title: Alkalinity production in intertidal sands intensified by lugworm bioirrigation.
abstract: Porewater profiles and sediment-water fluxes of oxygen, nutrients, pH, calcium, alkalinity, and sulfide were measured in intertidal sandflat sediments from the Oosterschelde mesotidal lagoon (The Netherlands). The influence of bioturbation and bioirrigation by the deep-burrowing polychaeteArenicola marinaon the rates and sources of benthic alkalinity generation was examined by comparing measurements in intact and defaunated sediment cores before and after the addition ofA. marinain summer and fall 2011. Higher organic matter remineralization rates, shallower O2penetration, and greater sediment-water solute fluxes were observed in summer, consistent with higher sediment community metabolic rates at a higher temperature. Lugworm activity stimulated porewater exchange (5.1 × in summer, 1.9 × in fall), organic matter remineralization (6.2 × in summer, 1.9 × in fall), aerobic respiration (2.4 × in summer, 2.1 × in fall), alkalinity release (4.7 × in summer, 4.0 × in fall), nutrient regeneration, and iron cycling. The effects of lugworm activity on net sediment-water fluxes were similar but more pronounced in summer than in fall. Alkalinity release in fall was entirely driven by metabolic carbonate dissolution, while this process explained between 22 and 69% of total alkalinity production in summer, indicating the importance of other processes in this season. By enhancing organic matter remineralization and the reoxidation of reduced metabolites by the sediment microbial community, lugworm activity stimulated the production of dissolved inorganic carbon and metabolic acidity, which in turn enhanced metabolic CaCO3dissolution efficiency. In summer, evidence of microbial long distance electron transport (LDET) was observed in defaunated sediment. Thus, alkalinity production by net carbonate dissolution was likely supplemented by anaerobic respiration and LDET in summer.
authors.affiliation: Laboratory of Analytical, Environmental & Geochemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Alexandra M F
authors.initials: AM
authors.lastname: Rao
authors.affiliation: Laboratory of Analytical, Environmental & Geochemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Sairah Y
authors.initials: SY
authors.lastname: Malkin
authors.affiliation: Laboratory of Analytical, Environmental & Geochemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium ; Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research, P.O. Box 140, 4400 AC Yerseke, The Netherlands.
authors.forename: Francesc
authors.initials: F
authors.lastname: Montserrat
authors.affiliation: Laboratory of Analytical, Environmental & Geochemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium ; Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research, P.O. Box 140, 4400 AC Yerseke, The Netherlands.
authors.forename: Filip J R
authors.initials: FJ
authors.lastname: Meysman
keywords: Arenicola; alkalinity; bioirrigation; bioturbation; calcium carbonate; diagenesis