Publication Date:
2012-07-24
Description:
Exchanges between sediment pore waters and the overlying water column play a significant role in the chemical budgets of many important chemical constituents. Quantification of such benthic fluxes requires explicit knowledge of the sediment properties and biogeochemistry. Alternatively, changes in water column properties near the sediment-water column interface can be exploited to gain insight into the sediment biogeochemistry and benthic fluxes. Here, we apply a 1-D diffusive mixing model to near-bottom water column profiles of 224Ra activity in order to yield vertical eddy diffusivities (KZ), based upon which we assess the diffusive exchange of inorganic carbon (DIC), nutrients and oxygen (O2), across the sediment-water interface in a coastal inlet, Bedford Basin, Nova Scotia, Canada. Near-bottom observations of DIC, O2 and nutrients provide flux ratios similar to Redfield values, suggesting that benthic respiration of primarily marine organic matter is the dominant driver. Furthermore, we did not observe any significant release of alkalinity (AT) from the sediments to the overlying water column, providing further insight into the dominant reactions taking place within sediments: the respiration of organic matter occurs largely under aerobic conditions or products of anaerobic processes are reoxidized quickly in oxygenated layers of the sediments. Finally, comparison with other carbon sources reveal the observed benthic DIC release as a significant contributor to the Bedford Basin carbon system.
Print ISSN:
1810-6277
Electronic ISSN:
1810-6285
Topics:
Biology
,
Geosciences
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