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.

滑轮脊（Pulley Ridge）是一系列沉没障壁岛系，分布于60至100米水深区间，延伸总长近200公里。该沉没脊体坐落于墨西哥湾东南部的佛罗里达台地（Florida Platform）之上，距佛罗里达州萨布尔角（Cape Sable）以西约250公里。该障壁岛链形成于全新世（Holocene）海侵的初始阶段，此后这些岛屿被淹没，最终被遗弃在佛罗里达台地的外缘区域。滑轮脊的南部区域栖息着虫黄藻共生造礁珊瑚（zooxanthellate scleractinian corals）、绿藻、红藻与褐藻等大型藻类（macro algae），以及兼具深水与典型浅水栖息习性的热带鱼类混合类群。该礁体群落所处的水深异乎寻常，其分布范围与控制其分布的核心因素此前均不明确。为解答上述疑问，来自美国地质调查局（U.S. Geological Survey）海岸与海洋地质项目的科研人员与南佛罗里达大学（University of South Florida）海洋科学系的学者合作，完成了滑轮脊最南端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）、侧扫声呐图像（sidescan-sonar imagery）与高分辨率地震反射剖面（high-resolution seismic-reflection profiling）技术，以明确该礁体赖以形成的地质基底；同时科研人员开展了载人深潜作业、遥控水下机器人（ROV）断面调查，以及海底照片与视频断面采集工作，以识别珊瑚类群并绘制其分布图谱。这套覆盖全面的数据集已完成整合，初步分析结果显示，该礁体并非与脊体系统绑定，而是分布范围更为广泛。目前尚不清楚礁体分布是受海洋环境条件控制，还是受障壁岛系统上覆基底的细微差异影响，这两点也将作为后续研究的核心课题。