Habitat Mapping in Belize's Barrier Reef Ecosystem

Authors: Colin Belby*, University of Wisconsin - La Crosse, Gretchen Gerrish, University of Wisconsin - La Crosse, Karl Radke, University of Wisconsin - La Crosse
Topics: Coastal and Marine, Field Methods, Applied Geography
Keywords: bathymetry, coral reef, sonar, Belize
Session Type: Poster
Day: 4/13/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

Accurate bathymetric mapping of reef ecosystems is required for the successful design and management of marine protected areas, and for understanding the physical and hydrodynamic needs of the organisms found within. Conventional side-scan and single-beam sonars are often used for mapping shallow marine habitats, but they have a steep learning curve and can be cost-prohibitive. Recreational grade side-scan fishfinders are relatively inexpensive and can be easily deployed from small vessels.The potential for using side-scan fishfinders for habitat mapping was evaluated in Belize’s South Water Caye Marine Reserve. Depths were mapped along 160 km of transects with a side-scan fishfinder and compared to those collected with a survey-grade sonar and an acoustic doppler current profiler (ADCP). Data from each unit produced similar bathymetric models, and the fishfinder had a mean depth difference of <10 cm when compared to the survey grade sonar. Substrate types, including sand, seagrass, and coral, are distinguishable on the fishfinder's georeferenced side-scan mosaics. Geotagged downward-facing GoPro images captured every 30 seconds along the transects helped validate the substrate types visible in the side-scan mosaics. Despite errors introduced by the low ocean currents relative to the boat speed, flow complexity at the barrier reef cuts is evident in the ADCP data. This study demonstrates that low-cost side-scan sonar units can be used to accurately map marine habitats. The spatial heterogeneity of the habitat properties mapped for this project will ultimately be analyzed to assess their impact on gene flow between bioluminescent ostracod populations.

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