Benthic Carbon Mineralization and Nutrient Turnover in a Scottish Sea Loch: An Integrative In Situ Study

Based on in situ microprofiles, chamber incubations and eddy covariance measurements, we investigated the benthic carbon mineralization and nutrient regeneration in a *65-m-deep sedimentation basin of Loch Etive, UK. The sediment hosted a considerable amount of infauna that was dominated by the brittle star A. filiformis. The numerous burrows were intensively irrigated enhancing the benthic in situ O2 uptake by *50 %, and inducing highly variable redox conditions and O2 distribution in the surface sediment as also documented by complementary laboratory-based planar optode measurements. The average benthic O2 exchange as derived by chamber incubations and the eddy covariance approach were similar (14.9 ± 2.5 and 13.1 ± 9.0 mmol m day) providing confidence in the two measuring approaches. Moreover, the non-invasive eddy approach revealed a flow-dependent benthic O2 flux that was partly ascribed to enhanced ventilation of infauna burrows during periods of elevated flow rates. The ratio in exchange rates of RCO2 and O2 was close to unity, confirming that the O2 uptake was a good proxy for the benthic carbon mineralization in this setting. The infauna activity resulted in highly dynamic redox conditions that presumably facilitated an efficient degradation of both Electronic supplementary material The online version of this article (doi:10.1007/s10498-016-9300-8) contains supplementary material, which is available to authorized users. & Ronnie N. Glud [email protected] 1 Nordic Centre for Earth Evolution, University of Southern Denmark, Odense, Denmark 2 Scottish Marine Institute, Scottish Association for Marine Science, Oban, UK 3 Arctic Research Centre, University of Aarhus, Aarhus, Denmark 4 Department of Environmental Sciences, University of Virginia, Charlottesville, VA, USA 5 Zayed University, Dubai Academic City, Dubai, United Arab Emirates 6 Centre for Coastal Biogeochemistry Research, Southern Cross University, Lismore, NSW, Australia 7 Water Studies Centre, School of Chemistry, Monash University, Clayton, VIC 3800, Australia 123 Aquat Geochem DOI 10.1007/s10498-016-9300-8