Table 1.
Coral bleaching susceptibility across taxa during previous bleaching events in the central Saudi Arabian Red Sea. Data from 2015 and 2010 were obtained from Monroe et al. 2018 and Furby et al. 2013, respectively.
Fig 1.
Study sites in the central Saudi Arabian Red Sea.
(a) Map of the Red Sea showing the location of the study region (black polygon). (b) Study sites between Rabigh and Yanbu surveyed in 2020 and 2022. Basemap satellite images accessed from World Imagery ESRI Tile Layer. Credits: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community.
Table 2.
Possible colony bleaching scenario codes with conditions for 2020 and 2022. The scenarios observed in our study in the central Red Sea are in bold. The first letter of the pair in each code describes the condition of the colony in 2020, and the second letter describes the colony in 2022. For example, a colony with the code ‘BA’ refers to a colony that exhibited partial bleaching in 2020 and normal coloration in 2022. The colors indicate simplified categories that were used in binomial logistic regression analyses and correspond to the colors in Fig 5.
Fig 2.
Average (± standard deviation) sea surface temperature (°C) across the seven study sites in the central Saudi Arabian Red Sea for in situ measurements (light blue) and MODIS data (gray) [127].
In situ data were collected with a WTW meter in 2020 and with CTD OceanSeven in 2022. Bleaching thresholds described for the region by NOAA Coral Reef Watch and Monroe et al. [63] are indicated by dotted lines.
Fig 3.
Degree Heating Weeks (DHW) for the Red Sea from October 1998 to October 2022 (a-f).
The black polygon includes the study region in the central Red Sea between Rabigh and Yanbu. Red polygons highlight bleaching events in (a) October 1998, (b) September 2010, (c) October 2015, and (d) October 2020 [131]. Basemap satellite images accessed from World Imagery ESRI Tile Layer. Credits: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community.
Fig 4.
Observed coral bleaching scenarios in the central Saudi Arabian Red Sea from October 2020 to October 2022.
(a) Example orthomosaic of site Blank 2 in 2022. The green polygon indicates a 2.5 m2 area along the transect, where five colonies illustrate example scenarios in (b) 2020 and (c) 2022. The colors of the circles correspond to different fates in 2022: no change (light green), recovery (dark green), partial mortality (yellow), complete mortality with the skeleton present (orange), and complete mortality with the colony absent (red). (d) Sankey diagram summarizing all the observed coral bleaching scenarios in 2020 (left-hand side) and 2022 (right-hand side) for the 700 hard and soft coral colonies surveyed across the seven sites. Line thickness is proportional to the number of colonies that exhibited a particular scenario.
Fig 5.
Percent of coral colonies in the central Saudi Arabian Red Sea that were (a) bleached (blue) and not bleached (green) in 2020 and (b) exhibiting survival (green) and mortality (orange) in 2022.
Numbers above bars indicate significantly different groups based on binomial logistic regression analyses, and taxa without numbers above were statistically similar to the rest. Groups 1 and 2 had significantly different bleaching rates, and Groups 3, 4, 5, and 6 had significantly different mortality rates.
Fig 6.
Sankey diagrams summarizing all observed coral bleaching scenarios in the central Saudi Arabian Red Sea in 2020 (left-hand sides) and 2022 (right-hand sides) for (a–d) winner and (e–g) loser hard corals pooled across the seven study sites.
Line thickness is proportional to the number of colonies that exhibited a particular scenario. (h) NMDS plot ordinating coral taxa based on their proportion of bleaching scenarios exhibited.
Fig 7.
Sankey diagrams summarizing all observed coral bleaching scenarios in the central Saudi Arabian Red Sea in 2020 (left-hand sides) and 2022 (right-hand sides) for loser soft corals (a) Sclerophytum and (b) Xeniidae pooled across the seven study sites.
Line thickness is proportional to the number of colonies that exhibited a particular scenario.