Local and climatic drivers of coral growth in Southwestern Atlantic turbid-zone reefs

Abstract

As tropical reefs decline, it is crucial to understand the role of coral growth drivers across different spatiotemporal scales. Here, we estimated growth variables (linear extension, bulk density, calcification) using skeletal band records (1926–2015) of two colonies of the Brazilian-endemic coral Mussismilia braziliensis collected at different distances from the shore (15 and 70 km offshore). We then explored the association between growth variables and local (temperature and turbidity) and larger-scale (climatic indices) potential drivers. For this task, we used Bayesian dynamic linear models, wavelet analyses, cross-correlations and Generalized Additive Models. Cross-shelf differences were found in the meso-architecture of colonies (coenosteum width, calice perimeter, and septa size) and in the associations between coral growth and potential drivers. With average smaller polyps and wider coenostea, the inshore colony grew faster and showed positive and negative associations with turbidity and water temperature, respectively, between 2003 and 2015. Interannual and multidecadal climatic oscillations also affected coral growth and indicated that inshore reefs may be more sensitive to large-scale climate variability. These findings highlight how anthropogenic forcing can affect corals that dwell near water quality/sedimentation tolerance thresholds.