Long-term recovery of reefs from bleaching requires local action to increase resilience

February 3, 2009
Coral bleaching -- in which corals expel their symbiotic algal partners and turn pale or white -- is one of the most visible impacts of climate change on marine ecosystems. Typically caused by higher-than-normal ocean temperatures, it can lead to widespread death of corals and is a major contributor to the rapid decline of coral reef ecosystems worldwide. Credit: Andrew C. Baker

In the journal Estuarine, Coastal and Shelf Science, University of Miami Rosenstiel School of Marine and Atmospheric Science Professor Dr. Peter Glynn, and 2008 Pew Fellow for Marine Conservation and Assistant Professor Dr. Andrew Baker, assess more than 25 years of data on reef ecosystems recovery from climate change-related episodes of coral bleaching. Coral bleaching - in which corals expel their symbiotic algal partners and turn pale or white - is one of the most visible impacts of climate change on marine ecosystems. Typically caused by higher-than-normal ocean temperatures, it can lead to widespread death of corals and is a major contributor to the rapid decline of coral reef ecosystems worldwide.

The paper, co-authored by Dr. Bernhard Riegl, associate director of the National Coral Reef Institute, represents the first comprehensive review of long-term global patterns in reef recovery following bleaching events. Bringing together the results of dozens of bleaching studies, the article reports that bleaching episodes set the stage for diverse secondary impacts on reef health, including coral disease, the breakdown of reef framework, and the loss of critical habitat for reef fishes and other important marine animals.

"Bleaching has resulted in catastrophic loss of coral cover in some locations, and has changed the coral community structure in many others," said Glynn. "These dramatic fluctuations have critical impacts on the maintenance of biodiversity in the marine tropics, which is essential to the survival of many tropical and sub-tropical economies."

However, the paper also shows that, while bleaching episodes have resulted in dramatic loss of coral cover in certain locations, reefs vary dramatically in their ability to bounce back from these disturbances. It also evaluates factors explaining why some species of coral recover better than others, as well as why some reef regions are recovering while others are not.

The study finds that reefs in the Indian Ocean are recovering relatively well from a single devastating bleaching event in 1998. In contrast, western Atlantic (Caribbean) reefs have generally failed to recover from multiple smaller bleaching events and a diverse set of chronic additional stressors such as diseases, overfishing and nutrient pollution. No clear trends were found in the eastern Pacific, the central-southern-western Pacific or the Arabian Gulf, where some reefs are recovering and others are not.

"These findings illustrate how coral reefs, under the right conditions, can demonstrate resilience and recover from bleaching, even when it initially appears catastrophic", said Baker. "What prevents them from doing so is the lethal prescription of combined, additional stressors that prevent them from recovering in-between recurrent bleaching events. If we can remove or reduce these stressors we might give reefs a fighting chance of surviving climate change".

The paper entitled "Climate change and coral reef bleaching: An ecological assessment of long-term impacts, recovery trends and future outlook" also discusses potential mitigation and intervention strategies that might maximize coral reef survival in the coming years. It concludes that bleaching disturbances are likely to become a chronic stress in many reef areas in the coming decades, and coral communities, if they cannot recover quickly enough, are likely to be reduced to their most hardy or adaptable constituents. Unless significant reductions in greenhouse gas emissions can be achieved within the next two to three decades, maximizing coral survivorship during this time may be critical to ensuring healthy reefs can recover in the long term.

Source: University of Miami Rosenstiel School of Marine & Atmospheric Science

Explore further: A stone, skip and a hop away from saving a bay

Related Stories

A stone, skip and a hop away from saving a bay

January 16, 2017

In Victoria's Port Phillip Bay, commercial and environmental interests can live in harmony, just like the vast variety of organisms that inhabit the bay's spectacular rocky reefs.

Software system labels coral reef images in record time

January 11, 2017

Computer scientists at the University of California San Diego have released a new version of a software system that processes images from the world's coral reefs anywhere between 10 to 100 times faster than processing the ...

Rising CO2 threatens coral and people who use reefs

November 9, 2016

As atmospheric carbon dioxide (CO2) levels rise, very few coral reef ecosystems will be spared the impacts of ocean acidification or sea surface temperature rise, according to a new analysis. The damage will cause the most ...

Recommended for you

Caves in central China show history of natural flood patterns

January 19, 2017

Researchers at the University of Minnesota have found that major flooding and large amounts of precipitation occur on 500-year cycles in central China. These findings shed light on the forecasting of future floods and improve ...

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Big_Oil_Sockpuppet
2.6 / 5 (5) Feb 03, 2009
Bleached corals look better.
theophys
2.8 / 5 (6) Feb 03, 2009
We could always just color in the coral with crayons and pretend there's nothing wrong.
GrayMouser
2.3 / 5 (6) Feb 03, 2009
"Typically caused by higher-than-normal ocean temperatures"

Which has not happened so they need to find another politically correct cause.
Velanarris
2.6 / 5 (5) Feb 04, 2009
"Typically caused by higher-than-normal ocean temperatures"

Which has not happened so they need to find another politically correct cause.
Truth is they don't knwo why coral bleaching occurs. There are multiple reasons, on the table including coral disease pandemics. After all, humans aren't the only species to undergo wide spread disease outbreaks.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.