Benthic and substrate cover data derived from photo-transect surveys in Kubulau, Fiji, 2009-09-16 to 2009-09-21.

Abstract

Underwater georeferenced photo-transect survey was conducted on September 16-21, 2009 at different sections of the reef flat, reef crest and reef slope in Kubulau, Fiji. For this survey a snorkeler or diver swam over the bottom while taking photos of the benthos at a set height using a standard digital camera and towing a surface float GPS which was logging its track every five seconds. A standard digital compact camera was placed in an underwater housing and fitted with a 16 mm lens which provided a 1.0 m x 1.0 m footprint, at 0.5 m height above the benthos. Horizontal distance between photos was estimated by three fin kicks of the survey diver/snorkeler, which corresponded to a surface distance of approximately 2.0 - 4.0 m. The GPS was placed in a dry-bag and logged its position as it floated at the surface while being towed by the photographer. A total of 9,646 benthic photos were taken. A floating GPS setup connected to the swimmer/diver by a line enabled recording of coordinates of each benthic. Approximation of coordinates of each benthic photo was done based on the photo timestamp and GPS coordinate time stamp, using GPS Photo Link Software (http://www.geospatialexperts.com). Coordinates of each photo were interpolated by finding the gps coordinates that were logged at a set time before and after the photo was captured. Dominant benthic or substrate cover type was assigned to each photo by placing 1 points over each image using the Coral Point Count excel program (Kohler and Gill, 2006). Each point was then assigned a dominant cover type, which represented the dominant benthic/substrate feature in the whole photo. Using a hierarchical benthic cover scheme containing four first-level categories (Coral, Algae, Seagrass, Non-living) and thirty second-level categories that was derived from Knudby et al. 2011. Benthic cover composition summary of each photo scores was generated automatically using CPCE program. The resulting benthic cover data of each photo was linked to gps coordinates, saved as an ArcMap point shapefile, in Geographic Coordinate System WGS 1984.