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Coral Reefs

Coral Reefs

Coral reefs are some of the most diverse ecosystems on the planet. Though they only occur in approximately one percent of the ocean, coral reefs are home to an estimated 25% of marine species. Often called the “rainforests of the sea,” coral reefs provide a variety of ecosystem services like coastal protection, economic benefits to fisheries like serving as a nursery for some fish species, and providing a habitat for marine organisms. This delicate, yet important ecosystem is made possible by the corals. Corals are unique organisms that come in many shapes and sizes. Corals are colonial organisms, which means they are composed of hundreds of organisms called “polyps.” There are two different types of corals: hard corals and soft corals. Hard corals are often referred to as “reef building corals” because the hard calcium carbonate structures they create are responsible for building the coral reef environment. The brilliant color of these corals comes from the mutually beneficial relationship between the coral polyps and single celled organisms called zooxanthellae. The zooxanthellae live in the tissue of the coral polyps, sharing space and nutrients. 

The unique marine ecosystem formed by these corals serves as a home to a variety of species of fish, crustaceans, marine mammals, and many other marine organisms. The habitat that reefs create is incredibly important for fisheries in the area. Reef-related fisheries around the world feed around a billion people and are estimated to be worth 172 billion dollars. In addition to this value reefs provide a variety of other valuable services such as storm protection, recreation, tourism, and medical discoveries. 

Despite their ecological and economic importance, coral reefs are in danger. Overfishing and fishing practices, warming seas, invasive species and pollution all threaten these ecosystems. It is estimated that more than 55 percent of the world's coral reefs are threatened by overfishing. Overfishing of a species disrupts the entire ecosystem because in many cases fish species have important roles in their ecosystems such as controlling algae populations. In addition to overharvesting, other facets of the fishing industry can be incredibly harmful to coral reef ecosystems such as destructive fishing methods like bottom trawling. Bottom trawling involves dragging a net across the bottom of the ocean, this damages and destroys corals. It also results in a significant amount of bycatch, unintentionally caught marine organisms. 

In addition to the fishing industry, warming seas as a result of climate change pose a serious threat to coral reefs. While many coral reefs are in warm shallow seas, these ecosystems are incredibly vulnerable to changes in temperature. Increases in temperature often lead to a phenomenon known as coral bleaching. This refers to the process by which corals expel the zooxanthellae, the tiny organisms that live on corals that give rise to the unique color of corals. By expelling their zooxanthellae, corals become white in appearance, hence the term “coral bleaching.” While coral bleaching does not necessarily kill the corals, it does put them under stress which can leave the corals much more vulnerable to disease and death. 


One of the other major threats to coral reefs are invasive species. Invasive species are species that have been introduced to an area by humans, either intentionally or unintentionally. These invasive species typically have no natural predators in the area which causes their population to grow rapidly. Invasive species often outcompete native species and lead to habitat degradation. In coral reefs, cargo ships and other boats are often responsible for releasing invasive species. In Hawaii, five species of invasive algae have been causing problems. Invasive species of algae are especially bad for coral reefs because they can blanket the reef, restricting access to sunlight for the photosynthetic organisms that live in the reef. In the Atlantic, specifically the Caribbean, lionfish have become invasive. Lionfish are a fish species native to the South Pacific or Indian Ocean. Lionfish are beautiful creatures that have been kept in home aquariums because of their unique appearance. The concern with lionfish is that they are a top level predator and their presence is disrupting the food web of coral reefs in the Caribbean. Lionfish are covered in extremely venomous spikes, making them incredibly unappetizing to any potential predator species in the Caribbean.


Lionfish and other invasive species are not the only unwanted guests in coral reefs, plastic and chemical pollution also pose threats to coral reef communities. Plastic pollution in the ocean is a major ecological issue. Massive patches of plastic waste float in the middle of most of our oceans. This plastic waste will take thousands of years to break down. In that time it will continue to do major damage to ecosystems and marine life. Small pieces of plastic are often picked up by marine animals like fish, sea turtles, and shorebirds who mistake them for food. Ingesting plastic has harmful effects on these marine animals. In addition to plastic pollution, chemical pollution such as fertilizer and pesticide runoff also has extremely detrimental impacts on marine ecosystems like coral reefs. This runoff can increase the presence of dead zones, which you can read more about in this blog post (insert deadzone link). 

Coral reef ecosystems are the backbone of many coastal communities and also of great ecological significance, so it is vital that we take steps to protect them from these threats. The establishment of marine protected areas goes a long way in protecting coral reefs from a variety of threats. In 2006, the Papahānaumokuākea Marine National Monument was established in the Hawaiian Islands and its size was expanded even more in 2016. It is the largest contiguous fully protected conservation area in the United States and one of the largest in the world. While these marine protected areas are incredibly important, other steps must be taken in order to address the threats facing coral reefs. Stricter rules must be established when it comes to fishing practices, especially near coral reefs. Programs to control and remove invasive species must be created and funded. In addition, companies need to move away from plastic in their products and in their packaging to address plastic pollution. Finally, action must be taken to address the changing climate and prevent further changes in global temperature. 

If you are looking for ways to help protect coral reefs yourself, here are some simple actions you can take: 

  1. Reduce your plastic consumption by using reusable alternatives, saying no to plastic when possible, and buying things packaged in compostable packaging (like our kelp chips!)
  2. Reduce your use of fertilizers and pesticides on your lawn. 
  3. Try to reduce your carbon footprint by saving energy and take public transport, walk, or bike if possible. 
  4. Use reef friendly sunscreen when going swimming in the ocean. 
  5. Support an organization like Coral Gardeners which helps to restore coral reefs.   



About the Author: Emma Gamble is a junior at the George Washington University majoring in Environmental Studies and minoring in public policy. Emma is passionate about incorporating greater sustainability into our food systems in order to create a greener future for people and the planet. Emma enjoys sailing, kayaking, and paddle boarding.