Understanding variation in coral bleaching responses across environmental gradients, taxa, and colony sizes is important to predict changes in community composition with climate change. Our aim was to quantify how bleaching severity varied with water velocity, cross shelf gradient, degree heating weeks (DHWs), surface complexity, depth, taxa, and colony size during the 2022 mild bleaching event on the central Great Barrier Reef (GBR).
During March and April 2022, we surveyed > 7000m2 of reef substrate using photogrammetry, and scored the bleaching severity of more than 5000 coral colonies belonging to 13 taxa.
A series of generalised linear mixed effects models were fitted to quantify the relationship between bleaching severity and the key biological and environmental factors.
The data includes the following variables:
Reef- unique identification for each reef:
OCCH - Chicken Reef,
OCDA- Davies Reef,
OCLB- Little Broadhurst Reef,
PA -Palm Islands
Exposure- prevailing wind exposure:
BA- back (leeward, protected)
FR- front (windward, exposed)
FL- flank (intermediate exposure)
LA- lagoon
Zone - depth zone (S = shallow, 3-8 m; D = deep, 9-15 m)
Site - unique identification for each site (replicate sites per reef). Labelled as: Reef_Exposure/ReplicateNumber/Zone
Plot - unique identification for each 12x6m plot (four replicates per site). Labelled as: Site_PlotReplicate
TL_id - colony identification number (unique for each colony within plot)
Taxa - taxonomic idenfitication of each colony:
Adgt - Acropora digitate spp.,
Pmas - Porites massive spp.,
Pver - Pocillopora verrucosa,
Acor - Acropora corymbose spp.,
Lobo_sp - Lobophyllia spp.,
Menc- Montipora encrusting spp.,
Gspp- Goniastrea spp.,
Spis - Stylophora pistillata,
Shys- Seriatopora hystrix,
Abra- Acropora branching spp.,
Pdam - Pocillopora damicornis,
Plat - Platygyra spp.,
Atab - Acropora tabular spp.
Bleaching - bleaching score:
1 - no bleaching,
2 - 1-50% of the colony area was bleached,
3- 51-95% of the colony area was bleached,
4 - 96-100% of the colony area was bleached,
5 - partial mortality,
6- whole colony mortality.
lat - site latitude
long - site longitude
ubedmean = horizontal water velocity at the bed (m/s). Extracted from Callaghan et al 2023- https://espace.library.uq.edu.au/view/UQ:8246441 .
Date_2022 = date of the initial survey in January 2022
Date_bleaching = date of the bleaching survey in March - April 2022
DHW - degree heating weeks (°C-weeks). Extracted from NOAA's daily 5km satellite dervied estimates: https://coralreefwatch.noaa.gov/product/5km/index_5km_dhw.php.
rugosity_plane: rugosity at the site, extracted from the reconstructed 3D models
fd_fugosity_plane: fractal dimension at the site, extracted from the reconstructed 3D models
slope: the slope of the site (in degrees), extracted from the reconstructed 3D models
Cross_shelf: cross shelf position (inshore or offshore)
log_area : colony area in (m2) (log10)
