The oldest sediment most recently recovered from the Arctic Ocean is a biosiliceous ooze nearly devoid of nonbiogenic particles and exhibiting small-scale color changes. Color variations are due to changes in iron and manganese content. These elements are probably of local hydrothermal origin, and the Mn precipitation may be bacteria-mediated. An iron silicate phase seems to form at the expense...

Unprecedented development along tropical shorelines is causing severe degradation of coral reefs primarily from increases in sedimentation. Sediment particles smother reef organisms and reduce light available for photosynthesis. Excessive sedmentation can adversely affect the structure and function of the coral reef ecosystem by altering both physical and biological processes. Mean sediment rat...

Implications for flow resistance and sediment transport Michael P. Lamb* , Fanny Brun and Brian M. Fuller Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125 *[email protected] Key Points: 1. Direct measurements of lift and drag forces were made on cobbles in steep flume experiments with shallow, rough flow over a planar bed 2. As flows shall...

Erosion and sedimentation are normal geologic processes which are usually accelerated by irrigating agricultural lands. Of the sediment in irrigation runoff, 70% was removed in a sedimentation pond. Removal efficiency correlated well with flow rate and sediment concentration. Pond design should provide maximum velocity reduction early in pending, allow adequate storage space for the larger part...

Dispersions of TiO2 particles are widely used as the main pigment in white inks for inkjet printers due to its brightness and high opacity. The TiO2 particles, however, have a high density, and so the possible fast settling of these particles can cause maintenance problems for the printers and lower the printing quality. We studied the effect of sodium dodecyl sulfate (SDS), a commonly used dis...

Plastic pellets are worldwide contaminants that accumulate in the ocean, especially in sandy beaches, where their historic standing-stock quantification relies on surface sediment samples. We demonstrated these particles present a three-dimensional instead of a simple along-across shore distribution, being found as deep as 2.0 m, with surface layers accounting for <10% of the total abundance in...

Suspended sediments produced from dredging activities, or added to the sediment budget via river runoff, are a concern for marine resource managers. Understanding the impact of suspended sediments on critical life history stages of keystone species like corals is fundamental to effective management of coastlines and reefs. Coral embryos (Acropora tenuis and A. millepora) and larvae (A. tenuis, ...

In shallow coastal ecosystems where most of the seafloor typically lies within the photic zone, benthic autotrophs dominate primary production and mediate nutrient cycling and sediment stability. Because of their different structure and metabolic rates, the 2 functional groups of benthic macrophytes (seagrasses, macroalgae) have distinct influences on benthic−pelagic coupling. Most research to ...

Arsenic (As) fractions in the sediments of seven lakes from East Plain Ecoregion and six lakes from Yungui Plateau Ecoregion, China, were investigated. Results indicated that the total As concentrations in sediment samples of lakes of the East Plain Lake Ecoregion are higher than those of Yungui Plateau Lake Ecoregion. Residual As is the main fraction in sediment samples of lakes from both ecor...

River ecosystems are influenced by contaminants in the water column, in the pore water and adsorbed to sediment particles. When exchange across the sediment-water interface (hyporheic exchange) is included in modeling, the mixing coefficient is often assumed to be constant with depth below the interface. Novel fiber-optic fluorometers have been developed and combined with a modified EROSIMESS s...