Carbonate coral sands are an integral part of the carbon and nutrient cycles in subtropical and tropical coastal environments. Recent studies indicate that nearshore carbonate sands may be hotspots for organic matter production and respiration, but the processes and their controls are poorly understood due to a lack of noninvasive in situ measurements. We deployed a new triple‐sensor aquatic eddy covariance instrument to quant...

Gulf of Mexico (GOM) ecosystems are interconnected by numerous physical and biological processes. After the Deepwater Horizon (DWH) disaster, these ecological processes facilitated dispersal of oil-spill toxicants or were damaged and broken. A considerable portion of post-DWH research focused on higher levels of biological organization (i.e., populations, communities, and ecosystems) spanning at least four environments (onshor...

Summary Microbial communities ultimately control the fate of petroleum hydrocarbons (PHCs) that enter the natural environment, but the interactions of microbes with PHCs and the environment are highly complex and poorly understood. Genome‐resolved metagenomics can help unravel these complex interactions. However, the lack of a comprehensive database that integrates existing genomic/metagenomic data from oil environments with p...

Summary The temperature dependency of denitrification and anaerobic ammonium oxidation (anammox) rates from A rctic fjord sediments was investigated in a temperature gradient block incubator for temperatures ranging from −1 to 40°C. Community structure in intact sediments and slurry incubations was determined using Illumina SSU rRNA gene sequencing. The optimal temperature ( T opt ) for denitrification was 25–27°C, whereas ana...

Pore‐water exchange caused by ebullition of small oxygen bubbles produced by microalgae in the surface layer of sand sediment at St. Joseph Bay (SJB), Gulf of Mexico, was contrasted with ebullition of larger methane bubbles generated by archaea in deeper layers of sub‐littoral sands at Hel Peninsula (HEL), Baltic Sea. At SJB, ebullition of O 2 ‐enriched bubbles in August 2011 averaged 225 ± 132 mL m −2 d −1 , and at a mean bub...

Based on noninvasive eddy correlation measurements at a marine and a freshwater site, this study documents the control that current flow and light have on sediment‐water oxygen fluxes in permeable sediments. The marine sediment was exposed to tidal‐driven current and light, and the oxygen flux varied from night to day between −29 and 78 mmol m −2 d −1 . A fitting model, assuming a linear increase in oxygen respiration with cur...

We report substantial tidal fluxes of dissolved black carbon (DBC) in a fire‐affected marsh in the northern Gulf of Mexico. DBC was molecularly determined as benzenepolycarboxylic acids in a tidal creek, adjacent rivers, and the coastal ocean. Supported by stable carbon isotope and in situ fluorescence measurements, three sources of dissolved organic carbon (DOC) were identified that mixed conservatively in the coastal system:...

We tested the hypothesis that dissolved organic carbon (DOC) is degraded when filtered through permeable shelf sediments. In a laboratory flume experiment the concave shape of DOC profiles observed in the upper 10 cm of Gulf of Mexico sublittoral sands was reproduced by the combination of DOC filtration and production in the sediment surface layer and mineralization and adsorption in the subsurface layer. Six percent to 14% of...

We examined nitrogen cycling over a 1‐yr period in shallow, sandy sediments at two contrasting sites near a barrier island in the northeastern Gulf of Mexico, and we provide here the direct determination of dinitrogen gas (N 2 ) production at ambient nitrate concentrations in permeable marine sediments. Nitrogen‐stable isotope tracer techniques were used to quantify N 2 ‐production rates and pathways in sediment cores and slur...

We conducted four field campaigns to evaluate benthic O 2 consumption and the effect of advective pore‐water flow in nearshore permeable sediments in the North Sea and Baltic Sea. Advective pore‐water transport had a marked effect on the benthic exchange of O 2 and TCO 2 in benthic chamber incubations, with the rates of exchange increasing by a factor of up to 2.5 when imposing flushing rates of 100‐300 L m −2 d −1 , compared...

Oxygen distribution and benthic mineralization rates were investigated in a permeable intertidal sand flat (permeability: 3.9 x 10 ‐11 m 2 ) in a transect from the low toward the high waterline. At all stations, oxygen penetrated several millimeters to centimeters into the sediments during inundation because of pore‐water advection. The wave‐ and current‐driven deep oxygen penetration caused high oxygen consumption rates (OCRs...

The effects of advective pore water exchange driven by shallow water waves on the oxygen distribution in a permeable (k = 3.3 x 10 −12 to 4.9 x 10 −11 m 2 ) natural sediment were studied with a planar oxygen optode in a wave tank. Our experiments demonstrate that pore water flow driven by the interaction of sediment topography and oscillating boundary flow changes the spatial and temporal oxygen distribution in the upper sedim...

Even though the O 2 concentration in the diffusive boundary layer overlying natural aquatic sediments usually varies over time, microprofiles with little or no error bars are abundant in the literature. These temporal concentration fluctuations are not accounted for in the conceptual models used to describe the diffusive boundary layer, and their effects on phenomena investigated through microprofile measurements are unclear....

The effects of surface gravity waves on pore‐water release from permeable sediment (k = 1.3–1.8 × 10 −11 m 2 ) in shallow water were studied in a wave tank. Our tracer experiments demonstrated that shallow‐water waves can increase fluid exchange between sandy sediment and overlying water 50‐fold, relative to the exchange by molecular diffusion. The main driving force for this increased exchange are the pressure gradients gener...

Advective transport of artificial and natural particles into permeable sediments was demonstrated in situ by field experiments in an intertidal Wadden Sea sandflat. Using dyed sediment, advective interfacial solute exchange was shown to reach down at least 1.5 cm below surface. Particle depth distributions depended on sediment permeability and particle size. Sandy sediments were found to efficiently trap particulate material....

In flume and field experiments we demonstrate that interfacial water flows, generated when bottom currents interact with sea bed topography, provide a fast and efficient pathway for the transport of suspended phytoplankton into subsurface layers of permeable sandy sediments. The advective transport, associated with small mounds and ripples as commonly found on shelf sediments, increased penetration depth of unicellular algae (...