mercury exposure to 0.3 pg/kg/day. This level is down slightly from the 1997 draft recommendation of 0.5 mg/kg/day (ES&T1998, 32(1), ,A). But ATSDR's reasoning seems to have litde to do with compromise. As in the draft recommendation, its analysis is based on the Seychelles study, including new data from Seychelles children at 62 months of age. However, the fined recommendation did include an evaluation of the Faeroe Islands study, which influenced die uncertainty factors that ATSDR used, according to ATSDR Division of Toxicology Director Christopher De Rosa ATSDR officials believe that the Seychelles study is most relevant to the U.S. population, De Rosa said, and that the neurodevelopmental delays documented in the Faeroe Islands come from exposure to polychlorinated biphenyls and other organochlorine compounds. When ATSDR released its new advisory, officials there emphasized the health benefits for Americans from eating fish, a point on which all public health officials agree. But for the first time, ATSDR made a distinction between the exposure to mercury from consuming commercial fish, which it says is low, and exposure to higher levels of mercury in fish caught in lakes and rivers. The agency also suggested that subsistence fishermen be particularly cautious about fish consumption. Meanwhile, EPA is standing firm behind its reference dose of 0.1 ug/ kg/day, according to Carl Mazza in the Office of Air and Radiation. EPA is restricted from taking any regulatory action to curb mercury emissions until the National Academy of Sciences (NAS) evaluation of EPA's reference dose is completed. The review, which is scheduled for completion in May 2000, will include a reassessment of the literature on mercury, including the Seychelles Island and Faeroe Island studies. EPA is under a court order to decide bv December 2000 whether mercurv emissions from coal-fired plants should be regulated Toxicologist Robert Goyer heads the 11-member NAS committee of epidemiologists, toxicologists, and experts in statistical design, which held its first meeting last month. —REBECCA RENNER
New research challenges fertilizer as cause of coral reef declines An unexpected research finding hinting that dramatic coral reefs losses in the Florida Keys are not caused by nutrient overenrichment is being called into question because it challenges the prevailing belief that human activities, such as coastal development, pollution, and overfishing, threaten 58% of the world's reefs. At the National Coral Reef Institute conference in April, Mark Hay, an ecologist at the Georgia Institute of Technology, presented findings showing that fertilizers do not boost the growth of seaweeds that compete with corals. Hay's experiments added nutrients to coral reef plots in Florida both near and far from human development. Contrary to expectations, at all sites he observed no
increase in seaweed growth. "This indicates that the seaweeds are not nutrient-limited, and that nutrients are not the main factor causing declines of corals," Hay said. But John Ogden, a marine ecologist at the University of South Florida in Tampa, disagreed, saying that fertilizing reefs with nutrients increases the growth of seaweeds, which shade and crowd out the corals. "A healthy reef is a balance between the corals that form the reef and the seaweeds that grow on the reef," he stated. Hay's inorganic nutrient additions did not match the organic forms delivered in sewage and stormwater runoff, he added, claiming that Hay's nutrient spikes XATPfP t " 0 o small and
Coral reef project aims to pinpoint hot spots Scientists from the United States and Australia launched a joint effort to improve coral reef monitoring and predict bleaching events at an international conference in Hawaii in June. The new effort pairs satellite and expert system observations from the National Oceanic and Atmospheric Administration (N0AA) with on-site data from two Australian research institutes. "The goal is to quantify sea surface temperatures using satellite data and see how precisely they predict bleaching of corals," explained Al Strong, an oceanographer with N0AA. If scientists can post predicted locations of hot spots on the Internet, reef managers can act to reduce other stressors such as recreational fishing and boating, Strong said. Strong has been able to predict bleaching events over broad general areas since 1997, using ocean surface temperature measurements from satellites. In 1998, Strong documented hot spots following an El Nino event that drove the world's most extensive coral bleaching and die-off to date. Every major reef area except the Central Pacific was hit, with mortality as high as 90% in parts of the Indian Ocean. Corals have a narrow range of temperature tolerance, and the high water temperatures associated with events like the 1998 El Nino can leave corals vulnerable to disease, damage, and death. When ocean temperatures exceed 28-30 °C, corals become stressed and eject the algae that live inside them and give them their color. Without the food that the algae provide them through photosynthesis, the corals appear bleached and can starve, Strong said. The increased ocean temperature predicted to accompany global warming means that bleaching and mortality may worsen in the years ahead, said D. James Baker, N0AA administrator. Predicting and assessing hot spots also will help scientists identify which reefs to monitor intensively and evaluate how temperature, ultraviolet light exposure, turbidity, and weather interact to cause bleaching. N0AA scientist Jim Hendee has developed computerized expert systems that scan U.S. and Australian weather data and post Internet alerts when conditions are conducive to coral bleaching. —JANET PELLEY
2 7 0 A • JULY 1, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
DID YOU KNOW? "Four of ten factories violated the Clean Air Act between Jnuary 1997 and December 1998." (Source: Environmental Working Group)
Scientists predict that up to 30% of the world's coral reefs could die over the next 20 years.
uncontrolled to mimic real fertilization events. While nutrient enrichment from sewage and runoff is known to have negative impacts in specific locales, such as Hawaii's Kaneohe Bay, its role in coral declines over wide areas such as the Caribbean "is very controversial," explained Ken Sebens, marine ecologist at the University of Maryland-College Park. The topic is receiving a great deal of attention because coral reefs are one of the most diverse and productive ecosystems in tropical oceans, and about 10% of the world's reefs are dead, said Richard Dodge, biologist at Nova Southeastern University in Flori-
da-Fort Lauderdale. Another 2030% could be lost in 10-20 years if present trends continue, he said. The causes of the declines are many, ranging from El Nino ocean-warming events to disease, and are poorly understood, Sebens said. Ogden hypothesizes that "elevated levels of nutrients are a fact of life on reefs from episodes such as deep water upwelling driven by the Gulf Stream or heavy rainfall that washes nutrients out to sea." Seaweeds can accumulate and store these nutrients for use when the water again becomes nutrient poor, he said. The Florida Keys are experiencing serious near-shore fertilization
that could be impacting the reefs, which are typically five miles offshore, Ogden believes. Research by Brian Lapointe, marine ecologist at Harbor Branch Oceanographic Institution in Fort Pierce, Fla., suggests that Caribbean coral reefs are exposed to chronically high levels of nutrients, Ogden noted. Lapointe has found that reef seaweeds have enzymes associated with elevated nutrients. Hay and Ogden both agreed that there is an urgent need for more monitoring to untangle the compound effects of fertilization, overfishing, increased C0 2 and ultraviolet light levels, and pesticide pollution. "Nutrient studies rely on knowing the concentration of nutrients and how plants take them up, but we don't have that information," Ogden concluded. JANET PELLEY
NASA's flagship satellite will revolutionize study of climate change Environmental scientists will gain a new global perspective on the Earth's climate with the launch of NASA's Terra satellite, scheduled for this month. Five separate instruments on the satellite will make comprehensive measurements of solar radiation, the atmosphere, the oceans, and the Earth's continents. Terra's array of instruments will produce many "firsts," including global maps of the pollutants methane and carbon monoxide in the lower atmosphere; simultaneous measurements of radiation and clouds; and measurements of both the amounts
and health of phytoplankton in the ocean. Terra also will produce data that are more accurate and detailed than before, said Terra's principal scientist, Yoram Kaufman at NASA's Goddard Space Flight Center in Greenbelt, Md. But perhaps more important is the fact mat Terra will gather all of this data simultaneously, from the same vantage point. "For the first time, we shall have detailed and accurate measurements of the whole Earth system—ocean, land, and atmosphere," Kaufman said. However, Terra, the billiondollar flagship of NASA's Earth Observing System (EOS)—a long-
term program designed to explore the planet and assess its health— has not escaped criticism. Some scientists view Terra and other EOS satellites as an unfocused and overly expensive approach to studying the Earth. Last year, a report by the National Academy of Sciences called for a climate change monitoring strategy that is more flexible and targeted than EOS. The report also criticized the U.S. Global Change Research ProQ7*9. TT1 which coordinates federal studies of environmental change for allowing satellites to absorb UD to 61% of the total federal climate change funding in 1998
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