In consideration of the rapid degradation of coral reef ecosystems, the establishment of models is helpful to comprehend the degradation mechanism of coral reef ecosystems and predict the development process of coral reef communities. According to the characteristics of complex ecosystem of tropical coral reefs in China, the coral reef functional group is the core level variable; combined with the multiple feedback effects of coral reef functional groups and environmental changes, the study presents a coral reef ecosystem dynamics model with hermatypic corals as the core. Based on the simulation of the assumed initial value and the internal feedback of the system, the results show that in the basic simulation (relative health conditions), the coverage area of live corals and coral reefs generally decreased first and then increased, and increased by 4.67% and 6.38% between 2010 and 2050, respectively. Based on the calibration model and the current situation of the studied area, the multi-factor disturbance effects of coral reef communities were simulated and explored by setting up three scenarios involving fishing policy, terrestrial deposition, and inorganic nitrogen emissions. Among them, in the single factor disturbance, the fishing policy exerts the most direct impact on the community decline; and the succession phenomenon is obvious; the terrestrial sedimentation has a faster and more integrated effect on the community decline; the effect of inorganic nitrogen emission on the community decline is relatively slow. In the double/multi-factor disturbance, the superimposed disturbance will aggravate the multi-source feedback effect of the coral reef communities development, accelerate the community decay rate, and make its development trajectory more complicated and diverse. This method provides a scientific and feasible method for simulating the damage of long-term coral reef community and exploring the development law and adaptive management of coral reef ecosystems. In the future, it can be further studied in the ecological restoration process and decision-making direction of coral reefs.
Figure 1. Block diagram of a coral reef ecosystem. ①②③ all mean predation.
Figure 2. Dynamics process of coral reef systems.
Figure 3. Coral coverage area fitting comparison. Estimated by existing research, 300 hm of coral reefs can support about 2 000 ind. crown-of-thorns starfish with an initial living coral coverage of 11.6%.
Figure 4. Simulation results of the functional group number of coral reef SD model.
Figure 5. Impact of single factor disturbance on the functional groups of coral reef ecosystem, the factors are fishing policy (scenarios F1), terrestrial deposition (scenarios F2) and total amount of inorganic nitrogen emissions (scenarios F3).
Figure 7. Impact of multiple factors disturbance on the functional groups of coral reef ecosystem, the combination of factors are fishing policy, terrestrial deposition and total amount of inorganic nitrogen emissions.
Figure 6. Impact of double factors disturbance on the functional groups of coral reef ecosystem, the combination of factors are fishing policy and terrestrial deposition (scenarios F4), fishing policy and total amount of inorganic nitrogen emissions (scenarios F5), terrestrial deposition and total amount of inorganic nitrogen emissions (scenarios F6).