The ecology of phototrophic corals in the lower photic zone remains poorly understood. Studies to date indicate that growth rates generally decrease as available light attenuates with depth and are very slow at depths > 40 m. Here, we provide detailed evidence for moderate growth for obligate zooxanthellate corals at extreme depths. Using reliable U–Th dating techniques, Leptoseris spp. from 70 to 110 m in Hawaii were determined to grow (linear extension) from 8.0 ± 3.0 to 24.6 ± 2.7 mm yr−1. Given the modest growth rates of other agariciids in well-lit shallow waters, these deep-water growth rates are unexpectedly high, suggest specialized physiology and help alter the traditional paradigm on photo-ecology in mesophotic coral ecosystems. The thin plate-like colonies of Leptoseris spp., which dominate the coral community in the lower photic zone throughout the Indo-Pacific, primarily grow radially and do not appear to appreciably thicken over time. In the lower photic zone, this growth strategy maximizes surface area with minimal calcification, thereby enabling Leptoseris to expand planar area more quickly than thickly calcified species. Photosynthetic and growth efficiencies may also be facilitated by the optical geometry of their skeletons, increased access to inorganic nutrients and cooler temperatures at depth. These robust growth rates have important implications on the recovery potential of MCE habitat in the event of disturbance.

中文翻译：

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低光区中的虫黄藻珊瑚生长速度适中

低光带中光养珊瑚的生态学仍然知之甚少。迄今为止的研究表明，随着可用光随着深度衰减，增长率通常会降低，并且在深度 > 40 m 时非常缓慢。在这里，我们提供了在极端深度的专性虫黄藻珊瑚适度生长的详细证据。使用可靠的 U-Th 测年技术，钩端螺旋体属。夏威夷的 70 到 110 m 被确定从 8.0 ± 3.0 增长（线性扩展）到 24.6 ± 2.7 mm yr-1。考虑到其他落叶螨在光线充足的浅水中生长速度适中，这些深水生长速度出乎意料地高，表明了专门的生理学，并有助于改变中光珊瑚生态系统中光生态学的传统范式。钩端螺旋体属的薄板状菌落，在整个印度太平洋低光区的珊瑚群落中占主导地位，主要呈放射状生长，随着时间的推移似乎不会明显增厚。在低光区，这种生长策略使表面积最大化，钙化最小，从而使钩端螺旋体能够比厚钙化物种更快地扩展平面区域。它们骨架的光学几何形状、更多的无机营养物质和更冷的深度温度也可能促进光合作用和生长效率。这些强劲的增长率对 MCE 栖息地在受到干扰时的恢复潜力具有重要意义。这种生长策略在最小钙化的情况下最大化表面积，从而使钩端螺旋体能够比厚钙化物种更快地扩大平面面积。它们骨架的光学几何形状、更多的无机营养物质和更冷的深度温度也可能促进光合作用和生长效率。这些强劲的增长率对 MCE 栖息地在受到干扰时的恢复潜力具有重要意义。这种生长策略在最小钙化的情况下最大化表面积，从而使钩端螺旋体能够比厚钙化物种更快地扩大平面面积。它们骨架的光学几何形状、更多的无机营养物质和更冷的深度温度也可能促进光合作用和生长效率。这些强劲的增长率对 MCE 栖息地在受到干扰时的恢复潜力具有重要意义。