Environmental▼News chemist at the South Dakota School of Mines and Technology and lead author on the new research. Previous studies have looked at total phosphorus and one of its components, soluble, reactive phosphorus, but have not focused on the dozen or more phosphorus-containing compounds that make up what has been labeled “soluble, unreactive phosphorus”. Termed “unreactive” because they don’t react in standard techniques used to measure phosphorus, such as the molybdate blue reaction, these forms of soluble phosphorus include polyphosphates, inositol phosphates, and phosphorus sorbed to mineral or organic compounds. These compounds have been neglected because many have been thought to be biologically unavailable and some are difficult to measure, Sundareshwar says. But new applications of techniques such as 31P nuclear magnetic resonance (NMR) spectroscopy are allowing a finer characterization of this fraction of the phosphorus pool, he says. Sundareshwar has used 31P NMR analysis to show for the first time that pyrophosphate (P2O47 –) can constitute more than 50% of the phosphorus in some coastal estuarine sediments. He demonstrated that soil microorganisms readily used the pyrophosphate and that its accumulation in coastal zones was directly related to human activities, such as industrial use and
fertilizer runoff. This finding is important because in some coastal zones, phosphorus availability can limit the growth of the bacterial community. “Our results suggest that the full extent of bioavailable phosphorus accumulation in estuaries is unknown because of the presence of pyrophosphate,” Sundareshwar says. Although plants in estuaries are limited by nitrogen, phosphorus is important because it can lead to bacterial overgrowth and zones of low oxygen, even in the absence of nitrogen-driven algal blooms, he says. This means that resource managers must abandon their current focus on nitrogen alone and work to curb both nitrogen and phosphorus inputs, he adds. NMR analysis of phosphorus is helping to determine why the treatment-engineered wetlands— designed to cut phosphorus in agricultural runoff down to safe levels before it enters the Everglades—are not meeting their target of 10 ppm total phosphorus, says Curt Richardson, director of the Duke University Wetland Center and a coauthor of the research presented at the ESA meeting. It turns out that the bacteria, algae, and plants in the wetlands convert the soluble, reactive phosphorus from fertilizers into dissolved organic phosphorus, which has been overlooked because it was considered an unreactive form of phospho-
Eutrophication implicated in deformed frogs The dramatic rise in the number of frog deformities can be traced, in part, to an increase in the eutrophication of waters where tadpoles hatch and metamorphose into frogs, according to ecologists Pieter Johnson at the University of Wisconsin, Madison, and Jonathan Chase at Washington University in St. Louis. Since the mid-1990s, when reports of frogs with extra, missing, or truncated limbs began to accumulate, researchers have considered excess exposure to contaminants, ultraviolet radiation, and parasites
as the most likely culprits. Previous work from Johnson’s group has linked the deformities to the presence of a parasitic trematode. Now, Johnson and Chase provide persuasive evidence that connects the prevalence of the parasite to the growing number of ponds swamped by nutrients, which may explain why the incidence of deformities has increased to more than 90% in some frog populations. The new work was published in July (Ecol. Lett. 2004, 7, 521–526). “Johnson and Chase present a
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rus, he says. Although it is biologically available, it is not taken up right away and stays suspended in the treated water as it flows into the Everglades. “Because it is not particulate, it doesn’t drop out of the water column onto the sediment. And because it is not orthophosphate, it is not taken up right away so it just flows out of the treatment wetlands,” he says. “The wetland designers didn’t count on the dissolved organic phosphorus not coming out and they will be lucky if they can get the total phosphorus levels down to 15–20 ppm,” he says. On the other side of the globe, changes in ocean mixing over the past decade due to strong El Niño weather patterns have led to a 70% decline in soluble, reactive phosphorus concentrations in the ocean off Hawaii, says Dave Karl, biological oceanographer at the University of Hawaii. Characterization of soluble unreactive phosphorus, which now makes up more than 90% of the phosphorus in the ocean, has helped researchers track how algae are now using it more than the disappearing soluble, reactive phosphorus. This has caused the algae community to shift toward a higher proportion of the less-edible bluegreen algae, he says. New applications for 31P NMR analysis of soluble unreactive phosphorus, including its use as an indicator of ecosystem health and restoration, are in the pipeline, Richardson adds. —JANET PELLEY
convincing argument supporting the eutrophication idea,” says zoologist Andrew Blaustein at Oregon State University in Corvallis. “I really believe that is the correct direction for looking at one of the ultimate major causes for amphibian deformities,” he adds. Others remain skeptical about eutrophication and parasites as the main explanation for frog deformities. “The bulk of reported deformities in the wild are truncations and deletions,” says David Skelly. “This doesn’t match the pattern of parasite infection, which is characterized by a high proportion of extra limbs,” adds the Yale ecologist who
PIETER JOHNSON (FROG), DANIEL SUTHERLAND (INSET)
The malformations in this northern leopard frog (Rana pipiens), which was taken from a pond near Minneapolis–St. Paul, Minn., were caused by a trematode parasite. The encysted Ribeiroia ondatrae parasite shown in the inset photo was removed from an infected frog.
is studying a large population of deformed frogs in the eastern United States that are not infected by parasites. Green scummy ponds full of algae and decaying organic matter are just the kind of habitat where “ramshorn” snails of the family Planorbidae thrive, says Chase. The snails are an essential host in the life cycle of the parasitic trematode, Ribeiroia ondatrae, shown by Johnson to cause the frog deformities. These ponds are usually close to farms or cattle operations, notes Johnson. In this latest work, the scientists evaluated total phosphorous concentration in the water of 27 Michigan ponds and characterized each pond’s population of snails and the proportions of different species. They found that ponds with higher phosphorus levels—above approximately 40 micrograms per liter—generally have more of the unwanted ramshorn snails that serve as host for the parasite. Johnson acknowledges that the data have limitations. “Nutrient data are very noisy as a rule, largely because it’s hard to measure productivity in a single variable,” he says. However, he also cites the finding that ponds with low nutrients often do not have any of the host ramshorn snails at all, which
means that the parasite can’t even exist in these ponds. Johnson and Chase also found that the number of amphibian infections was greater when the snail population was higher at 16 malformation hot spots scattered across the western and central United States. The parasite’s life cycle starts with an adult trematode laying an egg inside a heron or other frogeating waterfowl. The bird excretes the parasite eggs into a pond. After hatching, the young parasite finds its first home inside a ramshorn snail and then emerges some 20 days later to embed itself in a tadpole. Inside the tadpole, the parasite forms a cyst at the developing limb bud. By interfering with the tadpole’s limb development, the parasite causes a deformity, most often by making extra limbs. This deformed frog is then easy pickings for wading birds, which simultaneously consume the parasite and complete its life cycle. “The snail, frog, and parasite are entangled with each other in a complicated food web,” says Chase, who has studied the ecology of food webs in small ponds and the role of the snail in that web. This past spring, Johnson and Chase started experiments in artificial ponds to further test their hypothesis. —REBECCA RENNER
News Briefs Gloomy climate for Europe With average temperatures rising faster in Europe than elsewhere, adaptation strategies will be crucial in limiting climate change impacts, according to a report by the European Environment Agency (EEA). EEA predicts more frequent and more costly storms, floods, droughts, and other extreme weather. Over the past 20 years alone, economic losses resulting from weather- and climaterelated events have roughly doubled. While agricultural yields, particularly in northern Europe, are projected to profit from the changing temperature and precipitation patterns, EEA notes that crop harvests in many southern countries were down by as much as 30% following the heat wave in 2003. EEA warns that even with substantial reductions of greenhouse gas emissions over the coming decades, the observed rise in global temperature is expected to rise this century. Impacts of Europe’s Changing Climate: An Indicator-Based Assessment is at http://reports.eea.eu.int/climate_ report_2_2004/en.
EU laws poorly implemented European Union (EU) countries have “serious shortcomings” in how they implement EU environmental laws, according to a report from the European Commission (EC). France, Greece, Ireland, Italy, and Spain were the worst offenders. Across the EU, implementation of directives associated with water, waste, the protection of nature, and environmental impact assessments was particularly poor. In 2003, the EC recorded 88 cases where countries missed deadlines to write environmental directives into national law, and the environmental sector accounted for more than a third of all complaints and ongoing infringement cases concerning noncompliance with EU law. The Fifth Annual Survey on the Implementation and Enforcement of EU Environmental Law, which was released in August, is at http://europa. eu.int/comm/environment/law.
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