A Busse Balloon in the Lagoon: Herbivore Behaviour Generates Spatial Patterns in Coral Reef Ecosystems

Area of Science:

• Ecology
• Marine Biology
• Ecosystem Dynamics

Background:

• Bistable ecosystems can exist in alternative states, such as coral- or macroalgal-dominated reefs.
• Spatial processes and scale-dependent feedbacks are crucial but often underappreciated drivers of ecosystem dynamics.
• Self-organized spatial patterns can lead to phenomena like Busse balloons, enabling coexistence of states outside theoretical stability regions.

Purpose of the Study:

• To explore the role of spatial dynamics in maintaining alternative states in coral reef ecosystems.
• To investigate how herbivore behavior and mobility influence the stability of coral- and macroalgal-dominated states.
• To determine if spatial feedbacks can create conditions for macroalgal resilience even when coral dominance is predicted.

Main Methods:

• Utilized partial differential equations to model spatial processes in coral reef ecosystems.
• Focused on incorporating herbivore attraction to coral and their mobility as key parameters.
• Analyzed model outputs to identify conditions supporting spatial patterns and state coexistence.

Main Results:

• Herbivore attraction to coral created a spatial pattern, a Busse balloon, which enhanced macroalgal resilience.
• Observed pattern persistence in parameter regions where non-spatial models predicted uniform coral dominance.
• Demonstrated that herbivore association with coral can prevent a complete shift to a coral-dominated state.

Conclusions:

• Consumer space use and associated behaviors significantly impact ecosystem state transitions.
• Spatial feedbacks, driven by consumer-habitat interactions, are critical for understanding and managing bistable ecosystems.
• Explicitly accounting for spatial dynamics is essential for accurate predictions and conservation of ecosystems like coral reefs.