Echosounding in Estuaries: Lessons Learned from Operations and Data in Four Coastal Systems

The properties and dynamics of estuarine environments often exhibit strong spatial gradients and rapidly evolving structure that can be difficult to sample and resolve. High-frequency acoustic backscattering techniques spanning from 10 s to 100 s of kilohertz are well-suited for estuarine studies given that they can provide synoptic imaging, aid in discriminating between sources of acoustic backscattering, and in some cases quantify variables of interest. Here, we compare acoustic backscattering measurements obtained using vessel-based, towed, and underwater vehicle operations from the Columbia River, Connecticut River, James River, and Mobile Bay. These data are supported by other oceanographic measurements and circulation models. The sources of backscattering observed across these sites include bubbles, turbulent microstructure, stratification, suspended sediment, and biology. We focus on the quantification of and discrimination between areas dominated by unique processes, in addition to lessons learned regarding frequency selection and operations in estuarine environments.