Spectral reflectance library of corals and benthic features in the Cook Islands (Aitutaki)

Spectral reflectances of 118 samples were recorded in situ. An Ocean Optics USB2000 spectrometer was deployed in a custom made underwater housing with a 0.5 m fibre-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 fibre 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 a spectralon panel mounted on the diver's wrist to measure incident ambient light, and six to eight 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 six to eight individual spectral reflectances of the target. If an individual target spectral reflectance was visually 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.