Benthic remineralisation rates under contrasting sea-ice
conditions in the deep Arctic Ocean
R
ALFH
OFFMANNU. BRAECKMAN, I. SCHEWE, T. KRUMPEN,
AND F. WENZHÖFER
Sea ice
Water column Snow
Predicted Arctic Ocean
More light Higher primary production More organic matter Former Arctic Ocean
Are benthic
in the influenced by
decreasing seaice coverage and increasing primary production?
How?
Decreasing seaice coverage Increasing primary production
Increasing benthic remineralisation rates
Hypothesis
Arrigo et al., Geophysical Resrach Letters, Vol. 35, 2008 Boetius et al., Science, Vol. 339, 2013
Island
Spitsbergen
Fram
Strait
YB
SB
Permanently sea-ice
covered Former
Arctic
Ocean Highly
productive marginal
ice zone Seasonally
sea-ice covered Predicted
Arctic
Ocean
Sea-ice coverage
09.2001 – 08.2015 Daily data
©ESA
Sediment parameters
Biogenic sediment compounds Faunal data (size classes) Sediment Cores
Lander
©ESA
Sediment Cores
Oxygen fluxes: ex situ & in situ Diffusive oxygen uptake (DOU) = Bacterial remineralisation Method: Micro-profiling
Total oxygen uptake (TOU)
= Entire benthos remineralisation Method: Incubation
Lander
Angle: 90° = independent parameters
2.5 2.0
1.0
Ex situ 1200 m 1.5
0.5
In situ 1200 m
Ex situ 2500 m
In situ 2500 m Stations from seasonally seaice covered area
DOU [mmol O 2/m²d]
DOU [mmol O 2/m²d] 3.0 2.0
1.0
1000 1500 2000 2500
Permanently seaice covered Seasonally seaice covered Former Arctic Ocean
Predicted Arctic Ocean
Are benthic
in the influenced by
decreasing seaice coverage and increasing primary production?
How?
Answer:
Acknowledgment
Contact: ralf.hoffmann@awi.de
Crew of RV Polarstern, Lander technicians, Lab.-technicians
Ingo Schewe and Thomas Soltwedel (exp. leaders) Pier Luigi Buttigieg & Christiane Hassenrück
Funding by
Helmholtz Association (Germany) Max Planck Society (Germany)
Fonds Wetenschappelijk Onderzoek (Belgium) Sense Ocean (EU, Grand no. 614141)
FRAM
Abiotic Parameters
Food supply
Benthic community
Respiration rates
-30 -20 -10 0 10 20 30 40 50
0 100 200 300 400
Depth [mm bsf]
Oxygen concentration [µmol O2/l]
y = -0.1097x + 35.713 R² = 0.9843 -3
-2
-1
0
1
2
320 325 330 335
Sea Ice concentration 06.09.2015
Sampling
2014: 8 MUC + 2 Lander stations Mid – End of June
Depth: 1000 – 2500m
2015: 8 MUC + 2 Lander stations End of July – Mid of August Depth: 275 – 2600m
Four stations in both years
Test of compatibility of data
PCA on data biogenic data
Wilcoxon: p > 0.05 = compatible
(Cathalot et al., Plos ONE, 2015)
Timewise differences data over 15 years needed (Henson et al., Global Change Biology, 2016)
Test of compatibility of data
PCA on data biogenic data = not
compatible
High sea-ice cover
Sea-ice coverage
Low sea-ice cover
20 40 60 80 100
Sea-ice coverage [%] 09.2001 – 08.2015
0.0 0.5 1.0 1.5
1000 2000
C org [%]
Depth [m]
0 7 14 21
1000 1500 2000 2500
Org. matter [%]
Depth [m]
0 500 1000 1500 2000
1000 1500 2000 2500 Proteins [µg/ml sediment]
Depth [m]
0 2.5 5 7.5 10
1000 1500 2000 2500
FDA [nmol/ml h]
Depth [m]
0 2 4
1000 1500 2000 2500 Chl a [µg/ml sediment]
Depth [m]
High sea-ice cover Low sea-ice cover
Low sea-ice cover, in situ
TOU
y = -2E-05x + 1.2067 R² = 0.0011
y = -0.0004x + 2.0253 R² = 0.084
0 0.5 1 1.5 2 2.5 3 3.5
1000 1500 2000 2500
DOU [mmol O 2 m-2 d-1 ]
Depth [m]
