[Global, USA] 20 species of coral were added to the threatened species list bringing the number up to 22 from two. The U.S. National Oceanic and Atmospheric Administration has given the corals protection under the Endangered Species Act. Corals have experienced a precarious existence for more than a decade, but this move signals the public that without protection and intervention corals could disappear from the world’s oceans.
Coral is the foundation of the ocean ecosystem. Corals can live in their own but are better known for the fabulous limestone communities they create. Coral reefs support the myriad of life in earth’s seas. Coral are actually living creatures known as polyps; tiny, soft-bodied animals related to jellyfish and sea anemones. They attach to the ocean floor or to the structures left by past corals, and begin to bud into clones. The callicles, or hard calcium rich exoskeletons, that grow around the clones merge into a single formation. With the callicles to protect them, the clones live as a community that acts like a single organism. Communities grow over hundreds and thousands of years and join other colonies to form reefs in the shallow warm seas of continental shelves. Some of earth’s coral reefs began growing 50 million years ago.
People are familiar with the fantastic shapes and colors of corals, but the animals themselves are transluscent. The reefs’ colors come from the zooxanthalae, or algae that corals host. The reef and the algae live in a symbiotic relationship with the corals receiving most of their nutrients from the byproducts of the photosynthesis of the algae. (Many polyps also have tentacles to snare zooplankton or even tiny fish.) However, when the corals come under stress they evict their colorful tenants. Due to their subsequent white appearance this is known as bleaching and is the sign of severe ecological disruption – but not necessarily coral death.
Corals only cover one percent of the ocean’s floor. They build reefs in tropical waters that are shallow enough for sunlight to reach their resident algae. However, they support the existence of 25 percent of all marine creatures. The provide habitat for many fish that and the appropriate nursery for many more. So if the reefs disappear the entire ocean ecosystem may collapse.
The three main threats to coral are increasing ocean acidification, rising ocean temperature, and pollution, especially run-off from human agriculture and industry. For years scientists wondered why global air temperatures were not commensurate with models based on the amount of carbon dioxide being released into the atmosphere. It turns out the world’s oceans were soaking up much of the CO2 and other greenhouse gases. But the absorption of the extra chemicals has caused the oceans to become more acidic. The the ocean acidity has fallen 0.1 pH units which is equivalent to a 30 percent change in pH. The continuing change affects the ocean’s ability to sustain life.
Even though the ocean has been absorbing CO2, burning fossil fuels is pumping ever more greenhouse gases into the atmosphere and global temperature are rising. The average surface sea temperature is higher now than at any other time since humans began observations. Most marine life, notably the single celled creatures that form the basis of the food web, exist at a small range of optimum temperatures. Any change in ocean temperature may shift the balance of life. Human-caused pollution also disrupts the marine ecosystem and affects the corals. Oil spills, chemical dumps, agricultural runoff, storm water runoff, deforestation and coastal development all fill the ocean with sediments, toxins and pathogens that can kill off the coral reefs.
The listing of 20 corals at one time makes this the largest ever ruling under the Endangered Species Act. However, the proposed number of threatened corals was 83. Scientists had to choose the few corals facing the most severe danger rather than listing all of the corals needing protection. Corals are bioindicators of the health of the oceans. As they bleach or even die it means that other marine life may not be far behind. Many peoples around the world depend on the oceans to feed growing populations. If the seas empty of life there will be drastic consequences for humans. Only 20 species of coral were added to the threatened species list, but coral reefs around the globe are in peril.
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