Geographic Locations of Seabed Sediment Samples from the Stellwagen Bank National Marine Sanctuary Region (SB_SEDSAMPLES Shapefile)

The SEABed Observation and Sampling System (SEABOSS) was designed by the U.S. Geological Survey (USGS) for rapid and effective collection of seabed images and sediment samples in coastal regions. The observations from video and still cameras and the sediment data are used to explore the nature of the seafloor and, in conjunction with high-resolution geophysical data, to make interpretive maps of sedimentary environments and validate the acoustic remote sensing data. The SEABOSS is a simple system that can be deployed from both small and large surface vessels and operates in water depths up to 200 m. It incorporates two video cameras, a still camera, a depth sensor, and a modified Van Veen sediment sampler. The elements of the SEABOSS system used on Stellwagen Bank are housed within a stainless steel framework that measures 1.2 x 1.2 meters and weighs approximately136 kilograms overall. The frame has a stabilizer fin that orients the system as it drifts over the seabed. The height of the camera above the seabed (76 cm; 30 in) initially was determined by viewing an object hanging from the SEABOSS below the video camera; when the object touched the seabed, the camera height was appropriate for still photography. Later in the project, the camera height was determined by viewing a pattern of laser beams on the seabed. Two parallel lasers are set 20 cm apart on the SEABOSS frame and project onto the seabed for scale measurements. All of the system's elements are powered from the surface vessel through a conducting cable. Video displays include station number, water depth (from the depth sensor), and date, time, and geographic position (provided by a shipboard navigation system). During deployment, the camera system hangs directly below the side of the ship, and the recorded navigation data closely approximates the position of the camera system near the seabed. The ship is oriented so that wind and waves will not cause it to drift over the conducting cable attached to the SEABOSS. The winch operator uses a video feed from the system to maintain the camera at the proper height above the seabed and to avoid obstacles. The scientist uses the video to decide when to take a grab sample of seabed sediment.

Annual research cruises visited stations from 1993-2004 and took seabed sediment samples using the SEABOSS that was equipped with a modified Van Veen grab sampler, a still camera and video cameras. The modified Van Veen sediment grab sampler is located in the center of the SEABOSS frame. Before deployment, the grab's buckets (jaws) are opened by collapsing the extended arms to a near-horizontal position and locking them in place with two catches. The sampler operates passively to sample the seabed; it is not spring-loaded. To collect a sample, the SEABOSS is lowered to rest gently on the seabed, and the time is recorded for navigation purposes. When the cable is slack, the two locking catches automatically release by gravity. As the cable is retrieved, the grab sampler's arms are pulled upward closing the bucket around the sediment, and the SEABOSS is lifted off the seabed. Weight can be added to the SEABOSS frame, making it harder to lift off the seabed, which results in the grab buckets closing more tightly around the sediment. The SEABOSS is retrieved and set upon a wooden platform that keeps the sampler buckets and camera systems above the deck. The sampler's arms are maintained in the upright position by holding them or by maintaining tension on the cable; the doors on the upper sides of the buckets are opened; and the sediment is retrieved. For this project, the upper 2 cm of sediment, representing the surface of the seabed, was removed with a rectangular shovel 2-cm deep and stored in a plastic bag for analysis ashore. The remaining sediment was dumped into a tray located on the deck below the sampler, and the Van Veen grab was washed in preparation for the next site. Processing spanned the time period 1993 to 2004.

Grain size analyses of the 2628 sediment samples collected were performed at the USGS Woods Hole Coastal and Marine Science Center in Woods Hole, MA using a standard suite of analytical methods. Processing included the following steps: coarse fraction determined by sieve; fine fraction determined by Coulter Counter. Processing spanned the time period 1993 to 2004.

Station sediment sample analyses records were exported from the lab's database using Microsoft Excel 2007 (12.0.6504.5001) SP2 MSO (12.0.6425.1000). Some fields were deleted from the sediment lab analysis report that are unnecessary to our purpose. A mud weight percent column was added to the exported Excel spreadsheet since mud was found to be an important seabed characteristic in the Stellwagen region. Second, a quad column was added to organize the data into eighteen individual quadrangles. Third, Julian Day and time was complied in another column. Fourth an original Excel column, "Field ID" was reformatted as a text field for ease of import into ArcGIS. The reason being during the project, the station numbering scheme was not consistent, so that some station names used a decimal number format and some a number and letter format. For the purpose of this report, all sediment sample stations were renamed using the number and letter format for the station name where necessary. For example, station 3131.1 is now named 3131a. Lastly, headers were applied to the exported sediment sample Excel file. A check of the exported data was conducted against the lab's database to ensure consistency.

Using the sediment sample MS Excel spreadsheet of all seabed sediment samples taken in the 18 quadrangles, a shapefile was created in ESRI ArcCatalog 9.3.1.1850 by selecting the sediment sample excel table, right clicking on the table and selecting the "Create Feature Class" from "XY table" option in the drop-down menu. In the popup window that displays after selecting Create Feature Class, Longitude was applied to the "X Field" and Latitude was applied to the "Y Field". Next, clicking on "The Coordinate System of Input Coordinates" opens a second window where "Select a predefined coordinated system" was chosen. Navigate to Geographic Coordinate Systems North American Datum 1983, which will give the shapefile a projection in GCS NAD1983 (GRS 80). Lastly, specify an output for the shapefile.

Edits to the metadata were made to fix any errors that MP v 2.9.36 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). The link to the data in the Identification_Information section had to be fixed. Attempted to modify http to https where appropriate. Added a landing page link as the first link in the identification section. Moved the minimal source information provided to make it the first process step. Fixed the date format in the process steps. Updated the links to the field activities. Minor fixes to the attribute format for some attributes were needed. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent.

Added keywords section with USGS persistent identifier as theme keyword.