Fine-scale Benthic Habitat Mapping

Science Center Objects

Both ATRIS configurations was deployed in Dry Tortugas National Park (DRTO) to fill information gaps in the spatial coverage of existing habitat maps.

Along-Track Reef Imaging System

ATRIS (Along-Track Reef Imaging System) equipped for deep water survey. (Public domain.)

Benthic community composition, topographic relief, areal extent, and temporal stability are critical factors that contribute to the value of a given marine habitat. With the emergence of Marine Protected Areas (MPAs) as a priority management tool for protecting coral reef resources, knowledge of these essential habitat components is paramount for designing effective strategies for the management of marine reserves. For many MPAs, detailed information on benthic habitat components is sparse or not available.

To facilitate benthic mapping over large areas, yet still acquire high resolution images, USGS scientists developed the Along-Track Reef Imaging System (ATRIS), which has both deep and shallow configurations. Deep ATRIS is a towed vehicle carrying a high-speed digital camera that is capable of reaching depths of 25 m. Shallow ATRIS is a boat-mounted system that utilizes the same digital camera attached to a movable pole. Both ATRIS configurations were deployed in Dry Tortugas National Park (DRTO) to fill information gaps in the spatial coverage of existing habitat maps.

A secondary effort was to investigate the habitat requirements of threatened and endangered sea turtles within the DRTO. Relatively little is known about the habitat requirements or movements of juvenile sea turtles of any species in their aquatic environment. Similarly, knowledge of the ecology and movements of adult sea turtles using remote U.S beaches, such as those in the Dry Tortugas, is also limited. Fine-scale habitat data collected with ATRIS was integrated with acoustic and satellite telemetry data from tagged green, hawksbill, and loggerhead sea turtles. The merged data sets allow scientists to identify and characterize specific habitats used for foraging, grazing, and transitting into and out of DRTO. This information is critical for developing Federal recovery plans for all three sea turtle species.

photo of coral and sponges

Deep ATRIS image of corals, sponges, and octocorals at a depth of 20 m (66 ft). (Credit: Dave Zawada, USGS. Public domain.)

photo of hardbottom habitat

Shallow ATRIS image from a hardbottom habitat dominated by octocorals. (Credit: Dave Zawada, USGS. Public domain.)

Capture-recapture and satellite- and acoustic-tracking techniques are used to determine the amount of time endangered sea turtles spend in and around the various habitats and zones of the Park. Blood and tissue samples are also collected to gain important diet and genetic material, which reveal connections between sea turtles in Dry Tortugas National Park and others sampled previously at various locations throughout south Florida and the Caribbean. Currently, Dry Tortugas loggerheads represent a genetically distinct subpopulation. Individual sea turtles in several life stages are present in the Tortugas, and work is underway to determine whether individuals of the three species are resident year-round or only use the Park periodically.

Kristen Hart holds a tagged sea turtle on the edge of a boat

Kristen Hart releasing a satellite-tagged hawksbill sea turtle, August 2008, Dry Tortugas National Park. (Credit: Keith Ludwig, USGS. Public domain.)

Juvenile green sea turtle

Juvenile green sea turtle, Dry Tortugas National Park, August 2008. (Credit: Kristen Hart, USGS. Public domain.)

 

green sea turtle

Deep ATRIS image of a green sea turtle (Chelonia mydas) grazing a seagrass bed at a depth of 10 m (33 ft).  (Credit: Dave Zawada, USGS. Public domain.)

sea turtle crawling to the ocean

Tagged female loggerhead sea turtle (Caretta caretta) returning to the sea, East Key, Dry Tortugas National Park, May 2009. (Credit: Kristen Hart, USGS. Public domain.)