Modeling abundance, growth, and health of the solitary coral Scolymia wellsi (Mussidae) in turbid SW Atlantic coral reefs

Corals from the genus Scolymia have high-sediment-shifting capabilities and are generally associated with habitats with low light levels (shallow shaded/high-turbidity reefs and mesophotic reefs >30 m depth). Here, the spatio-temporal dynamics in abundance, growth, and health (i.e., proportion of bleached/dead tissue) of the solitary coral Scolymia wellsi was modeled in the Abrolhos Bank, eastern Brazil, using boosted regression trees. Models were built using a yearly time series (2006–2008) of digital images of fixed benthic areas (photo-quadrats) and fixed S. wellsi individuals ( n = 65). Samples were obtained in sites separated by up to 130 km and subjected to a wide range of biotic/abiotic conditions (as measured in situ and by remote sensing). Scolymia wellsi abundance was highest on inshore turbid reefs, although high nutrient availability (as inferred by the concentration of particulate organic carbon) and temperature were more important than turbidity (Kd 490 ) itself for explaining this latter pattern. Bleaching affected mainly larger (older) individuals inhabiting inshore reefs, where S. wellsi abundance was highest, possibly reflecting natural coral senescence and/or negative density-dependent effects. Coral growth declined with size and with increased contact with turf algae/cyanobacterial mats, these latter organisms well recognized as major competitors for benthic space and coral disease facilitators. Species-specific coral population studies exploring different spatial scales (reef scale and coral scale) and a wide range of biotic/abiotic conditions may provide important insights on the ecological processes operating at the reef community and ecosystem levels.