Benthic habitat mapping at Glacier Bay, Alaska: Integrating physical structure and biohabitats

Investigators:  Hooge, Philip N. & Paul R. Carlson
Duration:   Start Date: 10/1/2000             End Date:  9/31/2004
Facility Contact: Hooge, Philip N. (Alaska Science Center - Biological Science Office)
Facility Name:
     Alaska Science Center - Biological Science Office
     Glacier Bay Field Station
     Phone: 907-697-2637
     Fax: 907-697-2654

USGS Rebreather Evaluation Program

PROJECT DESCRIPTION: 

By using a combination of multibeam echosounding surveys, sidescan sonar, and ground-truthing efforts, we will map the benthic biohabitats of Glacier Bay to provide crucial habitat data necessary to interpret and respond to multiple resource issues facing the National Park Service.   Multibeam technology will be used to obtain detailed bathymetry and reflectance data indicative of substrate type and tied to precise locational data.    Multibeam surveys will be conducted as part of a joint effort with the State of Alaska utilizing R/V Media  in order to reduce the survey and to foster the sharing of benthic mapping methodologies and data with the State of Alaska Department of Fish and Game.  The bathymetric data will be processed in real time aboard the vessel.  We anticipate complete coverage of all areas in the Bay not side-scanned in previous years, but will first prioritize prior study areas, areas closed immediately to commercial fishing, and areas of known species concentrations.  Bathymetric surveys will be conducted in 2001 and 2002. Sampling in 2002 is contingent on funding. 

We will use areas previously ground-truthed by extensive dive work during 1999 and  2000 to calibrate the initial interpretation of habitat polygons.  Contingent on funding for ground-truthing efforts, we will conduct ground-truthing work from R/V Alaskan Gyre to test the predictions of preliminary habitat maps.  Ground-truthing will make use of multiple techniques depending on water depth, tidal currents, and visibility.  Areas to 160 feet depth will be ground-truthed with diver transects and digital videography.  Deeper areas will imaged with digital videography from both an ROV (remotely operated vehicle) and a drop camera.  Precise locational data for diver and camera-based ground-truthing will be obtained with a combination of differential GPS and sonar triangulation.  We will also submit a NURP (National Undersea Research Program) proposal for the Delta submersible to conduct further ground-truthing of deep areas.  In addition, sediment sampling will be performed with Shipek and Van Veen bottom grab-samplers. 

Final interpretation of habitat polygons will occur after ground-truthing is complete.  We will synthesize bathymetry, reflectance, geo-referenced ground-truthing data, sediment samples, hard-rock geology maps of surrounding areas, and extensive data on oceanographic patterns obtained since 1991, and will use geological interpolation and biological evaluation to determine meaningful habitats. 

After production of the final habitat maps, the data will be correlated with marine species data obtained previously from sonic- and radio-tagged animals, sampling surveys, and direct observation. 

APPLICATION OF RESEARCH: 

The Omnibus Consolidated and Emergency Supplemental Appropriations Act for Fiscal Year 1999 immediately closed parts of Glacier Bay National Park to commercial fishing, directed other parts to close after the lifetime of qualifying fishermen, and left some parts open to continued commercial fishing.  Senator Murkowski and the Alaska State Legislature, however, are challenging this legislation, and Alaska’s Governor, Tony Knowles, filed a lawsuit in late November 1999 against the Department of Interior over jurisdiction of the marine waters of Glacier Bay.  The result of the current legislation is a patchwork of marine reserve areas of varying sizes, shapes, and habitat types based primarily on political rather than biological criteria, with no information on their potential to act as reserves for commercially fished species.  Efforts are currently underway to examine the movement patterns, diet, and distribution of critical species as well as the oceanographic patterns of the Bay.  However, these studies are significantly hampered by the paucity of data on marine benthic biohabitats.  A unique opportunity exists at Glacier Bay for cooperative efforts between the Geological Division and the Biological Resources Division to provide critical missing information that will be directly used to address a management issue under intense scrutiny at the national level. 

By combining the fisheries and oceanographic expertise of the Glacier Bay Field Station with the geological expertise of the Western Region Coastal and Marine Geology Team, we will produce base data layers on marine benthic biohabitats needed for determining the efficacy of marine reserves at Glacier Bay, including: 1) the distribution and abundance of benthic habitat types within Glacier Bay; 2) the distribution and abundance of previously identified critical habitat, such as crab spawning areas; and 3) the relationships of sonic-tagged halibut, Tanner, king and Dungeness crab with benthic habitat types. 

In addition to addressing marine reserve issues, our data will also be used to understand multiple geological questions, including: 1) the location, distribution, and pattern of ice gouging in Glacier Bay; 2) patterns of the rapid and extensive glacial retreat observed in Glacier Bay; and 3) patterns of marine sedimentation in a recently deglaciated habitat. 

Finally, our data will be used to address several Hazards issues.  Glacier Bay is the premier destination for Southeast Alaska’s large international cruise ship industry.  It is also a prized destination for many private and tour vessels, yet adequate bathymetric data do not exist for extensive portions of the Bay.  In addition, because of the rapid rates of sedimentation and uplift much of the bathymetric information that does exist is questionable.  For example, side-scan sonar work in 1998 revealed a previously unknown spire of rock that rises from 600 feet to a depth of 30 feet, of the surface, within one nautical mile of the Bay’s major cruise ship route.  In addition, Glacier Bay was the site of large tour vessel groundings in both 1993 and 1999.  Besides presenting danger to the physical safety of boat passengers and crew, uncharted navigational hazards could result in significant oil spills endangering marine species throughout the Bay. 

PROGRESS:  01/01/2001 

As part of a separate SIS ( 5001252, closed in 2000), four-years of prior field work have been conducted side-scanning portions of Glacier Bay and developing protocols and methods for ground-truthing and determining biohabitats. The first multibeam mapping trip will be conducted in Glacier Bay in June of 2001. 

PRODUCTS: 

1.)    Benthic Biohabitats of Glacier Bay CDRom Set:  This is the primary product of this study to be used by a wide range of ancillary studies and resource issues.  This will be the the sidescan sonar mosaics, multibeam reflectance echosounding mosaics, bathymetric model, Groundtruthing digital point files, and interpreted geological polygons, oceanographic summary polygons, and benthic biohabitat map. 

2.)    Benthic mapping efforts in Glacier Bay(1996-2000): Side-scan sonar mosaics, ground truthing, and benthic habitat maps of selected areas in Glacier Bay. : This is a report of the efforts prior to the multibeam echosounding profiles. 

3.)    Benthic mapping efforts in Glacier Bay final report:  The final report detailing the methodology and results of multibeam echosounding and ground truthing efforts to map benthic biohabitats throughout Glacier Bay. This report will contrast the prior efforts utilizing just side-scan sonar with the combined methodologies.