The Coral Reef Ecosystem
Nicole Ward and Alexa Haris
Corals are ancient creatures with fossil records extending back 400 million years ago. Today, coral reefs are popular tourism sites meanwhile offering home to millions of species and presenting looming concerns for environmentalists and scientists.
Coral reefs are truly colonies. Corals themselves are anthozoans, the largest class of organisms within the phylum Cnidaria. Fellow anthozoans include sea fans, sea pansies, and anemones. The group primarily responsible for laying the foundations of and building up reef structures are stony corals (scleractinians) which make up the largest order of anthozoans. While many coral make up a reef, not all corals live as part of a colony. Stony corals have small polyps of about 1-3mm in diameter, however colonies can grow very large and weigh several tons. Some however, like Fungia species, are solitary and have single polyps that can grow as large as 25 cm (9.84 inches) in diameter. Reef structures form when colonizing coral excrete a skeleton of calcium carbonate (CaCO3) in a process called calcification. Calcification is a slow process but can happen at double the rate on a sunny day.
Coral reefs vary in different shapes, but all grow horizontally across the ocean floor. The National Oceanic and Atmospheric Association describes corals having branch shapes (elkhorn coral), coral that look like cigars or fingers (digitate corals), and broad plate shapes (foliose coral). Reef-building corals are restricted to geographic regions based on temperature, only occurring where the temperature does not fall below 18°C (64.4°F) for extended periods of time. Many corals optimally grow in water temperatures between 23° and 29°C (73.4° and 84.2°F). High light penetration and salinity of the ocean water are also important factors. Most corals require saline water ranging 32 to 42 parts per thousand. The number of coral reefs decline deeper in the ocean where heat from the sun is harder to feel. Across the world coral reefs can be found in more than 100 countries; most reefs are located between the Tropics of Cancer and Capricorn, in the Pacific Ocean, the Indian Ocean, the Caribbean Sea, the Red Sea, and the Persian Gulf. Corals are also found farther from the equator in places where warm currents flow out of the tropics, such as in Florida and southern Japan. Worldwide, coral reefs cover an estimated 110,000 square miles (284,300 square kilometers) and act as a habitat for many, many fellow marine species.
Animals found in the Coral Reef Ecosystem
Literally teeming with life, coral reefs offer a home to fish, corals, lobsters, clams, seahorses, sponges, and sea turtles just to name a few of the thousands of creatures that rely on reefs for their survival. The bluefin trevally is lucky to call Hawaii’s Maro Coral Reef home, as it is the largest coral reef in the Northern Hawaiian islands and part of the Papahānaumokuākea Marine National Monument. Purple nudibranchs also call reefs home. Nudibranchs, shell-less snails or sea slugs, are named for these tufted gills, as “nudibranch” comes from Latin and Greek words meaning “naked gills.” These shell-less gastropods have feather-like body extensions on their back and known for their bright colors. Nudibranchs like to live in shallow tropical waters, just like reefs. Many tropical fish find food and home within reefs such as the broad-barred goby. Broad-barred goby consume seaweed creeping up on coral reef estate. By eating sunlight-stealing seaweed, this fish species enables reefs to continue to grow. While the goby fish is a sign of an unhealthy reef, surgeonfish indicate healthy ones. Black striped white fish, convict surgeonfish roam reefs like sheep roam hills and eat algae growing on corals. Coral reefs host thousands of species and without them, many marine creatures lose a home and foodsource as reefs shrink in size. According to the EPA, approximately half a billion people globally depend on coral reef ecosystems for food, coastal protection, and income from tourism and fisheries.
Issues within the Coral Reef Ecosystem
Coral reefs are in fact endangered and face many challenges including ocean-level sea warming, acidification, bleaching, and invasive species. While some conservation efforts are happening such as coral reef farming in many places such as Puerto Rico and the U.S. Virgin Islands, coral reefs still fall victim to strong storms and oil tanker groundings. Global warming however, is the leading cause to challenges reefs face.
Global warming continues to raise temperatures as greenhouse emissions climb. Greenhouse gases such as carbon dioxide, methane, and water vapor trap the sun’s heat and create a warm blanket across the planet. Human activities such as car driving, factory production, and animal agriculture contribute tremendous amounts of greenhouse gases that accelerate the planet’s natural warm phases. The ocean in turn absorbs excess heat as a way to take away from the thermal skin, but overheats itself in the process. Absorbing the heat means to also absorb more carbon dioxide. When CO2 is absorbed by seawater, a series of chemical reactions occur resulting in the increased concentration of hydrogen ions resulting in acidification, one of the leading problems corals face. The ocean water where coral reefs reside becomes too acidic and carbonate ions are less abundant in the ocean water. Carbonate ions are the building block for structures such as shells and corals, having less ions makes building and maintaining shells for calcifying organisms difficult. Along with shallow and deep water corals, creatures such as oysters, clams, sea urchins, and calciferous plankton also depend on an abundance of carbonate ions.
Corals are a key species in many marine habitats, which is why issues such as bleaching deserve critical attention. Corals have a symbiotic relationship with a specific kind of algae called zooxanthellae living in their tissue. The algae are a main food source for corals and give them their color. As temperatures rise, the symbiotic relationship becomes stressed and the algae is expelled from the coral leaving the coral white as if poured over with bleach, hence “bleaching”. Coral reefs are not dead when bleaching occurs and can recover if temperatures return to normal. As global warming continues and if global carbon emissions do not reach a net-zero let alone negative emissions status, bleaching will continue and even healthy, resilient reefs will not be able to recover as temperatures increase. In 2005, the U.S. lost half of its coral reefs in the Caribbean in one year due to a massive bleaching event. The warm waters centered around the northern Antilles near the Virgin Islands and Puerto Rico expanded southward.
Corals reefs also compete with other species including the diadema sea urchin, sea grass, and the crown of thorns seastar for resources such as algae and sunlight. Crown of thorns sea stars (COTs) can be found in the Indo-Pacific and normally selectively feed on the coral tissue of fast-growing corals, which can create space for slower growing and rare corals. However, there have been outbreaks in which seastar overwhelm reefs and the coral cannot grow and recover at a fast enough pace. The cause of the outbreak is currently unknown, however human activities such as nutrient pollution and overfishing of COTs consuming predators such as tritons and napoleon wrasse may be factors. COTs sightings can sometimes suggest a decline in coral reef health. At the moment Australia has a task force dedicated to this issue. Coral reefs are being attacked from all sides and from different diseases, species, and human activities. It is important to protect reefs as they serve and provide for many other organisms.
Policies Addressing the Issues
Clean Water Act (CWA)
The Clean Water Act was originally passed in 1948 as the Federal Water Pollution Control Act, and later amended in the early 1970’s to provide a stronger structure. The Clean Water Act is one of the most critical policies that serves as a foundation for the protection of the waters of the United States. The CWA provides a framework for the regulation of pollutants into the waters. The CWA acknowledges coral reefs as a type of Special Aquatic Site that requires higher standards of protection. Keeping our oceans clean and preventing pollution is key to protecting coral reefs, and the Clean Water Act helps provide these protections for the country’s coral reefs.
National Marine Sanctuary Act (NMSA)
The National Marine Sanctuary Act is another critical law that is used to protect the coral reefs, and was initially passed in 1972. The primary goal of the NMSA is to protect valuable areas of marine habitats, such as coral reefs. Under the NMSA, the Secretary of Commerce can assign marine areas of the United States as a national sanctuary, on the basis of the areas educational, historical, scientific, and environmental value. The act supplies resources for the protection of these areas, and decides what activities are allowed to occur in the area, and the consequences for violating these rules. An example of the National Marine Sanctuary Act in action is in 2000 when the act allowed President Clinton to create the Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve, which is the largest nature reserve in the United States. The reserve focuses on conserving the coral reefs and studying the valuable ecosystem.
Endangered Species Act (ESA)
The Endangered Species Act was signed into law in 1973 and is another critical piece of legislation in the United States. To give an overview, the Endangered Species Act sets out rules and regulations in regards to species who have been listed under the act as either threatened or endangered. The ESA is involved with the protection of coral reefs. Currently there are 22 species of coral that have been listed as threatened, and 3 species that have been listed as endangered under the Endangered Species Act, and subsequently protected by it.
Coral Reef Conservation Act of 2000
The Coral Reef Conservation Act is another piece of legislation in the United States, used to protect the coral reefs. The goal of the act is to protect, support, and rehabilitate coral reefs through informed and sustainable management practices, the development of scientific research on the health of the reefs, and the support and funding of coral reef conservation organizations. Under this act there are four programs, which are the Coral Reef Conservation Program, the Coral Reef Conservation Fund, the National Coral Reef Action Strategy, and the National Program. Both the Coral Reef Conservation Program and the Coral Reef Conservation Fund deal with allocating funds to various administrations and organizations that are involved with coral reefs. The National Coral Reef Action Strategy deals with major internal and global issues in regards to the reefs, and outlines objectives for the conservation, monitoring, and research on the coral reefs. The goal of the National Program is to evaluate the health of the coral reefs by observing and repairing damages. The National Program additionally aims to educate the public on the coral reefs mainly through educational initiatives.
How Animals are Affected
There are countless species that rely on coral reefs for survival, so when the health of the coral reefs decline, these species are put in danger as well. Approximately, one fourth of the entire oceans’ aquatic life rely on coral reefs to survive as they use the reefs as a form of shelter. They also use the reefs as a form of protection when reproducing, looking for food, and raising their young. For species who are threatened or endangered, the destruction of the coral reefs could cause them to become extinct. Hawksbill sea turtles rely on coral reefs as food sources to grow sponges which they consume, thus without coral reefs the Hawksbill sea turtle will struggle to locate required nutrients to live. Spiny lobsters also use coral reefs for protection while molting. If these species become extinct, the coral reefs will become a less biodiverse ecosystem. In a study done in 2018, the diversity of fish populations was observed before and after a bleaching event occurred. Before the bleaching, when the coral was healthy and thriving, there were great amounts of biodiversity and specialization among the fish species. However, about six months after the bleaching event occurred, this great biodiversity diminished as almost all variations within fish species were lost. This loss of biodiversity is known as biotic homogenization.
What You Can Do
Reduce your Daily Impact
Taking actions in your everyday life can have a big impact. Climate change is the main cause of the destruction of the coral reefs, so do your part to lessen the effects of climate change the best that you can. Reduce your greenhouse gas emissions by opting for public transit, walking, or carpooling when those options are available to you. In addition, reduce your use of fertilizers and other chemicals on your lawn, because these chemicals can runoff into the water system, and contribute to the pollution of the oceans. Additionally, don’t forget to reduce, reuse, and recycle. Don’t buy in excess, and try to reuse and repurpose the things you already have, instead of buying new products. Hand in hand with that, buy second hand! The fashion industry is one of the biggest culprits of greenhouse gas emissions. The industry emits 10% of the world’s carbon emissions, and approximately 85% of all clothing textiles end up in landfills each year. So, avoid fast fashion and support brands that are doing their part to produce sustainably made clothing, or opt to shop at the thrift store instead! You may feel as though these small changes are not going to make a difference, but each change you make adds up!
If You’re Visiting Coral Reefs
If you’re going snorkeling or diving in an area with coral reefs, be responsible and don’t do anything to harm them. Don’t touch them because they can be easily damaged. Additionally, be aware of what you put on your body when you’re going to be near corals. Most sunscreens contain ingredients that can be damaging to corals, and could possibly kill them. Specifically, Oxybenzone (BP-3) is an ingredient found in a variety of sunscreens that has been known to have a few dangerous effects on developing coral. The effects include making them more vulnerable to bleaching, irregular skeleton development, DNA impairments, and abnormal deformities of young coral. So when shopping for sunscreen, make sure you check for this ingredient or do research online for environmentally friendly brands to buy – at Fanimal, we love Badger sunscreen but there are many others. An even better alternative would be to wear full body clothing when diving near coral, to eliminate the need for sunscreen in the first place.
Volunteer & Donate
Volunteer for beach clean ups in your area. Not only are you helping reduce the waste that goes into the ocean, but it can also be a very educational experience. Additionally, if you are financially able, you can donate to organizations whose missions are to help save the coral. There are tons of organizations that are hard at work to save the coral reefs, and your donations will help them with their missions. Some organizations include the Coral Reef Alliance, the Coral Restoration Foundation, and Save the Reef. So check out these organizations, and learn more about how you can help them achieve their goals.
Sources: Business Insider, Coral Digest, Coral Reef Alliance, Environmental Protection Agency, Global Change Biology, National Geographic, National Oceanic and Atmospheric Administration, National Ocean Service, One Green Planet, Smithsonian, Sustain Your Style