Classification of habitats and the general characterization of the seabed (benthic) is critical for supporting management, research, monitoring, and education within the national marine sanctuaries. Additionally, recent declines in various west coast groundfish stocks has created concern over establishing conservation efforts with an increasing focus being placed on examining important habitat linkages.

Because no single tool provides a comprehensive picture of the habitat, various sensors are being used to effectively map the benthic environment at the Olympic Coast national marine sanctuary. This mapping process involves integrating, analyzing, and interpreting several types of data at different spatial scales.

At the smallest spatial scale (<= 1:20,000) airborne LiDAR (light detection and ranging) is being investigated at the sanctuary for collecting bathymetry (depth) information in the nearshore zone. The basic principle of bathymetric LiDAR operation involves transmitting light sources from an instrument out to a target (ie seabed and sea surface) and measuring the time travel for these light sources to reflect back to the instrument, where time is ultimately transformed into a depth measurement. With airborne LiDAR bathymetry (ALB), the instrument is outfitted to a fixed-wing aircraft that travels at speeds much faster than possible through shipboard survey operations, thereby providing a more efficient means for acquiring data. Although ALB does permit mapping of the nearshore without exposing scientists to the dangers of the surf zone, it typically does not provide results at a comparably high resolution as that possible through shipboard acoustic survey methodologies. To find out more about LiDAR see the National Geodetic Survey Remote Sensing Division page on LiDAR.

At a medium sampling scale (1:1000-1:10,000), various types of shipboard hydroacoustic sensors are being used in the sanctuary to collect bathymetric and backscatter information. Rather than using light for measuring ranges, as with LiDAR, hydroacoustic sensors (or sonar) incorporate various properties of sound propagation into measuring physical properties of the seabed.

In general, multibeam echosounders are used to collect bathymetric information, and make it possible to create high resolution 3-dimensional renderings of the seabed. Bottom features such as sediment ridges, canyons, and rock outcrops are easily delineated with these sensors. Download a PDF summary illustrating an overview of Multibeam Survey Technique (544 kb)

Side-scan sonar is also used in the sanctuary to assist with identification of different seabed cover types (or substrates), such as mud, smooth sand, rippled sand, mixed sediment, or rocky features. Download a PDF summary illustrating an overview of Side-scan Sonar Survey Technique (244k)

At the largest spatial scale (1:10-1:1000) a variety of optical (i.e. video and cameras) and physical sampling techniques (i.e. sediment grab samples) allow scientists examine small sections of the seafloor at an even finer scale. These methods generally involve the use of specialized equipment, such as remotely operated vehicles (ROV) or towed camera bodies that are deployed from ships. These tools allow the gathering of more detailed information about a particular area of seafloor and can also be used to verify interpretations of the remotely sensed data that is collected through the aircraft and acoustic surveys. This highly detailed information is important for improving and expanding our knowledge and ability to accurately characterize and map the benthic habitats.

Video data collected from remotely-operated vehicles (ROV) or camera sleds, bathymetry data, sedimentary samples, and other sonar mapping techniques are being integrated to describe geological and biological aspects of habitat. Polygon features are then created and attributed with a hierarchical deep-water marine benthic classification scheme (Greene et al. 1999). The data can be used with geographic information system (GIS) software for display, query, and analysis. Go to the Data Catalog

Citation

Greene, H.G., M.M. Yoklavich, R.M. Starr, V.M. O'Connell, W.W. Wakefield, D.E. Sullivan, J.E. McRea, Jr., G.M. Cailliet. 1999. A classification scheme for deep seafloor habitats. Oceanologica Acta. 22(6):663

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