For each site, a transect was filmed for approximately 200m with a field of view of 0.5m width (Figure 2). A total of 36 transects were selected for video analysis based on the clarity of the footage. Figure 2The towed flying array mounted with high definition video. 2.2. Field SamplingTransects Idelalisib mw were videoed in September 2010 from a 15m fishing trawler. The survey employed a method of filming the seabed using a High Definition (HD) video camera mounted on a towed ��flying array�� described by Sheehan et al. [6] (Figure 2). The flying array is an aluminium sled that floats above the seabed, which makes it suitable for sampling epibenthos over variable seabed relief. A piece of chain is used to control height above the seabed and a drop weight is attached to the tow rope to provide extra stability and minimize the effect of the pitch and roll of the boat.

The system comprised an HD video camera (Surveyor-HD-J12 colour zoom titanium camera, 6000m depth rated, 720p: resolution 1280 �� 720 (0.9megapixels)) positioned at a 45�� angle to the seabed, three LED lights, mounted either side and below the camera, and two green laser pointers. The two laser pointers were mounted on the frame either side of the camera at a fixed distance apart to allow calibration of the field of view during video analysis. The flying array was deployed over the stern of the boat and an umbilical connected the camera to the surface control unit allowing control of the camera focus, zoom, and light intensity [6]. The boat was carefully controlled and towed the camera slowly (approx. 0.

4 knots) over the seabed in up to 2.4 knots of tidal flow. This method is cost effective, allowing large areas to be surveyed rapidly (e.g., Stevens and Connolly, [14]). It also has minimal impact on the seabed, which is essential for studies where there is interest in documenting change over time as it avoids confounding the results with impacts resulting from the survey method. Brefeldin_A The use of HD video provides data of a high quality, and also a data archive for future use.2.3. Video AnalysisVideo footage was analysed in two stages. To enumerate the abundant/encrusting species, including sponges, hydroids and algae, frame grabs were extracted at 5s intervals and overlaid with a digital quadrat (3Dive Frame Extractor Software). Frames were viewed and those that were not clear of obstruction, well focused and had the lasers within acceptable margins of the screen, were deleted (see Sheehan et al., [6] for details).