Quck answer
Coral reefs are diverse underwater ecosystems that play a vital role in marine life. They are made up of coral polyps, which are tiny animals that secrete calcium carbonate to form hard, rocky structures. These structures provide shelter, food, and breeding grounds for a vast array of marine species. Coral reefs also help protect coastlines from erosion and storm damage. However, coral reefs are under threat from a range of human activities, including overfishing, pollution, and climate change. To preserve these important ecosystems, it is essential to reduce these threats and promote sustainable practices.
Wildlife
The Structure and Conditions of Coral Reefs
Coral reefs, marked with red dots, are found mostly in tropical waters situated 30 degrees north and south of the equator.
Photo courtesy NOAA
If you go scuba diving in colder waters, you won’t come across coral reefs. Due to their exclusive association with zooxanthellae, which require warm water and sunlight to survive, the distribution of coral reefs is limited to 30 degrees north or south of the equator. The reefs in the Bahamas at 32 degrees north of the equator are an exception due to the warm water currents they receive from the Gulf of Mexico.
Reefs require saltwater environments with a specific salinity in addition to warm water that does not fall below 64.4 degrees Fahrenheit (18 degrees Celsius). As shown on the map, the majority of reefs are present in the Indian and Pacific oceans, which meet these requirements.
Finally, reefs thrive in clear waters that are low in nutrients. An excess of suspended material floating in the water hinders the sunlight necessary for the algae’s photosynthesis. Reefs can grow up to 3.9 inches (10 centimeters) annually in the following optimal conditions:
- Plentiful light
- Clear water
- Temperatures ranging from 73.4 degrees Fahrenheit to 84.2 degrees Fahrenheit (23 degrees Celsius to 29 degrees Celsius)
On sunny days, coral can produce calcium carbonate twice as swiftly as on cloudy days. Yet, even at 3.9 inches a year, a well-developed reef can take thousands of years to form. In reality, reefs are comparable to old-growth forests in terms of the number of years they represent [source: NOAA].
While corals form the basis of reefs, they are not the only inhabitants, and they incorporate a variety of plants and animals into their framework. Coral sand is one of the primary players. It is created by the erosive force of waves and currents against limestone and animal shells, as well as by the grinding teeth of certain fish. Coral sand gets trapped in crevices along the reef, and encrusting coralline algae acts as a glue, depositing a hard layer of solid calcium carbonate over the trapped sand to hold it in place. Together, the encrusting algae and coral sand repair damaged areas of the reef and help to stabilize it, especially in areas frequently affected by waves.
Although reefs have similar needs and basic components, they can be divided into three categories depending on where they form. Fringing reefs are the most prevalent. They originate directly from the shore and grow on the outer edges of land masses, forming a border that extends out to the sea. Barrier reefs are similar to fringing reefs in that they also encircle land masses, but they form a border at a distance, with a span of water separating them from the shore. Atolls are either circular or oval and enclose a lagoon of water. They develop when a fringing reef forms around a volcano that later sinks beneath the ocean’s surface while the reef continues to grow.
On the next page, you’ll learn about the specific zones that can be found in a reef as you dive through them.
FAQ
1. What are coral reefs?
Coral reefs are underwater structures made up of the skeletons of coral polyps, tiny animals that belong to the same family as jellyfish and sea anemones. These skeletons are made of calcium carbonate, a hard substance that gives the reefs their characteristic stony appearance.
2. Why are coral reefs important?
Coral reefs are incredibly important ecosystems that provide habitat for a huge variety of marine species. They are also important for humans as they protect coastlines from storms and erosion, support tourism and fishing industries, and even provide potential sources of new medicines.
3. How do coral reefs form?
Coral reefs begin to form when free-swimming coral larvae attach to a hard surface, such as a rock or shipwreck, and begin to multiply. Over time, these polyps secrete calcium carbonate to create a hard skeleton that provides a base for more coral to grow.
4. What is coral bleaching?
Coral bleaching occurs when coral polyps expel the algae that live inside them, causing the coral to turn white. This is often caused by increased water temperatures due to climate change or pollution, and can lead to the death of the coral if it persists for too long.
5. What threats do coral reefs face?
Coral reefs face a number of threats, including climate change, pollution, overfishing, and destructive fishing practices such as dynamite fishing. They are also at risk from coastal development and physical damage from boats and anchors.
6. How can we protect coral reefs?
We can protect coral reefs by reducing our carbon emissions to slow the rate of climate change, reducing pollution, and implementing sustainable fishing practices. We can also support organizations that work to protect coral reefs and avoid contributing to activities that damage them, such as buying souvenirs made from coral.
7. How do coral reefs support biodiversity?
Coral reefs support biodiversity by providing habitat for a huge variety of marine species, including fish, sharks, turtles, and many others. They also offer shelter and protection from predators and serve as breeding and feeding grounds for many species.
8. How are coral reefs studied?
Coral reefs are studied using a variety of methods, including visual surveys, remote sensing, and genetic analysis. Scientists also study the chemical and physical properties of the water surrounding the reefs to understand how they are affected by changes in the environment.
9. What is the future of coral reefs?
The future of coral reefs is uncertain, but there is hope that we can take action to protect and restore them. This will require a global effort to reduce carbon emissions, reduce pollution, and implement sustainable fishing practices, as well as a commitment to supporting scientific research and conservation efforts.
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