 |
| Titel |
Tracer studies on organic matter cycling by benthic fauna across the Arabian Sea (Indian margin) oxygen minimum zone |
| VerfasserIn |
Carol White, Clare Woulds |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048609
|
|
|
|
|
|
| Zusammenfassung |
| Organic matter cycling in marine sediments is of major global significance, acting as the
principal driver for many seafloor processes. While oxygen availability, sedimentation rates,
mineral surface interaction and organic matter supply are known key factors in organic matter
burial and preservation, the potentially critical role of benthic faunal communities (through
burrowing, ventilation, digestion and metabolic activity) remains poorly characterized or
quantified. Previous carbon and nitrogen isotope tracing experiments suggest oxygen and
organic matter availability control benthic carbon processes but it is unclear which of
these controls is dominant, or whether that dominance varies between contrasting
sites.
The Arabian Sea is characterized by an extensive oxygen minimum zone, typically at
150-1000 m water depth, creating a broad belt of hypoxic sediments sustained by
monsoon-driven upwelling and productivity, and restricted intermediate water ventilation.
Thus, Arabian Sea margins provide outstanding natural laboratories for biogeochemical
studies as they display large ranges in biological communities, organic matter fluxes and
sedimentary redox conditions.
Isotope tracing experiments were conducted on sediment cores recovered from depths of
500 m, 800 m and 1140 m on the Indian margin of the Arabian Sea, where oxygen
concentrations ranged from 0.2 to 20 μM. A constant dose (650 mg C m-2) of 13C- and
15N-labelled organic matter was added to cores as either algal detritus or lysine sorbed onto
montmorillonite. Following incubation for 2 or 7 days, in water baths at ambient seafloor
temperatures and oxygen concentrations, core top water was time-series sampled for δ13
dissolved inorganic carbon (DIC) analysis and fauna were picked from sediments for 13C and
15N analysis. Parallel experiments were conducted at deliberately manipulated oxygen
concentrations to simulate realistic potential fluctuations in Arabian Sea oxygen
availability.
We quantify the role of benthic fauna in the short-term processing of sedimentary
organic matter, and how this changes in response to manipulated oxygen levels and
organic matter quality. Generated carbon budgets are modeled and evaluated against
previous experiments, in order to characterize biological organic matter processing
on a global scale. The sites are classified using previously developed biological
carbon-processing patterns categories. Our results will be used to test the hypothesis that
oxygen exerts a threshold-type effect over biological carbon-processing patterns. |
|
|
|
|
|
|