Mapping Submerged Aquatic Vegetation Using Single-beam Sonar: Application for Natural Resource Management in Washington State

Submerged aquatic vegetation (SAV) provides important ecological functions for many marine organisms including fish, invertebrates, and birds. As a major marine land manager for the state of Washington, the Department of Natural Resources (DNR) is charged with providing economic and recreational opportunities for the state’s residents, while protecting environmental resources for future generations. In order to manage protected marine vegetation, the DNR Aquatic Assessment Monitoring Team (AAMT) is developing remote sensing techniques using a single-beam sonar system for monitoring SAV and physical site characteristics. Acoustic methods are advantageous because they are capable of high-resolution tidal and sub-tidal habitat mapping. Also, due of the speed and ease of data collection, single-beam sonar allows for investigations at multiple spatial and temporal scales. Current study sites are located in nearshore habitats throughout the Puget Sound, Grays Harbor, and Willapa Bay. Geo-referenced data are collected and processed to determine vegetative distributions and habitat characteristics at each site. We will map the occurrence of SAV to determine patch characteristics and associate changes in distributions with physical site properties and water quality parameters. These results can inform management decisions for the placement of buffer zones around protected marine vegetation, and provide information on the magnitude and source of vegetative patch dynamics