Environmental t News 3-D modeling substantiates perfluorinated theory
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n emerging theory that explains how PFOA (perfluorooctanoic acid) and other PFCAs (perfluorocarboxylic acids) have contaminated the Arctic has received a boost from a new modeling study published in this issue of ES&T (pp 924–930). The theory contends that Arctic contamination is due to atmospheric transport and breakdown of fluorotelomer alcohols, chemicals that are used in products that include stain protectors, microwave-popcorn bags, fast-food wrappers, polishes, and paints. The theory proposed by University of Toronto chemist Scott Mabury, Ford Motor Co. atmospheric chemist Tim Wallington, and colleagues is that air currents transport fluorotelomer alcohols from densely populated industrialized regions such as the northeastern U.S. to remote regions, including the Arctic. Along the way, chemical reactions in the atmosphere transform the fluorotelomer alcohols into PFOA and other PFCAs. Wallington and Mabury are among the authors of the study. Regulators are investigating PFOA, which is found at low levels in human blood, and other PFCAs because these compounds are ubiquitous in the environment, extremely persistent, and bioaccumulative to varying extents. Last summer, the U.S. EPA’s science advisory board recommended that the agency classify PFOA as a likely human carcinogen. In June 2004, Canada issued a temporary ban on some fluorotelomer compounds that could break down in the environment to PFOA and other PFCAs. DuPont estimates global production at 12 million kilograms, and sales of the fluorotelomer alcohols generate about $700 million
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3-D modeling predicts that concentrations of PFOA in the lower atmosphere are highest in the Arctic in the summer and in the northeastern U.S. and mid-Atlantic Ocean in winter. Blues represent low concentrations, and red-purples represent high concentrations.
annually, according to Dupont’s Global PFOA Strategy Update, released in January 2005. “This work makes the argument very well that fluorotelomer alcohols are a potential source of PFCAs,” says Roger Atkinson, an atmospheric chemist at the University of California, Riverside. He
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notes that similar atmospheric reactions are known to convert some of the chemicals that have replaced CFCs (chlorofluorocarbons). In their study, which used a sophisticated 3-D atmospheric chemistry model called IMPACT (J. Geophys. Res. 2004, 109, D04303D04303/1–D04303/42), © 2006 American Chemical Society
PFCAs (Environ. Sci. Technol. 2004, 38, 215A–216A). The model found that roughly 5% of the fluorotelomer alcohols in the atmosphere is converted to PFCAs. The resulting PFCAs are distributed throughout the northern hemisphere, with highest levels found in the Arctic and the mid-Atlantic Ocean. The model predicts that the levels peak in the Arctic during the summer, when they are roughly twice as high as the concentrations in the eastern U.S. But in winter, the highest concentrations are found in the eastern U.S. To test the validity of these predictions, the scientists are now measuring atmospheric concentrations. On an annual average basis, the model predicts that concentrations of PFCAs in the Arctic and U.S. atmosphere will be similar. The amount of PFOA produced from the 8:2 FTOH depends on the location (see figure) and the time of year, but ranges from 1 to 10%. This is the correct order of magnitude to explain the levels of PFOA that have been observed in Arctic wildlife, the authors note. —REBECCA RENNER
Microbes turn waste into a nanocatalyst Research published in this issue of ES&T (pp 1015–1021) describes how, in one elegant step, bacteria can recover precious metals from industrial waste solutions and deposit them as nanocrystal catalysts on their cell surfaces. By using the metal-covered bio mass to clean up toxic chromium wastes Cr(VI) from solution, the researchers demonstrated the ap proach’s potential as a sustainable technology. The experiments were targeted at palladium—a precious metal used in automotive catalytic converters, circuit boards, and other
electronic equipment. The metal’s high cost makes its reuse desirable. In addition, the EU’s 2003 Waste Electrical and Electronic Equipment directive promotes reuse, recycling, and other forms of recovery of precious metals from obsolete electronics devices such as televisions, computers, and cell phones. The use of these waste streams as the raw material for an effective nanocatalyst is a new and exciting sustainable technology, says corresponding author Amanda Mabbett, who conducted her research as a graduate student in the group of Lynne Macaskie at the University
News Briefs Climate changes insurance A report released in December by Ceres, a national coalition of investors, environmental groups, and nonprofits, finds that losses from weather-related insurance claims are rising faster than premiums, the population, and economic growth. This means that the impact of climate change will lead to even higher costs to both the insurance industry and those filing claims. In fact, climate change has already affected the state insurance plan in Massachusetts, which recently requested substantial rate increases to cover future natural disaster losses. Such a request is unprecedented in the insurance industry, because historical losses in a region are normally examined to calculate price increases. The report charges that both government and industry have failed to adequately study the problem and evaluate potential impacts.
Sustainable chemistry
As a $460 billion business in the U.S. alone, the chemical industry is an economic powerhouse. But, as the authors of a National Research Council (NRC) report released in December point out, “The effects of many chemicals on human health and the environment are far from benign and are largely unknown.” To move forward, the industry needs to become more sustainable; however, the report’s authors say there is a “lack of more coordinated effort to generate the science and technology to make it all possible.” Sustainability in the Chemical Industry lists eight grand research challenges to push the chemical industry toward an ideal of using renewable feedstocks and energy and generating zero waste.
february 1, 2006 / Environmental Science & Technology n 633
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the scientists released 1000 metric tons of 8:2 FTOH globally. 8:2 FTOH has an atmospheric lifetime of about a month; this gives it ample time to disperse widely throughout the northern hemisphere, including the Arctic. The model predicts that the concentrations of 8:2 FTOH in the atmosphere will only be 5 times higher in source regions such as the eastern U.S. than they are in the Arctic, according to Sanford Sillman, a University of Michigan atmospheric modeler and coauthor of the paper. The distinctive feature of the fluorotelomer alcohol’s atmospheric chemistry is that the 8:2 FTOH is most likely to be transformed into PFCAs in rural and remote locations, Sillman says. This is because the cascade of reactions that transform telomer alcohols into PFCAs involves hydroxyl and peroxy radicals. In polluted urban areas, NOx uses up the peroxy radicals. However, in rural and remote locations, where NOx is scarce, the 8:2 FTOH embarks on a cascade of reactions with hydroxyl and peroxy radicals that eventually yields
of Birmingham’s School of Biosciences (U.K.). Macaskie’s group is continuing to develop new technologies that use urban waste materials as part of a project funded by the Royal Society, the U.K.’s national academy of science. Mabbet and her colleagues exposed the microbes Desulfovibrio desulfuricans or E. coli to wastewater from automotive catalysts and electronic scrap disposal operations. In the presence of H2, the microbes helped to reduce the soluble Pd(II) from the waste to Pd(0), which precipitated together with other metals present in the wastewater—including aluminum, platinum, and silver—as nanocrystals on the microbes’ surfaces. Mabbett and her colleagues successfully used the resulting palladized biomass (now dead) in the presence of an electron donor to catalyze the reduction of carcinogenic Cr(VI) in water to noncarcinogenic Cr(III) in a bioreactor. The Cr(III) could then be removed from solution downstream by precipitation through an increase in pH. The bioreactors were still active after three months of operation. Interestingly, Mabbett’s team discovered that the cell-bound Pd(0) that they produced biologically was a more efficient catalyst than chemically produced Pd(0). This is probably due to its smaller particle size and, therefore, greater surface area, says Mabbett. The support of the catalyst by the bio-
Ping Yong
Environmentalt News
Cells of Desulfovibrio desulfuricans, shown in this transmission electron micrograph image, deposit nanocrystals of these precious metals with a high catalytic activity on their surfaces.
mass of the now-dead microbes and the presence of other materials, such as aluminum, in the waste solution, which became part of the catalyst, promoted the process. “The bio-produced nanocatalyst could work as an economic alternative to the chemical reduction of Cr(VI),” says Mabbett, who now works at the School of Molecular & Microbial Sciences and the Advanced Wastewater Management Centre at the University of Queensland (Australia). She reasons that the cost of chemicals that are necessary for chemical reduction could be saved and that biogenic hydrogen could potentially serve as an electron donor. Irene Wagner-Döbler of the German Research Centre for Biotechnology, however, feels that the data are too premature to warrant such claims. “Unless I see much more data on the long-term performance and the costs compared to other meth-
Arsenic-treated wood may have a toxic legacy Since the 1940s, wood treated with a preservative called chromated copper arsenate (CCA) has been used to erect hundreds of thousands of decks, docks, and fences. Although health and environmental concerns inspired industry to phase out CCA products for residential use in 2003, the agreement with the U.S. EPA did not apply to existing residential structures or to many industrial applications, such
as electricity and telephone poles or railway ties. Now, two research articles published in this issue of ES&T (pp 988–993, 994–999) indicate that arsenic leaching from these structures will continue to contaminate the environment for many decades. In their two-part study, researchers from the University of Miami, the University of Florida, and Florida International University looked
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ods for chromium removal, I am not convinced that this is a competitive method,” WagnerDöbler says. Mabbett points out that an optimization of the biocatalyst production is still necessary to produce a catalyst that can perform consistently. One drawback is that the presence of other metals in the waste solution used to generate the catalyst can influence its final performance; therefore, it may be desirable to mix waste so that a more consistent composition is attained, she says. In addition, Cu(II) present in the waste streams can poison the microbial enzyme hydrogenase, which is responsible for forming Pd(0) on the cells by transferring the electrons from H2 to Pd(II), Mabbett explains. “This is a really strong paper on the microbial way to make waste palladium into a material for metal remediation,” says Piet Lens of the department of environmental technology at the University of Wageningen (The Netherlands). “The microbial formation of nanocatalysts may not yet be the technique for tomorrow, but it is very promising. I see a good potential for industrial applications other than chromium removal as well,” Lens says. The palladized biomass can indeed also be used for the reductive dehalogenation of PCBs, says Mabbett. —ANKE SCHAEFER
at the arsenic leaching from wood under actual field conditions. Because of its warm, wet climate, Florida serves as the home for as much as 15% of the CCA-treated wood used in the U.S. Consequently, it is ground zero for studying possible impacts to soils and groundwater, says John Schert, director of the Florida Center for Solid and Hazardous Waste Management. “Nobody realized [CCA-treated wood] leached as much as it did and caused soil contamination problems, before this work,” Schert says.
Timothy Townsend, Univ. of Fl .
CCA-treated wood often ends up mixed in with other wood at construction and demolition debris recycling facilities, where it can be chipped into mulch that unsuspecting homeowners spread on their yards.
that by 2000 Florida had imported 28,000 metric tons of arsenic, 4600 of which have already leached into the environment. They predict that as much as 40% of the arsenic in this wood will leach out over its entire in-service lifespan, which varies from 9 to 13 years for products such as decks and is 40 years or more for utility poles. “Only a small fraction leaches in any given year [roughly 5%],” Solo-Gabriele explains. But because of the cumulative effects of all the in-service years, “the impacts can be significant, especially given the high concentrations of arsenic in the actual wood itself,” which on average is about 3100 mg/kg. That leaves 60% of the arsenic remaining in the wood when it’s discarded, typically in unlined construction and demolition (C&D) debris landfills. And when the researchers conducted a series of simulated landfill studies, they found that “the concentration of arsenic is much higher” than what leaches out during use, Solo-Gabriele says. The research is fueling “a lot of concern that over the long term, arsenic will start showing up in the groundwater beneath these landfills,” Schert says, adding that “there’s some evidence of that already.” CCA-treated wood qualifies as a hazardous waste under the federal Toxicity Characteristic Leaching Procedure, but unlike the EU, EPA exempted it from this classification, allowing the wood to be disposed of as a regular solid waste. In 2004, however, the agency did recommend that CCA-treated wood be disposed of in lined landfills where the leachate is collected and treated, and it could make this a requirement, according to Ross Elliott, with EPA’s Office of Solid Waste. Florida’s Department of Environmental Protection is already drafting regulatory changes to divert CCA-treated wood products directly to lined landfills and reduce the amount being recycled as mulch or wood fuel or disposed of in unlined C&D landfills. —KRIS CHRISTEN
News Briefs Ecosystem degradation wears on human health
Roughly 60% of the benefits that the global ecosystem provides—including fresh water, clean air, and a relatively stable climate—are being degraded or used unsustainably, warns a report by the World Health Organization (WHO). Human populations, particularly in poorer countries, are already experiencing the consequences, which could grow significantly worse over the next 50 years. Ecosystems and Human Well-Being: Health Synthesis documents how rapid ecosystem changes are already impacting or could impact human health. Some of the most serious problems, according to WHO, are degradation of fisheries and agricultural lands, contributing to the malnutrition of about 800 million people; depletion and contamination of water supplies, leading to waterborne infectious diseases; and dependency on fuels—such as wood and animal dung—for cooking and heating, causing indoor air pollution.
Europe grapples with unsustainable consumption
Reversing unsustainable trends in areas such as transport, energy, and agriculture is a big problem for Europe, according to the European Environment Agency’s 5-year environmental assessment. EU legislation has produced some improvements, such as cleaner water and air. The EU has also doubled its rates of waste recycling. But the report documents that, overall, Europe is not on track for a sustainable future. The European Environment—State and Outlook 2005 lists the key challenges as climate change, biodiversity, marine ecosystems, land and water resources, air pollution, and health. It advocates a gradual shift away from taxes on labor and investment toward taxes on pollution and the inefficient use of materials and land.
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During a one-year period, Helena Solo-Gabriele, an environmen tal engineer at the University of Miami and the corresponding author of the study, and her colleagues found average arsenic concentrations of 600 micrograms/ liter (µg/L) in rainwater runoff from a CCA-treated deck, more than 100 times higher than in runoff from an untreated deck. Both of the element’s more toxic inorganic forms, As(III) and As(V), were present; As(V) accounted for roughly 90% of the total arsenic released in the runoff. A layer of sand beneath the treated deck appeared to capture a significant portion of the arsenic runoff. There, the researchers found average arsenic levels of 30 milligrams/kilogram (mg/kg), which were 15–30 times higher than background levels of 3 µ/L. The researchers also found arsenic at levels up to 18 µ/L in the runoff water that percolated through the sand layer. By the close of the study, they had seen no evidence that maximum arsenic concentrations had been reached. Even more troubling, given Florida’s high groundwater table, is the fact that they found a higher ratio of the more soluble, mobile form, As(III), in the infiltrated rainwater. This finding suggests that microbial activity in the sand layer is converting some of the As(V) to As(III). After examining annual production statistics for CCA-treated wood, the researchers estimate
Environmentalt News Robot chemists push aside decades-old water quality analysis tool
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ton explains. Instead of 360 tests per hour, the USGS lab will now be able to process 600 tests per hour. “It’s a very powerful technology that’ll really change the way we A U.S. Geological Survey (USGS) and much less operator intervenwork,” he adds. lab was invaded by robots this tion and maintenance, according In use in the clinical world since January. In this case, a friendly, to Charles Patton, an analytical the 1980s, DA technology has been robotic technology will save USGS chemist at NWQL and the driving slow to catch on in environmentime and money by performing force in getting the DA system intal laboratories, and NWQL is one analyses for dissolved nutrients. tegrated. of the first to make the conversion. Thousands of waThe implications are ter samples annuenormous. ally come through For starters, the USGS the door at USGS researchers will be able from widely diverse to analyze all requests geographical locafor standard- and lowtions and all types concentration-range of streams, lakes, dissolved-nutrient data— reservoirs, and such as nitrate, nitrite, groundwaters. ammonia, and orthoThe robotic phosphate—on a single, technology, aulow-maintenance DA tomated discrete instrument. analyzer (DA) NWQL processes most instruments, is of the samples collected pushing aside the by USGS nationwide. continuous flow Consequently, “This analyzer (CFA) is a great test bed for This automated discrete analyzer began operating in January at the technology that validating new technoloU.S. Geological Survey’s National Water Quality Lab. The robot is exUSGS’s National gies and methods,” Patpected to dramatically speed up water sample process times and save the government money. Water Quality Labton notes, adding that oratory (NWQL) an upcoming paper with has used for decades. “It’s really just miniaturized, several thousand side-by-side data DA instruments perform the roboticized test-tube chemistry points will show that DA results are same routine determinations that where it’s very easy to do reruns statistically comparable with those CFA instruments do, but with suband dilutions that are difficult to of the CFA. stantially reduced sample volumes automate in a CFA system,” Pat—Kris Christen
Naturally occurring asbestos linked to cancer For the first time, exposure to small amounts of naturally occurring tremolite asbestos has been quantitatively linked to an increased risk of developing mesothelioma, a rare and deadly cancer, according to an epidemiological study published in October. Scientists say that the finding, together with growing data on the noncancer effects of exposure to tremolite asbestos, raises concerns for the growing numbers of families moving to the new housing developments springing up in Cal-
ifornia’s Sierra Nevada foothills. El Dorado Hills is perhaps the best known of these fast-growing boomtowns where asbestos-laden deposits are being unearthed to make way for new homes (Environ. Sci. Technol. 2003, 37, 426A–427A). Mesothelioma is a rare disease that is strongly related to exposure to asbestos—particularly occupational exposure. But environmental exposure has also caused mesothelioma in locations where tremolite asbestos is abundant, including areas in Greece, Corsica,
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Turkey, and New Caledonia. However, the exposure in these locations has not been quantified. “Mesothelioma has a long latency period,” says University of California, Davis, epidemiologist Marc Schenker, who led the study. “If all the [housing] growth and activity going on in these areas now is associated with an increased risk of mesothelioma, it will take 30–40 years to find out.” Schenker says it’s unacceptable to wait that long. “The debate needs to move beyond whether naturally occurring asbestos is an issue at all, to what is appropriate to do, what is reasonable to do, and what is good pub-
ECOLOGY & ENVIRONMENT
Scenes from a new science fiction movie? No, it’s researchers from the U.S. EPA sampling for tremolite asbestos in the dusty Sierra Nevada foothills.
able database that regulators and residents have been amassing for almost 10 years as they struggle to determine the risk from exposure to naturally occurring asbestos in the Sierra Nevada foothills. This spring, the U.S. EPA conducted activity-based personal sampling in El Dorado Hills and found high exposure levels associated with sports including mountain biking, baseball, jogging, and even just playing at a playground. The regulators’ next step is to sum up such exposures and then model the risk. The health situation is likely to remain uncertain, experts say, because current regulatory models fail to reflect the toxicity of tremolite. Exposure to amphibole asbestos also can cause noncancer diseases in proportion to exposure, according to researchers led by Lucy Peipins of the Agency for Toxic Substances and Disease Registry, who studied people exposed to tremolite asbestos in Libby, Mont. Their study found that out of about 6800 Libby residents who had chest X-rays, roughly 18% had scarred lungs, including about 40% of men over 65 (Environ. Health Perspect. 2003, 111, 1753–1759). Researchers led by James Lockey at the University of Cincinnati College of Medicine are studying plant workers exposed to tremolite-contaminated vermiculite ore that was used at a manufacturing plant in Maryville, Ohio, and are finding similar results. Out of 236 workers, more than one-quarter showed signs of scarred lungs. EPA estimates that its riskassessment activities will take months to complete. Even when these activities are finished, the results will still be subject to much uncertainty, according to EPA toxicologist Gerald Haitt. Given this reality, Bruce Case, a pathologist and epidemiologist at McGill University in Montreal (Canada), says that the most vital task right now is “a true and extensive mapping of the tremolite deposits and the disallowance of any construction at a reasonable distance from these deposits.” —REBECCA RENNER
News Briefs Hydrogen cars are the future
While many government leaders enthusiastically endorse hydrogenpowered fuel-cell vehicles as a way to environmentally friendlier and less oil dependent cars and trucks, the companies that build them see them as better products. The fuel-cell technology “allows us to transition from mechanical to electrochemical systems,” said Lawrence Burns, vice president for R&D and strategic planning at General Motors (GM). Speaking to journalists in October, Burns added, “A fuel-cell car will have one-tenth the moving parts [of a gasoline car].” GM’s prototype car builds on this concept by using “drive-by wire” technology to control functions. As a result, hydrogen cars should be a more reliable product. Reginald Modlin, director of environmental and energy planning at DaimlerChrysler, agrees that fuel-cell cars are the future, stating that, “We no longer consider [hydrogen cars] a concept.” GM and DaimlerChrysler predicts that commercial manufacture will start in 2012 or 2013. Other manufacturers, such as Ford, Toyota, and Honda, are testing their own fuel-cell cars. In the meantime, hybrid gasoline–electric cars and more fuelefficient gasoline engine designs provide “bridge” technologies. However, they will probably do little to slow the demand for more oil because of the growing market for automobiles worldwide, particularly in developing countries. Currently, 800 million vehicles are in use worldwide, and that number will grow to 1.1 billion by 2020, said Burns. “If all the engines improved [their fuel efficiency] by 25% today, it is only 6–7 years before petroleum demand starts growing again,” he warned.
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lic-health policy,” he asserts. In California, the overall risk of contracting mesothelioma is generally about one in a million. The new study, funded by the U.S. National Cancer Institute, found that people who live closer to ultramafic rock deposits, which typically contain asbestos, have higher risks than those farther away. For example, a person living within 4 miles of ultramafic rocks has about double the chance of contracting mesothelioma as someone 40 miles away, according to the data (Am. J. Respir. Crit. Care Med. 2005, 172, 1019–1025). “This study [links mesothelioma to] low levels of exposure to asbestos for the first time,” says Marcel Goldberg at the French National Institute of Health and Medical Research. Goldberg studies mesothelioma associated with naturally occurring tremolite asbestos in New Caledonia, a French territory in the South Pacific. To quantify the risk, Schenker and his colleagues pinpointed the physical locations of 2908 mesothelioma victims in California whose cases had been reported between 1988 and 1997. They determined how far these people lived from rocks that are likely to contain tremolite asbestos and compared the results with the same information for a control group of pancreatic cancer victims. (Pancreatic cancer is not linked to asbestos exposure, so it serves as an appropriate control.) The new research adds to a siz-
Environmentalt News Early-warning system may help coral reefs recover from bleaching
ERICH MUELLER
likely to die or have difficulty recovering, Strong says. Such high temperatures persisted for a record-setting 15–16 weeks in parts of the Caribbean this year, he The Internet alerts began in July, week, Strong explains. notes. NOAA can give advance warning Caribbean coral-reef Scientists reported that this warning of bleaching events bemanagers to start looking for signs year’s bleaching affected 75–80% cause of the lag time for corals to of coral bleaching in the next of the coral reefs off the U.S. Virgin respond to the onset of high tem2–4 weeks. By early fall, sustained Island of St. Croix, 85–95% in areas peratures, he adds. sea surface temperatures of 1 °C around Puerto Rico, and 70% of When bleaching warnings come above the normal maximum for those near Grenada. in, Keller and his colleagues alert that time of year had dive shops and tour generated the most boat operators to stay extensive bleaching off the reef. Divers and event ever recorded in boats stress the corthe Caribbean, says als through accidental Al Strong, a physical breakage and by stirring oceanographer with the up smothering sediU.S. National Oceanic ments, Keller explains. and Atmospheric Other activities, such Administration as applications of pes(NOAA). ticides and fertilizers, NOAA’s advance which scientists suswarnings of coral pect further stress reefs, bleaching events are can also be postponed, helping reef managStrong adds. Moreover, ers to launch monitorthe warning system, by ing efforts as well as carefully timing reef take action to lessen surveys, helps managother stresses on reefs ers identify oases of live Scientists can detect signs of stress to coral reefs two weeks beduring times of heat coral that can serve as fore widespread bleaching occurs. In this photo, a researcher is shock. The alerts are reservoirs for recolonizusing a PAM fluorometer to measure the photosynthetic activity of also opening a window ing nearby damaged ara greater starlet coral after coral bleaching has set in. on how to predict dameas, Keller says. age and enhance recovery of the “We get maps from NOAA’s The satellite data, in combinacorals. Coral Reef Watch Satellite Bleachtion with water mixing models, The goal is to mitigate mass ing Alert system that show elevated are beginning to reveal where scibleaching events, which are presea surface temperature and maps entists should search for bleachdicted to increase with rising globthat show how long those temperaresistant oases, Strong says. al temperatures. Experts point to tures have been occurring,” says Preliminary evidence from the mass bleaching as one of the reaBrian Keller, science coordinator Pacific island of Palau suggests sons why half the world’s coral for the Florida Keys National Mathat reef areas that experience the reefs are already dead or declinrine Sanctuary. The maps use data greatest amount of mixing, and ing (Environ. Sci. Technol. 2004, 38, from infrared-sensing satellites to therefore the biggest swings in 286A). provide alert messages for 24 coraltemperature, are better adapted “All the notice that the alerts reef ecosystems worldwide, Strong and more resilient to bleaching have given us really allowed us to says. The Caribbean also has more than corals in calm, warm lagoons. mobilize a team of scientists to than two dozen high-tech buoys “The Caribbean’s bleaching do surveys at sites throughout the that broadcast information about season is ending, and we’re beginCaribbean,” says Drew Harvell, water and air temperature and ning to see some recovery in the an ecologist at Cornell University. wind speed to satellites, says Eric Bahamas and the Florida Keys,” When sea surface temperatures Stabenau, an oceanographer with Stabenau says. By addressing other rise above tolerance thresholds, NOAA. stressors, such as pollution and the stress causes corals to reject Widespread bleaching sets in loss of seagrass beds and grazthe symbiotic algae that give them after a sea temperature rise of 1 °C ing fish important to coral health, their color and food. The corals above the average maximum for scientists can offer hope for mitiappear bleached and may die if that month persists for 4 weeks, gating the impacts of high temperdeprived of algae for more than a and after 8 weeks many corals are atures, he says. —JANET PELLEY 638 n Environmental Science & Technology / february 1, 2006
