366 Natural Resources Systems Copyright Goodheart-Willcox Co., Inc. Why Are We Losing Coral Reefs? Coral reefs are strong enough to protect our coastlines against erosion and other damage caused by strong ocean waves. They also provide habitat to a great variety of marine life to observe and catch for food. However, these complex, underwater ecosystems are also fragile and extremely susceptible to damage or death from anthropogenic (human-caused) threats. The major threats to our coral reefs include temperature changes, poor water quality, ocean acidification, unethical fishing practices, coastal development, and coral mining. Temperature Changes. The temperature of seawater is rising because of climate change. Warmer water temperatures cause the relationship between water corals and their symbiotic microalgae to break down and the coral loses its color and appears bleached. A difference of only 1° higher than the normal temperature for an extended period will kill the coral reef. Warmer water temperatures also allow disease-causing organisms that attack coral to grow faster. Poor Water Quality. Coral reefs need clean water to live and support the wetland ecosystem. Pollution from sources, such as sewage, land-based runoff, and industrial discharge, enters the waters surrounding coral reefs through point-source discharge and waterways that feed into the ocean. Some pollutants, such as fertilizer, increase the rapid growth of algae that can smother corals. Ocean Acidification. Seawater absorbs anthropogenic carbon dioxide (CO2) from the atmosphere. Although the oceans naturally absorb carbon dioxide, the higher levels of CO2 absorption are making the water more acidic. This is especially harmful to calcifying organisms, such as coral reefs, clams, oysters, and crabs. The excessive amount of CO2 prevents the exoskeletons from absorbing sufficient carbonate from the water, causing the exoskeletons to weaken. Unethical Fishing Practices. Unethical fishing practices, such as blast fishing with dynamite, cyanide fishing, and deepwater trawling cause physical damage to coral reefs and contaminate the surrounding water. Overfishing diminishes species and causes an imbalance in the food chain, which causes other organisms to overpopulate or die due to lack of food. Marine Ecosystems Coastal Development. Construction along coastlines and inland increases the amount of sediment that flows to the ocean. This sediment clouds the water, which deprives the coral of sunlight, and often contaminates the water with runoff pollutants. The destruction of other coastal wetlands, such as mangrove forests, also allows more sediment to reach the coral reefs. Coral Mining. Corals are harvested for use in aquariums, sold as souvenirs, and even for use as bricks or road fill. The removal of reef fishes and other reef life for aquariums also endangers coral reefs. Other threats include changes in salinity, outbreaks of predatory species, introduction of invasive species, leaking fuels, abandoned fishing nets, and careless boating, diving, and snorkeling. Many natural diseases become deadly to coral reefs because the cumulative effect of threats weakens a coral reef’s natural ability to recover. It is estimated that 25% of our coral reefs have been destroyed and two-thirds of the remaining coral reefs are threatened. The death of a coral reef is not just the death of one animal or one plant, it is the death of an entire ecosystem. Keep in mind that all of our actions, no matter how small, can contribute to coral reef destruction or help protect coral reef wetlands. Consider This 1. Which of the threats to coral reefs indicated in the summary would be the most practical to counteract? How would you propose repairing the situation? 2. How does the loss of coral reefs affect humans and the wildlife that depends on the coral? Rich Carey/Shutterstock.com