Asynchrony in coral community structure contributes to reef-scale community stability

Area of Science:

• Marine Ecology
• Coral Reef Ecosystems
• Ecosystem Stability and Resilience

Background:

• Global ecosystem degradation is recognized, but spatial and temporal variations in these impacts are understudied.
• Tropical coral reefs exhibit habitat heterogeneity, potentially leading to spatial mosaics of coral communities.
• Spatial insurance effects, where asynchronous dynamics across habitats stabilize communities, are hypothesized but not well-tested in coral reefs.

Purpose of the Study:

• To investigate the ecological implications of environmental and coral community variation over kilometers and years on tropical coral reefs.
• To evaluate the role of spatial asynchrony in coral community structure and stability in Moorea, French Polynesia.
• To explore the association between environmental condition asynchrony, coral community asynchrony, and overall community stability.

Main Methods:

• Studied coral community structure and environmental conditions from 2006-2019 at a single site with fringing, back reef, and fore reef habitats.
• Analyzed coral community structure variation among habitats and its relationship with environmental condition variation, particularly daily seawater temperature ranges.
• Assessed the role of wave-forced seawater flow in connecting habitats and facilitating larval exchange, noting interannual variations in connectivity strength.

Main Results:

• Coral community structure varied asynchronously among the studied habitats.
• Variation in daily seawater temperature ranges among habitats correlated with differences in coral community structure.
• Wave-forced seawater flow connected habitats, with varying strength over years, leading to periodic connectivity at 1-7 year intervals.

Conclusions:

• Connected habitats with asynchronous population dynamics can provide spatial insurance against coral extirpation, promoting community stability.
• Among-habitat community asynchrony is a key factor in maintaining coral reef resilience.
• These findings suggest that spatial heterogeneity and asynchronous dynamics are crucial for reef-wide coral community resilience.