Coral reefs are aragonite structures [see http://en.wikipedia.org/wiki/Aragonite] produced by living organisms, and are found in marine waters with little to no nutrients in the water. As noted in prior posts, high nutrient levels such as those found in runoff from agricultural areas can harm coral reefs by encouraging the growth of algae. Coral reefs support an extraordinary biodiversity even though they are located in nutrient-poor tropical waters. The process of nutrient cycling between corals, zooxanthellae [see http://en.wikipedia.org/wiki/Zooxanthellae], and other reef organisms ensures that fewer nutrients than one might normally anticipate are needed to support the biological community. Australian scientists recently published a report of their study of the Great Barrier Reef; the Great Barrier Reef is the largest in the world, composed of over 2,900 individual reefs and 900 islands. The researchers investigated 328 colonies of massive Porites corals [see http://en.wikipedia.org/wiki/Porites] from 69 locations. The largest corals are centuries old, and grow at a rate of just 1.5cm (roughly ½") per year. By looking at the coral skeletons, they determined that calcification — or the deposit of calcium carbonate — has declined by 13.3% throughout the Great Barrier Reef since 1990. Such a decline is unprecedented in at least the past 400 years. Global warming and increased oceanic acidity are blamed for the decline. Information about the study can be found at http://www.msnbc.msn.com/id/28436388/ and http://www.sciam.com/article.cfm?id=ocean-acidification-hits-great-barrier-reef. A study of 60 sites along the coast of Aceh, Indonesia, showed that reefs impacted by the 2004 tsunami were recovering in many areas more rapidly than anticipated. A decrease in coastal development and fishing, along with the transplantation of some corals into damaged areas, are believed to have assisted the recovery process. For more information about the study, see http://www.sciencedaily.com/releases/2008/12/081227225250.htm. Finally, high-resolution sonar images taken in early December have identified three huge deep-sea coral reefs off the coast of Florida. At depths of nearly 1,300 feet (400 meters), the recently discovered reefs are home to hundreds, if not thousands, of species, the researchers believe. These Lophelia corals are found in the deeper ranges of the Straits of Florida, but it is still not clear how extensive these reefs are. Lophelia corals grow less than a millimeter a year; yet, some of the corals found are believed to be 15,000 years old. For more information on the discovery, see http://www.innovations-report.com/html/reports/environment_sciences/expedition_uncovers_identified_coral_reefs_florida_124314.html and http://oceanexplorer.noaa.gov/explorations/islands01/log/sep24/media/lophelia.html.