Biogeographic Characterization of Benthic Composition within the Flower Garden Banks National Marine Sanctuary (2006 - 2007)

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A stratified random sampling design was employed to sample fish on the coral cap communities of the East and West Flower Garden Banks. The survey domain at each coral cap was designated as all areas shallower than 110 feet below sea level. Fine-scale (0.5 m) bathymetric data provided by the Flower Garden Banks National Marine Sanctuary was used to ascertain depths and slope. In 2006, the survey domain was partitioned into flat/gentle sloping (0-30 degrees) and steep sloping (>30 degrees) area and into East and West Banks. A continuous surface of slope estimates was produced for each Bank using a nearest neighbor filter on an aggregated resolution (5m X 5m) bathymetric grid derived from the original bathymetric dataset in ArcGIS (ESRI, 2006). The combination of two slope and two location groupings resulted in four strata. Survey sites were then randomly positioned in each stratum in ArcGIS (ESRI, 2006). Data were collected using 100m2 transects. Transects radiated from each point at a random bearing. In 2007, a sample frame consisting of mutually-exclusive 50m X 50m grid cells was produced and overlaid on each coral cap to exhaustively cover all diveable areas (i.e less than 110ft). Each grid cell was considered a sample unit and units were divided into six strata. Strata were defined using benthic habitat, location and depth. High (dominated by plate and head corals) and low relief (dominated by Madracis and rubble) coral categories were determined using a benthic habitat map generated by visual interpretation of multibeam data. Units were divided into deep (>105 ft) and shallow (less than 105 ft) groups based on the location of sampling unit centroids on multibeam bathymetric models. Location and high relief coral categories were divided by depth, low relief coral was not. Data were collected within 100m2 transects. Transects radiated from the centroid of each sample unit at a random bearing.Once in the field, the boat captain navigated to previously selected sites using a handheld GPS unit. On-site, divers were deployed and maintained contact with each other throughout the entire census. One diver was responsible for collecting data on benthic composition. This diver followed the belt-transect diver and recorded data on small-scale benthic habitat composition and structure within a 1m2 quadrat divided into 100 (10 x 10cm) squares at 4 separate positions along the transect. Each position was randomly chosen before entering the water such that there was one random point within every 6m interval along the transect. Percent cover was obtained as if looking at the quadrat in a two dimensional plane (i.e. a photograph) vs. three dimensions where percent cover could add up to greater than 100%. To estimate percent cover, the diver first positioned the quadrat at the chosen meter mark along a randomly chosen side of the transect tape. The remaining quadrats were placed on alternating sides of the transect at the last three locations. Data were collected on the following: 1) Logistic information - diver name, dive buddy, date, time of survey, site code, and meter numbers at which the quadrat is placed. 2) Habitat structure - In 2006, to characterize the benthic habitats of the dive site, the habitat diver first categorizes the habitat structure of the site (head corals, plate corals or Madracis-dominated). The habitat category to which a site is assigned should be made independently of the map so that in-situ data can be used for map validation. (continued)

(continued from above) In 2007, to characterize the benthic habitats of the dive site, the habitat diver identified the percentage of high- and low relief coral structure within a 25m radius circle of the centroid of the sampling unit. 3) Transect depth profile - the depth at each quadrat position. Depth is measured with a digital depth gauge to the nearest 1ft. 4) Abiotic footprint - defined as the percent cover (to the nearest 1%) of sand, rubble, hard bottom, fine sediments, and other non-living bottom types within a 1m2 quadrat. Rubble refers to rocks and coral fragments that are moveable; immovable rocks are considered hard bottom. The percent cover given as a part of the abiotic footprint should total 100%. In a hard coral area for example, despite the fact that living hard corals may provide 50% cover the underlying substrate is 100% hard substrate so this is what is recorded. The diver then estimates the height (in centimeters) of the hardbottom within each quadrat from the substrate to get a sense of bottom relief. 5) Biotic footprint - defined as the percent cover (to the nearest 0.1%) of macroalgae, live corals, sponges, gorgonians, and other biota (tunicates, anemones, zooanthids and hydroids) within a 1m2 quadrat. The remaining cover is recorded as bare substrate to bring the total to 100%. Again, the diver must use a planar view to estimate percent cover of the biota. Species covering less than 0.1% of the area are not recorded. Taxa are identified to the following levels: stony coral-species, algae-morphological group (macro, turf, crustose), sponge-morphological group, and gorgonians-morphological group. For stony corals, the approximate area covered by living coral tissue is recorded. Coral skeleton (without living tissue) is usually categorized as turf algae or uncolonized substrate. Data on the condition of coral colonies are also recorded. When coral is noticeably bleached, the entire colony is considered affected and is recorded to the nearest 0.1%. Diseased/dead coral refers to coral skeleton that has recently lost living tissue because of disease or damage, and has not yet been colonized by turf algae. Turf algae include a mix of short (less than 1cm high) algae that colonize dead coral substrate. 6) Maximum canopy height - for each soft biota type (e.g., gorgonians, sponges-except encrusting form, algae), maximum height is recorded to the nearest 1cm. 7) Abundance of queen conchs (Strombus gigas) - conch encountered within the 25m x 4m belt transect are enumerated. 8) Abundance of spiny lobsters (Pan ulirus argus) - a count of the total number of lobsters encountered within the 25m x 4m belt transect. 9) Abundance of long-spined urchin (Diadema antillarium) - a count of the total number of urchins encountered within the 25m x 4m belt transect. 10) Photos - 2 photos are taken in opposite directions at each location to document the surrounding habitat. Additional photos may be taken to document disease, bleaching or other events of note. 11) Marine debris - type of marine debris within the transect is noted. The size of the marine debris and area of habitat that it is affecting is also recorded along with a note identifying any flora or fauna that has colonized it. Data caveats: The mission in 2007 was aborted early due to Hurricane Humberto (September 2007). No sites were surveyed on the West Bank and only a subset of the sample of random sites selected on the East Bank were surveyed. Randomly selected sites on the East Bank were not sampled randomly. These data should not be aggregated to make synoptic population or community estimates for the East Bank. (end continuation)