Knowledge of water clarity is an essential component of coral reef ecology. While qualitative trends are well known, there are currently few published records of spectral—varying as a (relatively) continuous function of wavelength—water optical properties for these systems. The purpose of this study is to quantify trends in the range and variability of the spectral diffuse attenuation coefficient ( K d ) in coral reef and adjacent waters. Using a Biospherical PRR-800, 199 vertical profiles of downwelling spectral irradiance were collected across the reefs and nearby optically deepwaters of Bermuda and Hawaii. A single spectral K d was calculated for each profile. Results reveal water types ranging from clear oceanic to turbid coastal, with Bermuda and Hawaii showing similar patterns. K d roughly correlates with reef geomorphic zonation, consistent with well-known reef water characteristics: (a) Suspended sediments are ubiquitous on coral reef flats and in lagoons, chiefly comprising calcium carbonate, which is effectively spectrally flat and has the effect of increasing the overall magnitude of K d ; (b) reefs generate large amounts of dissolved organic matter, which becomes apparent in some lagoonal K d ; and (c) the K d data exhibit little indication of chlorophyll, which is typically very low in the water column above reefs. These patterns appear reproducible when compared with prior data from French Polynesia. The depth of the 1% light level varies accordingly, approximately 30 m, 45 m, 75 m, and 105 m for lagoon, reef flat, fore reef, and offshore, respectively. The data presented here provide some insight into trends in the spatial context of reef geomorphology and lay the foundation for a more quantitative understanding of reef water clarity and color and their importance to reef ecology.

中文翻译：

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珊瑚礁水域光谱扩散衰减的趋势和变异性

水清澈度的知识是珊瑚礁生态学的重要组成部分。虽然定性趋势是众所周知的，但目前很少有已发表的光谱记录——作为（相对）连续的波长函数变化——这些系统的水光学特性。本研究的目的是量化珊瑚礁和邻近水域光谱扩散衰减系数 (K d ) 的范围和可变性的趋势。使用生物圈 PRR-800，在百慕大和夏威夷的珊瑚礁和附近的光学深水区收集了 199 条向下流光谱辐照度的垂直剖面。为每个轮廓计算单个光谱 K d 。结果显示水类型从清澈的海洋到浑浊的沿海，百慕大和夏威夷显示出类似的模式。K d 与礁体地貌分带大致相关，与众所周知的珊瑚礁水特征一致： (a) 悬浮沉积物在珊瑚礁滩和泻湖中无处不在，主要包括碳酸钙，其光谱平坦，具有增加 K d 整体幅度的效果；(b) 珊瑚礁产生大量溶解的有机物质，这在一些泻湖 K d 中变得明显；(c) K d 数据几乎没有显示叶绿素的迹象，叶绿素在珊瑚礁上方的水柱中通常非常低。与来自法属波利尼西亚的先前数据相比，这些模式似乎可重现。1% 光照水平的深度相应变化，泻湖、礁坪、前礁和近海分别约为 30 m、45 m、75 m 和 105 m。