The Amazing World of Coral Reefs

The Amazing World of Coral Reefs

Coral reefs are one of the most diverse and valuable ecosystems on Earth. Often called the “rainforests of the sea,” coral reefs are home to a spectacular array of life. This article deeply delves into the wonders of coral reefs, their importance, and the threats they face in a rapidly changing world.

What Exactly Are Coral Reefs?

Coral reefs are created by tiny coral polyps, animals living in colonies. Polyps extract calcium carbonate from seawater to construct a hard, protective exoskeleton around themselves. Over many generations, the calcium carbonate skeletons of coral colonies form the foundations of immense coral reef structures.

Two Main Types of Coral Reefs

There are two main types of coral reefs:

Fringing Reefs

Fringing reefs grow seaward directly from shore in shallow waters, forming borders along coastlines and around islands. These reefs are the most common type.

Barrier Reefs

Barrier reefs are separated from land by broad, deep lagoons. Australia’s iconic Great Barrier Reef is the most significant in the world. At over 1,400 miles long, it is the only living structure visible from space!

Biodiversity Abounds in Coral Reefs

Coral reefs harbor incredibly high biodiversity. Although they cover less than 1 percent of the ocean floor, coral reefs are home to about 25 percent of all marine species. Just one reef can hold thousands of species! Some species living on coral reefs include Fish – Over 4,000 species inhabit coral reefs. They come in all colors, shapes, and sizes. Clownfish, parrotfish, butterflyfish, tangs, and angelfish are just a few. Corals – Over 800 species of hard and soft corals make up reef foundations. Seahorses – Seahorses expertly camouflage themselves among the coral. Sea turtles – Endangered turtles like hawksbills and green sea turtles rely on coral reefs for food and shelter. Sponges – Reef sponges provide homes for fish and filter seawater. Vibrant barrel sponges grow up to 6 feet wide! Crustaceans – Crabs, lobsters, and shrimps thrive in reefs. The peacock mantis shrimp packs one of the most potent punches in the ocean with club-like appendages. Echinoderms – Starfish, sea cucumbers, and sea urchins are just some coral reef echinoderms. Sharks & rays – Requiem sharks, whale sharks, manta rays, and stingrays cruise through reef waters. This is merely a tiny sample of the vast diversity found on coral reefs. New species are discovered here every year!

Why Are Coral Reefs So Productive?

Coral reefs are highly productive ecosystems. But what makes them so lively and dynamic? There are a few key reasons:

Warm Shallow Waters

Coral reefs only grow in warm, shallow waters, mostly in tropical or subtropical oceans. The average water temperature where reefs thrive is 70-85°F. These warm waters speed up marine life’s metabolic processes.

Sunlight Penetration

Deep waters allow sunlight to penetrate and reach reef organisms containing symbiotic algae. This photosynthesis provides nourishment for corals and the whole ecosystem.

Currents Bring Nutrients

Water currents constantly wash nutrients over reefs, fertilizing the ecosystem. Reef organisms can easily find ample food. This allows reefs to sustain such high densities of life.

Interconnected Habitats

Coral reefs comprise closely linked habitats, including corals, mangroves, seagrass beds, lagoons, and more. Organisms can quickly move between these zones to feed and breed.

The Vital Importance of Coral Reefs

Beyond being fascinating ecosystems teeming with life, coral reefs are vitally important. Here are some of the critical benefits they provide:

Shelter and Nurseries

Reef structures offer protection, shelter, and breeding grounds for marine creatures. With reefs, many species would retain their homes.


Vibrant reefs draw tourists for diving, snorkeling, and beach adventures. This offers significant revenue for tropical nations. The Great Barrier Reef alone brings Australia over $4 billion per year.

Coastal Protection

Coral reefs buffer coastlines from strong waves and storm impacts. They prevent erosion and property damage. Over 200 million people worldwide live within 30 miles of reefs.


Coral reefs support over 25 percent of all small-scale fisheries globally. And commercial fishing also relies on reef fish populations. About half a billion people rely on reef fish as their primary protein source.


Chemicals from reef species are being studied to develop new medicines that fight cancer, arthritis, viruses, and other diseases. Sea sponges alone have helped produce treatments for leukemia, herpes, and more.

Escalating Threats to Coral Reefs

Despite their importance, coral reefs are highly threatened ecosystems. Both local and global pressures are causing their decline. Major threats include:

Climate Change & Ocean Warming

Seawater temperatures are rising as oceans absorb more excess heat and CO2 from climate change. Even small temperature increases cause coral bleaching, where stressed corals expel algae. Prolonged bleaching causes coral death and reef decline.

Ocean Acidification

Higher atmospheric CO2 leads to more CO2 dissolving into seawater, lowering its pH. This ocean acidification makes it challenging for corals to build their calcium carbonate skeletons.


Agricultural runoff and untreated sewage can trigger algal blooms and create marine dead zones around reefs—toxins like fertilizers, pesticides, and oil spills poison reef ecosystems.

Overfishing & Destructive Fishing

Unsustainable fishing depletes key reef species that help maintain balance. Blast fishing and cyanide fishing kill corals to catch reef fish. Lost fishing gear entangles and kills reef creatures.

Coastal Development

Port construction, dredging, and filling for coastal hotels and infrastructure physically destroy reefs. Runoff from construction pollutes waters.

How Can We Protect Coral Reefs?

Despite the threats they face, there is hope for coral reefs. Protecting these precious ecosystems requires bold actions at both local and global scales:

Reduce Emissions and Ocean Warming

Transitioning to renewable energy and reducing greenhouse gases are needed to limit climate change and give corals a fighting chance. We must curb ocean warming and acidification.

Establish Marine Protected Areas

Designating marine parks where fishing and human activities are restricted allows coral reefs space to recover and regrow. No-take zones are especially beneficial.

Improve Fishing Practices

Sustainable fishing quotas, gear modifications, and bans on destructive practices like dynamite blast fishing can take pressure off reefs.

Reduce Pollution

Treating sewage, curbing agricultural runoff, and reducing plastic use can lessen land-based pollution harming coral reefs.

Protect Key Species

Guarding keystone grazers like parrotfish that clean algae off reefs helps prevent overgrowth and death. Sea urchin protection also boosts regeneration.


Coral reefs are crucial and fragile ecosystems we cannot afford to lose. Their dazzling biodiversity, ecological services, economic benefits, and natural wonder make them global treasures. With swift action to reduce local and climate threats, we can give coral reefs a fighting chance to survive and regrow in our rapidly changing oceans. Our future depends on living in balance with these rainforests of the sea.

Frequently Asked Questions

How long does it take coral to form a reef?

Fast-growing corals can take as little as ten years to form small coral colonies. But it takes centuries to millennia for vast coral reef structures to fully develop from accumulating calcium carbonate skeletons. The Great Barrier Reef was created over the past 20,000 years.

Where are the healthiest coral reefs located?

Some of the world’s healthiest remaining coral reefs are found in remote regions with limited human impacts, like the Phoenix Islands Protected Area in the Pacific and the Chagos Archipelago in the Indian Ocean.

How many species live on the Great Barrier Reef?

The Great Barrier Reef is home to over 1,500 species of fish, 400 species of corals, 4,000 types of mollusks, and 215 species of birds. New species are still being discovered here.

What percent of coral reefs are already lost?

Over 30 percent of the world’s coral reefs are estimated to be severely damaged, and over 60 percent are under immediate and direct threat. The rate of reef loss has accelerated in recent decades.

Can damaged coral reefs recover naturally?

Yes, if pressures are reduced, coral reefs have a natural resilience and can recover over time. But recovery takes many years and requires healthy herbivores to control algae growth and allow new corals to settle.