Project Title: AKCSI Project 10: Geological substrate and potential habitat map for deep sea corals and sponges in the Gulf of Alaska margin and the Aleutian shelf and slope regions
Project Summary

This project seeks to construct a potential habitat map for deep-sea coral and sponge, based primarily on substrate, covering the depth range 50 – 1500 m or deeper.

Anticipated Management Application(s)

The distribution of deep-sea corals and sponges is strongly tied to substrate characteristics.  Geology and oceanography control the distribution of substrates, and therefore the geology and oceanography of the seabed can be used to construct potential habitat maps for these species. These maps may then be combined with other types of information, e.g., bycatch in bottom trawls, for predictive modeling of species distribution. 

Specific sites in the Alaska region have been surveyed and high-resolution habitat (substrate) maps have been constructed, such as at a portion of the Fairweather Ground and at the offshore Edgecumbe Volcanic Field. These maps have contributed to our understanding of ecological patterns. However, at a regional scale this data compilation and interpretation has not been done.

Existing seafloor data sets for the Gulf of Alaska and Aleutian Ridge are adequate for creation of a broad-scale substrate and potential deep-sea coral and sponge habitat map at a resolution of 1-5 km. Data sets identified for this purpose include multibeam seafloor surveys for bathymetry and backscatter, side-scan surveys, single beam profiles, NOAA smooth sheet records, sediment data, existing seafloor imagery, and geological studies of the seafloor and adjacent areas on land.  

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Project Title: AKCSI Project 10: Geological substrate and potential habitat map for deep sea corals and sponges in the Gulf of Alaska margin and the Aleutian shelf and slope regions
Methods/Approach

This is a laboratory-based project for data mining and interpretation. Compilation of sonar data will be done at the AFSC and compilation of surficial sediment data will be done at the USGS.  Metadata for seafloor video and still photo imagery in the relevant regions will be collected.  While the imagery itself will not be included in the georeferenced database, characteristic images may be identified and linked to it during this project. Because the investigators are based in different locations, it will be necessary to transfer working copies of the database and products to multiple locations.

A potential habitat map for deep-sea coral and sponge, based primarily on substrate, will be constructed covering the depth range 50 – 1500 m or deeper.  Because this map is intended as input for probabilistic distribution models, the target resolution is that of the models, i.e., 1-5 km.  The potential habitat map will be based on the compiled and georeferenced data layers; groundtruth from any available seafloor imagery; and geological interpretation that takes into account the bedrock and tectonic patterns, sediment type and depth, oceanography, and seafloor morphology at the highest resolution available.  Geologic interpretation is used to understand a suite of seabed characteristics in terms of the processes that create them, and to use this understanding to extrapolate seabed characteristics in poorly sampled areas.

The project will build on recent and ongoing efforts to compile georeferenced, quality-controlled bathymetric and seabed data in a usable format.  First, at the AFSC, Mark Zimmermann is leading an effort to extract bathymetric soundings from NOAA smooth sheets at the resolution of the original data and to compile this information into edited, datum-shifted GIS layers in a modern projection.  In regions lacking multibeam surveys, these soundings are the highest-resolution information available on the shape of the seafloor.  Current efforts cover the Aleutian Islands to 500m depth and the central and eastern Gulf of Alaska to 1000m depth, the lower depth boundaries for NMFS trawl surveys in these areas.  As part of the Alaska Deep-Sea Coral and Sponge Initiative, this work will be expanded to include the remaining target areas in the Gulf of Alaska.  We will start the substrate interpretation with GIS layers already compiled by Zimmermann, but, as his work is still incomplete, we will also refer to the bathymetry compilation from Steve Lewis (IT Specialist, NMFS Regional Office, Juneau) which is currently available and provides broad coverage for the study area. We will use these bathymetry data in construction of a potential habitat map. 

Second, the usSEABED project at the U.S. Geological Survey, led by Jane Reid, has constructed a quality-controlled, georeferenced database of marine sediment data for regions around the U.S.  Data sets are publicly available for the Gulf of Mexico, Caribbean, Atlantic and Pacific margins.  For the Alaska region, the usSEABED database contains data from all known sediment samples, but for many areas, the only available sediment data are from NOAA smooth sheets.  These groundtruth data will be important for construction of a substrate map and prediction of deep-sea coral and sponge distribution.  This project will include further work on digitizing sediment records from the smooth sheets, under Jane Reid’s supervision.

Because this will be the first effort to construct regional-scale potential habitat maps for Alaska, using this suite of data sets, large uncertainty exists around the time and effort required to cover the full area at the desired resolution.  Furthermore, some of the data sets are not yet in place and will be developed as part of this project.   Thus, in years 1 and 2, the bathymetry and sediment maps will be compiled for the entire Gulf of Alaska and Aleutian Islands regions (some of this work is currently underway and some already completed). During FY13, the initial analysis of substrate types will begin using data from the central Gulf of Alaska. This analysis will continue as more sediment and bathymetry data layers become available in FY13. It is unclear whether the geological interpretation for the entire state can be completed by FY14, but the underlying bathymetry and sediment data sets and development of protocols for completing a geologically interpreted layer for the Gulf of Alaska and Aleutian Islands will be finished at a target resolution of 1-5 km. 

An initial trial of the approach and the utility of the various data sets will be conducted for Albatross Bank and Portlock Bank, on the outer shelf near Kodiak Island.  These sites have similar bedrock geology but different current regimes and sediment cover, and accordingly they have very different habitat potential for deep-sea corals and sponges.  Extensive groundtruth information exists, primarily from sediment samples collected in the 1980s and submersible dives in 2007.  Albatross Bank has also been a focus of usSEABED data analysis and quality control.  The results of this trial will be used to guide subsequent work and estimate the total effort necessary to complete this task for the entire Gulf of Alaska and Aleutian Islands.

For consistency with existing seafloor habitat maps in the Alaska region, the classification scheme of Greene et al. will be used.  This classification is compatible with NOAA’s Coastal and Marine Ecological Classification Standard (CMECS), but is designed for the deeper environments that are the focus of the Alaska Deep Sea Coral and Sponge Initiative.  The classifications accommodate multiple substrate characteristics, but may easily be queried to show simple categories such as hard, mixed, or soft bottom.   

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Project Title: AKCSI Project 10: Geological substrate and potential habitat map for deep sea corals and sponges in the Gulf of Alaska margin and the Aleutian shelf and slope regions
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