Antarctic biogeochemical fluxes influenced by melting glacier
Ralf Hoffmann
Braeckman U., Vázquez S., Pasotti F., Torstensson A., Wenzhöfer F.
Preliminary results
09.05.2016 2nd European Conference on Scientific Diving - Research in cold waters using scientific diving
2/17
Particle Release Ice
Scouring
Seafloor conditions
Benthic community
Biogeochemical flux
Photo: Anders Torstensson
Photo: Christof Berger, CC-By-3.0, https://pt.wikipedia.org/wiki/Recuo_dos_glaciares_desde_1850
How do glacier melting-related disturbances influence benthic communities and
biogeochemical fluxes?
3/17
Hypothesis
4/17
Benthic community Biogeochemical flux
Intensity of Disturbance
Potter Cove
5/17
ID
Potter Cove
LD HD
ID LD
Carlini-Station
Pasotti et al., Marine Ecology (2014) 1–18
LD
HD
ID
6/17
Total Oxygen Uptake = TOU
Diffusive Oxygen Uptake = DOU Nutrient fluxes
Sediment samples
Photo: Anders Torstensson
7/17
TOU = Entire benthos energy demand
DOU = Microbial energy demand &
chemical redox reactions Subflux of TOU
Photo: Anders Torstensson
Photos: Anders Torstensson, Ulrike Braeckman
8/17
LD ID HD
Depth 8-9 m 5-7 m 7-8 m
Ø Light
saturation 0.4% 4.1% 0.6 %
TOC [% of TC/ml
Sediment]
40 ± 6 75 ± 9 49 ± 2
Silt, 4-63µm 84 %
Sand, >63µm 62 % 72 % Chl a [µg/g]
(0-1cm) 12.5 ± 4.7 26.3 ± 4.0 5.1 ± 0.9
9/17
Seafloor conditions
DOU vs. TOU
10/17
Site DOU/TOU
[%]
LD 6
ID 4
HD 19
Macro- and Meiofauna
dominate oxygen fluxes
Benthic community biomass
Macrofauna biomass
Meiofauna biomass
Modified after Pasotti et al.
Supporting Information Marine Ecology, 2014
11/17
0.0 0.5 1.0 1.5 2.0
LD ID HD
Biomass [mg C org/10cm²]
~ 5% of macrofauna biomass per m²
0 10 20 30 40 50
LD ID HD
g AFDW m-2
Total oxygen influx
12/17
0 10 20 30 40 50 60
LD ID HD
Oxygen flux [mmol O 2/m²d]
Ammonium efflux
13/17
0 2 4 6 8 10 12
LD ID HD
Ammonium flux [mmol NH 4+ /m²d
Nitrite efflux
14/17
0 40 80 120 160
LD ID HD
Nitrite flux [µmol NO 2- /m²d
Hypothesis
15/17
Intensity of Disturbance
Benthic community Stress reaction
Increasing respiration
Biogeochemical flux
Areas of
intermediate disturbance increase
Decreasing
benthic biomass but accelerated biogeochemical fluxes
16/17
Thank you
Acknowledgement:
Dive leader: Freddy, Eziquel, José
Expedition participants: Katharina Zacher & Angela Wulff
Funded by:
IMCONet Project, AWI, DNA, IAA, University Gent, MPI Bremen
