The interaction between a fluid and a granular material plays a crucial role in a large class of phenomena such as river-bed morphology and river transport of sediments, aeolian sand dunes and ripples dynamics. Standard models involve deterministic continuum equations or, alternatively, Lattice Boltzmann and Lattice Gas Cellular Automata. We here introduce a toy-model to address the issue of ri...

Sulfide is a common product of marine anaerobic respiration, and a potent reactant biologically and geochemically. Here we demonstrate the impact on microbial communities with the removal of sulfide via electrochemical methods. The use of differential pulse voltammetry revealed that the oxidation of soluble sulfide was seen at +30 mV (vs. SHE) at all pH ranges tested (from pH = 4 to 8), while n...

Aggregations of Oreaster reticulatus (L.) in a large sand patch amid an offshore seagrass bed (Syringodium filiforme) off St. Croix (US Virgin Islands) were characterized by protracted fronts of high density (2-7 individuals m-2). Fronts mlgrated across the sand patch at approximately 7 m d-l and were refracted and deflected at the grassbed border. Intensive microphagous feeding effected a 2-fo...

Wintertime stratification on Oregon’s continental shelf often produces a near-bottom layer of dense fluid that acts as an internal waveguide on which nonlinear internal waves propagate. Shipboard profiling and bottom lander observations capture disturbances that exhibit properties of internal solitary waves, bores and gravity currents. Wave-like pulses are highly turbulent (instantaneous bed st...

Sound propagation in water-saturated granular sediments is known to depend on the sediment porosity, but few data in the literature address both the frequency and porosity dependency. To begin to address this deficiency, a fluidized bed technique was used to control the porosity of an artificial sediment composed of glass spheres of 265 μm diameter. Time-of-flight measurements and the Fourier p...

Fractional grain size and net amount of Be present was determined for 19 samples collected from the York River, Virginia, through the spring and summer. The data did not support the idea that there is a relationship between grain size and Be in the bed sediments. This noticeable lack of a trend could be a result of other factors controlling the adsorption of Be, such as salinity, pH and dynamic...

Faecal bacteria exist in both free-living and attached forms in estuarine waters. The deposition of sediments can take faecal bacteria out of the water column and to the bed. The sediments can subsequently be re-suspended to the water column, which can then lead to re-suspension of the faecal bacteria of the attached forms back to the water column. Therefore, the fate and transport of faecal ba...

Dissolved oxygen (DO) concentrations were quantified near the sediment–water interface to evaluate DO transfer to sediments in a laboratory recirculating flume and open channel under varying fluid-flow conditions. DO concentration fluctuations were observed within the diffusive sublayer, as defined by the time-averaged DO concentration gradient near the sediment–water interface. Evaluation of t...

The mat forming bacteria covering organic matter-enriched and anoxic marine sediments underlying a salmon farm in Southern Chile, were examined using 16S rRNA gene phylogenies. This mat was absent in the sea bed outside the direct influence of the farm (360 m outside fish cages). Based on nearly complete 16S rRNA gene sequences (~1500 bp), matforming filamentous cells were settled as the sulphu...

Sustaining good water quality in aquaculture ponds is vital. Without an aerator, the dissolved oxygen in ponds comes primarily from mass transfer at the water-ambient atmosphere interface. As sediment can seriously affect water quality, this study used indoor experiments to examine the nutrient (nitrogen and phosphorus) release mechanisms and fluxes from sediment in aquaculture ponds with movin...