Optical benthic imagery survey in a lacustrine basin using an autonomous underwater vehicle

Photographs are needed to map and characterize fine-scale benthic features and underwater habitats. Acoustic imaging methods lack sufficient resolution, colour and the ability to define many low reflectance features. Other optical methods such as LiDAR also lack spectral information important in the identification of biological features. Historically, photographs of benthic surfaces are collected over small areas or single line transects. Here techniques are developed and optimized to perform an extensive optical benthic survey remotely with an Autonomous Underwater Vehicle (AUV) over the area of a lacustrine basin. The technique was applied to surveys at Pavilion and Kelly Lake, B.C., and Lake Tahoe, CA, USA. The major challenges associated with the photographic surveys included overcoming AUV performance and stability issues associated with steep bathymetry, through-water light attenuation, limited light availability, and camera system limitations. Photographic imaging with a small AUV and CCD camera was optimized for the lacustrine environment, through manipulation of the non-optimal hardware. Benthic features were identified and mapped in Pavilion Lake, revealing profundal zonation patterns of previously unexplored epipelic flora.Applied Science, Faculty ofCivil Engineering, Department ofGraduat