Portfolio Effects and Synchrony in Coral Communities

Area of Science:

• Marine ecology
• Community dynamics
• Ecological stability

Background:

• Population asynchrony can stabilize community fluctuations via the portfolio effect.
• This stability can stem from random population fluctuations or predictable biological responses.
• Understanding these dynamics is crucial for predicting ecosystem resilience.

Purpose of the Study:

• To investigate coral community dynamics and population synchrony over nine years.
• To determine if coral population dynamics are driven by random fluctuations or predictable covariation.
• To assess the influence of disturbance regimes on coral community stability.

Main Methods:

• Analysis of a 9-year coral abundance time series from 15 sites.
• Statistical examination of population dynamics and inter-population covariation.
• Comparison of community stability during periods of low and high disturbance.

Main Results:

• Community abundance was stable from 2013-2017, linked to population asynchrony driven by random fluctuations.
• From 2018-2021, community abundance declined, associated with population synchrony, likely due to a predator outbreak.
• Coral populations showed spatial and temporal variability, with limited evidence for predictable covariation patterns.

Conclusions:

• Coral communities possess an inherent capacity for stability through portfolio effects.
• This stability is limited by the intensity and frequency of disturbance events.
• Disturbance regimes, such as predator outbreaks, can override stabilizing mechanisms and drive community decline.