ABSTRACT
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Model Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Ecological Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Mathematical Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Visualizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Simulated Effects of Eutrophication and Natural Disturbances on Coral to Algal Phase Shift Trajectories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Model Reef Trajectories: Effects of Starting Condition and Disturbances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Responses to Eutrophication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Combined Effects of Natural Disturbance and Human Impacts . . . . . . . . . . 117 Large-Scale and Long-Term Changes: Integration of Human Impacts and Natural Disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
There is increasing concern globally that enhanced runoff from human land uses is leading to degradation of coral reefs. Land-clearing, deforestation, excess fertilization of agriculture, and sewage runoff have all been implicated in contributing to nutrient and sediment overload of coral reef waters, leading to so-called “phase shifts,” in which areas formerly dominated by corals become overgrown by algae
(e.g., Smith et al., 1981; Hatcher et al., 1989; Done, 1992; Edinger et al., 1998). These changes have serious ecological, environmental, and economic consequences. On the Great Barrier Reef (GBR) in particular (Figure 1), there is concern that abundant macroalgae on inshore fringing reefs indicate degradation due to anthropogenic increases in terrestrial inputs of sediments and nutrients (Bell & Elmetri, 1995; reviewed in McCook & Price, 1997a; McCook & Price, 1997b; Wachenfeld et al., 1998; Atkinson, 1999; Prideaux, 1999).
