Hydroaccoustic pinging as a diver tool for underwater navigation in surveying Puget Sound Eelgrass (Zostera marina) densities

Senior thesis written for Oceanography 445

[author abstract] Advances in technology have led to a change from data limited, direct observations to much numerous, more remote data. Despite this trend direct observations are still an important source of information and invaluable means of ground truthing remote data collection. In oceanography the direct collection of data is much more difficult and is accomplished primarily using SCUBA. This study focused on the design and build of a low cost hydrophone-pinger system to aid in SCUBA navigation to fixed locations within two eelgrass (Zostera marina) beds off of San Juan Island, Washington. Study beds were different in size and shoot density was measured at each fixed location to examine the effects of bed size on density and subsequent colonization patterns. Three diver navigation methodologies to markers were timed and compared: the Hydrophone-pinger build, underwater compass navigation, and memory (dead reckoning). ANOVA results showed that the smaller bed had higher shoot density than the larger bed with a p value of 0.04, suggesting that beds colonized from a central radiating location rather than filling in patches. The piezo transducer element from the hydrophone-pinger ultimately led to a failure in the distance of sensitivity parameter objective.

University of Washington School of Oceanography