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Table of Contents
A coral reef ecosystem is a biologically diverse and populous underwater ecosystem characterized by reef-building corals. Coral reefs have been dubbed “rainforests of the sea” for their rich biodiversity. Aside from corals, other organisms such as fish, plants, sponges, and algae are found in coral reef ecosystems.
See the fact file below for more information on the Coral Reef Ecosystem, or you can download our 29-page Coral Reef Ecosystem worksheet pack to utilize within the classroom or home environment.
Key Facts & Information
CORALS, CORAL POLYPS, AND CORAL REEFS
- Corals are animals that are composed of thin layers of calcium carbonate produced by hundreds or thousands of soft-bodied invertebrates called coral polyps.
- Though they are animals, corals can’t produce food on their own.
- Coral polyps can be as tiny as a pinhead or reach a foot long.
- Coral polyps are responsible for building coral reefs, which serve as a habitat for a wide variety of marine life.
- Coral reefs are primarily made up of hard and soft corals, the two main types of corals.
- Hard or stony corals have rigid exoskeletons called corallites, while soft corals don’t have exoskeletons.
- Examples of hard corals are a star, brain, elkhorn, staghorn, tube, and pillar corals.
- Examples of soft corals are sea fans, sea rods, sea fingers, and sea whips.
- Coral reefs reportedly contain at least 25% of all aquatic species, which includes fish, crustaceans, mollusks, echinoderms, sponges, worms, tunicates, and cnidarians.
- Coral reefs support approximately 4,000 species of fish and 800 types of corals.
- They cover about 0.1% of the ocean floor and are usually found at shallow depths in tropical waters.
FORMATION AND GEOGRAPHY
- In the early 20th century, American geologist Reginald Daly put forward the theory that modern coral reefs formed during the last glacial period when melting ice from glaciers led to the rise of the sea level.
- Most coral reefs exist in tropical areas between the latitudes of 30 degrees North and 30 degrees South because of their symbiotic relationship with photosynthetic algae called zooxanthellae which thrive under specific salinity, temperature, and light conditions.
- Coral reefs are located in three main regions between 20 degrees North and 20 degrees South of the equator: the Indo-Pacific (the largest assemblage of reefs), the Western Atlantic, and the Red Sea (the smallest of the three).
IMPORTANCE OF CORAL REEFS
- Healthy coral reef ecosystems provide food, habitat, coastal protection, medicinal source, and income from fishing and tourism.
- People who live near coral reefs can benefit from them as a source of food and new medicine, job opportunities for local fisheries, and recreational purposes.
- Coral reefs also contribute to tourism in an area where scuba diving and snorkeling, and swimming offer fun water activities.
- The annual commercial value of United States fisheries from coral reefs is estimated to be more than $100 million by The National Marine Fisheries Service in 2001.
- Coral reefs serve as a home and breeding ground for more than 1 million aquatic species.
- They also help in protecting coastal infrastructure from storms, floods, tsunamis, and erosion.
- Indigenous communities around the world consider coral reefs culturally important.
TYPES OF CORAL REEFS
- English naturalist Charles Darwin identified three classical formations of coral reefs: a fringing reef becoming a barrier reef and then an atoll.
- The most common type of reef is the fringing reef.
- A fringing reef, also known as a shore reef, is mainly directly attached to or close to the seashore around a volcanic island or bordering a part of a continent.
- Fringing reefs grow in a shallow water channel that spans 50 to 100 meters.
- This type of reef is the most prone to damage due to exposure to human activities.
- The biggest fringing reef in the world is the Ningaloo Reef of Australia near the Indian Ocean.
- A barrier reef is a coral reef ecosystem that is separated from a mainland by a water lagoon (often 20 to 100 meters deep).
- It is usually found a few miles away from the shore.
- The Great Barrier Reef in Australia is the largest known barrier reef in the world.
- An atoll reef, simply called atoll, is a continuous barrier reef surrounding a lagoon in a shape that resembles a horseshoe or a ring.
- An atoll is commonly formed from fringing reefs around volcanic islands.
- There are 26 atolls in the Maldives alone.
- Other types of reefs include platform reefs (radially growing reefs found on continental shelves), patch reefs (small, isolated reefs that are often between fringing and barrier reefs and are surrounded by sand or seagrass), and ribbon reefs (long, narrow reefs typically associated with an atoll lagoon.)
ZONES IN A CORAL REEF
- Coral reefs can be divided into three major zones based on the kind of habitat and the difference in light intensity, water current, and level of detritus: the fore reef, the reef crest, and the back reef.
- These zones are ecologically interconnected by the exchange of marine life, seawater, and nutrients through oceanic processes.
- The fore reef, or reef front, is the outer part of a reef seaward of the reef crest towards the direction of the open sea.
- Where the water current is strongest is the reef crest because this is where the waves break over the reef.
- Corals in the reef crest are those that thrive under harsh conditions, such as high light intensity, and ultraviolet radiation, such as small-polyp corals.
- The back reef, or reef lagoon, includes the lagoon between the shore and the coral reef.
- Small patches of corals, sea grass, and sand are found in the back reef.
- Some coral reefs may have up to six zones: the reef surface (the shallowest part of the reef subject to surge and tides); the off-reef floor (the shallow sea floor surrounding a reef); the reef drop-off (habitat for reef fish and plankton on the cliff face); the reef face (the reef’s most diverse portion and found between the reef drop-off and reef floor); the reef flat (shallow area with chunks of coral and found to the leeward side of the reef crest); and the reef lagoon (an enclosed area that contains small reef patches).
SIGNIFICANT CORAL REEFS
- The Red Sea consists of 6,000-year-old fringing reefs located along a coastline that stretches 2,000 kilometers.
- The Great Barrier Reef, which is the largest barrier reef in the world, includes more than 2,900 individual reefs and 900 islands off Queensland, Australia.
- The second largest is the Mesoamerican Barrier Reef System which spans 1,000 kilometers in Honduras.
- The third largest is the Andros Barrier Reef in the Bahamas which measures 305 kilometers long.
- The Florida Reef Tract is the biggest continental reef in the United States.
- Spanning 26,000 square kilometers, the Philippines’ coral reef area is the second-largest in Southeast Asia.
- The highest known marine diversity in a coral reef ecosystem is found in the Raja Ampat Islands in the West Papua province of Indonesia.
THREATS TO CORAL REEFS
- Natural threats to coral reefs include storms, predators, and pathogens.
- Meanwhile, man-made threats such as pollution, destructive fishing practices, sedimentation, dredging, coastal development, and misuse of corals by touching or removing them.
- These natural and man-made threats cause stress and damage to coral reef ecosystems. Coral bleaching and death are possible results of these threats.
Coral Reef Ecosystem Worksheets
This fantastic bundle includes everything you need to know about the Coral Reef Ecosystem across 29 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about Coral Reef Ecosystems. A coral reef ecosystem is a biologically diverse and populous underwater ecosystem characterized by reef-building corals.
Complete List of Included Worksheets
Below is a list of all the worksheets included in this document.
- Coral Reef Ecosystem Facts
- Words To Remember
- Odd One Out
- Reef Type Search
- So Significant
- Reef or Wrong?
- Coral Reef or Not?
- Zoning Out
- Protect Coral Reefs Now
- Reefs Around The World
- Knowledge Recap
Frequently Asked Questions
What is a coral reef ecosystem?
A coral reef ecosystem is a diverse and complex system made up of coral colonies, fish, algae, and other marine organisms that live in and around coral reefs. Coral reefs are found in shallow, warm, and clear waters in tropical and subtropical regions around the world.
How do coral reefs benefit the environment?
Coral reefs provide many benefits to the environment, including supporting a diverse range of marine life, protecting shorelines from erosion, and cycling nutrients through the ecosystem. Coral reefs also help to maintain water quality and support local economies through tourism and fisheries.
What are some threats to coral reef ecosystems?
Coral reef ecosystems face many threats, including climate change, ocean acidification, overfishing, pollution, and physical damage from human activities such as boating and diving. These threats can cause coral bleaching, disease, and death, which can have devastating effects on the ecosystem.
How can we protect coral reef ecosystems?
To protect coral reef ecosystems, we need to take action to address the threats they face. This includes reducing greenhouse gas emissions to mitigate the impacts of climate change, managing fisheries sustainably, reducing pollution, and implementing policies to protect coral reefs from physical damage.
What is being done to conserve coral reef ecosystems?
There are many conservation efforts underway to protect coral reef ecosystems, including the creation of marine protected areas, restoration of damaged reefs, and public education and outreach programs. International organizations, such as the International Coral Reef Initiative, are also working to promote collaboration and action to conserve coral reefs around the world.
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