By Marco Lopez
The “rainforests of the sea” is an aptly placed pseudonym for coral reefs. Corals are tiny animals that together form colonies. We call those reefs. These organisms are uniquely part animal, plant, and stone.
While alone they can be as small as 2 millimetres, together, they establish living mosaics under the world’s oceans. They are one of the most important animals within the ocean ecosystem. These ancient animals have been in the oceans for over 5 million years, with some starting to form as far back as 50 million years ago.
Coral reefs cover just one-tenth of the ocean floor, and are primarily found in shallow tropical areas. Despite their relatively small ocean real estate, these reefs represent some of the most crucial and biodiverse parts of the oceans. Countless fish species, sponges, sea slugs, crabs, eels, and other marine organisms call coral reefs home.
This is made possible by the intricate, forest-like structures created by coral colonies. While some corals are soft, the architects of these underwater citadels are known as hard or stony corals. These include fascinating varieties like elkhorn, staghorn, brain, and table corals. Over many years, as these corals grow beside and atop each other, they give rise to the magnificent structures.
Coral float in the open as tiny larvae called Polyps and anchor themselves to rocks and hard ocean floor by building a limestone skeleton. These stone skeletons make up the structure of the reef, establishing an amazing partnership with algae, which produces the signature kaleidoscope of colours we see in coral reefs.
The coral and several types of algae called Zooxanthellae live together in symbiosis. The algae live inside some of the coral cells, and like plants, they convert sunlight into food, giving the coral the energy to grow, reproduce, and build its stoney skeleton.
What is Coral Bleaching?
When ocean temperature surpasses just 1 – 2 °C above the maximum monthly average, especially during the warmest part of the year, the Zooxanthellae leaves the coral due to heat stress. This turns the coral ghastly white – a phenomenon known as “Coral Bleaching”.
If the heat subsides, the algae will return, and the coral can recover – although some studies suggest they may be susceptible to diseases for some years following the shock.
If heat stress is prolonged, corals could die.
According to the National Oceanic and Atmospheric Administration (NOAA), if sea temperatures are 1°C greater than the historical monthly average for a duration of two months, it will lead to fatalities. If temperatures are 2°C greater than the monthly average, fatality could occur in one month.
In April of this year, (NOAA) announced and confirmed that a fourth global coral bleaching event was ongoing. Bleaching level heat stress has been extensive and continues across the Atlantic, Pacific, and Indian Ocean basins.
According to recent studies, the extreme heat being recorded all over the world since the start of 2024 is made three times more likely by human-caused climate change. The past 18 months of record-breaking ocean temperature have worsened the impact on the planet’s reefs and have driven the fourth global bleaching event.
This excessive heat also drives marine heat waves and impacts coral colonies and the life they sustain. Continued uncontrolled carbon emissions produced by human actions drive the global heating taking place – impacting life-sustaining organisms like coral. The ocean is storing an estimated 91% of the excess heat trapped in the Earth’s climate system by excess greenhouse gases.
CREWS in the Caribbean
Coral Reef Early Warning Systems or CREWS stations have been deployed across the Caribbean with the help of the Caribbean Community Climate Change Centre (CCCCC) and its partners.
CREWS network monitor various parameters that impact coral reef health in key stations across the Caribbean. The data is used by decision-makers to improve risk planning, management, and actions necessary to address the impacts of climate change.
The project, executed through a collaboration with NOAA, strengthens the region’s early warning mechanisms. It was carried out under the European Union Global Climate Change Alliance (EU-GCCA) Caribbean Support Project.
Besides providing a home for a multitude of marine species, coral reefs act as important barriers against storm surges and help to prevent erosion. Reefs provide jobs for local coastal communities, offer opportunities for recreation, support a vibrant tourism industry, and provide a source of protein and even medicines.
While we can observe and experience the visible effects of climate change on land, driven by ongoing greenhouse gas (GHG) emissions, we often overlook the silent suffering of countless organisms beneath the Earth’s oceans.
Feature image: Coral restoration site at Laughing Bird Caye National Park, August 2024. Placencia, Belize. Photo provided by Fragments of Hope.
