The classification of deep water benthic habitats around Tutuila, American Samoa

Lundblad, Emily

Among the widespread efforts to preserve and restore coral reef ecosystems are strategies by the National Oceanic and Atmospheric Administration's (NOAA) Coral Reef Task Force (CRTF). A standing objective is to map all U.S. coral reefs and, more specifically, to characterize priority deep water (greater than 30 m depth) reef systems in the U.S. and Trust Territories by 2009. This project seeks to satisfy the CRTF's objective for the coral reef systems around Tutuila, American Samoa by using high-resolution multibeam bathymetry, acoustic backscatter imagery, and in situ visual ground-truthing in an integrated Geographic Information System (GIS) to distinguish existing benthic habitats in Fagatele Bay National Marine Sanctuary (FBNMS), on Taema Bank, and at Coconut Point (Figure 1). Three research questions are asked in this ongoing project: (1) What are the significant coral reef habitats and their associated major species around Tutuila, American Samoa? (2) Using multibeam bathymetry, backscatter, underwater photography, and videography, is the classification of IKONOS imagery for habitats down to 30 m appropriate for the classification of benthic habitats below 30 m depth? If not, how should the classification be altered? (3) Where are the ¿hot-spots¿ for biodiversity in Fagatele Bay National Marine Sanctuary, on Taema Bank, and at Coconut Point, and how are they being used by living marine resources? Traditional methods used for benthic habitat and coral reef mapping are not capable of mapping areas deeper than ~30 m. For example, conventional SCUBA diving does not allow safe descent beyond about 60 m (200 feet) (Pyle 2001). High-resolution satellite imagery provides discernable habitats down to only 30 m. Submersibles explore in excess of 150 m (500 feet), but such deep-sea surveys are extremely costly. The high cost of submersible operations generally leads researchers to explore more abyssal depths with them, leaving the coral communities between 60 m and 150 m virtually unexplored (Pyle 2001). The project methods, outlined below, for data collection and analysis were chosen to fill the gap of knowledge between shallow coral reefs (less than 30 m depth) and the abyssal environment (greater than 200 m depth). These methods are among the most innovative techniques for benthic habitat mapping. The approach of using acoustic imagery and supplemental survey data is still being explored, and this project will contribute to the understanding and confirmation of such methods for future mapping efforts. Coral reef researchers and scientists along with every person in connection with coastal areas have a vested interest in the resulting maps and methods. Upon the completion of this project, benthic habitat mapping tools will be made available through NOAA's Coastal Services Center.

The classification of deep water benthic habitats around Tutuila, American Samoa

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