Shifts in reef coral competitive dominance under physical climate change

Two important changes occurring in oceans today are the increase in sea surface temperature and the decrease of carbonate saturation state. Warm ocean surface water fuels storms, and storms are well-known to be a major force that structures coral reef communities via cycles of destruction followed by reef recovery. Evidence suggests that the intensity of storms has significantly increased over the past 25 years and is expected to show a further increase as the atmospheric temperature rises. Ocean acidification reduces carbonate material production, slowing growth and decreasing material density of both the corals themselves and the reef structure they rely on for attachment and therefore increasing susceptibility to erosion. A mechanistic basis is used in this study for projecting how climate changes are likely to alter coral population dynamics and more particularly the competition dominance in coral reef. I use Integral Projection Model with a density dependent growth and recruitment where these vital parameters depend on the fraction of free space on the local reef to investigate how coral reef population competition dynamics will respond to ocean acidification and the increase of storminess. Competition for space is explicitly introduced into the model where the growth and the survival of the population dependent on the colonies' size as well as making the growth and recruitment density-dependent. Both growth and recruitment are controlled by the free-space available on the reef for the growing and newly settling colonies. The model makes good predictions of what we observe nowadays on the reef with a relative coral coverage of 35-40% and the findings seem to be pointing towards a shift in competitive coral reef dominance of Acropora tabulate species as the physical disturbance regimes increase. Increased bioerosion and storminess favours robust growth forms to the detriment of fragile fast growing colonies. The results provide a framework for assessing the ecological impact of more intense storms and weaker reef materials (calcium carbonate) on the propensity for several indicator species to maintain positive population growth in a space limited reef.

ISCED Categories

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0511 - Biology", "0521 - Ecology