Comparing Low-Cost DIY and Research-Grade Hyperspectral Imaging as Coral Reef Monitoring Tools

Hyperspectral imagers (HSIs) enable the non-invasive, spectrally resolved quantification of pigments. HSIs have many environmental research applications, including the monitoring of threatened ecosystems like coral reefs and evaluating the success of coral restoration efforts. However, the high cost of commercial HSIs has restricted wider uptake of the technology. Here, we tested the efficacy of a low-cost (~USD 200) and open-source HSI device (400–1000 nm, spectral resolution of ~2 nm Full width at half maximum (FWHM)) in coral bleaching research. Specifically, we evaluated its ability to quantify the concentration of key photosynthetic pigments (chlorophyll a, chlorophyll c2, diadinoxanthin, peridinin, and total pigment content) by comparing it against a research-grade (~USD 70,000) commercial hyperspectral camera using coral fragments subjected to varying levels of thermal stress. The low-cost HSI acquired coral reflectance spectra that were similar to those acquired by the commercial hyperspectral camera, with a mean spectral angle of 11.38 ± 3.82°. However, the low-cost device was unable to resolve differences in spectral magnitude to the same accuracy as the commercial HSI and did not detect differences among coral fragments at different levels of thermal stress. Thus, the current HSI device prototype is better suited for classification and diagnostic applications in which spectral shape is of greater importance than spectral magnitude. Partial least squares regression models built from the reflectance spectra of each HSI instrument showed very similar yet moderate performance when predicting key coral pigments (commercial HSI mean Root Mean Square Error of Prediction (%RMSEP) = 22.8%, low-cost HSI = 22.12%). While the current design of the low-cost HSI device has limitations, it shows potential for coral research at a fraction of the cost of commercial alternatives. The continued development of low-cost HSI platforms is accelerating rapidly across a variety of fields in environmental research, and improved designs have the potential to enhance coral reef monitoring and restoration efforts globally.