Visual surveys of the seafloor were conducted during 2007-2012 using a towed camera sled to groundtruth maps produced during the CA Seafloor Mapping Project. The camera sled (approximately 1 m x 1 m x 2 m in size) was equipped with an altimeter and a pair of scaling lasers set 15 cm apart. The sled had multiple digital video cameras and a digital still camera. The camera sled was towed above the seafloor at a speed of approximately one knot along transects roughly one nautical mile in length. A biologist (Lisa Krigsman) annotated video footage at sea from some (but not all) of these ocean cruises, assisting the staff from USGS to ground-truth seafloor maps along the California coast.
The remainder of the video analysis was performed in the laboratory. Observations were made during 10-second intervals at the top of every minute. During the video review process, benthic macro-organisms were identified to the lowest possible taxa. Components of benthic habitats, including primary (greater than 50 percent coverage within the viewed area during the 10-second sample) and secondary (greater than 20 percent coverage) substratum types (for example, rock, sand, etc., based on Tissot and others, 2006), biotic coverage, and biotic-complexity (organisms with complex structure, height greater than a meter, or in high numbers), also were evaluated and recorded in each 10-second interval. Data acquired directly from the cruises were used to populate the fields for abiotic complexity based on small-scale variations in height of the seafloor surface and abiotic slope (measured as low, medium, or high degree of complexity). Still photographs taken along each camera sled line also were used to help identify the benthic macro-organisms.
Observations were recorded into a spreadsheet using the video program MediaMapper (Red Hen Systems, Inc.), and held in digital data files. Data were recorded on cruise name, time, latitude, longitude, and camera-line number, in addition to the variables mentioned above (such as primary and secondary habitat, abiotic slope, abiotic complexity, biotic coverage, biotic complexity, and associated benthic macro-organisms).
Tissot, B.N., Yoklavich, M.M., Love, M.S., York, K., and Amend, M., 2006, Benthic invertebrates that form habitat on deep banks off southern California, with special reference to deep sea coral: Fishery Bulletin, v. 104, p. 167–181.