COS 59-10
Patterns of coral growth and shrinkage are linked to initial spatial configurations in coral reef benthic models
Embedded within the current state of a system is a wealth of ecological information, both structural and functional. For coral reef benthic systems that are inherently driven by spatial interactions, pivotal ecological information on the current state of the system encompasses spatial aggregation patterns or the random, uniform, or clumped distribution of organisms across space. These aggregation distributions translate to geometric configurations of spatial competition between coral, the principal reef-builders, and algae that have implications for the fate of corals, i.e. whether they grow or shrink. Consider two hypothetical coral colony scenarios with equivalent cover, but with one case having colonies in a clumped distribution (low perimeter/area ratio geometry) and the other with colonies in a uniform distribution (high perimeter/area ratio). The extent of coral colony borders (perimeter/area ratio) interacting with algae, may be advantageous (leading edges for growth) or detrimental (fronts of space loss), depending on the system attractor. Using a coral reef benthic model that simulates competition for space between coral and algae, I quantitatively investigate how differences in trajectory patterns of coral growth and shrinkage are linked to varying levels of initial coral spatial aggregation.
Results/Conclusions
Results reveal significant differences in the rate towards the system attractor as the level of initial coral aggregation increases. The dependence of the resulting trend on the system attractor was investigated by indirectly changing the competitive dynamic between coral and algae through manipulation of herbivory level. In a system with 30% herbivory (intact system), change in percent coral cover is highest, +10% in 10 years and +23.3% in 20 years, when initial aggregation level is low (meaning when initializing with a uniform distribution of corals) and lowest, -2% in 10 years and 0% in 20 years, at high initial aggregation levels. In the system with 10% herbivory (degraded), initial aggregation level does not appear to influence change in percent coral cover after 10 or 20 years. These results confirm that the competitive geometry arising from varying spatial aggregation patterns drives a significant quantitative effect on transient model trajectories and have tremendous implications for ecological description, prediction, and questions of conservation significance.