Fig 1.
Coral discoloration detection using image analysis.
Examples of coral discoloration from Palmyra and their respective causes, resulting from (a) elevated seawater temperatures leading to thermal stress (otherwise known as bleaching) or naturally through (b) predation, (c) disease, or (d) growth. An image digitization process for detecting coral discoloration using grayscale (see supporting information) is shown in (e).
Fig 2.
Coral community composition by habitat and year.
Non-metric multidimensional scaling (NMDS) based on Bray-Curtis dissimilarity measures of coral community composition by species (in terms of square-root-transformed percent cover data) within each quadrat. Points are color-coded by habitat, with shapes representing different time points in either 2009 or 2019.
Fig 3.
Live planar areas of coral colonies by species over time.
Discolored and normally-pigmented live planar areas (mean ± SE) for individual coral colonies over time from both habitats, by species. Colony sample sizes are shown on the top left.
Fig 4.
Coral discoloration by habitat and year.
Percent discoloration (mean ± SE) by habitat (Fore Reef in orange, Reef Terrace in red) corresponding to the percentile-based Degree Heating Weeks (DHW) at each observation time point, labeled by year. Pearson’s correlation coefficient is shown on the right of the trendlines.
Fig 5.
Discoloration comparison for the same coral colonies across two thermal anomalies.
Scatterplots comparing percent discoloration in 2009 and 2015 for individual coral colonies by species. Each point represents a coral colony, color-coded by habitat with orange for Fore Reef and red for Reef Terrace. The diagonal dashed line indicates the 1:1 slope in which colonies were discolored by the same amount in both years. If a colony was more discolored in 2015 than 2009, it would fall on the left of the diagonal line and if a colony was less discolored in 2015 than 2009 it would fall to the right of the line. Gray points are colonies that succumbed to whole-colony mortality by 2015.
Table 1.
Changes in coral colony live planar areas following thermal anomalies.
Table 2.
Coral colony fate based on discoloration severity.