March 7, 2017

Off the coast of Brazil, where the Amazon River spills into the Atlantic Ocean, scientists are taking the first up-close and personal look at the recently discovered Amazon Reef. Existence of the large coral reef was not confirmed until an oceanographic survey of the area in 2012. The survey’s findings were published in 2016, and in late January 2017, scientists began exploring the reef two-by-two in a small submarine, the exploration craft of the Greenpeace ship Esperanza.

The Greenpeace ship Esperanza recovers its two-person research submarine from a dive to the Amazon Reef in February 2017. Scientists are just beginning to explore the recently discovered reef off the coast of Brazil. Credit: © Marizilda Cruppe, Greenpeace

In the late 1950’s, a ship collected sponges—animals that often inhabit coral reefs—from the floor of the Amazon Delta. Because of the area’s oxygen-poor, murky-brown mix of freshwater and ocean saltwater, however, the possibility of a reef there was largely discounted. Coral reefs typically grow in clear saltwater that allows enough sunlight to support photosynthesis in their algae and plants. Photosynthesis is the process in which organisms use energy from sunlight to make food. In the following decades, colorful reef fish were spotted in the same part of the Amazon Delta, and speculation grew that a reef existed beneath the waves.

Fish swim above the corals and sponges of the Amazon Reef off the coast of Brazil. This photograph is one of the first taken from a submarine launched by the Greenpeace ship Esperanza. Credit: © Greenpeace

Finally, in 2012, a team of oceanographers led by Rodrigo Moura of the Federal University of Rio de Janeiro, began studying the Amazon Delta’s sea floor. Using acoustic sampling, the researchers mapped the area, and subsequent dredging brought corals, sponges, and other reef species to the surface, proving the reef’s existence. After further study, the team published its findings in the journal Science Advances in April 2016.

The Amazon Reef stretches 600 miles (970 kilometers) along the Brazilian coast and covers an area of 3,600 square miles (9,300 square kilometers) with a depth range of 100 to 400 feet (30 to 120 meters). Since their first dive in late January 2017, oceanographers have turned the submarine’s lights on a wide variety of sea life, including three new fish species, rare manatees, yellow-spotted river turtles, and giant river otters. Given the Amazon Reef’s singular nature as the only known reef at the mouth of a major river, it may harbor many more undiscovered animals or plants as well. Further dives will help scientists learn how the reef functions and further define the ecology of the vast Amazon River Basin.

At a time when most reef systems are rapidly declining because of overfishing, pollution, and climate change, the discovery of a thriving reef in an unlikely place is encouraging. The reef is likely already in trouble, however, as oil companies are scouting the area and preparing to drill for oil. Drilling could severely harm the reef, as could any oil leaked into the delta waters.

A crown of thorns starfish. Credit: © Khoroshunova Olga, Shutterstock

Monster Monday
May 16, 2016

Every part of its body is coated in venomous spines. It can survive losing limbs, or even being cut it in half. Researchers are building robots to hunt it down and kill it. Is it an evil alien? No, it is the crown of thorns.

The crown of thorns is a starfish. Also called sea stars, starfish are not actually fish. They are star-shaped members of a group of invertebrates (animals without a backbone) called echinoderms. Other echinoderms include such marine animals as sand dollars, sea cucumbers, and sea urchins. The crown of thorns has 8 to 21 arms arranged around a central disk. Adults typically measure about 10 to 14 inches (25 to 35 centimeters) across, including the arms.

Crown of thorns starfish live on coral reefs in the Indian and Pacific oceans. Coral reefs are the most diverse habitats in the ocean, providing homes for fish, shrimp, snails, and echinoderms. Small, colonial organisms called corals build reefs by forming stony skeletons. Over hundreds of years, these skeletons grow and expand into huge rocky structures, creating hiding places for all kinds of animals.

The crown of thorns feeds on corals, using the tiny mouth on the underside of its body. It chews away the soft parts of the coral, leaving only the bare skeleton. In healthy reefs, these starfish are an important part of the ecosystem. Their feeding damages or kills corals, but it also makes room for new corals to grow, similar to the way forest fires clear room for young trees. In recent years, however, some reefs have suffered vast outbreaks of the starfish. In large numbers, crown of thorns destroy the reef, mowing down corals faster than they can be replaced.

Why does this starfish have a population that can grow too large and threaten the existence of the reefs upon which it depends? Scientists aren’t entirely sure, but they suspect the population booms stem from human activities. When farmers use fertilizers in their fields, rainwater washes some of them into the ocean. Tiny plantlike life forms called phytoplankton feed on these excess nutrients and reproduce rapidly, causing their populations to explode. Biologists think that crown of thorns larvae (young), which are very small, float around in the current and feast on the abundant phytoplankton, allowing more of them to survive into adulthood. When these larvae mature and become larger, they fall to the ocean bottom and begin to feed on coral reefs. Scientists also suspect that people have helped crown of thorns populations to explode by overfishing the starfish’s few natural predators.

More research needs to be conducted to determine the cause of crown of thorns outbreaks in order to prevent them. In the meantime, coastal communities are focusing on ways to stop the outbreaks. Divers collect the “monsters” and bring them onto land or inject them with a poison that doesn’t harm the environment. This is tricky work, however. The sharp spines can puncture wetsuits and skin with ease and release toxins that cause sharp pain and swelling for days or weeks. The spines are brittle, so they often break off inside the victim, requiring surgical removal.

To stop outbreaks, Queensland University of Technology engineers have created a robotic submarine immune to the spines. The sub is designed to move around a reef, identify crown of thorns starfish using machine learning, and inject them with poison. The robot can work for up to eight hours at a time—all without a human pilot—and identify its quarry with 99 percent accuracy. The subs have not yet been used, but they may soon be needed to protect coral reefs from the menacing crown of thorns.

April 26, 2012

The government of the state of  Western Australia has announced plans to create a nearly 2,700-square-mile (7,000-square-kilometer) marine park about 185 miles (300 kilometers) northeast of Broome. The goal is to ensure greater conservation of the region’s Kimberley Coast. Less than 1 percent of this coastal area currently falls under government protection.

The Camden Sound Marine Park is designed to protect and conserve the Kimberley Coast's marine life, including coral reefs. (Image courtesy of Doug Perrine, Innerspace Visions)

The proposed Camden Sound Marine Park will be made up of several different zones: a “special purpose” zone for the protection of the estimated 22,000 humpback whales that live in the area during their calving season; a “wilderness fishing” zone, in which recreational fishers must release or eat their catch before leaving; and two “sanctuary” zones around the Champagny Islands and Montgomery Reef. The park contains areas of seagrass, coral reefs, tidal flats, and mangrove forests. It serves as a habitat for a wide variety of species, including dolphins, crocodiles, and dugongs.

Such conservation groups such as the WWF (World Wildlife Fund) and the Pew Environment Group support the project, but not everyone is satisfied. Australian Member of Parliament Sally Talbot–currently parliamentary secretary to the Minister for the Environment–strongly objects to the inclusion of any commercial fishing in the protected area. As currently planned, 23 percent of the park will be closed to all commercial fishing, and 48 percent will be closed to commercial trawl fishing. Trawl fishing involves the use of weighted, funnel-shaped nets that are dragged along the ocean bottom. Critics note that the practice damages the sea floor and often results in the catching of undersized or protected fish.

The park, which is expected to be created by mid-2012, is the first of four marine parks planned for the area. It will be managed jointly by the state government and traditional owners, including the Dambimangari and Uunguu peoples.

Additional World Book articles:

• Coral Reefs in Peril: A Special Report
• Paradise Found: A Special Report