By Henrylito D. Tacio
Recently, Agence France-Presse reported that the Marshall Islands “is experiencing its worst-ever coral bleaching as global warming threatens reefs across the entire northern Pacific.”
“The worst coral bleaching event ever recorded for the Marshall Islands has been occurring since mid-September,” Karl Fellenius, a Majuro-based marine scientist with the University of Hawaii, was quoted as saying.
C. Mark Eakin, manager of the US National Oceanic and Atmospheric Administration’s Coral Reef Watch program, confirmed the report. In fact, the recent observations showed the problem was widespread across the vast waters of the northern Pacific.
“Major bleaching was seen in Guam and the Commonwealth of the Northern Marianas Islands, the northwestern Hawaiian Islands, the Marshall Islands, and Kiribati,” Eakin pointed out.
Fellenius traced the massive coral bleaching due to climate change. “While bleaching can occur on very hot days in pools of water with little circulation (such as) very low tides on reef flats, it has become a global problem due to greenhouse gas emissions causing elevated temperatures under climate change,” he said.
Globally, high temperatures that change the climate around the world is one of the main reasons of the decimation of coral reefs. “There is no debate among marine scientists that climate change is for real,” said Dr. Robert H. Richmond, president of the International Society for Reef Studies. Coral reefs are among those that are greatly affected by the global warming phenomenon.
A sudden or abrupt change in temperature is bad for corals. “It leads to stress that cause coral bleaching, and eventually, death of corals. “Bleaching is not a good thing,” explained Dr. Terry Hughes, a distinguished professor at James Cook University, who convened the most recent International Coral Reef Symposium held in Cairns, Australia. “Thermal stress due to global warming is not good.”
According to Dr. Hughes, as global warming intensifies, coral bleaching would also increase at an unprecedented level. “Bleaching events are expected to increase in terms of frequency,” said Dr. Hughes, who has been a Fellow of the Australian Academy of Science since 2001.
“The surface of the world’s oceans has warmed by 0.7°Centigrade, resulting in unprecedented coral bleaching and mortality events,” said the statement released during the 2012 ICRS. The document was drafted by a working group of eminent scientists, brought together under the auspices of The Center for Ocean Solutions.
In a series of journals some years back, Science reported that climate change could trigger the death of coral reefs, with coral bleaching being the clearest sign. “A range of stresses, including disease, sedimentation, pollutants and changes in salinity can induce coral bleaching,” explains the face sheet disseminated by Great Barrier Reef Marine Park Authority (GBRMPA). “However, it is unusually high water temperatures that trigger the mass coral bleaching events that can extend over tens to hundreds (or even thousands) of kilometers.”
The GBRMPA is recognized as a world leader in managing reefs affected by coral bleaching. “Mass bleaching has now affected every reef region in the world,” it says. “A particularly severe, worldwide bleaching event occurred in 1998, effectively destroying 16 percent of the world’s reefs. Some areas lost 50-90 percent of their coral in this single event.”
In 2010, as much as 95 percent of the corals in the Philippines suffered bleaching after a warming event. “The bleaching has been observed at many other sites around the Philippines featuring mass mortality of corals,” a news report said.
Coral reefs are touted as the rainforest of the sea. Each coral formation is a colony of hundreds or thousands of tiny organisms (known as polyps) that jointly build a skeleton that forms the reef. The outside layer of each coral polyp is inhabited by tiny one-celled plants scientists called zooxanthellae.
Corals get up to 90 percent of their energy supply from the zooxanthellae that live within their tissues in a symbiotic relationship (a beneficial interaction between the coral and zooxanthellae). Stressful conditions cause the relationship to break down and the coral expel their zooxanthellae.
“Because zooxanthellae are the major source of color for most corals, the coral’s white skeleton becomes visible through their tissue,” the GBRMPA fact sheet points out. “Bleached corals begin to starve once they bleach.”
The Management of Bleached and Severely Damaged Coral Reefs traced coral bleaching as far back as 1870. However, since the 1980s, bleaching events have become more frequent, widespread and severe.
While some corals are able to feed themselves by capturing plankton and edible particles from the water, most corals struggle to survive without their zooxanthellae. “If stressful conditions subside, corals can regain their zooxanthellae, return to normal coloration and survive,” the GBRMPA fact sheet says.
Recovery of severely damaged reefs caused by bleaching can take a long time, even on relatively healthy reefs. In addition, “the corals that repopulate a damaged reef may be significantly different from what existed before bleaching,” the GBRMPA fact sheet says.
Recovery is even slower if there are other stressors like poor water quality, overfishing or disease. “Where reefs are already stressed, recovery can take many decades, or even centuries,” GBRMPA says. “(But) a healthy, resilient reef will recover more quickly from bleaching.”
In some instances, even if corals survived from bleaching, they are now more susceptible to diseases, according to a study which appeared in the journal Ecology. “Traditionally, scientists have attributed coral declines after mass bleaching events to the bleaching alone,” says Marilyn Brandt, the leader of the study.
Warmer water temperatures can also lead to increased incidences of coral disease, which, unlike most bleaching, can cause irreparable loss of coral tissues. In many cases, bleaching and disease occur concurrently on coral reefs. Brandt and her colleagues wondered if the occurrences of bleaching and disease were linked beyond simply occurring under the same conditions. “Coral bleaching and coral diseases are both related to prolonged thermal stress,” says Brandt.
There seems to be no glimmer of hope. By the end of this century, the consensus statement said with the current rate of carbon dioxide emissions, the sea surface temperatures will further become hotter by at least 2-3° Celsius. Not only that, sea-level will rise by as much as 1.7 meters.
“Projected increases in global temperatures under climate change scenarios suggest that (coral bleaching) will continue over coming decades, placing greater stress on reefs globally,” the GBRMPA warns. “This also has significant implications for the millions of people who depend on reefs for food, income, and protection from ocean waves.”
In the Philippines, destruction of coral reefs means disaster. “Coral reefs are home to thousands of marine species, and losing them will spell disaster for our ecosystems, not to mention the thousands of Filipinos who depend on them for food and as sources of livelihood,” reminds Senator Loren Legarda, Chair of the Senate Committee on Climate Change.
Some 50 million Filipinos are dependent on the coastal ecosystem that comprises mangroves, seagrass beds, and coral reefs. Some 40 percent of the country’s coral reefs today are assessed as “poor” – up from the previous 27 percent. Only one percent is considered to be “pristine.”
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