Intertidal coral reef teeming with life, showcasing resilient corals and sponges.

Coral Comeback? How Reefs Are Adapting to Climate Change

Elliot Brynn in Climate & Environment August 2025 • 4 min read.

"Discover the surprising resilience of coral reefs and the sea sponges that may hold the key to surviving future El Niño events."

Coral reefs around the world are facing unprecedented challenges from human impacts and global climate change. Rising ocean temperatures, ocean acidification, and the increasing frequency of extreme weather events like El Niño are threatening the health and survival of these vital marine ecosystems. However, some organisms inhabiting marginal habitats may be adapting to higher levels of physiological stress. This raises the possibility that insights can be gleaned into how coral might be saved.

A recent study focused on emergent intertidal coral reefs in Bahia, Brazil, examined the long-term impacts of the 1997-98 El Niño event on reef fauna. These reefs, which experience significant daily fluctuations in temperature and solar radiation, offer a unique opportunity to study the resilience of coral species and reef communities under extreme conditions. The 17-year biodiversity survey (1995-2011) assessed the impact of the major El Niño event on the reef fauna and tracked subsequent recovery, revealing surprising insights into the adaptability of certain species.

Intertidal reefs may be more resilient to climatic events and provide important insights into the adaptation of reef fauna to future ocean warming.

Differential Responses: Resilience and Decline

Intertidal coral reef teeming with life, showcasing resilient corals and sponges.

The study revealed a mixed picture of resilience and decline among different reef organisms. Two dominant coral species, Favia gravida and Siderastrea stellata, showed remarkable tolerance to the El Niño-associated stress. Their densities remained relatively stable throughout the survey period, suggesting a high degree of adaptation to fluctuating environmental conditions. However, other taxa experienced significant declines.

Molluscs, bryozoans, and ascidians suffered severe declines in diversity and abundance and had not recovered to pre-El Niño levels by the end of the study. Echinoderms were reduced to a single species in 1999, although diversity levels had recovered by 2002. This variability in response highlights the complex and nuanced impacts of climate events on reef ecosystems.

Here's what the study found:

Coral Resilience: Two coral species showed high tolerance to El Niño stress.
Decline in Other Taxa: Molluscs, bryozoans, and ascidians suffered significant losses.
Echinoderm Recovery: Echinoderms recovered diversity after an initial reduction.
Sponge Success: Sponges were not impacted and increased in density.

Notably, sponge assemblages were not negatively impacted by the 1997-98 event. In fact, their densities increased by the end of the study, suggesting a potential competitive advantage under the altered environmental conditions. This observation aligns with growing recognition of sponges as resilient reef inhabitants that may thrive in a changing climate.

Hope for the Future

The study's findings underscore the complex and varied responses of reef organisms to climate-related stressors. While the overall composition of the reef community has shifted, the resilience of certain coral and sponge species offers a glimmer of hope. These species may represent valuable models for understanding temperature adaptation in reef organisms and could inform conservation efforts aimed at enhancing reef resilience in the face of ongoing climate change. Further research into the physiological mechanisms underlying their tolerance could provide crucial insights for protecting these vital ecosystems.

About this Article -

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This article is based on research published under:

DOI-LINK: 10.1371/journal.pone.0093209, Alternate LINK

Title: Differential Responses Of Emergent Intertidal Coral Reef Fauna To A Large-Scale El-Niño Southern Oscillation Event: Sponge And Coral Resilience

Subject: Multidisciplinary

Journal: PLoS ONE

Publisher: Public Library of Science (PLoS)

Authors: Francisco Kelmo, James J. Bell, Simone Souza Moraes, Rilza Da Costa Tourinho Gomes, Eduardo Mariano-Neto, Martin J. Attrill

Published: 2014-03-27

Everything You Need To Know

Where did researchers focus their study on coral reefs adapting to climate change, and why was this location particularly insightful?

The study focused on emergent intertidal coral reefs in Bahia, Brazil, specifically examining the long-term effects of the 1997-98 El Niño event on reef fauna. This location is valuable because these reefs experience significant daily temperature and solar radiation fluctuations, offering a unique opportunity to study coral and reef community resilience under extreme conditions. By conducting a 17-year biodiversity survey from 1995 to 2011, researchers tracked the impact of the El Niño event and subsequent recovery, providing insights into the adaptability of certain species. Missing from the study is information about the specific physiological mechanisms that allow these corals to survive such extreme conditions, an area ripe for future research.

What specific coral species showed resilience to the El Niño event, and how did other reef organisms fare in comparison?

Two dominant coral species, Favia gravida and Siderastrea stellata, displayed remarkable tolerance to the El Niño event, maintaining relatively stable densities throughout the survey period. This suggests these species possess a high degree of adaptation to fluctuating environmental conditions. However, other taxa like molluscs, bryozoans, and ascidians experienced significant declines and failed to recover to pre-El Niño levels by the study's end. Echinoderms initially decreased to a single species but later recovered in diversity. These varying responses highlight the complex and nuanced impacts of climate events on reef ecosystems. The study did not delve into the specific reasons why these other species were less resilient, pointing to a need for further investigation into the varying sensitivities within reef communities.

How did sponge populations respond to the El Niño event, and what does this suggest about their role in changing reef ecosystems?

Sponge assemblages were not negatively impacted by the 1997-98 El Niño event. Their densities increased by the end of the study, indicating a potential competitive advantage under the altered environmental conditions. This aligns with growing recognition of sponges as resilient reef inhabitants that may thrive in a changing climate. The study highlights sponges' role in a changing climate, though it doesn't explore the specific ecological roles sponges might play in supporting or altering the overall reef ecosystem as coral populations change.

What implications does the resilience of specific coral and sponge species have for the future of coral reef conservation efforts?

The resilience of certain coral species, like Favia gravida and Siderastrea stellata, along with the success of sponge assemblages, offers a glimmer of hope for the future of coral reefs. These species may serve as valuable models for understanding temperature adaptation in reef organisms. Further research into the physiological mechanisms underlying their tolerance could provide crucial insights for conservation efforts aimed at enhancing reef resilience in the face of ongoing climate change. Understanding how these resilient species interact with and potentially support other reef inhabitants could be vital for future conservation strategies.

How does the El Niño Southern Oscillation (ENSO) impact coral reefs, and what does the study reveal about coral adaptation to these events?

The El Niño Southern Oscillation (ENSO) is a climate pattern that significantly impacts ocean temperatures and weather patterns worldwide. The 1997-98 El Niño event caused substantial stress on coral reef ecosystems, leading to coral bleaching and mortality. However, the study showed that certain species, like Favia gravida and Siderastrea stellata, exhibited resilience to these stressors, suggesting that adaptation to such climate events is possible. The increasing frequency and intensity of ENSO events due to climate change pose an ongoing threat to coral reefs, making the study of resilient species crucial for conservation efforts. The study does not address the potential impacts of other climate change related stressors, such as ocean acidification, on these same reef systems.