As the physical effects of human impacts on Earth continue to worsen, the coral reefs in our oceans are experiencing a mass bleaching that essentially renders them lifeless and incapable of supporting many species that depend on them for survival.
Evidence shows that coral reefs have been in existence for about 3.5 billion years and have grown significantly over time. They are found along the coastal areas of continents or islands in shallow tropical waters near the equator.
In total, they cover an area of over 280,000 square kilometers on the planet and are home to 25 percent of all known marine fish species. Even though that number seems high, the total area only takes up about .5 percent of the entire marine environment.
The largest coral reef is the famed Great Barrier Reef located on the coast of Australia, which is comprised of over 3,000 separate reef systems and is home to thousands of species of marine and plant life. The second largest are the coral reefs in Belize in Central America. Closer coral reefs can be found in Florida, Hawaii and Puerto Rico.
They are primarily composed of a foundation and structure of calcium carbonate from living and dead stony corals (scleractinia) that builds up when each individual coral organism, or polyp, secretes a skeleton. Over time, these tiny polyps, which usually average one to three millimeters in diameter, can slowly form massive structures that can weigh several tons.
One way scleractinia corals grow is by receiving nutrients and energy from capturing planktonic organisms. The other way is by having a symbiotic relationship with zooxanthellae, which are microalgaes that live within the protected coral polyp tissues that help with nutrient production through photosynthetic activities.
If you've seen pictures of coral reefs, you've probably remarked on the beautiful colors that the corals seem to radiate. But, it's actually the zooxanthellae that give the corals their color when they live within their clear tissues.
Thousands of species live in or nearby the coral reefs due to the incredibly high productivity and biodiversity in coral reefs, and because of that they have been referred to as the "tropical rainforests of the oceans" or "rainforests of the seas." They're even called the "medicine cabinets of the 21st century" by some because of their close link with medicine.
People everywhere benefit from coral ecosystems in many ways, such as protecting shores from the impacts of waves and lessening the damage from storms, and by increasing tourism and thus helping the economy in certain areas. One of the main benefits has come from researching and bioprospecting the organisms found in coral reefs, which has even helped identify some of the most toxic compounds known to man and potentially beneficial chemical compounds. These findings have lead to the discovery and development of many medicines people use globally, including those used to treat cancer, asthma, arthritis, ulcers, bacterial infections, heart disease, viruses, induce and ease labor, and several others. Coral chemicals are even used in the creation of cosmetics and sun block. To put it simply, coral reefs are a necessity for our way of life.
But, the impacts of human actions have caused a great deal of stress on the coral reefs, mostly in the few last decades. Even in Iowa, where we aren't located near any coral reefs, we are still part of the problem because of our impacts on the environment. Currently, 60 percent of coral reefs are threatened by human activity. Within 10 years, it's estimated that we will completely lose approximately 30 percent of coral reefs.
As a common response to the stress, coral reefs might experience coral bleaching. This occurs when the photosynthetic pigments and densities of zooxanthellae decline, resulting in a pale appearance. If the stress is short-term, the zooxanthellae can recover, but if the issue persists then it can't recover and the coral will eventually die.
Coral bleaching can be triggered by many factors, sometimes in combination, which makes it hard to determine the exact cause of it. One of the most common causes is related to climate change and variation in water temperature, because most corals can only live in fairly specific temperatures. Other human-related causes include pollution, carbon dioxide emissions, ocean acidification, sediment runoff, increase of human population and tourism, overfishing, and coastal development.
From Iowa, the threat to coral reefs might not seem like much of an issue, or at least one that you'll ever have to deal with. Many people don't care about what happens thousands of miles away or think it doesn't pertain to them. But just the medical advancements alone are significant enough to constantly affect your life. So join the "think green" trend, and think about how your actions can affect the environment.