A Comparison of the Diagnostic Accuracy of in-situ and Digital Image-Based Assessments of Coral Health and Disease

Last modified: 
May 29, 2020 - 10:45am
Type: Journal Article
Year of publication: 2020
Date published: 05/2020
Authors: John Burns, Grady Weyenberg, Travis Mandel, Sofia Ferreira, Drew Gotshalk, Chad Kinoshita, Micah Marshall, Nicholas Del Moral, Shane Murphy, Kailey Pascoe, Alexandra Runyan, Alexander Spengler, Brittany Wells, Danielle Wilde, Roberto Pelayo
Journal title: Frontiers in Marine Science
Volume: 7

The prevalence of coral disease is steadily increasing throughout the global ocean, and there is a growing need for efficient methods for detecting and monitoring coral health. At present, coral health assessments are primarily conducted using in-situ surveys, which record visual observations of disease in the field. Recent technological advancements allow researchers to instead collect high-resolution imagery of benthic habitats, and these images can be used in conjunction with digital tools to assess the health of coral colonies at a later time. However, little is known about the relative efficacy or diagnostic accuracy of these two approaches. This study contrasts the diagnostic accuracy of in-situ and digital methodologies for detecting diseases and adverse health conditions affecting corals. Multiple 1 m2 plots are surveyed on coral reefs located on both the windward and leeward side of Hawaii Island. For each plot, an in-situ visual analysis of coral health is conducted by a diver and images are collected and rendered into a high-resolution orthomosaic for subsequent digital analysis. Both methods assess the same coral colonies, resulting in paired health diagnoses for multiple health conditions. Lacking a gold-standard diagnosis of health conditions, a latent class model is used to estimate the sensitivity (true positive rate) and specificity (true negative rate) of both methods. We find that in-situ assessments of coral health have a higher sensitivity and lower specificity in detecting health conditions when compared to digital analyses based on orthomosaics. However, the effect size is relatively modest, indicating that while the in-situ method provides a more sensitive diagnostic approach, the techniques are of comparable accuracy, and should both be considered viable methods of characterizing and monitoring coral health.

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