Table 1.
Definition of functional groups.
Fig 1.
Qualitative model to assess the relative impacts of nutrients and predation on COTS populations.
COTS outbreak overview, with human activities leading to increased nutrients (Nutrients) and fishing mortality (Fishing) of COTS predators (Pred). (a) No self-regulating feedback on COTS, with predator benefitting from COTS. (b) Positive self-regulating feedback on COTS, with predator benefiting from COTS (c) No self-regulating feedback on COTS with predators not deriving significant benefit from consumption of COTS (d) Positive self-regulating feedback on COTS with predators not deriving significant benefit from consumption of COTS. Rectangles denote external pressures, circles denote biological system components. New elements of the model structure introduced from one model to the next are denoted by *. Where elements have been removed they are depicted by a dashed line.
Table 2.
Qualitative response predictions for press perturbations to models in Figs 1–5.
Fig 2.
Nutrient input hypothesis for COTS closed and open population.
COTS A: COTS adult, COTS J: COTS juvenile, COTS L: COTS larvae. (a) Closed COTS population where coral facilitates COTS juveniles. (b) Closed COTS population with no facilitation of COTS juveniles by corals (COTS juveniles increase with nutrient addition due to the effect of nutrients on COTS larvae therefore positive effects from nutrients flow directly to them) (c) Open COTS population where coral facilitates COTS juveniles (d) Open COTS population with no facilitation of COTS juveniles by corals.
Fig 3.
Effects of nutrients on COTS (open population) and reef invertebrates.
Invert: reef invertebrates, CCA: crustose coralline algae, COTS A: COTS adult, COTS J: COTS juvenile. (a) Coral facilitates invertebrate predators. (b) No facilitation by corals. (c) Coral facilitates invertebrate predators with no effect of nutrients on CCA (d) No facilitation of invertebrates by corals and no effect of nutrients on CCA.
Fig 4.
Model of effects of nutrients on a broader range of larval groups.
Effects of nutrients (Nutrients) on COTS (open population), reef invertebrates (Invert), and large (Fish L) and small (Fish S) predatory fishes; CCA: crustose coralline algae, COTS A: COTS adult, COTS J: COTS juvenile. (a) Nutrients facilitate larvae of invertebrates and fish groups as well as CCA. (b) Nutrients facilitate invertebrates and CCA only. (c) Nutrients facilitate fish but not invertebrates or CCA. (d) Nutrients facilitate CCA only.
Fig 5.
Example of a more complex set of models of COTS -coral interactions.
Effects of fishing (Fishing) and nutrients (Nutrients) on COTS open populations. Predicted responses to press perturbations were examined for each model for Nutrients or Fishing alone, and then Nutrients and Fishing in combination. (a) Nutrients benefit larvae of COTS as well as invertebrates, fish assemblages show high level of interaction through competition and predation. (b) Nutrients benefit larvae of COTS as well as invertebrates, fish assemblages show low levels of interaction (c) Nutrients benefit COTS larvae alone, fish assemblages show low levels of interaction (d) Nutrients benefit COTS larvae alone, fish assemblages show high levels of interaction. COTS A: COTS adult, COTS J: COTS juvenile, Fish L: targeted large fish predators, Fish N: non-target fish predators, Fish S: targeted small fish predators, Invert: invertebrates, Triton: Giant Triton. COTS A: COTS adult, COTS J: COTS juvenile, Fish L: targeted large fish predators, Fish N: non-target fish predators, Fish S: targeted small fish predators, Invert: invertebrates, Triton: Giant Triton.