Breakdown: Why a warming ocean is harmful to coral reefs

MEMPHIS, Tenn. (WMC) - Coral reefs harbor the highest biodiversity of any ecosystem globally and directly support over 500 million people worldwide, but they’re also among the most threatened ecosystems on Earth.

One of the most important threats facing coral reefs on a global scale is a big one: climate change.

Scientific evidence now clearly indicates that the Earth’s atmosphere and ocean are warming, and that these changes are primarily due to greenhouse gases derived from human activities, says National Oceanic and Atmospheric Administration (NOAA).

Climate change poses a major threat to coral reefs. — Climate change poses a major threat to coral reefs.(NOAA)

As temperatures rise, reefs around the world have suffered from mass coral bleaching events. Bleaching is when corals expel the microscopic algae that live in their tissues. Without these algae, corals’ tissues become transparent, exposing their white skeleton. This is called coral bleaching.

While a bleached coral is not dead, and corals can survive bleaching events, they are under greater stress, are less resistant to other threats such as disease, and are thus subject to mortality.

Corals get their color from pigments in their symbiotic algae, which provide food to corals... — Corals get their color from pigments in their symbiotic algae, which provide food to corals through photosynthesis. This partnership breaks down during periods of extreme heat stress, and the corals expel the algae.(NOAA)

Some scientists predict that 90% of global reefs will experience severe bleaching annually by 2055.

Data from the US National Oceanic and Atmospheric Administration (NOAA) shows that the average global sea surface temperature has increased by approximately 32°F per decade over the past 100 years.

Data from the US National Oceanic and Atmospheric Administration (NOAA) shows that the average... — Data from the US National Oceanic and Atmospheric Administration (NOAA) shows that the average global sea surface temperature – the temperature of the upper few metres of the ocean – has increased by approximately 0.13°C per decade over the past 100 years.(International Union for Conservation of Nature (IUCN))

Additionally, the ocean absorbs approximately one-third of the atmosphere’s excess carbon dioxide, resulting in a more acidic ocean. This causes a reduction in pH levels which decreases coral growth and structural integrity.

Climate change will affect coral reef ecosystems, through sea level rise, changes to the frequency and intensity of tropical storms, and altered ocean circulation patterns.

Millions of people depend on coral reefs to protect them from storm surges and waves. As sea surface temperatures rise, hurricanes, cyclones, and typhoons that damage coral reefs become stronger. Heavy rainfall from the storms can also erode coastal lands and bring more polluted runoff into the ocean.

When combined, all of these impacts dramatically alter ecosystem function, as well as the goods and services coral reef ecosystems provide to people around the globe.

Beyond their intrinsic value and the roles they play in supporting vast numbers of marine species, coral reefs also provide a plethora of functions that benefit humans.

There are also many things you can do to ensure that you are environmentally conscious when you visit coral reefs or coastal areas. These include things such as hiring local guides to support the economy, removing all trash from an area, never touching or harassing wildlife in reef areas, and avoiding dropping your boat anchor or chain nearby a coral reef.

Finally, stay informed and spread the word! Educate yourself about why healthy coral reefs are valuable to the people, fish, plants, and animals that depend on them. Your excitement will help others get involved.

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