Scientists have discovered that a catastrophic coral die-off event off the coast of Costa Rica was caused by an extreme weather event that resulted in rapid sea temperature drops of up to 10 degrees.
Cold water shock to catastrophic coral collapse
(Photo : Lukasz Larsson Warzecha/Getty Images)
Climate change-induced marine heat waves have been linked to mass mortality on some of the world's most iconic coral reef systems, as per ScienceDaily.
Scientists have discovered that the primary cause of a catastrophic coral die-off event was an extreme weather event that resulted in rapid sea temperature drops of up to 10 degrees.
When combined with a widespread increase in harmful algal blooms, the extent of reef collapse in Costa Rica's Eastern Tropical Pacific in 2009 was unusually high.
The two factors resulted in coral cover decreasing by 20% to 100% at some sites, with levels of recovery varying significantly in the years since.
Researchers say their findings in a new study published in the journal PeerJ show that upwellings, which cause sea temperatures to plummet suddenly, are a key factor to consider when trying to manage reef systems.
The study was carried out by an international team of scientists led by the University of Plymouth, in collaboration with partners such as Raising Coral and ACG, which promote coral reef conservation in Costa Rica.
The two factors resulted in coral cover decreasing by 20% to 100% at some sites, with levels of recovery varying significantly in the years since.
Researchers say their findings in a new study published in the journal PeerJ show that upwellings, which cause sea temperatures to plummet suddenly, are a key factor to consider when trying to manage reef systems.
The study was carried out by an international team of scientists led by the University of Plymouth, in collaboration with partners such as Raising Coral and ACG, which promote coral reef conservation in Costa Rica.
They examined changes in coral cover and the composition of six marginal reefs in relation to thermal highs and lows using 25 years of reef survey and sea surface temperature data.
They were able to do so by painting a comprehensive picture of local coral health status and quantifying the magnitude of coral population declines, as well as establishing the implications for effective conservation and restoration strategies.
The lack of overall coral recovery in the decade since the initial event, according to the study, indicates that the region's ecosystem has reached a tipping point.
As a result, they propose a locally tailored - but globally scalable - approach to coral reef declines that is based on resilience-based management and restoration while also taking into account coral health dynamics.
With careful management, such measures could allow reefs to recover and continue providing ecological and societal ecosystem services in the face of escalating climatic threats.
Read more: Corals That Experience Heat Stress are More Likely to Tolerate High Water Temperatures
How do coral reefs die?
Coral reefs are under constant threat from a variety of global and local issues, such as climate change, declining water quality, overfishing, pollution, and unsustainable coastal development, as per UNEP.
"Coral reefs are one of the most vulnerable ecosystems in the world to the ravages of human activity," says Gabriel Grimsditch, a marine ecosystems expert with the United Nations Environment Programme (UNEP).
They are particularly vulnerable to climate change and rising ocean temperatures, and mass coral bleaching and mortality events are expected to become more frequent and intense as temperatures rise.
Corals expel the microscopic symbiotic algae zooxanthellae from their tissues when they are exposed to these environmental stressors.
Corals become more sensitive to environmental stressors and turn pale or white because this is their primary food source, hence the term 'coral bleaching.'
Corals must re-absorb zooxanthellae to recover from bleaching, which is only possible when the effects of environmental stressors are reduced.
According to the "Status of Coral Reefs of the World 2020" report, which was co-produced by UNEP, the International Coral Reef Initiative (ICRI), the Global Coral Reef Monitoring Network (GCRMN), and various international partners, 14% of the world's corals were lost between 2009 and 2018.
Without drastic action to limit global warming to 1.5°C, live coral on reefs may decline by 70-90 percent by 2050. Even if greenhouse gas emissions are drastically reduced, global ocean temperatures may take decades to stabilize.
Decision-makers must be decisive in leading urgent climate action to ensure the survival of coral reefs.
For example, including coral reefs as a priority ecosystem in the Post-2020 Biodiversity Framework of the UN Convention on Biological Diversity would hold governments, businesses, and other stakeholders accountable for protecting their health.
Beyond the goals of the Paris Agreement, decision-makers must go beyond the UN Climate Change Conference in Glasgow to ensure the future of coral reefs.
Related article: Corals Grown in Labs Help Restore Critically Endangered Reefs
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