CORAL REEFS

Coral reefs are often referred to as the “rainforests of the sea” due to their high biodiversity. They provide a habitat for a vast array of marine species, including fish, invertebrates, and algae. Coral reefs also protect coastlines from erosion and provide economic benefits through tourism and fisheries.

What is Coral

Despite their plant-like appearance, corals are actually animals rather than plants. These marine organisms belong to a group called cnidarians, which also includes jellyfish and sea anemones. Coral polyps, the individual units that make up coral colonies, are tiny invertebrates with tentacles surrounding a central mouth.

Distinguishing feature of corals is their ability to build calcium carbonate skeletons, which collectively form the intricate structures we recognize as coral reefs.

One fascinating aspect of coral biology is their partnership with algae called zooxanthellae. These algae live within the coral polyps, exchanging essential nutrients through photosynthesis for a safe place to thrive.

 

Image credit: goo

This teamwork between corals and algae is crucial for the health and vitality of coral reefs. However, when corals face stressors like warmer waters or pollution, they expel the algae, causing coral bleaching.

Coral bleaching leads to the loss of vibrant colors and weakens the corals, making them more susceptible to disease. This not only affects the corals but also disrupts the entire reef ecosystem, impacting the many creatures that rely on it.

Image credit: Brett Monroe Garner / Getty Images

Architects of underwater cities

Coral polyps extract calcium carbonate from seawater and use it to construct their hard skeletons, which form the structure of the reef over time. As each polyp grows, it secretes more calcium carbonate, gradually adding to the reef’s size and complexity. Over thousands of years, countless generations of coral polyps contribute to the formation of massive coral reef ecosystems, providing habitats for a diverse array of marine life.

Coral reefs form a vital link in the intricate web of marine ecosystems, interconnected with various habitats. Adjacent seagrass beds provide important nursery grounds for reef fish, while mangrove forests offer shelter and nutrients crucial for the growth of coral colonies.

The Structure of Coral reefs

After the coral larvae settles and attaches to the solid structure, the coral reef building proces can start. As the reef grows it takes one of the three main forms:

Fringing reef

The most common type of reef.  They grow near the coastline around islands and continents, usually separated by narrow, shallow lagoon. Prime example is Ningaloo Reef along the western coast of Australia.

Barrier reef:

Similar to the fringing reef, but further from the shore. Think Great Barrier Reef in Australia.

Atoll:

Usually ring shaped reefs or series of islets surrounding a body of weater – lagoon, sometimes with central island.  Channels between islets connect the lagoon with the ocean. Think of Maldives, Polynesia, and Micronesia.

Coral reproduction

Coral spawning is a remarkable natural event where corals release their eggs and sperm into the water simultaneously, often synchronizing their reproduction with specific environmental cues, such as lunar cycles or water temperature. This synchronized mass spawning, which typically occurs once a year, is crucial for the survival and genetic diversity of coral populations.

One way corals mate is through external fertilization, where the released eggs and sperm mix freely in the water column. This method allows for genetic exchange between different coral colonies, promoting diversity and resilience within coral populations.

Alternatively, some corals engage in internal fertilization, where the eggs are fertilized within the polyp’s body before being released into the water. This strategy offers advantages in environments with stronger water currents, ensuring better chances of successful fertilization.

Image credit: Fred Bavendam/Minden Pictures

Where to find corals

Corals are found in a variety of marine environments around the world, but they typically thrive in warm, tropical waters within specific latitudinal bands. The greatest diversity of coral reefs is found in tropical regions near the equator, roughly between 30 degrees north and 30 degrees south latitude. However, some corals can also be found in subtropical and temperate regions, particularly along coastlines with warm currents, extending as far as 40 degrees north and south latitude.

5 major areas where you can find coral reefs

The Great Barrier Reef, located off the northeastern coast of Australia in the Coral Sea, is the largest coral reef system on Earth, spanning approximately 2,300 kilometers (1,430 miles) in length. Its remarkable biodiversity boasts over 1,500 species of fish, 411 types of hard coral, and countless other marine creatures, making it one of the most biologically diverse ecosystems in the world.

The Coral Triangle, located in Southeast Asia, encompasses the waters of Indonesia, Malaysia, the Philippines, Papua New Guinea, Timor-Leste, and the Solomon Islands. This region is renowned as the “Amazon of the Seas” due to its extraordinary marine biodiversity, hosting over 600 species of coral and more than 3,000 species of fish. Stretching across approximately 5.7 million square kilometers (2.2 million square miles), the Coral Triangle supports vital ecosystems such as coral reefs, mangroves, and seagrass beds, serving as a crucial nursery ground for numerous marine species.

The Caribbean Coral Reefs, which include the Mesoamerican Reef, are situated across the Caribbean Sea, encompassing areas off the coasts of Mexico, Belize, Honduras, and various Caribbean islands. The Mesoamerican Reef, also known as the Great Mayan Reef, is the largest barrier reef in the Western Hemisphere, stretching approximately 1,000 kilometers (620 miles) from the northern tip of the Yucatan Peninsula down to the Bay Islands of Honduras.

The Red Sea Coral Reefs span along the Red Sea coastlines of Egypt, Sudan, Eritrea, Djibouti, Israel, Jordan, and Saudi Arabia. This region is renowned for its unique and diverse marine life, including vibrant coral formations, colorful fish species, and fascinating underwater landscapes. The Red Sea Coral Reefs stretch approximately 2,000 kilometers (1,240 miles) in length, providing crucial habitats for a wide range of marine organisms. These reefs are highly valued for their ecological significance, supporting important ecosystem functions such as biodiversity, coastal protection, and fisheries.

The Coral Reefs of the Western Indian Ocean are found along the coasts of Madagascar, Mozambique, Tanzania, Kenya, Somalia, and the Seychelles. Spanning a diverse range of habitats, from shallow coastal areas to deeper offshore reefs, these ecosystems support a wealth of marine biodiversity. Coral reefs in this region are characterized by their intricate coral formations, vibrant fish communities, and important nursery grounds for numerous species.

Benefits

Coral reefs are among the most biodiverse ecosystems on the planet, supporting an extraordinary array of marine life, including over 25% of all marine species despite covering less than 1% of the ocean floor.

Coral reefs serve as vital nursery grounds for countless marine species, providing shelter and food for juvenile fish, crustaceans, and other organisms during critical stages of their life cycle.

Coral reefs contribute significantly to global fisheries, providing habitat and breeding grounds for numerous commercially important fish species. Healthy reefs sustain fish stocks, supporting millions of people who depend on fishing for food and livelihoods.

Coral reefs act as natural barriers, reducing the impact of waves and storm surges on coastlines. They help dissipate wave energy, protecting shorelines from erosion and minimizing damage caused by hurricanes and tsunamis.

Coral reefs help stabilize sediments and prevent coastal erosion by trapping sand and debris, maintaining the integrity of coastal habitats such as beaches, mangroves, and seagrass beds.

Coral reefs play a crucial role in carbon cycling and climate regulation. They absorb and store vast amounts of carbon dioxide, helping mitigate climate change by reducing greenhouse gas concentrations in the atmosphere.

Healthy coral reefs enhance the resilience of coastal communities to climate-related hazards such as sea-level rise and extreme weather events. They provide natural buffers against coastal erosion and flooding, supporting adaptation efforts in vulnerable regions.

Coral reef organisms produce bioactive compounds with potential pharmaceutical applications. Research on reef organisms has led to the discovery of new drugs and treatments for various diseases, highlighting the value of reef biodiversity for medical science.

Coral reefs hold cultural significance for many indigenous communities and coastal societies worldwide. They provide inspiration for art, folklore, and spiritual practices, fostering a strong sense of identity and connection to the marine environment.

Coral reefs attract millions of tourists annually, generating substantial economic revenue through recreational activities such as diving, snorkeling, and eco-tourism. Coastal communities benefit from tourism-related jobs and businesses that rely on the health of reef ecosystems.

Threats

Rising sea temperatures cause coral bleaching, disrupting the symbiotic relationship between corals and algae. Increased frequency and intensity of storms can also damage reef structures.

Increased carbon dioxide levels in the atmosphere lead to ocean acidification, hindering coral calcification and growth, and weakening coral structures.

Runoff from land-based activities introduces pollutants such as sediment, nutrients, and chemicals into coastal waters, leading to coral stress, disease outbreaks, and reduced water quality

Unsustainable fishing practices, including destructive methods like blast fishing and cyanide fishing, deplete fish stocks and disrupt the delicate balance of reef ecosystems.

Urbanization, tourism infrastructure, and coastal construction can result in habitat destruction, sedimentation, and pollution, directly impacting coral reef health.

Extraction of coral for building materials and souvenirs degrades reef habitats and reduces the structural integrity of coral formations.

HOW can I help Corals

No matter how far you live from the ocean, the consequences of your daily actions will impact coral reef habitats in the end. As rivers flow into the ocean, everything we introduce into them inevitably reaches these delicate ecosystems. Let’s reconsider our actions to be more ocean-friendly.

Play it safe

Never take any coral from the ocean. When diving or snorkeling, pay attention to not damage the coral, keep your equipment secured, and avoid direct contact. Do not use sunscreen containing substances that can damage corals. These substances include:

  • Oxybenzone (Benzophenone-3)
  • Octinoxate (Ethylhexyl Methoxycinnamate)
  • Octocrylene
  • 4-Methylbenzylidene Camphor (4-MBC)
  • Butylparaben
  • Octocrylene

Get involved

Join Coral Restoration

Take a part in the coral restoration project

Image credit: Corales de Paz