Chyrene Moncada

INTRODUCTION Most organic matter synthesized by phytoplankton and macroalgae in the ocean is in the form of biopolymers, high molecular weight (HMW) compounds including polysaccharides and proteins (Biersmith & Benner, 1998; Hedges et al., 2002; Percival & Mcdowell, 1990). A considerable fraction of these biopolymers is processed and degraded by heterotrophic microbial communities, which respire the organic carbon back to CO2 (Azam & Malfatti, 2007).

Permeable sandy sediments cover at least half of the continental margins and are highly biogeochemically active because of their permeability. Due to the efficient sediment–water exchange of organics and electron acceptors, the mineralization processes occur at much higher rates than in silts or clays (Boudreau et al. 2001; Huettel et al. 2014).

Abstract Intertidal permeable sediments are crucial sites of organic matter remineralization. These sediments likely have a large capacity to produce reactive oxygen species (ROS) because of shifting oxic-anoxic interfaces and intense iron-sulfur cycling. Here, we show that high concentrations of the ROS hydrogen peroxide are present in intertidal sediments using microsensors, and chemiluminescent analysis on extracted porewater.