Mapping and quantifying morphological parameters of eelgrass (Zostera marina) beds in eastern Cape Cod Bay, MA using an interferometric sonar system


Eelgrass plays an integral role as both a primary producer and an ecosystem engineer in the coastal environment. For this reason, a quantitative, high-resolution method of mapping is needed for ecosystem managers to monitor and protect these important habitat areas. An interferometric sonar system is ideal for mapping seagrass beds because it collects collocated backscatter and 3D bathymetric data simultaneously. The backscatter data can provide georeferenced acoustic imagery needed to document the location and spatial heterogeneity of eelgrass beds, and the bathymetry can provide volumetric measurements of the vegetation such as biomass. In this study, an interferometric sonar system was used to map and obtain certain measurable attributes of Zostera marina beds located in eastern Cape Cod Bay, Massachusetts. Preliminary data show that the top of the canopy is being consistently detected in the bathymetry over eelgrass beds as revealed by the backscatter. A distribution map was created using backscatter data and a statistically based backscatter-clustering program (QTC SwathView), which allowed the selection of a smaller area within which more in-depth sampling and measurements could be taken. The bathymetric data from this area was used to attempt calculations of seagrass density and biomass using surfacedifferencing calculations between digital terrain models of the detected canopy and the seafloor. Data collection for this project, including thorough groundtruthing via diver survey, benthic grab samples and towed video, will continue through the 2011 summer field season and into the fall. Overall, using an interferometric sonar system to map seagrass beds will make monitoring efforts for this important habitat more efficient and yield high quality data due to its ability to collect collocated bathymetric and backscatter data simultaneously.


Center for Coastal and Ocean Mapping

Publication Date


Journal Title

Coastal and Estuarine Research Federation Meeting, Daytona Beach, FL

Conference Date

Nov 6 - Nov 10, 2011

Document Type


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