Exceptionally preserved fossil biotas of the Burgess Shale and a handful of other similar Cambrian deposits provide rare but critical insights into the early diversification of animals. The extraordinary preservation of labile tissues in these geographically widespread but temporally restricted soft-bodied fossil assemblages has remained enigmatic since Walcott's initial discovery in 1909. Here...

[1] Hyporheic exchange and biogeochemical reactions are difficult to quantify because of the range in fluid-flow and sediment conditions inherent to streams, wetlands, and nearshore marine ecosystems. Field measurements of biogeochemical reactions in aquatic systems are impeded by the difficulty of measuring hyporheic flow simultaneously with chemical gradients in sediments. Simplified models o...

In the base grant project, Impact of Stream-Subsurface Exchange on Fine Sediment Dynamics in Streams funded through Drexel University, the objectives were to examine the complex interactions between high sediment loadings, downstream transport of suspended sediment, stream-subsurface exchange and siltation of stream beds. Results demonstrate that stream-subsurface exchange delivers suspended se...

Denaturing gradient gel electrophoresis (DGGE) was employed to resolve PCR-amplified nifH sequences from vegetated and unvegetated sediments from two oligotrophic seagrass bed sites on San Salvador Island, Bahamas, in order to assess diazotroph species composition. All DGGE profiles from these sites showed the same prominent bands. These bands were sequenced, yielding 67 different nifH sequence...

the river kabini which is tributary of cauvery drains through industrial area at nanjangud, karnataka. out of the sediment load carried by the river, 2micron the clay fraction was analyzed for total heavy metal contents and advanced statistical techniques such as cluster analysis and correlation matrix were applied in order to investigate the source of heavy metal concentration in the sediments...

PCB congener concentrations in the water column of a highly industrialized river catchment, the Aire/Calder, in N.E. England were determined weekly on a routine basis, and 2 hourly through selected high flow (flood) events. Bed, suspended and floodplain sediment PCB congener concentrations were also determined along transects of the rivers investigated. Weekly monitoring revealed that the sum o...

The bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) by the filter-feeding soft-shell clam Mya arenaria was evaluated at three sites near Boston (MA, USA) by assessing the chemical activities of those hydrophobic organic compounds (HOCs) in the sediment bed, water column, and organisms. Polyethylene samplers were deployed to measure the activities ...

[1] Shallow coastal lagoons are environments where a dynamic equilibrium exists between water quality and seagrass cover. Dense seagrass canopies limit the resuspension of bed sediments thereby creating a clearer water column and a positive feedback for seagrass growth. Positive feedbacks are often associated with the existence of bistable dynamics in ecosystems. For example, a bare and a seagr...

the sarghaye-sarnish watershed, with elongated shape and about 70.654 km2 area, is located in south of mashhad. sarghaye and sarnish rivers are the main ones in this watershed. the purpose of this study is to investigate grain size varietions based in sedimentary links and its relation to textural parameters such as sorting, skewness and kurtosis, as well as identification of sedimentary lithof...