Composite Sidescan-Sonar Mosaic, Pulley Ridge: UTM, Zone 17 Projection (COMPOSITE_UTM.TIF)

Pulley Ridge is a series of drowned barrier islands that extends almost 200 km in 60-100 m water depths. This drowned ridge is located on the Florida Platform in the southeastern Gulf of Mexico about 250 km west of Cape Sable, Florida. This barrier island chain formed during the initial stage of the Holocene marine transgression. These islands were then submerged and left abandoned near the outer edge of the Florida Platform. The southern portion of Pulley Ridge hosts zooxanthellate scleractinian corals, green, red and brown macro algae, and a mix of deep and typically shallow-water tropical fishes. This reef community is in unusually deep water, and its extent and the controls on its distribution were unknown. To address these questions scientists from the U.S. Geological Survey Coastal and Marine Geology Program in cooperation with scientists from the University of South Florida Department of Marine Sciences have completed a detailed mapping of the southernmost 35 km of Pulley Ridge. The area was mapped using multibeam bathymetry, sidescan-sonar imagery, and high-resolution seismic-reflection profiling to define the geologic framework on which the reef is established. Submersible dives, remotely operated vehicle (ROV) transects, and transects of bottom photographs and video were collected to identify the corals and to map their distribution. This extensive suite of data has been compiled and preliminary analysis of the data suggests that the reefs are not tied to the ridge system, but instead are more broadly distributed. Whether reef distribution is controlled by oceanographic conditions or by subtle differences in the substrate that overlies the barrier island system is unclear, and are topics of continued research.

普利岭（Pulley Ridge）是一系列淹没的障壁岛，在60至100米水深范围内延伸近200公里。该淹没脊坐落于墨西哥湾东南部的佛罗里达台地（Florida Platform），距佛罗里达州萨布尔角（Cape Sable）以西约250公里处。该障壁岛链形成于全新世海侵（Holocene marine transgression）初期阶段，此后这些岛屿被海水淹没，最终废弃于佛罗里达台地外缘附近。普利岭南部区域栖息着虫黄藻型石珊瑚（zooxanthellate scleractinian corals）、绿藻、红藻与褐藻等大型藻类，以及兼具深水与典型浅水特征的热带鱼类群落。该珊瑚礁群落在异常深的水域中发育，其分布范围与调控其分布的机制此前尚不明确。为解答上述问题，美国地质调查局（U.S. Geological Survey）海岸与海洋地质项目组与南佛罗里达大学海洋科学系的科研人员合作，完成了对普利岭最南端35公里区域的详细测绘工作。本次测绘采用多波束测深（multibeam bathymetry）、侧扫声呐影像与高分辨率地震反射剖面（high-resolution seismic-reflection profiling）技术，以明确珊瑚礁赖以发育的地质基底框架。研究团队还开展了载人潜水器下潜、遥控水下机器人（remotely operated vehicle，ROV）断面调查，以及海底照片与视频采集工作，以识别珊瑚种类并绘制其分布图谱。该套大规模数据已完成整合，初步分析结果显示，珊瑚礁并非局限于该脊系范围，而是呈现更为广泛的分布态势。目前尚不清楚珊瑚礁的分布究竟受海洋水文条件调控，还是受覆于障壁岛系统之上的基底细微差异影响，这也将成为后续研究的核心课题。