Grab Analyses

Grab samples were collected using a Shipek grab, which was lowered to the bottom by a hydraulic winch. The grab contained a spring-loaded bucket, which was triggered when the device contacted the bottom. Upon contact, the bucket snapped closed, scooping sediments as it cut through the substrate. The sediments were then confined within the bucket as the device was lifted onto the boat deck.

Benthic Community Analysis

Grab samples were prepared in the field for benthic analyses by gently washing the sediments through a sieve and transferring the contents into a labeled cloth bag that was immersed and stored in a solution of formaldehyde and seawater. In the laboratory at Barry A. Vittor & Associates, Inc., Mobile, Alabama, organisms were separated from the remaining debris, identified, and counted. Identifications were to the lowest practical identification level (LPIL) when not to the species level.

Sediment Analysis

Sediment samples were placed in numbered bags and frozen until they could be analyzed for sediment texture and organic content. Tierra Consulting, Inc., Mobile, Alabama, performed laboratory analyses of sediment texture. Each sample was washed with deionized water, dried, and weighed. The coarse fraction (sand/silt) was separated from the fine fraction (clay) by sieving. Sediment texture of the coarse fractions was determined by passing the sediment through nested sieves, and the weight of the material collected on each sieve was recorded. A Particle Size Analyzer was used to analyze the fine fraction. Sediment texture descriptions followed the Wentworth classification as described in Folk (1974).

Total organic carbon (TOC) analyses were done at the USACE Waterways Experiment Station, Vicksburg, Mississippi, using a weight-loss-upon-ignition procedure (APHA 1992, method 5310A). After thoroughly mixing the thawed contents of the bag, two 10-gram samples of sediment were removed, dried, weighed, ignited at 500 degrees Celsius to burn off organic material, and reweighed. TOC was assumed to be the weight lost upon ignition and expressed as a percentage.

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