in sea ice and waters of the central Arctic during summer 2011

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Primary Productivity

in sea ice and waters of the central Arctic during summer 2011

Mar Fernández Méndez ¹

mfernand@mpi-bremen.de

Ilka Peeken ², Eva-Maria Nöthig ² and Antje Boetius ¹

1 HGF-MPG Group for Deep Sea Ecology and Technology (MPI/AWI)

2 PEBCAO Group (AWI)

24^th April 2012 IPY Conference Montreal

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Mar Fernández Méndez

Mar Fernández Méndez 2

POC DIC

DOC

6CO₂ + 6H₂O → C^{Chl a} ₆H₁₂O₆ + 6O₂

Sea Ice

Melt Ponds Water column

Introduction

Primary Productivity in the central Arctic Ocean

What are the relative contributions to Primary Productivity of the different phototrophic communities in the central Arctic?

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Water column Sea Ice Melt Ponds

Methods

Sampling

20 ml

14C radioactive isotope

1 µCi/ml ¹⁴C

Temperature: -1.9 °C Light: 10 mE/m² s Incubation 24 h

Potential Net Primary Production rate (µg C L^-1 d^-1)

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Results TransArc 2011

M.Nicolaus

Circulation in the subsurface and intermediate layers of the Arctic Ocean (Rudels et al. 2011)

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Surface waters

Microscopy pictures by Henrieke Tonkes

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Surface waters

NPP (µg C · L -1 ·d -1) Pacific waters

+P -N

Mixed waters -P -N

Mixed waters

+P +N Atlantic waters

-P +N

Ellen Damm

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Surface waters

0 2 4 6 8 10 12 14 16

201 205

207 209

212 214

216 218

220 221

222 223

225 226

227 228

229 230

233 235

239 240

242 245

247 248

250 252

Station

NPP (µg C/ L d)

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9

Chl a (µg/L)

NPP Chl a

Atlantic region:

high biomass but low activity.

Pacific region:

low biomass

high activity ^Atlantic_{–P +N} ^Mixed_{+P +N} ^Pacific_+P-N ^Mixed_-P-N

Post-Bloom situation

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Ice

Microscopy pictures by Kristin Hänselmann

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Ice

0 50 100 150 200 250

203

209

212

218

222

227

230

235

239

245

250 Station

NPP (µg C / L d)

Top Middle Bottom

0 1 2 3 4 5 6

Chl a (µg / L)

Top Middle Bottom

Multiyear Ice

Bottom part of the ice is not

always the most active.

Higher activity in Atlantic region.

Atlantic –P +N

Pacific +P-N Mixed

+P +N

Mixed -P-N

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Melt Ponds

Mario Hoppmann

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Melt Ponds

0 50 100 150 200 250 300 350 400 450 500

203

209

212

218 222

227 235

239 245

250

Station

NPP (µg C/ L d)

0 5 10 15 20 25 30

Chl a (µg/L)

NPP Chl a Aggregates (~10 cm)

Open Closed

Melt pond algae are more

active before reefreezing

170 (µg Chl a/L) 7000 (µg C/L d)

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0% 20% 40% 60% 80% 100%

212 222 227 235 239 245 250

Station

% NPP (µg C*µg Chl a^-1*d^-1)

Surface waters Sea Ice

Melt Ponds

0 50 100 150 200 250

Surface Water

Sea Ice Melt Ponds

NPP (µg C* µg Chl a-1 * d-1)

All

Sea Ice algae contribute the most to NPP activity per Chl a

August

September

Biomass normalized rates: carbon uptake per Chl a

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Integrated rates

Sea ice NPP integrated is one order of magnitude lower as the entire mixed layer.

NPP (mg C*m^-2*d^-1)

Water mixed layer Sea Ice

One order of magnitude lower!

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Other variables

Water Ice Melt Ponds

TEP (µg C/L) 0,09±0,03 0,48±0,14 0,11±0,3

POC (µg C/L) 92 ± 40 1788 ± 1862 7422 ± 20542 C:N molar ratio 7 ± 1 10 ± 3 11 ± 4

Nitrate (µM) 0,07 – 3,7 0,07 – 1,6 0,2– 8,1 Phosphate (µM) 0,09 – 0,8 0,02 – 0,2 0 – 0,6 Silicate (µM) 0,7 – 12,2 0,2 – 8,8 0 – 11,8

• Highest concentrations of carbon present in ice and melt ponds.

• C:N ratios in sea ice and melt ponds reflect detritus deposition.

• Nutrient concentrations are lower in the ice.

• Nitrate was never depleted in melt ponds.

Kai-Uwe Ludwischowski

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Conclusions

 Comparing volumes of sea ice, melt ponds and surface waters, ice algae contribute most of the NPP.

 NPP is not limited to the bottom part of the ice in autumn.

 Before refreezing, melt ponds sustain the highest NPP rates.

 Phytoplankton in surface waters is more active in autumn in Mixed waters probably due to nitrate availability and less

grazing.

 Comparing areal potential NPP rates (not considering light and nutrient limitation), sea ice contributes 1:9 of total

productivity.

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Outlook

• Infer the limiting factors for NPP by performing Photosynthesis- Irradiance curves and Nutrient bioassays.

• Upscaling NPP rates to the entire Arctic.

• Comparing surface water NPP rates with Net Community

Production in situ measurements with O₂/Ar Method (N.Cassar)

• Reveal the key groups responsible for carbon fixation.

• Determine the carbon transfer rates from melt pond algae to bacteria.

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Mar Fernández Méndez 17 17

Summary

Acknowledgements

Ursula Schauer Kristin Hänselman Gerhard Dieckmann Erika Allhusen

Ellen Damm

Elisabeth Helmke Estelle Kilias

Kai Uwe Ludwischowski Marcel Nicolaus

Christian Katlein

Crew RV Polarstern Christian Katlein

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Pacific waters -P -N

Pacific waters +P -N

Mixed waters

+P +N Atlantic waters

-P +N

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Nutrient concentrations in surface waters

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-1 0 1 2 3 4 5

201 205 207 209 218 233 235 260

NPP (µg C/L d)

Station Surface

Chl a max

0 10 20 30 40 50 60 70

201 205 207 209 218 233 235 260

NPP/Chl a (µg C/ µg Chl a d)

Station Surface

Chl a max

Surface vs Chl a max

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Water under the ice

0 5 10 15 20 25 30 35 40

203 209 212 218 222 227 230 235 239 245 250

NPP (µg C/L d)

Station

Comparison Water under Ice and CTD water

WUI 0 WUI 5 W 5

W ChlaMax

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22

Proposal

1. Limitation of PP in sea ice algae

Light 1000µE

Light 10-100 µE 1m

40m

Pycnocline

Thinner ice

Melting ice stabilizes mixed layer

Ice blooms can last 2-3 months

Brine drainage

Vertical mixing of Nutrients New nutrients

SUMMER POST-BLOOM

CO₂

Recycled Nutrients Nutrients

depleted

Will higher light intensities due to thinner ice boost PP in the ice in summer or will it be limited by nutrient supply?