Object-oriented simulation of coral competition in a coral reef community

A 3-dimensional individual-based model, the ReefModel, was developed to simulate the dynamical structure of coral reef community using object-oriented techniques and Smalltalk/V language. Interactions among six functional groups of reef organisms: tabular coral, foliaceous coral, massive coral, macroalga, corallivorous gastropod and herbivorous fish were examined. Results from the simulation of interaction among the three coral groups are presented here. The behaviours of the coral groups were described with simple mechanistic rules that were derived from their general behaviours (e.g. growing habits, competitive mechanisms) observed in natural coral reef communities. All corals were allowed to grow in a 3-dimensional spatial environment. The model was implemented to explore the competitive mechanisms governing coral community structure. Simulation results suggest that a fast-growing habit with overtopping competitive mechanism is probably the most effective strategy for corals to gain spatial dominance in a coral community under stable environmental conditions. In addition, multimodality exists in the final states of individual coral group as a result of small random spatial events that occurred during the early stages of interactions among the corals in the community. This suggests that alternative stable states may exist in a coral community as a result of inter-specific coral competition.