Steeb, Philip, Kretschmer, Kerstin, Linke, Peter and Treude, Tina (2012) Response and efficiency of the benthic microbial methane filter under non-steady state conditions. [Poster] In: The Lübeck Retreat, Collaborative Research SFB 574 Volatiles and Fluids in Subduction Zones: Climate Feedback and Trigger Mechanisms for Natural Disasters. , 23.-25.05.2012, Lübeck . The Lübeck Retreat: final colloquium of SFB 574; May 23-25, 2012: program & abstracts. ; p. 31 .

Abstract

The microbial benthic methane filter of the ocean floors globally retains approximately 80-90% of the
ascending greenhouse gas methane through anaerobic oxidation of methane (AOM). However
natural and catastrophic fluctuations of methane fluxes (caused e.g. by gas hydrate melting,
earthquakes, slope failure) can challenge the capability of this greenhouse gas sink. We ask: How
efficient can the methanotrophic community adapt its activity to methane flux changes, what is its
response time and what is the efficiency of the benthic filter in this time.
To answer these questions, a new sediment-flow-through-system was developed. The system holds
intact sediment cores and simulates natural condition of seepage with a diffusive supply of sulfate
from the top and an advective transport of methane from the bottom. Sampling holes allow monitoring
the key parameters (sulfate, sulfide, pH, Redox, Total Alkalinity) over the entire sediment depth.
For our experiments, sediment from three different methane-rich environments were used: (1) gassy
sediments from Eckernförde Bay (German Baltic) without naturally occurring advective fluid transport,
(2) sediments with high advective transport from a methane seep within an oxygen minimum zone on
the continental margin (Quepos Slide, Costa Rica), and (3) methane-seep sediments from the center
of a mud volcano (North Alex Mud Volcano, Eastern Mediterranean Sea). Two different advective
methane flow rates (15.3 and 153 mmol CH4 cm-'yr-1, fluid flow 10.9 and 109 cm yr-1) were applied
for replicate sediment cores (upper 20cm) of the respective environments. The poster will present
results of the long-term experiment and compare the response of the different sediment types to the
varying methane and fluid flow rates.

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