Coral Reef

Known among oceanographers and biologists as the Rainforests of the Ocean, these reefs form some of the most biologically rich ecosystems on Earth. Although 4,000 species of fish and 800 species of reef-building corals have been described in the scientific literature to date, experts have barely begun to record the total number of species found within those complex habitats and new species are added every year (with 36 new species identified in research surveys in the Papuan reefs of the South Pacific in 2006 alone). Coral reefs have been compared to tropical rainforests since both thrive under nutrient-poor conditions where nutrients are largely tied up in living matter but support rich communities through very efficient recycling processes. And secondly, both habitats exhibit very high levels of species diversity. Author’s Note: That said, coral reefs and other marine ecosystems contain more varied life forms than do land habitats. In addition, coral-related species tend to be widely distributed therefore they are less threatened by species extinction than tropical forests (it may be that global warming will eventually trump that generalization). For additional and copious information on coral reefs from the Department of Marine Sciences of the University of Puerto Rico, Mayagüez, see their wonderful online source: http://geology.uprm.edu/Morelock/GEOLOCN_/corgeol.htm.

Real World Example: Although the Capricorn reefs at the southern end of the Great Barrier Reef comprise only three percent of the area of the Great Barrier complex, they support 859 species of fish and 72 percent of the complex’s coral species (in total the Great Barrier Reef has 1,464 species of fish). This richness of fish species, which accounts for 4.5 percent of the world’s total, compares roughly with Costa Rica’s diversity of plant and mammal species, three and 4.7 percent of the world’s total respectively, yet Costa Rica’s land mass is four times as large as the Capricorn portion of the Great Barrier Reef.

Real World Problem: We’re all familiar with the concept of the straw that broke the camel’s back. When you’re loading a camel, it’s difficult for many reasons to know if or when collapse will occur. How strong is the camel in the first place? Is it young and vigorous or older and easily tired? Is it rested and healthy? Does it have one or more hidden predispositions to physical collapse, such as a weakened spine or atrophied muscles or internal organ damage? In the face of many unknowns a bit of caution is a wise strategy when loading the beast, especially if you need the camel tomorrow, the next day, and so on. The real problem, with camels and other things of value, is that once significant physical damage is done it is a fiendishly difficult process to reverse or repair. Removing the last and the penultimate straws will not resurrect the injured animal or restore it to its previous condition of well-being.

Much like the camel, no single event causes ecological collapse; well, at least not typically (for purposes of this discussion we’ll ignore natural and human-generated catastrophic events that are associated with systemic collapse). Collapse is difficult to predict based on the response of the system to earlier stresses and insults. The recent history of coral reefs and their human-induced alteration suggests that collapse is indeed possible and even probable over time. In fact, those ecosystems may be considerably closer to worldwide collapse than is realized. Moreover, the effects of different stresses affecting coral reefs are likely to accumulate on a logarithmic rather than a linear scale because of negative synergistic relationships that may develop between various types of stressors, including overfishing, land-based pollution (human sewage and chemical contaminants-nutrients and herbicides-pesticides), and climate change/global warming. All of which combine to cause a rise in diseases that target reef organisms.

Recently, many prominent marine researchers in the United States and abroad have stated that the Earth is rapidly approaching what is thought of as the “tipping point,” which when reached may trigger changes in the World Ocean that would be irreversible in terms of a human time-line. Evidence supporting that viewpoint includes the widespread bleaching of coral in Fall 2005 in the Gulf of Mexico and the southern Caribbean, ranging from Texas to Trinidad, that killed broad swaths of coral (as much as 20 percent of given colonies), in part because ocean temperatures were up to two degrees Fahrenheit above average monthly maximums, causing heat stress in the organisms. Although some reefs in the Gulf of Mexico and the Caribbean have begun to recover from that deadly bleaching event, if temperatures continue to rise it could occur again, killing additional coral, as happened in the summer of 2010. Interested students should note that since 1975, more than 90 percent of the reefs in the Florida Keys have lost their living coral cover. Thus, we are not talking about a short-term problem.

Damaged coral reefs, like crippled beasts of burden, provide fewer ecological services and are likely to be prohibitively expensive to restore. For example, coral reefs in the Florida Keys generate more eco-tourist dollars than any other ocean locality on Earth. But when those reefs are dead the tourist dollars will likewise be moribund and resurrecting either in our lifetime will be nearly impossible. Saving reefs may not be as easy as it sounds since the only real solution is politics, not science. Establishing no-take zones in endangered reefs will help a good deal but when global warming is one of the main culprits, location-specific solutions pale in significance. Reefs have come and gone throughout the geological record and have come back again and again. But the geoscientists’ view of the Earth is through a very long lens. A short time for them is in the range of millions of years. And that means if coral reefs suffer systematic collapse, humans most likely will not be around to see them ever again as living entities, even if eventually they do stage a successful comeback.
Author's Note: In the early 2000s, researchers with the USGS Center for Coastal Geology in St. Petersburg, Florida; University of Miami; NASA; and the University of South Carolina published research correlating the westward airborne transport of several hundred million tons of African dust from the Sahara and the Sahel over the Atlantic Ocean to the Caribbean, Central America, and South America with the decline of coral viability in the Caribbean as well as to human health problems, especially the increase in asthma in populations in the Caribbean and Florida. They demonstrated that the dust contains spores, viruses, pathogens, and heavy metals—including mercury and arsenic, elevated levels of lead-210 and beryllium-7, a naturally-occurring radioactive isotope—that are deleterious to the health of Caribbean coral and humans. Of particular importance was the presence of a soil fungus, Aspergillus sydowii, that has proved deadly to Caribbean sea fans and other coral. Consequently, rising seawater temperature is likely to be only one of several potential causes of the decline in coral health and viability. 

Additional Author’s Note: In mid-December 2016, scientists at the Australian Research Council’s Centre of Excellence for Coral Reef Studies based at James Cook University reported that Australia’s Great Barrier Reef has suffered its worst ever coral bleaching due to higher than normal water temperatures in 2015 and 2016. Professor Terry Hughes, director of the ARC, stated that “Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef.” About 67 percent of the shallow-water corals in the northern part of the Great Barrier Reef have died over the last eight to nine months. The affected section stretches northward about 430 miles from Port Douglas (Queensland, Australia) to Papua New Guinea. According to the scientists, nearly all corals surveyed on some reefs in that northern section were dead, resulting in the largest loss of corals ever recorded for the Great Barrier Reef.