Data Management Plan

This dataset contains a point shapefile with benthic habitat classifications of vertical relief, geomorphological structure, substrate, and biological cover for selected points along various Remotely Operated Vehicle (ROV) underwater video transects in the US Virgin Islands.NOAA's NOS/NCCOS/CCMA Biogeography Team, in collaboration with NOAA vessel Nancy Foster and territory, federal, and private sector partners, acquired Remotely Operated Vehicle (ROV) underwater video data in the US Virgin Islands from 2/18/04 to 3/5/04. Data was acquired with a towed Minibat and georeferenced and visually interpreted by CCMA employees. Data is in UTM zone 20, datum WGS84.

Process Steps:

• 2004-03-01 00:00:00 - Video Acquisition:The NOAA ship Nancy Foster was used to collect underwater video of benthic habitats from February 22 to March 1, 2004. The seven transects collected traversed 30.5 km and provided approximately 10 hrs of video. Video was acquired using a downward pointing camera mounted on a towed underwater platform called the MiniBat. The MiniBat provided limited control of depth and was used to position the camera as close to 2 m off the bottom as possible. The camera height off the bottom ranged from 0.5 m to 10 m and averaged approximately 3 m. This range of differences translated into a range of camera field of views from approximately 0.5 m X 0.5 m to 10 m X 10 m with an average of 3 m X 3 m. Ship velocity and correspondingly camera velocity was approximately 1 m/s. All video was taken during daylight hours to guarantee sufficient ambient light levels for visual interpretation. Video was recorded onto MiniDV tapes as it was acquired. Time and GPS position as recorded by Trimble GPS units were fed into the video using a Horita GPT-50 real time video titler. Time, ship velocity, tow cable length, and shipboard GPS coordinates were recorded along with the video. This data was used to estimate the MiniBats geographic position using a layback method. The layback method adjusts the ship's GPS position by the distance of the Minibat's relative position to the ship which is estimated by the tow cable length. Similar studies using this layback method have estimated positional accuracy is within 50 m (CRED, 2001).
• 2004-12-01 00:00:00 - Benthic Habitat InterpretationThe benthic habitat was characterized by visual interpretation of video images by two video interpreters. Video on the MiniDV tapes were displayed on a television using a digital video camera or miniDV cassette recorder. A transparent sheet demarcated with a 10 X 10 grid was fitted to the television screen to facilitate percent cover estimates. The video was paused every 10 seconds and the image was interpreted for three components of benthic habitat: structure, substrate and biological cover. Structure referred to the broad-scale habitat class within the entire field of view. Based on previous benthic habitat work in the area (Kendall et al., 2001) the structure designation was chosen from either 1) colonized pavement, 2) colonized pavement with sand channels, 3) sand, 4) scattered coral and rock in sand, or 5) other (with description). Substrate described the visible abiotic components of the benthic habitat. The four substrate classes, considered mutually exclusive and exhaustive were 1) consolidated material, 2) sand, 3) rubble (particles ~ 2-10 cm) and 4) cobble (particles < 10 cm). Substrate was measured to the nearest percent of the visible bottom. An estimate of rugosity was approximated by the vertical range of substrate in the field of view and was classified as either high (> 0.3 m) or low (<0.3 m).Biological cover referred to the biotic component of the seafloor and was divided among five mutually-exclusive categories differentiated by their size and shape. These were 1) sponge (Phylum Porifera), 2) soft coral (Subclass Octocorallia and subclass Ceriantipatharia), 3) hard coral (Subclass Hexacorallia), and 4) fleshy algae and 5) algae veneer. The sum of all cover categories provided an estimate of total colonization. If a biological cover component could not be unquestionably identified as one of the five cover categories it was only added to the total colonization estimate.Interpretation results were inputed into an Excel spreadsheet, with a single record for each sample point. These sample points and their associated benthic habitat attributes were then imported in ESRI ArcMap and converted into point shapefiles.

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