Local Stressors Reduce Coral Resilience to Bleaching

TLDR

Coral bleaching, the loss of symbiotic dinoflagellates, is increasing in frequency and geographic extent as climate warming intensifies. The study investigates whether chronic local stress diminishes or enhances coral resistance and resilience to episodic bleaching events. After a major bleaching event, Montastraea faveolata at high‑stress sites showed suppressed growth for at least eight years, while low‑stress sites recovered in 2–3 years, demonstrating that chronic stress reduces coral fitness and resilience and that mitigating such stress could improve resilience to climate change.

Abstract

Coral bleaching, during which corals lose their symbiotic dinoflagellates, typically corresponds with periods of intense heat stress, and appears to be increasing in frequency and geographic extent as the climate warms. A fundamental question in coral reef ecology is whether chronic local stress reduces coral resistance and resilience from episodic stress such as bleaching, or alternatively promotes acclimatization, potentially increasing resistance and resilience. Here we show that following a major bleaching event, Montastraea faveolata coral growth rates at sites with higher local anthropogenic stressors remained suppressed for at least 8 years, while coral growth rates at sites with lower stress recovered in 2-3 years. Instead of promoting acclimatization, our data indicate that background stress reduces coral fitness and resilience to episodic events. We also suggest that reducing chronic stress through local coral reef management efforts may increase coral resilience to global climate change.