Coral reef monitor adds new alert levels to keep up with soaring ocean temperatures | CBC Radio (2024)

As It Happens

Ocean temperatures are rising so dramatically that the organization that monitors threats to coral reefs worldwide has added threenew alert categories.

Alert Level 5 means 'risk of near-complete mortality' from coral bleaching, says Coral Reef Watch

Coral reef monitor adds new alert levels to keep up with soaring ocean temperatures | CBC Radio (1)

Sheena Goodyear · CBC Radio


Coral reef monitor adds new alert levels to keep up with soaring ocean temperatures | CBC Radio (2)

Ocean temperatures are rising so dramatically that the organization that monitors threats to coral reefs worldwide has added threenew alert categories.

Coral Reef Watch is a program run by the U.S. National Oceanic and Atmospheric Administration that uses satellites and computer models to monitor heat risk to reefs.

Marine scientists and conservationists use the system's data to understand the impact of warming temperatures on coral reefs, which are diverse marine ecosystems and a key indicator of ocean health.

"Unfortunately, last year got so hot in the wider Caribbean that our pre-existing alert system really was not doing a very good job reflecting just how severe the heat stress had gotten," Derek Manzello, director of Coral Reef Watch, told As It Happens host Nil Köksal.

"With the new alert level system, this allows us to inform [conservation] managers and scientists as to what the anticipated impacts of these heat stress levels may be."

What is coral bleaching?

Coral reefs are lush marine ecosystems that spring up around colonies of skeleton-covered invertebrates called hard corals.

Corals get their bright colours from algae that live inside their tissues. But when they become stressed, often due to temperature fluctuations, they expel the algae and turn bone white — a phenomenon known as coral bleaching.

Without its algae, the coral is extremely vulnerable to disease and starvation. If the algae doesn't return, the coral will die — turning rich habitats into skeletalgraveyards.

Coral reef monitor adds new alert levels to keep up with soaring ocean temperatures | CBC Radio (4)

Coral reefsonly occupy about one per cent of the ocean's floor, Manzello says, but one in four documented marine species interacts them at some point in their life cycle.

"The coral reefs are the rainforests of the sea," he said. "As coral reefs die, we're losing this immense biodiversity."

'Risk of near-complete mortality'

Since it first launched in 2009, Coral Reef Watch has used two alert categories for monitoring heat risk to coral reefs— Level 1, which means reefs are at risk of coral bleaching, and Level 2, which means indicates the risk of"mortality of heat-sensitive corals."

But in December 2023 — on the heels of a massive summer marine heatwave — the group added three more alert levels, which it unveiled publicly this month.

Level 3 indicates a risk of multi-species mortality for corals, Level 4 means more than half the corals in a reef could die, and Level 5 means "risk of near-complete mortality."

Coral reef monitor adds new alert levels to keep up with soaring ocean temperatures | CBC Radio (5)

"An alert Level 5 condition really represents the most extreme, worst-case scenario, that you could anticipate happening on a coral reef from heat stress," Manzello said.

"This is analogous to a Category 5 cyclone or hurricane in that the impacts from an alert Level 5 bleaching event are expected to be severe and drastic."

Before 2023, he says there were only three instances of heating at this level described in scientific literature.

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That's what happened to several reefs during the summer heatwaves of 2023, the effects of which were documented in a NOAA-University of Queensland studypublished in December.

The Sombrero Reef off the Florida Keys experienced 100-per-cent coral mortality in July 2023, according to the Florida-based Coral Restoration Foundation.

"This was, you know, devastating for people that had been spending years of their lives trying to restore these reefs," Manzello said.

Impacts on humans

Stacy Jupiter, a marine scientist in Fiji for the Wildlife Conservation Society, welcomes the changes to Coral Reef Watch's alert system.

"I believe the changes are necessary in order to demonstrate that the levels of heat accumulation experienced now around the globe are currently relatively greater than the highest alert levels previously issued," she told CBC in an email.

While the Wildlife Conservation Society uses Coral Reef Watch's alert system in his research, Jupiter says increased heat is just one of several predictors of coral bleaching.

Coral reef monitor adds new alert levels to keep up with soaring ocean temperatures | CBC Radio (6)

Nevertheless, shesays the degree of ocean warming in 2023 and 2024 has been "unprecedented in modern times" and "is, indeed, very concerning."

Some can be explained by El Niño, a natural weather pattern that starts in the tropics, marked by part of the Pacific Ocean's surface warming up.

"It is a little bit hard to say if we will continue to see the same elevated ocean temperatures in the coming years, but we can't discount that we are approaching some tipping points in the Earth's critical regulatory systems,"Jupiter said.

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Manzello says there needs to be a lot more time and financial investment in coral reef protection, including the field of "assisted evolution," in which scientists study the genetics of more heat-tolerant corals, and use that information "to breed corals for the future."

If we don't find innovative ways to preserve coral reefs, he says we'll all feel the impact.

Coral reefs produce compounds used in medicine, provide habitat for fish that people eat, are a key component of tourism industries around the world and protect coastal areas from the impacts of powerful storms.

"In my mind, coral reefs are the most beautiful natural habitat that exists on planet Earth," he said.

"The fact that these are just dying across a global scale every year, I think it's really an ecological tragedy that's unfolding right before our very eyes."

Interview with Derek Manzello produced by Leslie Amminson

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How are coral reefs affected by high temperatures? ›

Rising (or even falling) water temperatures can stress coral polyps, causing them to lose algae (or zooxanthellae) that live in the polpys' tissues. This results in “coral bleaching,” so called because the algae give coral their color and when the algae “jump ship,” the coral turns completely white.

What is the coral reef early warning system? ›

AIMS keeps a close watch on coral reefs along the Great Barrier Reef by maintaining a network of weather stations, temperature loggers and oceanographic moorings. These measure and transmit (some in near real time) sea surface temperature, wind speed, humidity, air pressure data and ocean circulations.

Why is coral reef monitoring important? ›

Coral reefs host some of the highest concentrations of biodiversity and economic value in the oceans, yet these ecosystems are under threat due to climate change and other human impacts. Reef monitoring is routinely used to help prioritize reefs for conservation and evaluate the success of intervention efforts.

Why are coral reefs disappearing at an alarming rate? ›

Coral reefs are some of the most important ecosystems in the oceans. Many around the world are dying at an alarming rate due to ocean acidification and rising water temperatures from climate change.

What temperature kills coral reefs? ›

Corals and their zooxanthellae prefer water that's not too hot, but not too cold - water temperatures over 86° F or under 64° F can be harmful. When water gets too warm, zooxanthellae release compounds due to the heat stress which inadvertently harm the coral.

How do coral reefs regulate temperature? ›

When the temperature soars, coral reefs might cool off by creating their own clouds. Research from the Great Barrier Reef off the Australian coast shows that corals are packed full of the chemical dimethyl sulphide, or DMS.

Is coral reef under threat? ›

Coral reefs are in decline in the U.S. and around the world. Many scientists now believe the very existence of coral reefs may be in jeopardy unless we intensify our efforts to protect them (Frieler et al.

Which reef is under threat? ›

Climate change is the greatest threat to the Great Barrier Reef, threatening its very existence.

What is the early warning system for climate? ›

Early Warning Systems (EWS) are a proven cost-effective disaster risk reduction and climate change adaptation measure which has been demonstrated to save lives, livelihoods and ecosystems in the face of climate-related hazards.

How do people monitor coral reefs? ›

Data are collected through diving surveys of shallow-water (0-30 meters) areas. Scientists and coastal managers then use these data to evaluate coral reef and fish population management strategies, document endangered or invasive marine species, and assist with local monitoring efforts.

How do scientists monitor coral reefs? ›

The National Coral Reef Monitoring Program (NCRMP) monitors coral health using belt transects in U.S. States and Territories (American Samoa, Commonwealth of the Northern Mariana Islands, Florida, Guam, Hawaii, Puerto Rico, U.S. Virgin Islands).

How are coral reefs monitored? ›

Reef surveys involve three approaches: Manta tow surveys of reef-wide coral cover, crown-of-thorns starfish numbers, amount of coral bleaching, numbers of coral trout and sharks. Fixed site surveys of the animals and plants on the coral reef surface using photography.

Is coral still dying? ›

Coral reefs around the world are indeed still at great risk. A comprehensive survey by Canadian researchers in 2021 shows that the world's oceans have lost about half of their coral cover since the 1950s.

Will coral reefs disappear in 2050? ›

With the planet already warming approximately 1.1°C (2.0°F) due to human activities since the end of the 19th century, these declines in corals could be reached by 2050 or sooner. It's not feasible for scientists to monitor the state of every coral reef each year.

Will coral go extinct? ›

In fact, in just the next 20 years, 70-90% of all coral reefs will die, so you won't have to wait long. The two key factors in this extinction are the rising ocean temperatures from climate change and acidic water from pollution.

How does temperature affect the growth of coral? ›

Previous studies have shown that low salinity and high temperature can cause a stress response in corals, resulting in decreased photosynthetic efficiency, inability to provide essential nutrients through zooxanthellae, affecting survival and growth [8,9].

What can happen to corals if the water temperature gets too high for too long? ›

However, if the temperature gets significantly above the bleaching threshold or stays high for an extended period of time, severe bleaching will occur and some corals can eventually die.

What is the damage to coral reefs by excessively warm water? ›

Corals may become so physiologically stressed that they begin to expel their symbiotic zooxanthellae, which leads to bleaching, and in many cases, death. Increased sea surface temperatures, decreased sea level and increased salinity from altered rainfall can all result from weather patterns such as El Niño.

Are coral reefs sensitive to heat? ›

While most corals live in the warmth of the tropics, the water can become too warm for them. When waters heat up, corals get stressed and go through a process called bleaching which makes them look as white as their skeletons.

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