Elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the Columbia River basin and the Washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments. The biomarkers include: an homologous series of long-chain n-alkanes derived from the surface waxes of higher plants; phenoli...

Coastal regions are potential zones for production of methane which could be governed by ecological/environmental differences or even sediment properties of a niche. In order to test the hypothesis that methanogenesis in most marine sediments could be driven more by proteins than by carbohydrates and lipid content of labile organic matter (LOM), incubation experiments were carried out with sedi...

Vertical and temporal variations of acid-volatile sulfides (AVS) and simultaneously extracted metals (SEM) in sediment can control biological impacts of metals. To assess the significance of these variations in field sediments, sediments spiked with cadmium, copper, lead, nickel, and zinc were deployed in Narragansett Bay for four months and recolonization by benthic organisms investigated. In ...

Methylation of mercury (Hg) is the crucial process that controls Hg biomagnification along the aquatic food chains. Aquatic sediments are of particular interest because they constitute an essential reservoir where inorganic divalent Hg (Hg II ) is methylated. Methylmercury (MeHg) concentrations in sediments mainly result from the balance between methylation and demethylation reactions, two oppo...

Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological processes that release or retain phosphorus in marine sediments. To gain more insight in the role of ...

Background: The present study was carried out to assess the seasonal variations, source apportionment, and risk assessment of heavy metals (Cd, Cr, Cu, Fe, Mn, Pb, and Zn) in the surface sediments from the Khanpur Lake, Pakistan. Methods: Composite samples are collected and processed to measure the concentrations of heavy metals in Ca(NO3)2 extract and acid extract of the sediments using flame ...

An increasing proportion of the Earth's surface is illuminated at night. In aquatic ecosystems, artificial light at night (ALAN) may influence microbial communities living in the sediments. These communities are highly diverse and play an important role in the global carbon cycle. We combined field and laboratory experiments using sediments from an agricultural drainage system to examine how AL...

Phosphorus (P) is a key nutrient for marine organisms. The only long-term removal pathway for P in the marine realm is burial in sediments. Iron (Fe) bound P accounts for a significant proportion of this burial at the global scale. In sediments underlying anoxic bottom waters, burial of Fe-bound P is generally assumed to be negligible because of reductive dissolution of Fe(III) (oxyhydr)oxides ...

The sources and historical deposition of 16 polycyclic aromatic hydrocarbons (PAHs) were investigated in dated sediment cores from the Pichavaram mangrove-estuarine complex. The ΣPAH flux in mangrove and estuarine sediments are 0.064 ± 0.031 μg/cm 2 /yr and 0.043 ± 0.020 μg/cm 2 /yr, respectively. The PAH flux in sediments increases up-core coinciding with rapid urbanization since the 1970s. Th...

Methylmercury has been thought to be produced predominantly by sulfate-reducing bacteria in anoxic sediments. Here we show that in circumneutral pH sediments (Clear Lake, CA) application of a specific inhibitor of sulfate-reducing bacteria at appropriate concentrations typically inhibited less than one-half of all anaerobic methylation of added divalent mercury. This suggests that one or more a...