MPEG Animation of the Southern Portion of the Pulley Ridge Study Area

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米的水深范围内延伸近200公里。该淹没海岭位于墨西哥湾东南部的佛罗里达台地，距佛罗里达州塞布尔角以西约250公里处。这套障壁岛链形成于全新世海侵初期阶段，随后这些岛屿被淹没并被遗弃在佛罗里达台地的外缘附近。普利岭的南部区域栖息着具虫黄藻共生的造礁石珊瑚（zooxanthellate scleractinian corals）、绿藻、红藻与褐藻等大型藻类，以及深水区与典型浅水区热带鱼类的混合类群。该珊瑚礁群落所处水深异乎寻常，其分布范围与控制其分布的因素此前尚不明确。为解答这些问题，美国地质调查局（U.S. Geological Survey）海岸与海洋地质项目组联合南佛罗里达大学海洋科学系的科研人员，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（sidescan-sonar imagery）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框架。此外，研究团队还开展了载人潜水器下潜、遥控无人潜水器（ROV）断面勘测，以及海底照片与视频的断面采集工作，以识别珊瑚种类并绘制其分布情况。这套丰富的数据集已完成整合，初步数据分析表明，该珊瑚礁群并非依附于该海岭系统分布，而是呈现更为广泛的分布格局。目前尚不明确珊瑚礁的分布究竟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，相关问题仍是当前持续研究的课题。