Coral reef resources
Coral reefs are vital marine ecosystems predominantly found in shallow waters of the Indo-Pacific and Western Atlantic regions, with lesser-known cold-water reefs existing at greater depths globally. These reefs provide essential services, such as protecting shorelines from erosion and storm damage, and they support a rich biodiversity that includes countless species of fish, invertebrates, and unique marine plants. Historically, coral has been used in construction and various cultural artifacts, while modern applications extend to traditional medicine and bioprospecting, revealing potential treatments for chronic pain and cancer sourced from reef organisms.
However, coral reefs are facing significant threats from human activities, including pollution, overfishing, and climate change, resulting in widespread degradation and loss of biodiversity. As ecosystems that contribute substantially to local and global economies through tourism and fishing, the health of coral reefs is increasingly recognized as critical to human well-being. Conservation efforts, such as establishing marine protected areas, are being implemented to safeguard these delicate environments, although stronger protective measures are needed to ensure their survival. The interconnectedness of coral reef health and human health emphasizes the importance of sustainable practices to preserve these irreplaceable resources for future generations.
Coral reef resources
Where Found
Typical coral reefs occur in shallow water ecosystems of the Indo-Pacific and Western Atlantic regions. Lesser known cold-water reefs are found at depths between 40 and 3,000 meters along continental shelves, continental slopes, seamounts, and fjords worldwide.
Primary Uses
Reefs protect shorelines from wave action and storm damage. Historically, coral has been used in bricks and for mortar. Other uses include souvenirs, aquarium specimens, and even human bone grafts.
The diverse array of plants, invertebrate animals, and vertebrate life that a reef supports are used by humans as food, living and preserved displays, and traditional medicine. Bioprospecting has identified a promising chronic-pain treatment from a reef mollusk. Two possible cancer drugs and an anti-asthma compound have been isolated from reef sponges.
Technical Definition
Corals are animals in the phylum Cnidaria, kin to jellyfish. As members of the class Anthozoa, they are closely related to sea anemones. Reef-building corals secrete calcium carbonate (CaCO3) skeletons that surround the individual soft-bodied organisms comprising the colony. The living layer mounts itself on layer upon layer of the unoccupied skeletons of its ancestors.
Corals are carnivorous, capturing and stinging zooplankton with tentacles surrounding the single opening that serves as mouth and anus. Corals derive a greater amount of nourishment from photosynthetic algae living within cells lining their digestive cavity. Bleaching refers to the loss of these endosymbionts, called zooanthellae, from the coral host or loss of pigment from the algae. Coral may or may not recover from a bleaching episode.
Description, Distribution, and Forms
According to the Global Coral Reef Monitoring Network, 20 percent of reefs have been lost, 24 percent risk imminent collapse because of human pressure, and 26 percent are threatened with collapse over time. Threats to this diverse, productive, complex, and fragile are wide-ranging. Some of the damage originates from imbalances on land. Nutrient excesses run off farms and end up in the oceans, feeding explosive reproduction of bacteria. The bacteria use up the available oxygen, creating uninhabitable “dead zones.” Another chain reaction begins with deforestation. Increased washes large amounts of soil into the waterway, increasing water turbidity, which blocks light to the coral’s zooanthellae. Particulate matter also settles onto the corals, smothering them. Pollution from the construction and operation of marinas, prawn farms, plants, sewage treatment works, and hotels further degrades the reefs. Ship grounding, channel dredging, deep-water trawling, oil and gas exploration, laying of communication cable, dynamite and cyanide fishing, and tourism each take a toll.
Environmental stress renders corals more susceptible to disease. Disproportionate changes in herbivores and predators further disrupt life on the reef. Reduced herbivory by sea urchins or parrot fish allows algae to replace corals. When tritons, large predatory snails, are harvested for their showy shells, population explosions of the crown-of-thorns starfish can decimate reefs.
Storms, such as the 2004 tsunami in the Indian Ocean, shatter and smother large numbers of corals. change will likely expose the reefs to intolerable temperature fluctuations. Low temperatures in 1968, high temperatures in 1987, and major El Niño and La Niña events in 1998 each caused wide-ranging bleaching. Rising levels of carbon dioxide, combined with warmer seawater, inhibit formation of the corals’ skeletons.
Designating marine protected areas (MPAs), of which the United States has two hundred, is intended to enhance the management and monitoring of unique ocean ecosystems such as coral reefs. However, fishing and resource extraction are allowed to continue in MPAs, so reef requires stronger protection, such as “no-take areas.”
Australia’s Global Coral Reef Monitoring Network publishes the Status of Coral Reefs of the World biannually. It includes recommendations for reef conservation from more than eighty countries. Nearly one-half of the coral reef countries and states have populations under 1 million. Roughly half of those have less than 100,000 inhabitants. It stands to reason that with less international political clout, banding together advances protection of the reefs.
An area equal to 1 percent of the world’s oceans, 190 million kilometers, is covered by coral reefs. Indonesia has the largest area of warm-water (18°-32° Celsius) reefs. Norway is estimated to have the most cold-water (4°-13° Celsius) coral reefs. Cold-water reefs occupy depths below light penetration. Rather than relying on photosynthetic algae, cold-water reefs are supplied particulate and dissolved organic matter and zooplankton by currents. Species diversity of coral and associated organisms is lower, and the reefs grow more slowly than their tropical counterparts.
Individual corals are measured in millimeters. Together, billions of these animals form reef structures as imposing as Australia’s Great Barrier Reef, which is 2,000 kilometers long and 145 kilometers wide. This is even more impressive when one realizes that a reef may grow as little as 1 meter in one thousand years.
Dependent upon coral species and physical environment, reefs can be branching, massive, lobed, or folded. On a larger scale, reefs are fringing, barrier, atoll, or platform. Fringing reefs extend from the shoreline. Barrier reefs run parallel to the coast, separated from shore by a lagoon. An atoll is a living reef around a central lagoon. Platform reefs lie far offshore, in calm waters; they are flat-topped with shallow lagoons.
History
Coral reef history stretches back hundreds of millions of years. Coral larvae that gave rise to modern-day reefs settled on during the Holocene epoch, ten thousand years ago. Humans have been exploiting reef resources for the past one thousand years. Atlantic warm-water reefs are less diverse than those of the Pacific. Reasons for this disparity include lower temperatures, younger geologic age of the ocean, and lower sea levels during the Ice Age in the Atlantic than in the Pacific.
Charles Darwin published The Structure and Distribution of Coral Reefs in 1842. One hundred years ago, the world’s reefs were healthy. Pollution and sedimentation had not emerged as problems, and natural fish populations were harvested sustainably.
In the 1950’s, the of reef formation, reef zonation and productivity, and the role of disturbance were areas of study advanced considerably with the widespread use of scuba gear. During the 1980’s, research shifted to human impact and decline of coral reefs and how to conserve and restore reefs.
The study of cold-water reefs awaited necessary instrumentation and deep submersibles, available only since the late 1990’s. Within the same time frame, the Kyoto Protocol limited carbon emissions, one-third of the Great Barrier Reef was designated a no-take area, and sea urchins returned the balance to Caribbean reefs, each a measure that promises to improve the health of coral reefs.
Obtaining Reef Resources
Coral reefs support the marine aquarium trade and luxury live food markets. Fishes and reef organisms are captured by hand, hook and line, spear, nets, and trawl nets. Overfishing has led to reliance on methods with indiscriminate by-catch and habitat destruction via dynamite and cyanide fishing. Handling and transfer mortality drive extraction rates even higher in order to meet global demand.
Uses of Reef Resources
The main uses of coral reefs are their ecosystem services. The vivid interdependency of the diversity they support rivals that of tropical rain forests. Hundreds of species of coral support thousands of other organisms, including, but not limited to, algae, seagrass, plankton, sponges, polychaete worms, mollusks, crustaceans, echinoderms, and fish. More than one-half of all marine fish species are found on coral reefs and reef-associated habitats. Larger predators, such as sharks and moray eels, feed on the fish. The extensive coral reef food web cycles nutrients in oligotrophic (nutrient-poor) tropical waters.
Over millennia, coral reefs have formed landmasses rising up from the sea. The Maldives, Tuvalu, the Marshall Islands, and Kiribati are atoll countries sitting atop coral islands. The Florida keys are well-known coral islands.
Calcification in corals, mollusks, and others sequesters one-third of human-induced CO2 emissions. Loss of this carbon sink would exacerbate the effects of climate change. The value of that cannot be measured. Tourism, fishing, and ecosystem services are valued at hundreds of billions of dollars annually. Used in traditional medicine for centuries, reef organisms continue to be studied for use in Western medicine. Antiviral, antifungal, and anticancer products; inflammatory response mediators; and even sunblock are under development, some of which have already been administered to patients. Marine is a multibillion-dollar industry, with strong growth potential. Ultimately, the health of humanity is tied to the health of the reefs.
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U.S. Environmental Protection Agency
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