Relating tensile strength to acoustic and biological properties of sediments along a mud-sand gradient in Mobile Bay, AL

Nearshore and estuarine sediments experience varying sediment inputs that create sharp gradients in sediment properties over fairly small vertical and horizontal distances. In this study, we explored the sand-mud transition in sediment cores collected from Mobile Bay, AL, with acoustic and geotechnical approaches. A custom built instrument was used to measure depth profiles of tensile strength at cm-scale resolution. These measurements were compared to acoustic sound speed and attenuation across a range of frequencies. Cores collected exhibited a horizontal gradient from sand to mud across the study area with a sandy layer on top of muddier sediment in most cores. This study explicitly examines the relationship between acoustic sound speed and attenuation and strength-related properties of sediments such as cohesion that can be measured in situ more easily than textural properties (e.g., porosity and grain size). We compare our data to in situ normal incidence measurements and portable free fall penetrometer data as well as infaunal community composition to better relate acoustic, geotechnical, and biological properties across a gradient of sediments.