referred to as pteropods) were classified to the morpho-species in the >100 µm size

fraction according to the taxonomic concept of Hemleben et al. (1989) and Bé &

Gilmer (1977). The two size fractions, 63-100 µm and >100 µm, were combined after

morphometric analyses and classification of particles for later analyses (Table S4.2).

Weighing was carried out with microbalance (XP2U, Mettler Toledo, precision 0.1

µg), in a climatized weighing room. Before weighing, samples were stored in the

weighing room for 12 hours to acclimatize.

Planktic foraminifer calcite mass is calculated from individual planktic foraminifer test

weight according to discrete size and species, i.e., Globigerina bulloides, Turborotalita

quinqueloba, Globorotalia inflata, and Globorotalia crassaformis. Test weights of the

63-100 µm test size fraction are extrapolated from weights of the larger test size

fractions.

Pteropods of the three species Limacina inflata, Limacina retroversa, and Limacina

helicina were counted from the 63-µm and >100-µm size fractions or referred to as

pteropod fragments if no classification was possible. Whole pteropod shells and

fragments from the >100-µm size fraction were weighed to directly determine their

CaCO3 (aragonite) mass.

CaCO3 weight of planktic foraminifers was calculated for the minimum diameter (>63

µm) of tests, aggregates, and fragments. Accordingly, the data on CaCO3 mass are

minimum estimates. Aggregates of planktic foraminifers usually consist of two or




more tests, and fragments of larger planktic foraminifer specimens are often solid shell.

In addition, undefined fragments and aggregates >63 µm, which often consisted of, or

contained small calcareous particles, were a very minor portion of the CaCO3 budget

(Table S3.2). Planktic foraminifer test calcite mass is determined for each sampling

interval of each sediment trap, and for each species, by applying the respective faunal

counts (Table S3.2), weight data (Table SM.1) and assemblage size distributions

(Figure S6.1). Ströhlein

The aragonite weight of pteropods >400 µm was determined by weighing the total

pteropod assemblage, i.e., all species and fragments together. The weight of pteropods

in the 63-400-µm fractions was determined from faunal counts and by applying weight

data after Bednarsek et al. (2012, and oral communication with N. Bednersek, 2012)

(Table S3.2). The weight of both fractions is given as pteropod weight (Table SM.2).

(iii) Fine-fraction coccolithophore CaCO3 fluxes

Coccolithophore CaCO3 fluxes were estimated from the determination of fine-fraction

carbonate weights in the <20 and 20-63-µm fractions (e.g. Ziveri et al. 2007). A

sample aliquot (1/80) was wet-sieved over a 20-µm mesh, and the two size fractions

were filtered on a polycarbonate membrane filter (0.4 µm pore size, 47 mm diameter).

After drying at 40°C, the filters with the residue were leached in 10 ml 1% HNO3

solution, placed in ultrasound for 10 minutes and then left for an additional 12 h prior

to the analysis. Calcium content of the samples was determined by inductively coupled

plasma atomic emission spectroscopy (ICP-AES) Perkin Elmer, Optima 4300DV

(UAB). Overall accuracy based on replicate analysis amounted to better than 1%

(relative standard deviation). Ca2+ concentrations (in µg) were then converted into




CaCO3 by extrapolating the CaCO3 content of each aliquot to the total sample,

considering duration days and trap aperture area (Table S3.1).

Fragments/Aggregates

The cumulative sum of individual CaCO3 fractions, i.e. foraminifer, pteropods, fine

fraction, accounts for 51-70% (annually-integrated) of total CaCO3 measured

analytically. In Figure 2c we refer to this difference as fragments. The difference may

be explained by a combination of several factors: (i) numerous small pteropod

fragments (Table S3.2(b)) that we were unable to remove and quantify, (ii) pteropod,

foraminifer fragments and coccoliths in fecal pellets and aggregates, (iii) the fact that

we used minimum test size for foraminifer-CaCO3 mass calculations, and (iv) an

unidentified CaCO3 fraction.

Punctuated flux regime at [HNLC]M6-‐S and Si:PIC ratios

The punctuated flux pattern at [HNLC]M6-S is unusual in its brevity, when compared

to other PFZ fluxes. In total three deployments were made in high nutrient low

chlorophyll waters south of the Islands, which all showed identical flux patterns

(Supplementary Figure A). Unfortunately the [HNLC]M2-(2000m) and [HNLC]M6-

(2000m) trap data could not be used in a quantitative way due to severe contamination

by fish debris (Pollard et al., 2009; Salter et al., 2008; 2012). However, the qualitative

similarity in flux profiles from low productivity waters strongly supports that the

[HNLC]M6-S trap worked effectively and the flux regime, although unusual, appears

to be characteristic of this HNLC region. A detailed analysis of diatom assemblages

in these trap samples showed that these mass-pulse export events occur at the end of




the growing season and consist primarily of empty frustules of large diatoms (Salter et

al. 2012).

Si:PIC annual flux ratios

The qualitative trap samples [HNLC]M2-(2000m), [HNLC]M6-(2000m) and

[+Fe]M5-(2000m) were combined with the quantitative trap samples [+Fe]M10-N,

[+Fe]M5-NE and [HNLC]M6-S to calculate the average annual Si:PIC ratios

(Supplementary Figure B). The Si:PIC ratios at the iron fertilized site [2.6±0.6 (n=3)]

are significantly lower (P<0.005; two-tailed t-test) than at the unfertilized site [11±2.2

(n=3)]. Examining these ratios from the qualitative trap samples supports the

conclusions based on the quantitative trap data (presented in the manuscript) that iron

fertilization does not enhance biogenic Si and PIC fluxes similarly, rather it enhances

PIC fluxes relative to Si and POC. The observable decrease in POC:PIC ratios

occurring as a function of iron fertilization is therefore primarily attributable to an

increase in PIC flux, rather than enhanced remineralisation of POC export from iron-

fertilized production (e.g. Jacquet et al. 2008).

Calculation of size-normalised weights

Following the automated particle analysis of dried foraminifera specimens described

above, foraminifera species were sorted from each sediment trap cup to create sample

sub-sets from different regions (e.g. [+Fe] vs HNLC) and different seasons (Table

SM.1). Each of these sample sub-sets was dry-sieved to isolate foraminifera

specimens into different size fractions which were subsequently weighed. Weighing

was carried out with a microbalance (XP2U, Mettler Toledo, precision 0.1 µg) in a

climatized weighing room. Before weighing, samples were stored in the weighing




room for 12 hours to acclimatize. Multiple tests within a given size fraction were

weighed. The size normalised weight (SNW) within a given size fraction was

calculated as 𝑆𝑁𝑊 =𝑊!!/𝑛, where, 𝑊!

! is the weight of n number of species i, and n

is the number of individual tests weighed.

Fronts and 10% sea-‐ice isoline

Orsi et al. (1995) and Moore et al (1999) fronts are open-access products.

Sallée et al. (2008) fronts are not open-access, data was provided by Observatoire

Midi-Pyrénées. The product merges satellite sea level anomalies and climatological

argo float data to compute mean sea level. Weekly products for the period 1992-2013

were obtained. A climatology was computed as the median position of each (PF or

SAF) front. Product and references are can be found at : http://ctoh.legos.obs-

mip.fr/applications/mesoscale/southern-ocean-fronts.

A climatological 10% sea ice concentration was calculated using data from the

National Snow & Ice Data Center. Monthly Sea Ice Concentrations were taken from

Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data (from 1979 to

2013) http://nsidc.org/data/nsidc-0051. The bold grey line is the position of the

climatological median of the 10% sea ice concentration.




Supplementary Figure A Punctuated flux profiles in the HNLC area south of the

Crozet Plateau. Sediment trap flux records from three deployments (a) M2 2000m,

(b) M6 2000m and (c) M6 3000m. Flux records from M2 2000m and M6 2000m

could not be used quantitatively due to severe contamination by fish debris.




Supplementary Figure B| Annual Si:PIC molar ratios. Annual flux data from three

qualitative sediment trap records M2-2000m, M5-2000m, and M6-2000m were

combined with the quantitative data of M10-2000m ([+Fe]M10-N), M5-3000m

([+Fe]M5-NE), and M6-3000m ([HNLC]M6-S) to calculate average annual Si:PIC

molar ratios. Sediment trap deployment stations M10 and M5 were in [+Fe] and M2

and M6 in [HNLC] waters (see Fig. S1 for deployment locations). Error bars are ± 1

σ. The Si:PIC ratios at the iron fertilized site [2.6±0.6 (n=3)] are significantly lower

(P<0.005; two-tailed t-test) than at the unfertilized site [11±2.2 (n=3)].



SI-‐Methods Page 10 of 11

Table SM.1 Calcite mass (µg) of foraminifersby species and test size fraction

Foraminifer

Sample Code size interval (µm) 63-100 100-125 125-150 150-200 200-250 250-315 315-400 400-500 500

size mid-point (µm) 112.5 137.5 175 225 282.5 357.5 450 600 T. quinqueloba 36A1 0.5 0.5 0.6 2.6 6.0 T. quinqueloba 36A4 0.8 0.9 1.1 1.7 4.2 T. quinqueloba 38B1 0.9 1.0 1.2 1.9 4.5 T. quinqueloba 38B5 0.8 0.9 1.1 1.6 3.9 T. quinqueloba 39B1 0.5 0.8 1.6 4.0 G. bulloides 36A1 0.8 1.2 3.4 5.4 9.5 14 26 33 G. bulloides 36A4 0.9 1.3 3.6 6.0 9.2 15 27 35 G. bulloides 36A17 1.0 1.5 4.0 7.0 11 19 30 40 G. bulloides 38B1 0.6 1.0 3.1 4.9 10 16 28 36 G. bulloides 38B5 0.7 1.1 3.2 5.2 8.4 14 27 34 G. bulloides 38B19 0.6 1.0 1.7 2.5 5.1 19 33 44 G. bulloides 39B1 3.7 6.0 9.5 16 G. bulloides 39B6 0.5 0.9 1.7 4.0 5.9 11 20 28 N. pachyderma 36A1 0.7 0.9 1.7 4.0 9.0 12 N. pachyderma 36A4 0.5 0.7 1.2 2.7 7.5 11 N. pachyderma 38B1 0.4 0.6 1.1 2.5 6.5 9.5 N. pachyderma 38B5 0.4 0.5 0.8 1.8 5.0 7.5 N. pachyderma 39B1 1.2 2.6 5.1 8.2 N. pachyderma 39B6 0.7 0.9 1.7 3.9 9.0 12 17 G. inflata 36A17 1.5 3.5 6.0 10 18 34 53 75 G. inflata 38B19 1.4 3.0 5.0 8.0 16 30 46 66 G. crassaformis 36A17 1.1 1.9 3.0 6.0 13 25 40 60 G. crassaformis 38B19 1.1 1.9 3.0 6.0 13 26 41 62


Salter et al. SI Methods Carbonate counter pump stimulated by natural iron Fertilization in the Polar Frontal Zone

SI-‐Methods Page 11 of 11

Table SM.2 Calcite mass (µg) of foraminifers, pteropods and radiolarids (>400 µm)

Sample Foraminifers Number of Specimens Weight (µg)

M5-B-19 Globorotalia inflata 7 304 M5-B-19 Globigerina bulloides 3 96 M5-B-19 Globorotalia crassaformis 3 131

Pteropods

M10-A-1 Limacina helicina 6

2028 Limacina retroversa 9

M10-A-2 L. helicina 2

2627 L. retroversa 12



M10-A-4 L. retroversa 1 64


38 L. retroversa 1

M5-B-1 L. helicina 1



67 Clio sulcata 1

M5-B-3 L. retroversa 21 4724





M5-B-7 undef. pteropod fragments 4 207


Salter et al. SI-S1 Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone

SI-‐S1 Page 1 of 1

Supplementary Information S1

Figure S1 | Study area and location of sediment trap deployments. a, Satellite

composite of chlorophyll a for the month of October for the Southern Ocean. Colour

indicates satellite-derived chlorophyll-a concentration as shown in scale bar. b,

Merged SeaWiFS/MODIS (sea-viewing, wide-field-of-view sensor/moderate-

resolution imaging spectroradiometer) chlorophyll a image for the eight-day peak

bloom period 23–30 October 2004. Solid and dashed lines show mean and eddy

circulations, respectively, with the sub-Antarctic Front (SAF, the northern boundary of

the Antarctic Circumpolar Current) and the Agulhas Return Current (ARC) shown

bold. Sediment trap deployment locations are marked as M10 ([+Fe]-N), M5 ([+Fe]-

NE), M6 ([HNLC]-S) and M2. Thin white lines are the 2,000-m depth contour, with

the main Crozet Islands (Île de la Possession, Île de l’Est) seen at 46.5°S, 52°E.

Coordinates for sediment trap deployment locations are: M10, 44° 29.95′ S, 49° 59.92′

E; M5, 46° 00.00′ S, 56° 05.00′ E; M6, 49° 00.03′ S, 51° 30.59′ E. Taken from Pollard

et al. 2009.




Table S2| Summary of Southern Ocean datasets that partition carbonate fluxes between CaCO3 producers. Green Q’s denote

quantitative reference to fluxes in the cited manuscript, orange D’s denote a descriptive mention of fluxes in the cited manuscript and

red crosses indicate the absence of information. The columns Ind._tot. and CaCO3_tot. are total fluxes of CaCO3-‐bearing functional groups

[pteropods, foraminifer or coccolith(-‐ophore)s] either as individuals (ind.) or calcium carbonate biomass (CaCO3). Ind.Sp. or CaCO3_Sp.

are fluxes of identified species within a CaCO3-‐bearing functional group either as individuals or CaCO3 biomass. The numbers in

parentheses correspond to data-‐sources: (1) Roberts et al. 2011 (2) Howard et al. 2011 (3) Northcote and Niel 2005 (4) Tesi et al. 2012

(5) King and Howard 2001 (6) Donner and Wefer 1994 (7) King and Howard 2003 (8) King and Howard 2005 (9) Acconero et al. 2003

(10) Collier et al. 2000 (11) Pilskaln et al. 2004 (12) Wefer and Fischer 1991 (13) Honjo et al. 2000 (14) Salter et al. this study (15). See

Supplementary References for further details.

Pteropods Foraminifer Coccolith(-‐ophore)s

Site Depth Days CaCO3 (g m-‐2) Ind._tot. Ind._Sp. CaCO3_tot. CaCO3_Sp Ind._tot. Ind._Sp. CaCO3_tot. CaCO3_Sp Ind._tot. Ind._Sp. CaCO3_tot. CaCO3_Sp

47-‐1000 1060 153 5.1 Q (1) Q (1) Q (1) X Q (7) Q (7) X X X X X X

47-‐1000 2000 405

Q (1) Q (1) Q (1) X X X X X X X X X

47-‐1000 2000 385

Q (1) Q (1) Q (1) X X X X X X X X X

47-‐1000 2000 312

Q (1) Q (1) Q (1) X X X X X X X X X

47-‐2000 2050 153 8.6 Q (1) Q (1) Q (1) X X X X X X X X X

47-‐2000 2000 405

Q (1) Q (1) Q (1) X X X X X X X X X

47-‐2000 2000 385

Q (1) Q (1) Q (1) X X X X X X X X X




47-‐2000 2000 378

Q (1,2) Q (1,2) X X X X X X X X X X

47-‐2000 2000 312

Q (1) Q (1) Q (1) X X X X X X X X X

47-‐3800 3850 153 6.8 X X X X Q (7) Q (7) X X X X X X

51-‐3100 3080 153 13.1 X X X X Q (7) Q (7) X X X X X X

54-‐800 830 153 4.2 X X X X Q (7) Q (7) X X X X X X

54-‐1500 1530 153 2.9 X X X X Q (7) Q (7) X X X X X X

M10[+Fe]-‐N 2000 352 4.6 Q (14) Q (14) Q (14) X Q (14) Q (14) Q (14) Q (14) Q (15) Q (15) Q (14) Q (15)

M10[+Fe]-‐NE 3000 357 6.4 Q (14) Q (14) Q (14) X Q (14) Q (14) Q (14) Q (14) Q (15) Q (15) Q (14) Q (15)

M6[-‐Fe]-‐S 3000 363 0.7 Q (14) Q (14) Q (14) X Q (14) Q (14) Q (14) Q (14) Q (15) Q (15) Q (14) Q (15)

NCR 1000 243 -‐ X X X X Q (5,8) Q (5,8) X X X X X X

SCR 1000 340 -‐ X X X X Q (5,8) Q (5,8) X X X X X X

NCR 300 243 -‐ X X X X Q (5,8) Q (5,8) X X X X X X

SCR 300 340 -‐ X X X X Q (5,8) Q (5,8) X X X X X X

PK rise 415 426 6.23 X X X X Q (5,8) Q (5,8) Q (3) X X X X X

e CF 400 426 4.65 X X X X Q (5,8) Q (5,8) Q (3) X X X X X

PF-‐1 700 421 10.5 X X X X X X X X X X X X

PF-‐3 614 356 10.3 X X X X X X X X X X X X

PF-‐3 3196 356 7.5 X X X X X X X X X X X X

PF-‐5 654 200 1.3 X X X X X X X X X X X X

PF-‐5 3219 200 0.33 X X X X X X X X X X X X

PF-‐7 636 255 1.67 X X X X X X X X X X X X

PF-‐7 3056 255 0.42 X X X X X X X X X X X X

PF-‐8 687 365 1.08 X X X X X X X X X X X X

PF-‐8 3110 365 2.50 X X X X X X X X X X X X

SGI 2000 365 1.00 X X X X X X X X X X X X

WSI 2966 760 0.03 X X X X D (12) D (12) D (12) D (12) X X X X

WSIII 3710 120 2.00 X X X X D (12) D (12) D (12) D (12) X X X X




WSVIII 2453 760 0.03 X X X X D (12) D (12) D (12) D (12) X X X X

WS-‐3 360 384 2.94 X X X X Q (6) Q (6) X X X X X X

WS-‐4 352 360 0.95 X X X X Q (6) Q (6) X X X X X X

KG-‐1_500 494 330 2.3 X X X X X X X X X X X X

KG-‐1_1600 1588 360 5.2 X X X X X X X X X X X X

KG-‐2 693 344 -‐ X X X X X X X X X X X X

KG-‐3 687 162 -‐ X X X X Q (6) Q (6) X X X X X X

K1 1034 364 0.27 X X X X X X X X X X X X

K3 1024 349 0.16 X X X X X X X X X X X X

KAST-‐1 678 365 0.5 X X X X X X X X X X X X

KAST-‐2 960 365 0.2 X X X X X X X X X X X X

eBS 1034 365 0.3 X X X X X X X X X X X X

FRUELA 500 351 0.7 X X X X X X X X X X X X

FRUELA 1000 351 13.8 X X X X X X X X X X X X

WS-‐1 863 423 0.01 X X X X Q (6) Q (6) X X X X X X

WS-‐2 4456 304 1.00 X X X X Q (6) Q (6) X X X X X X

BO-‐1 450 368 11.6 X X X X X X X X X X X X

BO-‐1 2194 365 1.8 X X X X X X X X X X X X

BO-‐1-‐2-‐3 456 307 2.2 X X X X X X X X X X X X

BO-‐1-‐2-‐3 2183 307 1.4 X X X X X X X X X X X X

BO-‐3/4 507 331 0.3 X X X X X X X X X X X X

BO-‐3 2251 365 0.7 X X X X X X X X X X X X

BO-‐5 515 365 0.7 X X X X X X X X X X X X

BO-‐5 2251 365 0.2 X X X X X X X X X X X X

D-‐1995-‐95m 95 -‐ 2.4 X X X X X X X X X X X X

D-‐1996-‐180m 180 -‐ 1.5 Q (9) Q (9) Q (9) Q (9) Q (9) Q (9) X X X X X X

D-‐1997-‐180m 180 -‐ 1.6 Q (9) Q (9) Q (9) Q (9) Q (9) Q (9) X X X X X X




D-‐1996-‐868m 868 -‐ 1.1 X X X X X X X X X X X X

D-‐1996-‐868m 868 -‐ 0.0 X X X X X X X X X X X X

Rats upper 200 340

X X X X X X X X X X X X

Rats upper 200 365


Rats lower 420 340


Rats lower 420 365


MT upper 123 365


A3 322 289 0.6 X X X X X X X X X X X X

RSM-‐A 230 466


RSM-‐A 719 641


RSM-‐B 230 230 15.7 X X X X X X X X X X X X

RSM-‐B 519 519 8.7 X X X X X X X X X X X X

RSM-‐C 230 230 13.2 X X X X X X X X X X X X

RSM-‐C 493 493 0.8 X X X X X X X X X X X X

Mooring B 224 385 0.6 X X X X X X X X X X X X

Mooring B 560 385 0.6 X X X X X X X X X X X X

AESOPS-‐7a 465 425 16.3 X X X X X X X X X X X X

AESOPS-‐7b 206 425 10.8 D (10) D (10) Q (10) D (10) X D (10) S-‐Q (10) X X X X X

AESOPS-‐7b 481 425 27.8 X X X X X X X X X X X X

Kerfix 640 200


PZB-‐1 1400 365 0.9 Q (11) Q (11) X X Q (11) Q (11) X X X X X X

PZB-‐1 3400 365

Q (11) Q (11) X X Q (11) Q (11) X X X X X X

PZB-‐2 3300 331 0.6 Q (11) Q (11) X X Q (11) Q (11) X X X X X X

O-‐900 900 366 1.1 X X X X Q (4) Q (4) X X X X X X

O-‐1300 1300 364 0.7 X X X X Q (4) Q (4) X X X X X X

O-‐2400 2400 364 0.2 X X X X Q (4) Q (4) X X X X X X

O-‐3700 3700 366 0.6 X X X X Q (4) Q (4) X X X X X X




1000 290 0.7 X X X X X X X X X X X X

MS-‐1 1981 425 6.8 D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) X X

MS-‐2 982 425 11.8 D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) X X

MS-‐3 1003 425 12.8 D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) X X

MS-‐4 1031 425 10.7 D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) X X

MS-‐5 937 425 0.6 D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) D (13) X X

M6-‐6 200 425 5 D (10) D (10) Q (10) D (10) X X S-‐Q (10) X X X X X

Antares-‐M2 1300 353 6.0 X X X X X X X X X X X X





Salter et al. SI S3 Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone



Table S3.1 | Sediment trap deployment information and data a, M10[+Fe]-N, b, M5[+Fe]-

NE, and c, M6[-Fe]-S. All flux rates are integrated over the sampling interval. Sampling cups

in bold are those in which detailed analysis of CaCO3 fractions was carried out.

1 Total CaCO3 fluxes determined from measurements of total and organic carbon (see

Methods). 2 CaCO3 fluxes calculated from the foraminifer and pteropod shells in size fraction >63 µm (see

Table S3.2). 3 CaCO3 fluxes in <20 and 20-63 µm fraction determined by ICP-AES (See Methods) 4 Total number of sampling days for sediment trap deployment period. 5 Annual total CaCO3 fluxes integrated from all sediment trap sampling cups during the

deployment period 6 Total CaCO3 fluxes integrated from sediment trap sampling cups in which detailed CaCO3

analysis was conducted. 7 Percentage of annual total CaCO3 fluxes accounted for by the sediment trap sampling cups in

which detailed CaCO3 analysis was conducted. 8 Percentage of total annual CaCO3 flux accounted for by different CaCO3 fractions.

Table S3.2 Foraminifer and Pteropod data. a, Total number of particles >63µm per class

and sediment trap sampling interval. Data from a 1/8th wet split. b, Planktic foraminifer and

pteropod flux >63µm shell size per square meter per day. c, Planktic foraminifer and pteropod

CaCO3 mass (mg) per class and sediment trap sampling interval. Data on foraminifer species

refer to the size fraction >100 µm. Data on total foraminifer and total pteropod mass include all

classes and size fractions >63 µm. Pteropod CaCO3 relative to foraminifer CaCO3 mass is given

as pteropod %. Data from a 1/8th split. d, Planktic foraminifer (pl.f.) and pteropod CaCO3 mass

(mg) per square meter and day.




Table S3.1 (a) M10[+Fe]-N Open Date Close Date Interval CaCO3 Flux1 Foram2 CaCO3 Ptero2 CaCO3 <20µm3 CaCO3 20-63µm3 CaCO3 POC Depth: 2000-m (dd/mm/yyyy) (dd/mm/yyyy) #Days mg m-2 mg m-2 mg m-2 mg m-2 mg m-2 mg m-2 M10-A-1 21/12/2004 02/01/2005 12 556 260 38 63 13 68 M10-A-2 02/01/2005 16/01/2005 14 725 351 67 119 11 56 M10-A-3 16/01/2005 30/01/2005 14 798 170 64 237 13 54 M10-A-4 30/01/2005 20/02/2005 21 917 221 9 127 98 85 M10-A-5 20/02/2005 20/03/2005 28 621 136 5 137 70 77 M10-A-6 20/03/2005 17/04/2005 28 372 168 6 30 46 37 M10-A-7 17/04/2005 15/05/2005 28 n.d n.d n.d n.d n.d n.d M10-A-8 15/05/2005 12/06/2005 28 n.d n.d n.d n.d n.d n.d M10-A-9 12/06/2005 10/07/2005 28 n.d n.d n.d n.d n.d n.d M10-A-10 10/07/2005 07/08/2005 28 n.d n.d n.d n.d n.d n.d M10-A-11 07/08/2005 04/09/2005 28 n.d n.d n.d n.d n.d n.d M10-A-12 04/09/2005 02/10/2005 28 n.d n.d n.d n.d n.d n.d M10-A-13 02/10/2005 16/10/2005 14 n.d n.d n.d n.d n.d n.d M10-A-14 16/10/2005 30/10/2005 14 n.d n.d n.d n.d n.d n.d M10-A-15 30/10/2005 13/11/2005 14 n.d n.d n.d n.d n.d n.d M10-A-16 13/11/2005 27/11/2005 14 n.d n.d n.d n.d n.d n.d M10-A-17 27/11/2005 08/12/2005 11 583 236 0 55 25 62 Total [A1-A17] 3524 n.d. n.d n.d n.d. n.d. Total [(A1-A6)+A17] 45726 1541 188 768 276 439 Percentage n.d 348 4.18 178 6.08 n.d




Table S3.1 (b) M5[+Fe]-NE Open Date Close Date Interval CaCO3 Flux1 Foram2 CaCO3 Ptero2 CaCO3 <20µm3 CaCO3 20-63µm3 CaCO3 POC Depth: 3195-m (dd/mm/yyyy) (dd/mm/yyyy) #Days mg m-2 mg m-2 mg m-2 mg m-2 mg m-2 mg m-2 M5-B-1 28/12/2004 09/01/2005 12 459 185 26 36 6 36 M5-B-2 09/01/2005 23/01/2005 14 563 222 0 54 10 37 M5-B-3 23/01/2005 06/02/2005 14 925 277 102 92 11 56 M5-B-4 06/02/2005 27/02/2005 21 992 353 34 112 14 48 M5-B-5 27/02/2005 27/03/2005 28 1487 591 33 249 19 70 M5-B-6 27/03/2005 24/04/2005 28 126 37 1.7 10 18 6.7 M5-B-7 24/04/2005 22/05/2005 28 763 210 5.3 108 14 45 M5-B-8 22/05/2005 19/06/2005 28 301 54 0 55 10 85 M5-B-9 19/06/2005 17/07/2005 28 12.8 n.d n.d n.d n.d 4.3 M5-B-10 17/07/2005 14/08/2005 28 4.1 n.d n.d n.d n.d 5.2 M5-B-11 14/08/2005 04/09/2005 21 0.0 n.d n.d n.d n.d 4.0 M5-B-12 04/09/2005 25/09/2005 21 0.0 n.d n.d n.d n.d 4.6 M5-B-13 25/09/2005 16/10/2005 21 26.5 n.d n.d n.d n.d 5.0 M5-B-14 16/10/2005 30/10/2005 14 0.0 n.d n.d n.d n.d 0.2 M5-B-15 30/10/2005 13/11/2005 14 4.4 n.d n.d n.d n.d 0.8 M5-B-16 13/11/2005 27/11/2005 14 0.0 n.d n.d n.d n.d 0.4 M5-B-17 27/11/2005 11/12/2005 14 0.2 n.d n.d n.d n.d 0.1 M5-B-18 11/12/2005 18/12/2005 7 0.2 n.d n.d n.d n.d 0.2 M5-B-19 18/12/2005 20/12/2005 2 774.4 239 0 59 14 98 Total [B1-B19] 3574 64395 - - - 507 Total [(B1-B8)+B19] 63916 2169 202 776 116 482 Percentage 997 348 3.28 128 1.88 95




Table S3.1 (c) M6[-Fe]-S Open Date Close Date Interval CaCO3 Flux1 Foram2 CaCO3 Ptero2 weights <20µm3 CaCO3 20-63µm3 CaCO3 POC Depth: 3160-m (dd/mm/yyyy) (dd/mm/yyyy) #Days mg m-2 mg m-2 mg m-2 mg m-2 mg m-2 mg m-2 M6-B-1 05/01/2005 16/01/2005 11 517 205 2.9 36 23 85 M6-B-2 16/01/2005 30/01/2005 14 0.7 n.d. n.d. n.d. n.d. 0.4 M6-B-3 30/01/2005 13/02/2005 14 0.1 n.d. n.d. n.d. n.d. 0.02 M6-B-4 13/02/2005 06/03/2005 21 4.8 n.d. n.d. n.d. n.d. 1.9 M6-B-5 06/03/2005 03/04/2005 28 1.0 n.d. n.d. n.d. n.d. 0.3 M6-B-6 03/04/2005 01/05/2005 28 143 119 0.1 46 21 64 M6-B-7 01/05/2005 29/05/2005 28 0 n.d n.d n.d n.d 5.2 M6-B-8 29/05/2005 26/06/2005 28 0 n.d. n.d. n.d. n.d. 1.7 M6-B-9 26/06/2005 24/07/2005 28 0.2 n.d. n.d. n.d. n.d. 0.7 M6-B-10 24/07/2005 21/08/2005 28 0.1 n.d. n.d. n.d. n.d. 0.4 M6-B-11 21/08/2005 11/09/2005 21 0 n.d. n.d. n.d. n.d. 2.2 M6-B-12 11/09/2005 02/10/2005 21 1.6 n.d. n.d. n.d. n.d. 0.3 M6-B-13 02/10/2005 16/10/2005 14 0.1 n.d. n.d. n.d. n.d. 0.2 M6-B-14 16/10/2005 30/10/2005 14 0 n.d. n.d. n.d. n.d. 0.1 M6-B-15 30/10/2005 13/11/2005 14 0.1 n.d. n.d. n.d. n.d. 0.03 M6-B-16 13/11/2005 27/11/2005 14 0 n.d. n.d. n.d. n.d. 0.3 M6-B-17 27/11/2005 11/12/2005 14 0 n.d. n.d. n.d. n.d. 0.1 M6-B-18 11/12/2005 18/12/2005 7 0 n.d. n.d. n.d. n.d. 0.9 M6-B-19 18/12/2005 25/12/2005 7 0.5 n.d. n.d. n.d. n.d. 0.1 M6-B-20 25/12/2005 01/01/2006 7 0.4 n.d. n.d. n.d. n.d. 0.2 M6-B-21 01/01/2006 03/01/2006 2 0 n.d. n.d. n.d. n.d. 0.5 Total [B1-B21] 3634 6705 - - - 165 Total [B1+B6] - 6606 324 3.0 83 44 149 Percentage - 997 508 0.58 138 6.78 90




Table S3.2 (a)

Sediment trap sample cup M10 M10 M10 M10 M10 M10 M10 M5 M5 M5 M5 M5 M5 M5 M5 M5 M6 M6

A1 A2 A3 A4 A5 A6 A17 B1 B2 B3 B4 B5 B6 B7 B8 B19 B1 B6 Sample cup interval (days) 12 14 14 21 28 28 11 12 14 14 21 28 28 28 28 2 11 28

planktic foraminifers G. bulloides 336 480 160 400 200 416 384 192 272 832 768 1216 58 220 140 264 152 56 G. crassaformis 0 0 0 0 0 0 104 0 0 0 0 0 0 4 8 112 0 0 G. inflata 16 0 0 0 0 0 208 0 0 0 0 0 0 4 0 144 56 0 N. pachyderma 2096 3152 1360 1248 472 648 464 2544 4208 4144 5776 5552 234 1372 340 736 1808 880 T. quinqueloba 528 1952 992 992 544 776 504 432 592 1072 864 2320 56 452 84 136 616 0 unclassified 63-100 µm 2224 4432 5264 6384 5184 4520 3840 1414 1648 2960 5880 18960 1776 9040 1040 3040 4176 420 aggregates 32 128 32 32 56 72 40 16 16 144 128 544 48 72 108 56 128 24 fragments 0 144 512 400 256 208 112 16 16 288 608 336 25 220 112 120 96 32 pteropods L. helicina 6 2 3 0 2 0 0 1 5 4 4 3 0 0 0 0 0 0 L. inflata 16 32 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0 L. retroversa 9 12 9 1 1 0 0 25 0 37 6 9 1 0 0 0 0 0 unclassified pteropods 16 112 48 16 64 24 8 0 1 24 0 16 10 0 0 0 0 12 pteropod fragments 128 320 272 64 40 48 0 112 0 592 128 32 4 20 0 0 16 0




Table S3.2 (b)

Sediment trap sample cup M10 M10 M10 M10 M10 M10 M10 M5 M5 M5 M5 M5 M5 M5 M5 M5 M6 M6 A1 A2 A3 A4 A5 A6 A17 B1 B2 B3 B4 B5 B6 B7 B8 B19 B1 B6

Sample cup interval (days) 12 14 14 21 28 28 11 12 14 14 21 28 28 28 28 2 11 28

planktic foraminifers G. bulloides 448 549 183 305 114 238 559 256 311 951 585 695 33 126 80 2112 221 32 G. crassaformis 0 0 0 0 0 0 151 0 0 0 0 0 0 2 5 896 0 0 G. inflata 21 0 0 0 0 0 303 0 0 0 0 0 0 2 0 1152 81 0 N. pachyderma 2795 3602 1554 951 270 370 675 3392 4809 4736 4401 3173 134 784 194 5888 2630 503 T. quinqueloba 704 2231 1134 756 311 443 733 576 677 1225 658 1326 32 258 48 1088 896 0 unclassified 63-100 µm 2965 5065 6016 4864 2962 2583 5585 1885 1883 3383 4480 10834 1015 5166 594 24320 6074 240 aggregates 43 146 37 24 32 41 58 21 18 165 98 311 27 41 62 448 186 14 fragments 0 165 585 305 146 119 163 21 18 329 463 192 14 126 64 960 140 18 pteropods L. helicina 8 2 3 0 1 0 0 1 6 5 3 2 0 0 0 0 0 0 L. inflata 21 37 0 0 0 0 0 0 0 0 0 0 0 0 0 0 12 0 L. retroversa 12 14 10 1 1 0 0 33 0 42 4.6 5 1 0 0 0 0 0 unclassified pteropods 21 128 55 12 37 14 12 0 1 27 0 9 6 0 0 0 0 7 pteropod fragments 171 366 311 49 23 27 0 149 0 677 98 18 2 11 0 0 23 0




Table S3.2 (c)

Sediment trap sample cup M10 M10 M10 M10 M10 M10 M10 M5 M5 M5 M5 M5 M5 M5 M5 M5 M6 M6 A1 A2 A3 A4 A5 A6 A17 B1 B2 B3 B4 B5 B6 B7 B8 B19 B1 B6

Sample cup interval (days) 12 14 14 21 28 28 11 12 14 14 21 28 28 28 28 2 11 28

G. bulloides 2.6 4.1 0.5 3.3 1.9 3.3 2.7 1.6 1.6 5.4 5.5 9.4 0.5 1.7 0.8 1.4 1.3 0.4 G. crassaformis 0 0 0 0 0 0 2.2 0 0 0 0 0 0 0.2 0.2 3.3 0 0 G. inflata 1.2 0 0 0 0 0 5.5 0 0 0 0 0 0 0.1 0 5.5 0.7 0 N. pachyderma 9.4 9.5 3.1 3.7 1.4 1.9 0.9 8.1 9.8 7.2 9.3 9.4 0.5 3.2 0.7 1.5 6.1 6.4 T. quinqueloba 1.5 4.7 1.9 1.6 1.0 1.4 0.8 0.8 1.2 1.8 1.4 4.0 0.1 0.9 0.2 0.3 0.5 0 unclassified 63-100 µm 1.3 2.6 3.7 4.5 3.5 3.1 2.3 1.0 1.1 1.8 3.8 11.5 1.1 6.3 0.7 2.0 2.7 0.3 aggregates 0.3 0.6 0.4 0.1 0.2 0.4 0.2 0.1 0.1 0.6 0.9 1.9 0.1 0.5 0.5 0.6 1.3 0.2 fragments 0 0.3 1.1 0.6 0.4 0.4 0.3 0.03 0.03 0.5 1.3 0.6 0.04 0.3 0.2 0.4 0.2 0.1 total foraminifers 16.2 21.9 10.6 13.8 8.5 10.5 14.7 11.6 13.9 17.3 22.1 37 2.3 13.1 3.4 14.9 12.8 7.4 total pteropod 2.4 4.2 4.0 0.5 0.3 0.3 <0.01 1.6 <0.01 6.4 2.1 2.1 0.1 0.3 0 0 0.2 0.01

pteropod % 13 16 27 4 3 3 <0.01 12 <0.01 27 9 5 5 3 0 0 1.4 0.1




Table S3.2 (d)

Sediment trap sample cup M10 M10 M10 M10 M10 M10 M10 M5 M5 M5 M5 M5 M5 M5 M5 M5 M6 M6

A1 A2 A3 A4 A5 A6 A17 B1 B2 B3 B4 B5 B6 B7 B8 B19 B1 B6 Sample cup interval (days) 12 14 14 21 28 28 11 12 14 14 21 28 28 28 28 2 11 28

G. bulloides 3.4 4.7 0.5 2.5 1.1 1.9 3.9 2.1 1.9 6.2 4.2 5.4 0.3 1.0 0.5 11.0 1.8 0.2 G. crassaformis 0 0 0 0 0 0 3.2 0 0 0 0 0 0 0.1 0.1 26.5 0 0 G. inflata 1.6 0 0 0 0 0 8.0 0 0 0 0 0 0 0.1 0 43.8 1.1 0 N. pachyderma 12.5 10.9 3.5 2.9 0.8 1.1 1.3 10.8 11.2 8.3 7.1 5.4 0.3 1.8 0.4 12.1 8.8 3.7 T. quinqueloba 2.0 5.4 2.1 1.2 0.6 0.8 1.1 1.0 1.4 2.1 1.1 2.3 0.1 0.5 0.1 2.2 0.8 0 pl.f. unclassified 63-100 µm 1.7 3 4.3 3.4 2.0 1.8 3.3 1.3 1.3 2.1 2.9 6.6 0.6 3.6 0.4 16.3 3.9 0.2 pl.f. aggregates 0.3 0.6 0.4 0.1 0.2 0.4 0.2 0.1 0.1 0.7 0.6 1.1 0.1 0.3 0.3 4.6 1.8 0.1 pl.f. fragments 0 0.3 1.2 0.4 0.2 0.2 0.4 0.03 0.03 0.6 1 0.4 0.02 0.2 0.1 2.8 0.3 0.1 total foraminifers 21.7 25.1 12.1 10.5 4.9 6.0 21.4 15.4 15.8 19.8 16.8 21.1 1.3 7.5 1.9 119 18.6 4.3

total pteropod 3.2 4.8 4.5 0.4 0.2 0.2 <0.01 2.2 <0.01 7.3 1.6 1.2 0.06 0.19 0 0 0.3 <0.01





Calculation of Ψ

The ratio of CO2 released:carbonate precipitated depends on the physicochemical

properties of seawater and increases with decreasing buffering capacity

(Frankignoulle et al, 1994):

Ψ = 𝜕(𝐶𝑂!)𝜕(𝐶𝑂!!!)

= −

𝜕𝑝𝐶𝑂!𝜕(𝐶𝑂!!!)𝜕𝑝𝐶𝑂!𝜕(𝐶𝑂!)

where 𝜕(𝐶𝑂!) and 𝜕 𝐶𝑂!!! refer to variation of dissolved 𝐶𝑂! and 𝐶𝑂!!!,

respectively. The buffer factors 𝜕𝑝𝐶𝑂!/ 𝜕(𝐶𝑂!) and 𝜕𝑝𝐶𝑂!/ 𝜕(𝐶𝑂!!!) can be used to

describe the dynamics of the seawater carbonate system during calcification and used

to estimate the resulting release of CO2 (Zondervan et al. 2001).

To calculate Ψ we used the R package “seacarb”, April 2014 (http://cran.r-

project.org/web/packages/seacarb/index.html) and the psi function:

psi(flag, var1, var2, S=35, T=20, P=0, Pt=0, Sit=0, pHscale="T",

kf="dg", k1k2="m06", ks="d")

flag, var1, var2 = 15, Alkalinity, Dissolved Inorganic Carbon (mol kg-1)

S=salinity (psu)

T=temperature (°C)

P=hydrostatic pressure (bar)

Pt = Phosphate (mol kg-1)

Sit = Silicate (mol kg-1)

K1, K2 = Constants taken from Millero et al. 2006

Kf = Constant from Dickson and Riley, 1979 (in Dickson and Goyet, 1994)

Ks = Constant from Dickson, 1990




Table S4.1 Calculation of Ψ at sediment trap deployment locations

Pressure dbar

Salinity psu

Temperature °C

Phosphate µmol kg-1

Silicate µmol kg-1

Alkalinitya

µmol kg-1 DICa µmol

kg-1 Ψ M10.1 [20.12.2004]

M10.1 [+Fe] 6.9 33.79 6.20 1.46 1.01 M10.1 [+Fe] 11.8 33.79 6.20 1.48 1.02 2285.1 2106.7 0.75

M10.1 [+Fe] 22.1 33.79 6.11 1.50 1.05 2285.7 2108.1 0.75 M10.1 [+Fe] 42.0 33.79 5.79 1.50 2.63 2285.1 2115.1 0.76 M10.1 [+Fe] 62.3 33.79 4.98 1.60 5.08 2286.5 2124.0 0.76 M10.1 [+Fe] 82.4 33.83 4.23 1.90 10.61 2284.5 2132.5 0.78 M10.1 [+Fe] 103.4 33.86 4.01 1.74 11.84 2286.3 2142.9 0.79 M10.1 [+Fe] 129.4 33.89 3.68 1.76 14.67

M10.1 [+Fe] 153.8 33.90 3.41 1.88 16.80 2287.5 2142.5 0.79 M10.1 [+Fe] 180.2 33.95 3.45 1.79 17.87

M10.1 [+Fe] 205.6 33.98 3.23 1.84 20.64 2288.8 2151.1 0.80 Average

0.77

±1σ

0.02 M10.2 [15.01.2005]

M10.2 [+Fe] 7.9 33.70 8.75 1.22 1.26 M10.2 [+Fe] 13.1 33.70 8.74 1.22 1.22 2272.6 2082.0 0.74

M10.2 [+Fe] 22.9 33.70 8.65 1.23 1.25 2271.4 2083.2 0.74 M10.2 [+Fe] 42.8 33.76 6.61 1.49 2.28 2280.0 2107.9 0.76 M10.2 [+Fe] 63.3 33.78 5.99 1.55 3.50 2279.4 2119.2 0.77 M10.2 [+Fe] 82.9 33.81 5.05 1.71 6.88 2282.2 2129.7 0.78 M10.2 [+Fe] 103.3 33.87 4.24 1.69 6.31 2287.3 2132.8 0.78 M10.2 [+Fe] 128.3 33.87 3.81 1.84 14.78

M10.2 [+Fe] 153.7 33.91 3.49 1.85 17.28 2283.0 2148.7 0.80




M10.2 [+Fe] 204.3 33.98 3.21 1.88 19.88 2287.6 2152.5 0.80 Average

0.77

±1σ

0.02 M5.1 [27.12.2004]

M5.1 [+Fe] 9.3 33.72 6.40 1.32 1.59 M5.1 [+Fe] 14.4 33.72 6.40 1.33 1.63 2281.3 2101.9 0.75

M5.1 [+Fe] 24.3 33.72 6.38 1.50 1.73 2279.3 2101.8 0.75 M5.1 [+Fe] 44.9 33.73 6.24 1.35 1.71 2281.9 2102.4 0.75 M5.1 [+Fe] 64.7 33.73 6.19 1.36 1.66 2280.8 2104.7 0.75 M5.1 [+Fe] 84.8 33.73 6.11 1.37 1.74 2283.7 2105.2 0.76 M5.1 [+Fe] 105.4 33.74 5.26 1.68 3.68 2284.9 2120.8 0.77 M5.1 [+Fe] 155.8 33.82 3.27 1.82 14.36 2284.3 2145.4 0.81 M5.1 [+Fe] 206.1 33.91 2.91 1.93 17.62 2288.2 2155.7 0.81 Average

0.77

±1σ

0.02 M6.1 [21.11.2004]

M6.1 [HNLC] 4.1 33.81 2.70 1.83 19.03 2281.2 2137.9 0.79 M6.1 [HNLC] 8.9 33.81 2.70 1.82 19.31 2282.6 2137.6 0.79 M6.1 [HNLC] 39.0 33.81 2.70 1.73 18.68

M6.1 [HNLC] 59.5 33.81 2.69 1.81 19.34 2282.0 2137.6 0.79 M6.1 [HNLC] 79.5 33.81 2.64 1.81 19.23 2281.2 2137.1 0.79 M6.1 [HNLC] 99.9 33.81 2.57 1.93 21.28 2281.8 2137.5 0.80 M6.1 [HNLC] 126.1 33.81 2.45 1.87 20.82 2281.4 2140.1 0.80 M6.1 [HNLC] 151.0 33.83 2.25 1.87 22.76 2281.4 2144.0 0.80 M6.1 [HNLC] 176.0 33.85 1.88 2.01 26.82 2283.8 2149.8 0.81 Average

0.80

±1σ

0.004




M6.2 [03.01.2005] M6.2 [HNLC] 10.8 33.81 4.14 1.53 2.08

M6.2 [HNLC] 15.8 33.81 4.14 1.50 2.01 2284.8 2124.0 0.77 M6.2 [HNLC] 26.1 33.81 4.14 1.51 2.03 2284.2 2125.6 0.78 M6.2 [HNLC] 45.4 33.81 4.15 1.51 2.06 2284.4 2124.5 0.77 M6.2 [HNLC] 65.1 33.81 4.14 1.54 2.02 2284.7 2125.4 0.78 M6.2 [HNLC] 86.5 33.82 3.62 1.66 4.53 2284.7 2132.9 0.78 M6.2 [HNLC] 108.1 33.82 2.98 1.82 13.97 2284.5 2141.6 0.80 M6.2 [HNLC] 157.2 33.85 1.95 1.89 24.29 2284.7 2152.0 0.81 M6.2 [HNLC] 207.5 33.90 1.75 1.90 27.71 2287.7 2157.9 0.82

0.79

0.02

a data taken from Bakker et al. 2007




Table S4.2 Calculation of carbonate counter pump strength at WML

POC at WML (gross CO2

sink)a CaCO3 at

WMLb PICc Ψd Ψ*PIC (CO2

source) POC at WML (net CO2 sink)e

{[(gross CO2 sink) – (net CO2 sink)] / (gross

CO2 sink)}*100f M10[+Fe]-N mmol m-2 yr-1 mg m-2 yr-1 mmol m-2 yr-1

mmol m-2 yr-1 mmol m-2 yr-1 %

Sed. Trap (Constant b)g 265 4572 45.7 0.77 35.2 230 13.3 Sed. Trap (Regional b)g 116 4572 45.7 0.77 35.2 81 30.3 DIC defecit (90%)h 250 4572 45.7 0.77 35.2 215 14.1 DIC defecit (75%)h 625 4572 45.7 0.77 35.2 590 5.6 Thorium (150-m)i 642 4572 45.7 0.77 35.2 607 5.5 Thorium (200-m)i 483 4572 45.7 0.77 35.2 448 7.3 M5[+Fe]-NE

Sed. Trap (Constant b) 412 6391 63.9 0.77 49.2 363 11.9 Sed. Trap (Regional b) 155 6391 63.9 0.77 49.2 106 31.7 DIC defecit (90%) 160 6391 63.9 0.77 49.2 111 30.8 DIC defecit (75%) 400 6391 63.9 0.77 49.2 351 12.3 Thorium (150-m) 642 6391 63.9 0.77 49.2 593 7.7 Thorium (200-m) 483 6391 63.9 0.77 49.2 434 10.2 M6[HNLC]-N

Sed. Trap (Constant b) 128 660 6.6 0.79 5.2 123 4.1 Sed. Trap (Regional b) 420 660 6.6 0.79 5.2 415 1.2 DIC defecit (90%) 130 660 6.6 0.79 5.2 125 4.0 DIC defecit (75%) 325 660 6.6 0.79 5.2 320 1.6 Thorium (150-m) 194 660 6.6 0.79 5.2 189 2.7 Thorium (200-m) 146 660 6.6 0.79 5.2 141 3.6




a Annual or seasonal (see g-i) estimate of POC export at the base of the Winter Mixed Layer (WML)15

b Conservative estimate of CaCO3 production in WML based on annual CaCO3 fluxes measured from deep-ocean sediment trap deployments.

Does not account for dissolution between base of WML and sediment trap deployment depth (See Supplementary Information 5)

c Conversion of CaCO3 flux (mg m-2 yr-1) to PIC flux (mmol m-2 yr-1).

d Average Ψ value from winter mixed layer (see Table S4.1)

e Net CO2 sink calculated by subtracting the product of Ψ*PIC from gross CO2 sink.

f Difference (percent decrease) of net and gross CO2 sinks.

g POC sink calculated from annual estimates of deep-ocean (2-3km) POC export (as measured by sediment traps) and normalised to the base of

the WML using the equation Fwml = Fd (WML/d)-b, where d is sediment trap deployment depth and the exponent b is either set at 0.86 (constant)

(Martin et al. 1987); and 0.5 [+Fe] and 1.3 [HNLC] (variable) (Buesseler et al. 2006).

h DIC seasonal drawdown taken from Bakker et al. 2007. Calculations in Table S4.2 assume 90 and 75% remineralisation of POC in the Winter

Mixed Layer (WML).

i Thorium export are seasonal estimates taken from Pollard et al. 2009.




Supplementary Information S5:

Figure S5| Calcite and aragonite saturation depth M5[+Fe]-NE and b, M6[HNLC]-

S. a,b, ΩCa (black circles) and ΩAr (white squares). Inverted grey triangles mark the

sediment trap deployment depth (cf. Table S5). The omega values were calculated

with the Matlab CO2sys code, as available via CDIAC, using dissolved inorganic

carbon and total alkalinity data, in situ temperature, pressure, salinity, silicate and

phosphate (Bakker et al. 2007, Van Heuven et al. 2009). Total pH scale K1 and K2

dissociation constants (Bakker and Nielsdottir, 2006): refit by Dickson and Millero

(Dickson and Millero, 1973, Bakker and Pollard, 2007) and kSO4 constant (Merbach

et al. 1979) were used.

Table S5| Calcite and aragonite saturation depth See Figure S5 caption for details

on the calculation of omega values, ST= Sediment trap

Calcite ST deployment depth

Ω Ca ST deployment depth Depth at ΩCa=1 Δ Ω=1 and ST dep. Depths

M5[+Fe]-NE 3195 0.91 2863 -332 M6[HNLC]-S 3160 1.03 3269 109

Aragonite ST deployment depth

Ω Ar ST deployment depth Depth at ΩAr=1 Δ Ω=1 and ST dep. Depths

M5[+Fe]-NE 3195 0.60 509 -2686 M6[HNLC]-S 3160 0.67 697 -2463

(i) Calcite dissolution

Accurately correcting for calcite dissolution in the water column is difficult, although

it certainly occurs to some degree (Supplementary Information 8). In our study area the




calcite saturation horizons were quite similar in the [+Fe] and HNLC waters (Fig. S6

and Table S6). The sediment trap deployed in the [+Fe] waters was around 330m

below the calcite saturation horizon. Any calcite dissolution from foraminifer tests

during sinking would enhance the effect of a carbonate counter pump relative to what

we report in the manuscript. Considering the similarity of the calcite saturation

horizons between iron regimes we assume that calcite dissolution would have occurred

to a similar degree.

(ii) Aragonite dissolution

The aragonite saturation horizon was comparable in both the [+Fe] and HNLC regimes

and thus sinking pteropod shells should have been exposed to the same water column

(2563-2686m) of under-saturated water before reaching the sediment trap depth.

However, the dissolution of aragonite mass is probably dependent on the period of

exposure to under-saturated waters which depends on the unknown sinking modes of

the pteropod shells. Furthermore, dissolution of aragonite shells can occur in waters

close to supersaturation (Bednersek et al. 2012). Despite these difficulties in

quantifying pteropod shell dissolution, it is reasonable to assume that these artefacts

would have affected the aragonite fluxes in the [+Fe] regime proportionally more than

those from the HNLC regime. The pteropod aragonite fluxes were enhanced 64-68

times upon iron fertilization, e.g. compare with calcite example above.

Correcting for calcite and aragonite dissolution would clearly enhanced the magnitude

of an iron-fertilized carbonate counter-pump relative to what we report in the

manuscript. The estimates should thus be considered as conservative.




Supplementary Information 6

Figure S6 | Average size of foraminifer tests. Minimum test diameter and variance

(ANOVA) of Globigerina bulloides (N= 623), Neogloboquadrina pachyderma (N =

3168), and Turborotalita quinqueloba (blue, N = 1231) over the sampling intervals at

traps [+Fe]-M10 (white circles), [+Fe]-M5 (grey circles), and [HNLC]-M6 (black

circles); p<0.0001 in all three cases. See Table S3.1 for information on the sampling

intervals.

Fig S6.1(a)




Fig S6.1(b)

Fig S6.1(c)




Table S6| Seasonal and regional differences in foraminifer size-normalised weights (µg)

Foraminifer Size class (µm)* Min [+Fe] Max [+Fe] Min [HNLC] Max [HNLC] T. quinqueloba 150-200 1.7 2.6 1.6 1.6 N. pachyderma 150-200 1.8 4.0 2.6 3.9 G. bulloides 250-315 5.1 9.5 5.9 9.5 G. bulloides 315-400 14 19 11 16

*Discrete size classes selected from continuous size-distributions (Figure S6.1)



SI-‐7 Page 1 of 1

Supplementary Information 7

Figure S7 Geochemical signature of exported particles in relation to Southern

Ocean fronts. Sediment trap deployment locations relative to front positions should

only be taken to indicate whether they are north or south of the fronts. SAZ data is

from Trull et al. 2001 and MS data is from AESOPS Honjo et al. 2000. Black bars

are Si:PIC ratios <1. Note the transition from silicate- to carbonate-dominated export

across the Subantarctic Front into the Subantarctic Zone. Despite the proximity of the

iron-fertilized Crozet bloom to the SAF, the geochemical signature of particles is

characteristic of Polar Frontal zone flux suggesting minimal influence of Subantarctic

Zone production.




Supplementary Information 8 Table S8.1| Synthesis of all published sediment trap deployments >150 days in the Southern Ocean. Annual estimates of flux are taken

directly from cited references or from Honjo, S. and Francois, R.; U.S. JGOFS Synthesis & Modeling Project Data. U.S. JGOFS. iPub: May

2005. 16/04/2014' http://usjgofs.whoi.edu/mzweb/data/honjo/sed_traps.html JGOFS particle flux database. The column front refers to the

position of the sediment trap mooring either south of the Polar Front (<PF), between the Polar Front and Sub-Antarctic Front (PF-SAF) or

between Sub-Antarctic Front and Sub-Tropical Front (SAF-STF). To the best of our knowledge this represents all published estimates fitting

our criteria. We have compiled the list from JGOFS databases in addition to our own literature searches.

Reference Site Start End Depth Days Lat Long POC (g m-2)

CaCO3 (g m-2)

SiO2 (g m-2)

POC:PIC Si:PIC

Zone

Trull et al. 2001 47-1000 SAZ 21.09.97 21.02.98 1060 153 46° 46' S 142° 04' E 0.76 5.10 0.71 1.2 0.5 Trull et al. 2001 47-1000 SAZ 21.07.09 30.07.00 2000 405 47° S 142° E

Trull et al. 2001 47-1000 SAZ 08.10.00 28.10.01 2000 385 47° S 142° E Trull et al. 2001 47-1000 SAZ 10.10.05 18.10.06 2000 312 47° S 142° E Trull et al. 2001 47-2000 SAZ 21.09.97 21.02.98 2050 153 46° 46' S 142° 04' E 0.84 8.60 1.27 0.8 0.5

Trull et al. 2001 47-2000 SAZ 21.07.09 30.07.00 2000 405 47° S 142° E Trull et al. 2001 47-2000 SAZ 08.10.00 28.10.01 2000 385 47° S 142° E Trull et al. 2001 47-2000 SAZ 21.09.03 03.10.04 2000 378 47° S 142° E Trull et al. 2001 47-2000 SAZ 10.10.05 18.10.06 2000 312 47° S 142° E Trull et al. 2001 47-3800 SAZ 21.09.97 21.02.98 3850 153 46° 46' S 142° 04' E 0.57 6.80 0.85 0.7 0.4

Trull et al. 2001 51-3100 SAZ 21.09.97 21.02.98 3080 153 51° 00' S 141° 44' E 0.60 13.10 3.01 0.4 0.8 Trull et al. 2001 54-800 PFZ 21.09.97 21.02.98 830 153 53° 45' S 141° 45' E 0.53 4.20 4.61 1.1 3.9




Trull et al. 2001 54-1500 PFZ 21.09.97 21.02.98 1530 153 53° 45' S 141° 45' E 0.51 2.90 3.62 1.5 4.5 Salter et al. 2012 M10[+Fe]-N PFZ 21.12.04 08.12.05 2000 352 44° 30' S 50° 00' E 0.44 4.60 2.67 0.8 2.1 Salter et al. 2012 M10[+Fe]-NE PFZ 28.12.04 20.12.05 3000 357 46° 00' S 56° 05' E 0.48 6.40 4.66 0.6 2.6 Salter et al. 2012 M6[-Fe]-S PFZ 05.01.05 03.01.06 3000 363 49° 00' S 51° 30' E 0.15 0.70 2.47 1.9 13.4 Nodder and Northcote, 2001 NCR SAZ 14.09.96 15.05.97 1000 243 42.5 S - 7.50 -

Nodder and Northcote, 2001 SCR SAZ 09.06.96 15.05.97 1000 340 44.5 S - 1.80 - Nodder and Northcote, 2001 NCR SAZ 14.09.96 15.05.97 300 243 42.5 S - 3.70 - Nodder and Northcote, 2001 SCR SAZ 09.06.96 15.05.97 300 340 44.5 S - 1.50 - Northcote and Niel, 2005 PK rise SAZ 14.05.98 14.07.99 415 426 50°16'S 171°30'E

6.23

Northcote and Niel, 2005 e CF SAZ 14.05.98 14.07.99 400 426 52°37'S 174°08'E

4.65 Wefer and Fischer, 1991 PF-1 PFZ 15.01.87 29.02.88 700 421 50.15'S 5.77'E 2.70 10.50 7.12 2.1 2.4

Fischer et al. 2000 PF-3 PFZ 01.01.90 23.12.90 614 356 50.13'S 5.83'E 3.18 10.30 10.13 2.6 3.5 Fischer et al. 2002 PF-3 PFZ 01.01.90 23.12.90 3196 356 50.13'S 5.83'E 4.61 7.50 4.22 5.1 2.0 Fischer et al. 2002 PF-5 PFZ 15.05.92 01.12.92 654 200 50.1'S 5.91'E 0.48 1.30 0.40 3.0 1.1 Fischer et al. 2002 PF-5 PFZ 15.05.92 01.12.92 3219 200 50.1'S 5.91'E 0.17 0.33 0.03 4.3 0.3 Fischer et al. 2002 PF-7 PFZ 19.04.94 30.12.94 636 255 50.15'S 5.83'E 0.55 1.67 1.41 2.8 3.0 Fischer et al. 2002 PF-7 PFZ 19.04.94 30.12.94 3056 255 50.15'S 5.83'E 0.40 0.42 0.73 8.0 6.3 Fischer et al. 2002 PF-8 PFZ 01.01.95 01.01.96 687 365 50.18'S 5.9"E 0.14 1.08 0.73 1.1 2.4 Fischer et al. 2002 PF-8 PFZ 01.01.95 01.01.96 3110 365 50.18'S 5.9"E 0.51 2.50 3.29 1.7 11.8 Pudsey and King, 1997 WSI SIZ xx.xx.88 xx.xx.90 2966 760 63.15'S 42.68'W 0.09 0.03 0.09 22.5 9.6 Pudsey and King, 1997 WSIII SIZ xx.xx.88 xx.xx.90 3710 120 63.95'S 40.88'W 6.20 2.00 33.59 25.8 60.0 Pudsey and King, 1997 WSVIII SIZ xx.xx.88 xx.xx.90 2453 760 62.08'S 40.60'W 0.22 0.03 0.78 55.0 83.6 Wefer and Fischer, 1991 WS-3 SIZ 16.01.88 04.02.89 360 384 64°54'S 02° 34' W 2.36 2.94 11.73 6.7 14.2 Wefer and Fischer, 1991 WS-4 SIZ 03.03.89 08.04.89 352 360 64°54'S 02° 34' W 0.16 0.95

1.4

Wefer et al. 1988 KG-1_500 SIZ 31.12.83 25.11.84 494 330 62°15'S 57° 31' W 6.83 2.30 12.31 3.0 2.3 Wefer et al. 1988 KG-1_1600 SIZ 01.12.83 25.11.84 1588 360 62°15'S 57° 31' W 5.39 5.20 18.24 1.0 1.5 Wefer et al. 1990 KG-2 SIZ 04.12.84 13.11.85 693 344 62°15'S 57° 31' W 0.35 -




Wefer et al. 1990 KG-3 SIZ 26.11.85 07.05.86 687 162 62°15'S 57° 31' W 1.10 - Kim et al. 2005 K1 SIZ 25.12.98 24.12.98 1034 364 61°45'S 54° 59' W 5.17 0.27 8.50 159 112.5

Kim et al. 2005 K3 SIZ 29.12.00 13.12.01 1024 349 61°42'S 55° 01' W 0.68 0.16 1.57 35.4 34.9 Kim et al. 2004 KAST-1 SIZ 27.12.99 27.12.00 678 365 61°45'S 54° 59' W 6.80 0.50 11.21 115 81.7 Kim et al. 2004 KAST-2 SIZ 27.12.99 27.12.00 960 365 62°15'S 57° 38' W 2.20 0.20 3.41 79.7 53.0 Khim et al. 2005 eBS SIZ 25.12.98 25.12.99 1034 365 61°46'S 54° 59' W 5.20 0.30 9.53 159 126.1 Palanques et al. 2002 FRUELA-500 SIZ 01.03.95 15.02.96 500 351 63'S 60'W 0.40 0.70 0.43 4.0 2.1 Palanques et al. 2002 FRUELA-1000 SIZ 01.03.95 15.02.96 1000 351 63'S 60'W 18.60 13.80 99.35 11.2 25.6 Fischer et al. 1988 WS-1 SIZ 20.01.85 19.03.86 863 423 62°27'S 34° 46' W 0.02 0.01 20.0

Wefer et al. 1990 WS-2 SIZ 20.01.87 20.11.87 4456 304 64°55'S 02° 30' W 0.17 1.00 1.4 Fischer et al. 2000, 2002 BO-1 POOZ 01.01.91 31.12.92 450 368 54.3'S 3.4'W 2.70 11.60 24.84 1.9 7.7

Fischer et al. 2000, 2002 BO-1 POOZ 01.01.91 31.12.92 2194 365 54.3'S 3.4'W 0.50 1.80 8.22 2.4 16.8 Fischer et al. 2000, 2002 BO-1-2-3 POOZ 01.01.92 03.11.92 456 307 54.3'S 3.4'W 0.51 2.20 3.26 2.0 5.4 Fischer et al. 2000, 2002 BO-1-2-3 POOZ 01.01.92 03.11.92 2183 307 54.3'S 3.4'W 0.46 1.40 1.36 2.7 3.4 Fischer et al. 2000, 2002 BO-3/4 POOZ 01.01.94 28.11.94 507 331 54.3'S 3.4'W 0.14 0.30 1.65 3.5 17.7 Fischer et al. 2000, 2002 BO-3 POOZ 01.01.93 31.12.93 2251 365 54.3'S 3.4'W 0.63 0.70 0.22 7.9 1.2 Fischer et al. 2000, 2002 BO-5 POOZ 01.01.95 31.12.95 515 365 54.3'S 3.4'W 0.51 0.70 7.55 6.4 40.4 Fischer et al. 2000, 2002 BO-5 POOZ 01.01.95 31.12.95 2251 365 54.3'S 3.4'W 0.13 0.20 2.36 6.5 50.6 Acconero et al. 2003 D-1995-95m SIZ 19.02.95 07.12.97 95 - 75°06'S 164° 13' E 1.46 2.40 2.77 5.1 4.1 Acconero et al. 2003 D-1996-180m SIZ 19.02.95 07.12.97 180 - 75°06'S 164° 13' E 2.05 1.50 12.29 11.4 29.3 Acconero et al. 2003 D-1997-180m SIZ 19.02.95 07.12.97 180 - 75°06'S 164° 13' E 0.46 1.60 0.74 2.4 1.7 Acconero et al. 2003 D-1996-868m SIZ 19.02.95 07.12.97 868 - 75°06'S 164° 13' E 2.22 1.10 21.46 16.4 67.8 Acconero et al. 2003 D-1996-868m SIZ 19.02.95 07.12.97 868 - 75°06'S 164° 13' E 0.96 0.00 6.88 800 2456.6 Weston et al. 2013 Rats upper SIZ 25.01.05 31.12.05 200 340 67°34'S 68° 14' W 1.47

3.34

Weston et al. 2013 Rats upper SIZ 01.01.06 31.12.06 200 365 67°34'S 68° 14' W 2.61

3.39 Weston et al. 2013 Rats lower SIZ 25.01.05 31.12.05 420 340 67°34'S 68° 14' W 1.32

3.94

Weston et al. 2013 Rats lower SIZ 01.01.06 31.12.06 420 365 67°34'S 68° 14' W 3.86

6.24




Weston et al. 2013 MT upper SIZ 01.01.05 31.12.06 123 365 67°55'S 68° 24' W 2.00

4.73 Rembauville et al. unpub. A3 POOZ 21.10.11 07.09.12 322 289 50°38'S 72° 02' E 1.18 0.60 3.11 15.6 17.6

Dunbar et al. 1998 RSM-A SIZ 13.01.90 24.02.91 230 466 76.50'S 167.51'W 4.99

24.49 Dunbar et al. 1998 RSM-A SIZ 13.01.90 07.02.92 719 641 76.50'S 167.51'W 4.58

35.94

Dunbar et al. 1998 RSM-B SIZ 17.01.90 01.01.92 230 230 76.51'S 174.99'W 7.02 15.70 11.90 3.7 2.7 Dunbar et al. 1998 RSM-B SIZ 17.01.91 09.02.92 519 519 76.51'S 174.99'W 4.09 8.70 7.93 3.9 3.3 Dunbar et al. 1998 RSM-C SIZ 22.01.90 22.02.92 230 230 72.50'S 172.50'W 2.48 13.20 4.18 1.6 1.1 Dunbar et al. 1998 RSM-C SIZ 22.01.90 22.02.92 493 493 72.50'S 172.50'W 0.76 0.80 6.09 7.6 26.1 Langone et al. 2000 Mooring B SIZ 15.12.94 04.01.96 224 385 74.01'S 175.01'W 0.35 0.60 0.89 4.9 5.3 Langone et al. 2000 Mooring B SIZ 15.12.94 04.01.96 560 385 74.01'S 175.01'W 1.44 0.60 5.37 20.0 32.0 Collier et al. 2000 AESOPS-7a SIZ 28.11.96 27.01.98 465 425 76.49'S 177.87'W 10.53 16.30 5.82 5.4 1.3 Collier et al. 2000 AESOPS-7b SIZ 28.11.96 27.01.98 206 425 76.50'S 178.02'W 4.98 10.80 3.12 3.9 1.0 Collier et al. 2000 AESOPS-7b SIZ 28.11.98 27.01.98 481 425 76.50'S 178.02'W 12.18 27.80 7.10 3.7 0.9 Miquel et al. 1998 Kerfix PFZ 09.04.93 14.01.95 640 200 50.7'S 68.4'E 0.70

Pilskaln et al. 2004 PZB-1 SIZ 30.12.98 30.12.99 1400 365 62°28'S 72°58' E 0.90 0.90 8.70 8.2 33.9 Pilskaln et al. 2004 PZB-1 SIZ 30.12.98 30.12.99 3400 365 62°28'S 72°58' E

2.87

Pilskaln et al. 2004 PZB-2 SIZ 10.03.00 04.02.01 3300 331 63°27'S 76°09' E 0.40 0.60 4.77 5.7 29.2 Tesi et al. 2012 O-900 POOZ 10.01.99 11.01.00 900 366 63°26'S 178°03' E 0.90 1.10 18.27 6.8 57.0 Tesi et al. 2012 O-1300 POOZ 10.01.99 09.01.00 1300 364 63°26'S 178°03' E 0.40 0.70 8.43 5.0 42.8 Tesi et al. 2012 O-2400 POOZ 10.01.99 09.01.00 2400 364 63°26'S 178°03' E 0.20 0.20 4.20 6.9 62.1 Tesi et al. 2012 O-3700 POOZ 10.01.99 11.01.00 3700 366 63°26'S 178°03' E 0.50 0.60 9.95 6.1 57.4 Hu et al.2008 Trap SIZ 30.12.98 13.12.99 1000 290 63'S 73'E 0.80 0.70 5.47 9.5 27.9 Honjo, et al 2000 MS-1 SAZ 28.11.96 27.01.98 1981 425 53°02'S 174°44' E 1.00 6.80 0.23 1.2 0.1 Honjo, et al 2000 MS-2 SAZ 28.11.96 27.01.98 982 425 56°54'S 170°10' E 1.70 11.80 7.03 1.2 2.1 Honjo, et al 2000 MS-3 PFZ 28.11.96 27.01.98 1003 425 60°17'S 170°03' E 2.30 12.80 12.87 1.5 3.6 Honjo, et al 2000 MS-4 SIZ 28.11.96 27.01.98 1031 425 63°09'S 169°54' E 2.20 10.70 25.62 1.7 8.6 Honjo, et al 2000 MS-5 SIZ 28.11.96 27.01.98 937 425 66°10'S 169°40' E 1.90 0.60 7.54 27.1 46.2




Collier et al. 2000 M6-6 SIZ 28.11.96 27.01.98 200 425 73.54'S 176.89'E 2.00 5.00 2.20 3.0 1.5 Trequer unpublished Antares-M2 PFZ 13.02.94 22.01.95 1300 353 52'S 61.6'E 1.10 6.00 22.17 1.5 13.2 Treguere unpublished Antares-M2 PFZ 13.02.94 01.02.95 4000 353 52'S 61.6'E 0.57 5.00 14.32 1.0 10.2 Trequer unpublished Antares-M3 SIZ 21.2.94 09.02.95 3500 353 63°01'S 70°57' E 0.16 0.25 1.44 5.3 20.6 Treguere unpublished Antares-M3 SIZ 21.2.94 09.02.95 1300 353 63°01'S 70°57' E 0.11 0.08 0.95 11.0 40.7


Salter et al. SI-S8 Carbonate counter pump stimulated by natural iron fertilization in the Polar

Frontal Zone


POC:PIC ratios and depth

Figure S8.1| Changes in POC:PIC ratios with depth in different regions of the

Southern Ocean. Numbers adjacent to bars represent the number of observations

used to calculate a mean for each category. Error bars are ±1 standard deviation of

the mean (bars). Frontal regions are grouped according to Table S8.1 and Fig. 3(b).

The comparison of POC:PIC and Si:PIC annual export ratios in the Southern Ocean is

complicated by multiple sediment trap deployment depths. POC:PIC ratios are

expected to decrease with depth as organic matter is preferentially remineralised over

inorganic carbon. These changes tend to be most pronounced in the upper 1000m of

the ocean. A significant portion of the data we use for comparison in Figure 3b is at

bathypelagic depths (>1000m). However, it is worth noting that POC:PIC ratios do

not appear to uniformly decrease with depth in the Southern Ocean, particularly

deeper than 1000m (Fig. S8.1). Using a sub-set of the sediment trap deployments



Frontal Zone


from Table S8.1, whereby sediment traps were deployed at multiple depths in the

same location and at the same time (Table S8.2) indicates non-uniform changes in

POC:PIC ratios with depth. In the majority of cases (>70%), POC:PIC ratios increase

with depth, reflecting significant CaCO3 dissolution.

Table S8.2| Synthesis of multi-depth deployments from Southern Ocean.

Decrease and increase refer to change in POC:PIC ratio in relation to change in depth

(δ m) of sediment trap moorings.

Data Source Mooring

Name Frontal Position Depth

POC:PIC δ m

δ POC:PIC Change

Trull et al. 2001 47-1000 SAF-STF 1060 1.2 Trull et al. 2001 47-2000 SAF-STF 2050 0.8 990.0 -0.4 Decrease

Trull et al. 2001 54-800 PF-SAF 830 1.1 Trull et al. 2001 54-1500 PF-SAF 1530 1.5 700.0 0.4 Increase

Fischer et al. 2000 PF-3 <PF 614 2.6 Fischer et al. 2002 PF-3 <PF 3196 5.1 2582.0 2.6 Increase




Wefer et al. 1988 KG-1_500 <PF 494 3.0 Wefer et al. 1988 KG-1_1600 <PF 1588 1.0 1094.0 -1.9 Decrease

Fischer et al. 2000;2002 BO-1 <PF 450 1.9 Fischer et al. 2000;2002 BO-1 <PF 2194 2.4 1744.0 0.5 Increase

Fischer et al. 2000;2002 BO-1-2-3 <PF 456 2.0 Fischer et al. 2000;2002 BO-1-2-3 <PF 2183 2.7 1727.0 0.7 Increase



Frontal Zone


Fischer et al. 2000;2002 BO-5 <PF 515 6.4 Fischer et al. 2000;2002 BO-5 <PF 2251 6.5 1736.0 0.1 Increase

Acconero et al. 2003 D-1996-180m <PF 180 11.4 Acconero et al. 2003 D-1996-868m <PF 868 16.4 688.0 5.0 Increase

Dunbar et al. 1998 RSM-B <PF 230 3.7 Dunbar et al. 1998 RSM-B <PF 519 3.9 289.0 0.2 Increase

Dunbar et al. 1998 RSM-C <PF 230 1.6 Dunbar et al. 1998 RSM-C <PF 493 7.6 263.0 6.0 Increase

Langone et al. 2000 Mooring B <PF 224 4.9 Langone et al. 2000 Mooring B <PF 560 20.0 336.0 15.1 Increase

Collier et al. 2000 AESOPS-7b <PF 206 3.9 Collier et al. 2000 AESOPS-7b <PF 481 3.7 275.0 -0.2 Decrease

Tesi et al. 2012 O-1300 <PF 1300 5.0 Tesi et al. 2012 O-3700 <PF 3700 6.1 2400.0 1.1 Increase

Trequer et al. 1998 Antares-M2 PF-SAF 1300 1.5 Treguere et al. 1998 Antares-M2 PF-SAF 4000 1.0 2700.0 -0.5 Decrease

Treguere et al. 1998 Antares-M3 <PF 1300 11.0 Trequer et al. 1998 Antares-M3 <PF 3500 5.3 2200.0 -5.7 Decrease


Salter et al. Supp. Refs. Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone

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