Dissolved Organic Matter Export from Surface Sediments of a New England Salt Marsh
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GENERAL WETLAND SCIENCE
Dissolved Organic Matter Export from Surface Sediments of a New England Salt Marsh Hayley N. Schiebel 1
&
Francesco Peri 2 & Robert F. Chen 2
Received: 6 February 2019 / Accepted: 6 August 2019 # Society of Wetland Scientists 2019
Abstract Salt marshes sequester a large amount of carbon via sedimentation, but seasonal and climate change impacts on sediment carbon biogeochemistry are not well-understood. This study investigates the export of dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) from New England salt marsh sediment seasonally and under possible expected drought conditions. Surface sediment total organic carbon (TOC) values shifted seasonally depending on the overlying dominant plant species suggesting that vegetation and inundation frequency and duration are key factors in sediment TOC fluctuations. Fall sediment samples leached more DOC than summer samples, were compositionally similar to the estuarine water column, and compositionally different from fresh plant matter. Thus, the seasonal TOC pulse incorporated into surface sediments could be a dominant source of DOC to the estuary in the fall and that summer contributions are presumed to be from upstream DOM sources based on optical properties. Sediments leached more DOC under drought than non-drought conditions due to induced cracking in the sediment enhancing organic matter degradation. This study suggests the majority of DOM exported laterally from salt marshes comes from surface sediments (versus plant matter) and that temperature and sea-level rise could affect seasonal and drought pulses of DOC from the marsh. Keywords Salt marsh . Sediment . DOC . Seasonality . Drought . Export
Introduction Salt marshes provide many ecosystem services including storm attenuation (Möller et al. 2014), fish nursery habitats (Short et al. 2000), ecotourism (Burger et al. 1995), and natural water filtration (Gopal 1999). Additionally, these ecosystems may sequester up to an order of magnitude more carbon dioxide (CO2) per area than their terrestrial counterparts (e.g., rainforests; Mcleod et al. 2011). Coastal wetland carbon sequestration rates are estimated to be up to 0.55 Pg C yr.−1 (Bauer et al. 2013) with 90 Tg C yr.−1 (16% of total sequestration) buried in sediments (versus plant biomass; Mcleod et al. 2011; Macreadie et al. 2013).
* Hayley N. Schiebel [email protected] 1
Center for Urban Ecology and Sustainability, Suffolk University, 20 Somerset Street, Boston, MA 02108, USA
2
School for the Environment, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, MA 02125, USA
Because organic matter is highly concentrated in salt marsh sediments (Chmura et al. 2003; Duarte et al. 2005; Donato et al. 2011; Breithaupt et al. 2012; Pellegrini et al. 2015; Chen et al. 2016), the remineralization of this material could release large amounts of dissolved carbon if not otherwise sequestered (Bouillon et al. 2008). Salt- and inundationtolerant plants that thrive in salt marshes exist in
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