Benthic Invertebrate Communities and Habitat Characterization of the Pourtalès Terrace, Florida with Analysis of the Deepwater Coral Habitat Areas of Particular Concern and the East Hump Marine Protected Area

摘要

The Pourtalès Terrace is a gently curved, narrow triangular platform that parallels the Florida Keys for 213 km running from southern Key Largo to between Key West and the Marquesas Keys. The main Terrace surface begins in 200 m and dips gently to approximately 450 m, where the Pourtalès Escarpment slopes steeply to the deep floor of the southern Straits of Florida. The Terrace platform exhibits a wide variety of Neogene-age geological features, including high-relief ledges, mounds, sinkholes and deep-water biogenic build-ups called bioherms. Previous research revealed dense and diverse benthic assemblages dominated by stylasterid hydrocorals, octocorals and sponges.Many Terrace features also represent popular, long-term fishing targets. Due to concerns about resource sustainability, (National Oceanic and Atmospheric Administration (NOAA) and the South Atlantic Fishery Management Council (SAFMC) included the Terrace in the Comprehensive Ecosystem-Based Amendment 1 (CE-BA 1, June 2010) that protects deep-water Coral Habitat Areas of Particular Concern (CHAPCs) along the southeastern U.S continental margin by prohibiting use of a variety of potentially damaging bottom fishing gear. NOAA also established the East Hump Marine Protected Area (MPA) as a Type II MPA, permanently closed to fishing for and possession of snapper and grouper species.To develop a more robust database on Terrace habitats and resources, a research cruise (September 2011) used ROV Kraken 2 to survey 14 sites both inside and outside the CHAPC and MPA for biological diversity, density, and distribution, with a focus on deep-sea coral and sponge assemblages. The surveys resulted in 58 h of videotape, 2,866 images, and collected 150 specimens of benthic invertebrates. All dive sites were mapped with multibeam sonar.This project used Coral Point Count with Excel extensions (CPCe)©, PRIMER 6.1.10 beta, JMP© statistical software, and Environmental Systems Research Institute (ESRI) ArcMap 10.3 Geographic Information Systems (GIS) to quantitatively analyze transect images and video from the ROV transects. This information was used to characterize dive sites in terms of benthic invertebrate faunal communities, depth, and topography; and compare results relative to protected versus unprotected sites.Of the 14 sites surveyed 10 were analyzed and split into 42 transects of approximately 30 m2 based on five depth and location bin classes. Each site was initially separated into habitat types based on qualitative geomorphologic features for statistical analysis (i.e., mound slope, mound wall, mound top, deep mound, valley, Lophelia mound, sinkhole), using methods established by Reed et al. (2011; 2014). In initial analysis, depth and location were found to be superior to geomorphology as an indicator of what was driving differences in communities among transects. As a result each transect was placed into one of five depth and location bin classes based on depth (m) of each image and location relating to CHAPC/MPA area borders: West 150-300 m (12 transects), North Central 150-250 m (14), Central 250-300 m (8), South 450-500m (5) and South 500-550 m (3).Distinct differences in communities of each depth and location bin class in relation to percent cover and organism density were apparent. Communities vary strongly among bins with some similarities: e.g., West 150-300, North-Central 150-250, and Central 250-300 all included Stylaster miniatus (Stylasteridae): South 450-500 and South 500-550 included Paramuricea sp. 3 among their most dominant species. Also similar species were found within similar depth ranges. Protection status (within CHAPC, CHAPC/MPA, or No Protection) did not affect differences in communities, suggesting protection regulations have not been implemented long enough to show significant differences between protected and unprotected sites. Several new geologic features were found e.g., the southernmost Lophelia pertusa coral mound in U.S. waters. Some important features were described that lie outside of CHAPC/MPA borders, suggesting new borders should be designated.Results showed a strong relationship between depth and location in forming deep-water communities, and that these factors could be used as proxies for creating habitat maps in unmapped areas. These results will also provide managers and scientists with a valuable baseline for assessing benthic invertebrate communities, their changes over time, and the effectiveness of protected areas on the Pourtalès Terrace.