Variability of cold‐water coral mounds in a high sediment input and tidal current regime, Straits of Florida
Variability of cold‐water coral mounds in a high sediment input and tidal current regime, Straits of Florida
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佛罗里达海峡高沉积物输入和潮流状况下冷水珊瑚丘的变化
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发表时间：
2012
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影响因子：
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通讯作者：
S. Purkis
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作者：
T. Correa;M. Grasmueck;G. Eberli;J. Reed;K. Verwer;S. Purkis
冷水珊瑚丘的形态和发育被认为主要受当前制度的控制。然而，这项研究揭示了普遍存在的底流方向与丘陵形态(即足迹形状和方向)以及水流强度和丘陵大小(即足迹面积和高度)之间的相关性。这些发现是基于对高分辨率地球物理数据集的定量分析，该数据集是由自主水下航行器从大巴哈马海岸坡脚的三个冷水珊瑚丘点收集的。这三个地点(总面积80 km2)平均有14个珊瑚丘 Km−2，表明大巴哈马岸坡是一个主要的珊瑚丘区。在所有三个地点，都可以在土丘表面观察到活的珊瑚群落，这证明了土丘的活跃生长。形态计量学分析表明，这些地点的土丘在高度(1~83 m)、面积(81~6 00 000 m2)、形状(土丘纵横比0·1：1)和方位(土丘最长轴线0~180°)上存在显著差异。自主水下航行器测量的海底水流数据描绘了大约每六小时一次的南北流动。这股海流的潮汐性质及其在逆转过程中的间歇性偏离被解释为有助于观测到的丘状复杂性。造成土丘形态测量变化的另一个因素是不同地点和不同地点之间的泥沙沉积速率不同。在大多数地方，沉积速率略落后于土丘的增长速度，导致土丘发展成大型结构。在沉积速率高于土丘生长速率的地方，沉积物部分或全部掩埋土丘。丘体的空间分布和排列也可能与重力物质沉积有关，如三维测深中的地貌特征(例如坡度破坏和线性地形高程)所表明的那样。总而言之，沉积速率、当前状况和下伏地形的变异性导致巴哈马大岸坡上珊瑚丘的分布、发展和形态具有极高的变异性。
Cold‐water coral mound morphology and development are thought to be controlled primarily by current regime. This study, however, reveals a general lack of correlation between prevailing bottom current direction and mound morphology (i.e. footprint shape and orientation), as well as current strength and mound size (i.e. footprint area and height). These findings are based on quantitative analyses of a high‐resolution geophysical dataset collected with an Autonomous Underwater Vehicle from three cold‐water coral mound sites at the toe of slope of Great Bahama Bank. The three sites (80 km2 total) have an average of 14 mounds km−2, indicating that the Great Bahama Bank slope is a major coral mound region. At all three sites living coral colonies are observed on the surface of the mounds, documenting active mound growth. Morphometric analysis shows that mounds at these sites vary significantly in height (1 to 83 m), area (81 to 6 00 000 m2), shape (mound aspect ratio 0·1 to 1) and orientation (mound longest axis 0 to 180°). The Autonomous Underwater Vehicle measured bottom current data depict a north–south flowing current that reverses approximately every six hours. The tidal nature of this current and its intermittent deviations during reversals are interpreted to contribute to the observed mound complexity. An additional factor contributing to the variability in mound morphometrics is the sediment deposition rate that varies among and within sites. At most locations sedimentation rate lags slightly behind mound growth rate, causing mounds to develop into large structures. Where sedimentation rates are higher than mound growth rates, sediment partially or completely buries mounds. The spatial distribution and alignment of mounds can also be related to gravity mass deposits, as indicated by geomorphological features (for example, slope failure and linear topographic highs) in the three‐dimensional bathymetry. In summary, variability in sedimentation rates, current regime and underlying topography produce extraordinarily high variability in the distribution, development and morphology of coral mounds on the Great Bahama Bank slope.