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Habitat Mapping in Olympic Coast National Marine Sanctuary
Understanding the distribution and abundance of seafloor substrates can be useful for supporting
management, research, monitoring, and education within the national marine sanctuaries (Barr
2003). It is also useful for addressing concerns ranging from submarine cable engineering
projects to cultural resource identification and protection. Seabed characterization was
recently described as providing an important contribution to the sustainable management of
groundfish fisheries (Kassakian and Ostdahl 2005) and has been integral to the Pacific Coast
groundfish management (PFMC 2004) plan for the past several years. With amendment of the
Magnuson-Stevens Act of 1996, evaluation and mitigation of the effects of habitat loss or
degradation on their specific fishery was mandated, and essential fish habitat (EFH) became a
high priority management issue (see related article on 'What Do Deep Corals Have To Do With
Essential Fish Habitat').
In 2002, Olympic Coast National Marine Sanctuary (OCNMS) chose benthic habitat characterization
as a high priority for the site, and has since devoted money and staff effort toward
understanding the seafloor environment. Although several sources of historic sediment grab
sampling existed within the area (Venkatarathnam and McManus 1973; Nittrouer 1978; Sternberg
1986; Reid et al. 2001), it became evident that medium-scale acoustic geological sampling could
better provide an effective means for describing the marine habitat (Greene et al. 1999;
Valentine et al. 2003), and that technological innovations such as side scan sonar and multibeam
sonar could better assist with delineating ocean-floor substrates (Mitchell and Hughes Clark
1994; Auster et al. 1999; Cochrane and Lafferty 2002; Huvenne et al. 2002; Dartnell and Gardner
2004). Results from annual mapping offer a snapshot of current ground conditions, help guide
research and management activities and provide a baseline for assessing the impacts of various
threats to important habitat.
In 2004, 2005, and 2006, side scan sonar was used to map several regions of the seafloor in the
northern OCNMS in water depths ranging from 330 to 1,150 feet (Intelmann and Cochrane 2006). The
side scan sonarimages provide information about the hardness of the substrate by the reflected
acoustic signal received from the seafloor. Objects that appear white in the imagery indicate a
hard substrate and dark "shadows" seen near objects provide insight into their size (height above
the seafloor) and shape. While side scan sonar does provide a remote impression about the nature
of the seafloor, these indications need to be confirmed. Video, photographs or physical samples
are used to confirm or refine the interpretation of the side scan data. The two main types of
acoustic mapping used by the sanctuary are side scan sonar, to provide an understanding of the
substrate type such as sand, gravel, cobble, boulders or bedrock, and multibeam echosounding,
which provides information on depth, slope and roughness. The acoustic backscatter from
multibeam echosounding can also provide information on substrate type. We also use image
textural analysis to automate substrate classification, reducing the subjectivity in the
interpretations.
Side scan imagery successfully revealed areas of hard complex rocky seafloor that can provide
critical habitat for growth of deep-sea coral and sponge communities. Knowledge of these rocky
areas enabled our research team to find and document the presence of coral communities through
use of high-resolution videography at 14 of the 15 sites they dove on. The video obtained from a
remotely operated vehicle (ROV), bathymetry data, sedimentary grab samples, and the side scan
sonar imagery will be integrated to describe the geological and biological aspects of habitat for
these areas and polygon features will be created and attributed with a hierarchical deep-water
marine benthic classification scheme (Greene et al. 1999). The data can then be used with
geographic information system (GIS) software for display, query, and
analysis.
As we process the video and still photography, we will be interested to see what percent of
glacial erratics had coral or sponge cover versus those without, and whether factors such as
station depth, fishing intensity, and site location and bathymetry play a role. Along with our
fishery biologist colleagues, we will also be looking at fish densities in relation to substrate
habitat. We also will be consulting with marine geologists to find out more about the hard
substrate habitats observed, such as a large wall feature about 500 meters long and 100 meters
wide, riddled with thousands of burrows and the consolidated sediment benches observed on the
canyon walls.
References
Auster, P.J. Michalapoulos, R. Robertson, P.C. Valentine, K. Joy, and V. Cross. 1999. "Use of
acoustic methods for classification and monitoring of seafloor habitat complexity." In: Linking
Protected Areas With Working Landscapes. Sciense and Management of Protected Areas Association,
Wolfsville, Nova Scotia. N.W. Munro and J.H.M. Wilison (eds.) 186-197.
Barr, B. 2003. "US Geological Survey NOAA/National Marine Sanctuary Program÷s seabed mapping
initiative." 2002-2003 National Marine Sanctuary Annual Report.
Cochrane, G.R., and K.D. Lafferty. 2002. "Use of acoustic classification of sidescan sonar data
for mapping benthic habitat in the Northern Channel Islands, California." Continental Shelf
Research 22: 683-690.
Dartnell, P., and J.V. Gardner. 2004. "Predicting seafloor facies from multibeam bathymetry and
backscatter data." Photogrammetric Engineering & Remote Sensing. 70(9): 1081-1091.
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
Huvenne, V.A.I., Ph. Blondel, and J.P. Henriet. 2002. "Textural analyses of sidescan sonar
imagery from two mound provinces in the Porcupine Seabight." Marine Geology (189):323-341.
Intelmann, S.S. and G.R. Cochrane. 2006. "Benthic Habitat Mapping in the Olympic Coast National
Marine Sanctuary: Classification of side scan sonar data from survey HMPR-108-2002-01: Version
I." Marine Sanctuaries Conservation Series MSD-06-01. U.S. Department of Commerce, National
Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries, Silver Spring, MD.
13pp. http://www.sanctuaries.noaa.gov/science/
conservation/intelmann.html
Kassakian J. and M. Ostdahl. 2005. "Improving the sustainability of fisheries off Washington's
outer coast through benthic habitat mapping and characterization." Memorandum to Washington State
Policy Working Group. November 3, 2005. Magnuson-Stevens Act, 16 U.S.C. 1801 et seq.
Mitchell, N.C., and J.E. Hughes Clark. 1994. "Classification of seafloor geology using multibeam
sonar data from the Scotian shelf." Marine Geology 121: 143-160.
Nittrouer, C.A., 1978. "The process of detrital sediment accumulation in a continental shelf
environment: an examination of the Washington shelf." PhD Thesis, University of Washington,
Seattle, WA. 243p.
Pacific Fishery Management Council, 2004. Pacific coast groundfish fishery management plan for
the California, Oregon, and Washington groundfish fishery as amended through Amendment 17.
Pacific Fishery Management Council. Portland, OR. 145 pp.
Reid, J. A., Jenkins, C., Field, M. E., Gardner, J. V. and Box, C. E. 2001. USSEABED: defining
the surficial geology of the continental shelf through data integration and fuzzy set theory.
Geological Society of America Annual Meeting, Boston, MA. Abstracts with Programs 33:A106.
Sternberg, R.W. 1986. "Transport and accumulation of river-derived sediment on the Washington
continental shelf, USA." Journal of the Geological Society of London, v. 143, p. 945-956.
Valentine, P.C., G.R. Cochrane, and K.M. Scanlon. 2003. "Mapping the seabed and habitats in
National Marine Sanctuaries." Marine Technology Society. 37(1): 10-17.
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