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The World's Oceans
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By MICHAEL GRACZYK, Associated Press Writer Wed Jul 23, 5:39 AM ET HOUSTON - A "dead zone" in the Gulf of Mexico off the Texas-Louisiana coast this year is likely to be the biggest ever and last longer than ever before, with marine life affected for hundreds of miles, a scientist warned. "It's definitely the worst we've seen in the last five years," said Steve DiMarco, a Texas A&M University professor of oceanography who for 16 years has studied the Gulf of Mexico dead zone, so named because the oxygen-depleted water can kill marine life. The phenomenon is caused when salt water loses large amounts of oxygen, a condition known as hypoxia that is typically associated with an area off the Louisiana coast at the mouth of the Mississippi River. The fresh water and salt water don't mix well, keeping oxygen from filtering through to the sea bottom, which causes problems for fish, shrimp, crabs and clams. This year's dead zone has been aggravated by flood runoff from heavy spring rains and additional runoff moving into the Gulf from record floods along the Mississippi. DiMarco, joined by researchers from Texas A&M and the University of Georgia, just returned from an examination of 74 sites between Terrebonne and Cameron, La. He said the most severe hypoxia levels were recorded in the mid-range depths, between 20 and 30 feet, as well as near the bottom of the sea floor at about 60 feet. Some of the worst hypoxic levels occurred in the western Gulf toward the state line. "We saw quite a few areas that had little or no oxygen at all at that site," DiMarco said Tuesday. "This dead zone area is the strongest we've seen since 2004, and it's very likely the worst may be still to come. "Since most of the water from the Midwest is still making its way down to the Gulf, we believe that wide area of hypoxia will persist through August and likely until September, when it normally ends." Last year, DiMarco discovered a similar dead zone off the Texas coast where the rain-swollen Brazos River emptied into the Gulf. The zone off Louisiana reached a record 7,900 square miles in 2002. A recent estimate from the National Oceanic and Atmospheric Administration and Louisiana State University shows the zone, which has been monitored for about 25 years, could exceed 8,800 square miles this year, an area roughly the size of New Jersey. DiMarco said a tropical storm or hurricane likely would have no impact on this year's zone, believed to be caused by nutrient pollution from fertilizers that empty into rivers and eventually reach the Gulf. |
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The World's Oceans
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 A third of reef-building corals around the world are threatened with extinction, according to the first-ever comprehensive global assessment to determine their conservation status. (Credit: Copyright Conservation International) ScienceDaily (July 11, 2008) — A third of reef-building corals around the world are threatened with extinction, according to the first-ever comprehensive global assessment to determine their conservation status. The study findings were published today by Science Express. Leading coral experts joined forces with the Global Marine Species Assessment (GMSA) -- a joint initiative of the International Union for Conservation of Nature (IUCN) and Conservation International (CI) -- to apply the IUCN Red List Categories and Criteria to this important group of marine species. "The results of this study are very disconcerting," stated Kent Carpenter, lead author of the Science article, GMSA Director, IUCN Species Programme. "When corals die off, so do the other plants and animals that depend on coral reefs for food and shelter, and this can lead to the collapse of entire ecosystems." Built over millions of years, coral reefs are home to more than 25 percent of marine species, making them the most biologically diverse of marine ecosystems. Corals produce reefs in shallow tropical and sub-tropical seas and have been shown to be highly sensitive to changes in their environment. Researchers identified the main threats to corals as climate change and localized stresses resulting from destructive fishing, declining water quality from pollution, and the degradation of coastal habitats. Climate change causes rising water temperatures and more intense solar radiation, which lead to coral bleaching and disease often resulting in mass coral mortality. Shallow water corals have a symbiotic relationship with algae called zooxanthellae, which live in their soft tissues and provide the coral with essential nutrients and energy from photosynthesis and are the reason why corals have such beautiful colors. Coral bleaching is the result of a stress response, such as increased water temperatures, whereby the algae are expelled from the tissues, hence the term "bleaching." Corals that have been bleached are weaker and more prone to attack from disease. Scientists believe that increased coral disease also is linked to higher sea temperatures and an increase in run-off pollution and sediments from the land. Researchers predict that ocean acidification will be another serious threat facing coral reefs. As oceans absorb increasing amounts of carbon dioxide from the atmosphere, water acidity increases and pH decreases, severely impacting corals' ability to build their skeletons that form the foundation of reefs. The 39 scientists who co-authored this study agree that if rising sea surface temperatures continue to cause increased frequency of bleaching and disease events, many corals may not have enough time to replenish themselves and this could lead to extinctions. "These results show that as a group, reef-building corals are more at risk of extinction than all terrestrial groups, apart from amphibians, and are the most vulnerable to the effects of climate change," said Roger McManus, CI's vice president for marine programs. "The loss of the corals will have profound implications for millions of people who depend on coral reefs for their livelihoods." Coral reefs harbor fish and other marine resources important for coastal communities. They also help protect coastal towns and other near-shore habitats from severe erosion and flooding caused by tropical storms. Staghorn (Acroporid) corals face the highest risk of extinction, with 52 percent of species listed in a threatened category. The Caribbean region has the highest number of highly threatened corals (Endangered and Critically Endangered), including the iconic elkhorn coral (Acropora palmata) which is listed as Critically Endangered. The high biodiversity "Coral Triangle" in the western Pacific's Indo-Malay-Philippine Archipelago has the highest proportions of Vulnerable and Near-Threatened species in the Indo-Pacific, largely resulting from the high concentration of people living in many parts of the region. Corals from the genera Favia and Porites were found to be the least threatened due to their relatively higher resistance to bleaching and disease. In addition, 141 species lacked sufficient information to be fully assessed and were therefore listed as Data Deficient. However, researchers believe that many of these species would have been listed as threatened if more information were available. The results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures. "We either reduce our CO2 emission now or many corals will be lost forever," says Julia Marton-Lefèvre, IUCN Director General. "Improving water quality, global education and the adequate funding of local conservation practices also are essential to protect the foundation of beautiful and valuable coral reef ecosystems." Coral experts participated in three workshops to analyze data on 845 reef-building coral species, including population range and size, life history traits, susceptibility to threats, and estimates of regional coral cover loss. The reef-building corals assessment is one group of a number of strategic global assessments of marine species the GMSA has been conducting since 2006 at Old Dominion University in Norfolk, Virginia. Other assessments are being conducted on seagrasses and mangroves that are also important habitat-forming species, all marine fishes, and other important keystone invertebrates. By 2012, the GMSA plans to complete its comprehensive first stage assessment of the threat of extinction for over 20,000 marine plants and animals, providing an essential baseline for conservation plans around the world, and tracking the extinction risk of marine species. The results of the coral species assessment will be placed on the IUCN Red List of Threatened Species in October 2008. Currently, the assessments can be found at http://www.sci.odu.edu/gmsa/about/corals.shtml.
Adapted from materials provided by Conservation International |
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The World's Oceans
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By Michael Christie FORT LAUDERDALE, Florida (Reuters) - Half of U.S. coral reefs are in poor or fair condition, threatened by climate change and human activities like sports fishing, shipping and the release of untreated sewage, a U.S. government report said on Monday. Reefs in the Caribbean, in particular, are under severe assault and coral in the U.S. Virgin Islands and off Puerto Rico had not recovered from 2005, when unusually warm waters that led to massive bleaching and disease killed up to 90 percent of the marine organisms on some reefs. "The evidence is warning us that many of our coral reef ecosystems are imperiled and we as a community must act now," said Kacky Andrews, program manager of the Coral Reef Conservation program at the National Oceanic and Atmospheric Administration. The new NOAA report on the state of coral reefs in the United States and Pacific territories, including Palau and Guam, was presented at a meeting of coral reef scientists in Fort Lauderdale, Florida. It was the third such report and the second to be based on actual monitoring of reefs. The reefs were classified as excellent, good, fair or poor based on such things as water quality, fish population and the threats they faced. The last report was issued in 2005 when warm Atlantic waters killed off large swaths of coral through bleaching, a condition that occurs when environmental stresses, like heat, break down the symbiotic relationship between coral polyps and unicellular algae that give them color. Half the coral reefs off the U.S. Virgin Islands and Puerto Rico were killed that year, said Jenny Waddell, a marine biologist at NOAA's Center for Coastal Monitoring and Assessment. On some reefs, the fatality rate reached 90 percent, she said. A series of powerful hurricanes also devastated coral reefs off the Florida Keys in 2005. HUMAN EFFECTS But scientists at NOAA said coral reefs had been suffering for much longer due to a warming climate and other "stressors," many due to human activity, such as overfishing and damage caused by ship anchors. "It is important to note that these declines did not happen overnight, they did not happen during the last three years," said Andrews. "The degradation has happened over the past several decades and recovery may require similar time frames. Although there are a number of measures that we can implement in order to promote conservation, there are no quick fixes." The NOAA report was based on reef monitoring in 15 areas in the Atlantic and Pacific. It said that reefs near populated areas tended to suffer more intense threats due to coastal development and recreational activities like boating, diving and fishing, but even remote reefs were affected by climate change. Reefs in the vast Pacific Ocean tended to be more resilient, with a greater diversity of both coral and fish, NOAA scientists said. While Pacific reefs had been able to start recovering from worldwide bleaching in 1998, Caribbean reefs had not. Human activity had not just left Caribbean reefs battered, but also pretty tame in terms of marine life, said Alan Friedlander, a NOAA marine biologist based in Hawaii. "When you dive in remote parts of the Pacific you really feel like an intruder, like you don't belong there and the big guys let you know. You feel way down the food chain," he said. (Editing by Cynthia Osterman) © Thomson Reuters 2008 All rights reserved |
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The World's Oceans
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ScienceDaily (July 3, 2008) — It's not just about climate change anymore. Besides loading the atmosphere with heat-trapping greenhouse gases, human emissions of carbon dioxide have also begun to alter the chemistry of the ocean--often called the cradle of life on Earth. The ecological and economic consequences are difficult to predict but possibly calamitous, warn a team of chemical oceanographers in the July 4 issue of Science, and halting the changes already underway will likely require even steeper cuts in carbon emissions than those currently proposed to curb climate change. Ken Caldeira of the Carnegie Institution's Department of Global Ecology, writing with lead author Richard Zeebe of the University of Hawaii and two co-authors*, note that the oceans have absorbed about 40% of the carbon dioxide (CO2) emitted by humans over the past two centuries. This has slowed global warming, but at a serious cost: the extra carbon dioxide has caused the ocean's average surface pH (a measure of water's acidity) to shift by about 0.1 unit from pre-industrial levels. Depending on the rate and magnitude of future emissions, the ocean's pH could drop by as much as 0.35 units by the mid-21st century. This acidification can damage marine organisms. Experiments have shown that changes of as little as 0.2-0.3 units can hamper the ability of key marine organisms such as corals and some plankton to calcify their skeletons, which are built from pH-sensitive carbonate minerals. Large areas of the ocean are in danger of exceeding these levels of pH change by mid-century, including reef habitats such as Australia's Great Barrier Reef. Most marine organisms live in the ocean's sunlit surface waters, which are also the waters most vulnerable to CO2-induced acidification over the next century as emissions continue. To prevent the pH of surface waters from declining more than 0.2 units, the current limit set by the U.S. Environmental Protection Agency in 1976, carbon dioxide emissions would have to be reduced immediately. "In contrast to climate model predictions, such future ocean chemistry projections are largely model-independent on a time scale of a few centuries," the authors write, "mainly because the chemistry of CO2 in seawater is well known and changes in surface ocean carbonate chemistry closely track changes in atmospheric CO2." Although the ocean's chemical response to higher carbon dioxide levels is relatively predictable, the biological response is more uncertain. The ocean's pH and carbonate chemistry has been remarkably stable for millions of years--much more stable than temperature. "We know that ocean acidification will damage corals and other organisms, but there's just no experimental data on how most species might be affected," says Caldeira. "Most experiments have been done in the lab with just a few individuals. While the results are alarming, it's nearly impossible to predict how this unprecedented acidification will affect entire ecosystems." Reduced calcification will surely hurt shellfish such as oysters and mussels, with big effects on commercial fisheries. Other organisms may flourish in the new conditions, but this may include undesirable "weedy" species or disease organisms. Though most of the scientific and public focus has been on the climate impacts of human carbon emissions, ocean acidification is as imminent and potentially severe a crisis, the authors argue. "We need to consider ocean chemistry effects, and not just the climate effects, of CO2 emissions. That means we need to work much harder to decrease CO2 emissions," says Caldeira. "While a doubling of atmospheric CO2 may seem a realistic target for climate goals, such a level may mean the end of coral reefs and other valuable marine resources." * James Zachos, University of California, Santa Cruz, and Toby Tyrrell, Southampton University, U.K.
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