The effect of allometric scaling in coral thermal microenvironments

• Published in: PloS one Vol. 12; no. 10; p. e0184214
• Main Authors: Ong, Robert H, King, Andrew J C, Kaandorp, Jaap A, Mullins, Benjamin J, Caley, M Julian
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12.10.2017; Public Library of Science (PLoS)
• Subjects: Allometry; Analysis; Animal behavior; Animals; Anthozoa; Anthozoa - physiology; Approximation; Biology and Life Sciences; Bleaching; Body size; Body temperature; Body Temperature Regulation - physiology; Civil engineering; Climate change; Colonies; Computational fluid dynamics; Computer simulation; Cooling rate; Coral reefs; Corals; Earth Sciences; Ecosystem; Energy budget; Environment; Environmental aspects; Environmental conditions; Evolution; Flow velocity; Fluid dynamics; Geometric constraints; Heat; Heating and cooling; Hot Temperature; Hydrodynamics; Irradiance; Marine ecology; Marine sciences; Mathematical analysis; Mathematical morphology; Mechanical engineering; Metabolism; Microenvironments; Models, Theoretical; Morphology; Mortality; Physical characteristics; Physical Sciences; Physiological aspects; Physiology; Scaling; Stresses; Temperature; Temperature effects; Temperature rise; Temperature rise effects; Thermal stress; Trends; Turbulence; Turbulent flow; Water flow; Australia; Perth Western Australia Australia
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0184214

A long-standing interest in marine science is in the degree to which environmental conditions of flow and irradiance, combined with optical, thermal and morphological characteristics of individual coral colonies, affects their sensitivity of thermal microenvironments and susceptibility to stress-induced bleaching within and/or among colonies. The physiological processes in Scleractinian corals tend to scale allometrically as a result of physical and geometric constraints on body size and shape. There is a direct relationship between scaling to thermal stress, thus, the relationship between allometric scaling and rates of heating and cooling in coral microenvironments is a subject of great interest. The primary aim of this study was to develop an approximation that predicts coral thermal microenvironments as a function of colony morphology (shape and size), light or irradiance, and flow velocity or regime. To do so, we provided intuitive interpretation of their energy budgets for both massive and branching colonies, and then quantified the heat-size exponent (b*) and allometric constant (m) using logarithmic linear regression. The data demonstrated a positive relationship between thermal rates and changes in irradiance, A/V ratio, and flow, with an interaction where turbulent regime had less influence on overall stress which may serve to ameliorate the effects of temperature rise compared to the laminar regime. These findings indicated that smaller corals have disproportionately higher stress, however they can reach thermal equilibrium quicker. Moreover, excellent agreements between the predicted and simulated microscale temperature values with no significant bias were observed for both the massive and branching colonies, indicating that the numerical approximation should be within the accuracy with which they could be measured. This study may assist in estimating the coral microscale temperature under known conditions of water flow and irradiance, in particular when examining the intra- and inter-colony variability found during periods of bleaching conditions.