The Mini SEABOSS was designed specifically for the USGS Woods Hole Science Center's 26-foot research vessel Rafael. This system is equipped with two video cameras, a digital still camera, and a Van Veen grab sampler. This system, weighing approximately 200 lbs., can be used to depths up to 40 meters. The grab itself is raised and lowered with a 3/16-inch Aramid fiber winch-line with a breaking strength of 5,600 pounds. The davit is secured when the Mini SEABOSS is in the water. The electrical cable is on a spring-wound take-up reel with electrical slip rings that is mounted aft of the sampler. This arrangement protects the 0.38-in. multi-conductor cable and keeps the Mini SEABOSS correctly oriented with the boat. This multi-conductor cable enables communication between the ship's lab and the Mini SEABOSS system. The digital camera, a Minolta Dimage 7Hi, is mounted in a machined Delrin housing with a flat port and is set for 2560 x 1920 pixel images at the "fine" setting for compression. This allows the camera to be used for over 200 images with a 1 GB Compact Flash card without downloading. The system also has a 50 Watt/second flash unit powered by 8 AA batteries. Two battery-powered lasers are set 15 cm apart for scale measurements. The red laser dots can usually be seen in the photo depending on the bottom type and the distance to the sea floor. A third battery powered laser is positioned at an angle so that when it intersects the other lasers, the Mini SEABOSS is at the optimum height off the bottom for a still photograph (optimal height is generally 75 cm above the bottom). The camera is set to a manual focus and set to a default focus distance (50 cm) once the camera is powered up. The default focus distance is slightly less than the optimum height above the seafloor to account for optical distortion under water.
Video images were collected at 40 sample locations and digital photographs were collected at 36 of the 40 sample locations using the USGS Mini SEABOSS (Blackwood and Parolski, 2001). The sample locations were selected based on variation in the acoustic backscatter within the sidescan-sonar mosaic, with the objective of characterizing broad areas of different backscatter intensity. With the Mini SEABOSS deployed, the research vessel was allowed to drift with occasional power from the vessel to control drift direction. Video was collected over a total of 696 meters of lakefloor. Video drift position was derived from the HYPACK navigation files based on the start and end times of the drift. For some portions of the drift, there was no navigation, so the position was derived from the time and position in the video at 30-s intervals. Latitude and Longitude for sample locations 1 and 8 were derived solely from the video as HYPACK files were not saved to disk at these sample locations. Bottom photographs were generally taken immediately prior to collecting a sediment sample with the SEABOSS. A unique navigation position was not recorded when the bottom photographs were collected, however the time of photo collection was recorded.
Grab samples of the surficial sediment were collected at 39 sample locations, typically at the end of a drift. Sample location 26 was not sampled, as the sediment was too coarse (boulders). However, bottom photographs and video were collected. The upper 2 cm of sediment was scraped from the surface of sediment samples for texture analysis. At sample locations 1 and 7, two sub-samples were collected due to the apparent bi-modal nature of the lakefloor and sample. One sub-sample was collected from the upper 2 cm, and the 2nd sub-sample was collected from the base of the sample (2 to 10 cm depth). (Two individual sites were occupied at Station 1, whereas only one site was occupied at Station 7. The one sample collected at Station 7 was subsequently sub-sampled). Sediment samples were collected at locations with relatively fine-grained sediment (sand or mud). Samples were not collected in gravel or cobble areas where gravel prevented full closure of the sampler and resulted in a washed-out sample (sample location 26).
A total of 41 bottom samples were submitted for grain-size analysis. Grain-size analysis was performed at the USGS Sediment Laboratory at WHCMSC using methods described by Poppe and others (2005).
Note: A small bit of water entered the camera housing during survey operations. This is reflected as a blurred 'dot' on the bottom photographs. The camera remained operational and data collection continued despite the 'water mark'.
