Coral Reef Dynamics - Phase Shifts & Alternative Stable States

Herbivory

Fishing Pressure

0.20

Grazer Abundance

0.50

Browser Abundance

0.30

Climate Stress

Sea Surface Temperature (+°C)

+0.0°C

Ocean Acidification

0.0

Reef Parameters

Coral Growth Rate

0.05

Algae Growth Rate

0.15

Coral Recruitment

0.03

Disturbance Events

Coral-Dominated State

Coral

Turf Algae

Macroalgae

Sand/Bare

Bleached

Reef Benthos

Cover Dynamics Over Time

Phase Space (Hysteresis)

Herbivore Functional Groups

Coral Cover

Macroalgae Cover

Turf Algae

Herbivore Biomass

High

Resilience

Low

Bleaching Risk

Disturbances

Years

Alternative Stable States & Hysteresis (Mumby et al. 2007)

Coral State: High coral cover suppresses algae through competition for space. Macroalgae State: Dense macroalgae inhibit coral recruitment and recovery. Hysteresis: Once shifted to algae, reef may not recover even if stressors removed - herbivory must exceed original threshold. Browser fish are critical for preventing macroalgae from reaching size refuge.