Spectral reflectance library of selected biotic and abiotic coral reef features in Glovers Reef, Belize

Underwater spectral reflectance was measured for selected biotic and abiotic coral reef features of Glovers Reef, Belize from March 6 - 10, 2005. Spectral reflectance's of 63 different benthic types were obtained in-situ. An Ocean Optics USB2000 spectrometer was deployed in an custom made underwater housing with a 0.5 m fiber-optic probe mounted next to an artificial light source. Spectral readings were collected with the probe (bear fibre) about 5 cm from the target to ensure that the target would fill the field of view of the fiber optic (FOV diameter ~4.4 cm), as well as to reduce the attenuating effect of the intermediate water (Roelfsema et al., 2006). Spectral readings included for one target included: 1 reading of the covered spectral fibre to correct for instrument noise, 1 reading of spectralon panel mounted on divers wrist to measure incident ambient light, and 8 readings of the target. Spectral reflectance was calculated for each target by first subtracting the instrument noise reading from each other reading. The corrected target readings were then divided by the corrected spectralon reading resulting in spectral reflectance of each target reading. An average target spectral reflectance was calculated by averaging the eight individual spectral reflectance's of the target. If an individual target spectral reflectance was visual considered an outlier, it was not included in the average spectral reflectance calculation. See Roelfsema at al. (2006) for additional info on the methodology of underwater spectra collection.

2005年3月6日至10日，针对伯利兹格洛弗礁（Glovers Reef）的选定生物与非生物珊瑚礁特征，开展了水下光谱反射率测量工作。本次研究原位获取了63种不同底栖类群的光谱反射率数据。实验采用部署于定制水下防护壳内的海洋光学（Ocean Optics）USB2000光谱仪，配套0.5米光纤探头，探头旁安装有人工光源。采集光谱读数时，将裸光纤探头置于距目标约5厘米处，一方面确保目标完全覆盖光纤视场（Field of View, FOV）直径约4.4厘米的范围，另一方面削弱中间水体的衰减效应（Roelfsema等，2006）。单目标的光谱读数包含三类：1组覆盖裸光纤的仪器噪声校正读数、1组佩戴于潜水员腕部的光谱白板（Spectralon panel）读数（用于测量入射环境光），以及8组目标物光谱读数。单目标的光谱反射率计算流程如下：首先从其余所有读数中扣除仪器噪声读数，随后将校正后的目标读数除以校正后的光谱白板读数，得到单条目标光谱反射率。通过对8条目标光谱反射率取平均，得到该目标的平均光谱反射率。若某条目标光谱反射率经目视判定为异常值，则将其排除在平均反射率计算之外。有关水下光谱采集方法的更多细节，可参考Roelfsema等（2006）的研究成果。