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Protected. The Kingman reef in the North Pacific ocean will be covered by Bush's new plan.

Credit: Rob Shallenberger/USFWS

President George W. Bush has designated three national monuments around 11 Pacific islands, White House officials said today. The marine preserves, which include the Mariana Trench, the Rose Atoll in American Samoa, and several islands in the central Pacific, spans 505,000 square kilometers--about the size of Spain--making it the largest area ever protected in one swoop.

The move, which has become known as Bush's Blue Legacy, tops his 2006 designation of 360,000 square kilometers of ocean off the Northwestern Hawaiian Islands as a national monument. It bans commercial fishing in waters 92 kilometers off these islands, which are already patrolled by the Coast Guard. But the monument falls far short of the 2.2 million square kilometers that many marine biologists had called for. That expanded area would have encompassed the islands' entire exclusive economic zones, which currently allow fishing by only U.S. vessels and reach out 370 kilometers offshore.

The Central Pacific monuments were proposed jointly by the Marine Conservation Biology Institute and the Environmental Defense Fund (EDF). Marine biologist Jane Lubchenco of Oregon State University, Corvallis, a board member of EDF, has been nominated to head the National Oceanic and Atmospheric Administration. If confirmed, she will oversee how these monuments are managed.

Several species will benefit from Bush's actions, says Jim Maragos, a marine scientist specializing in the pacific at the Fish and Wildlife Service. Blue-water fish such as yellowfin, bigeye tuna, and marlin--all in decline--will be big winners because they breed in these waters. So will sharks, birds, turtles, and dolphins accidentally caught by the tuna long-line fleets. And, notably in the Marianas, volcanic formations that mimic the effects of ocean acidification will be preserved for research. The islands themselves will get little added benefit from the preserves, as they are already protected.

Further details of the plan will be provided Tuesday afternoon when Bush formally announces the designations.

"This move, coupled with the strong team the Obama Administration is putting in place, gives the ocean a fighting chance," said Vikki Spruill, president of the Ocean Conservancy in Washington, D.C.

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Map of misery.
Red and orange areas indicate highly impacted areas of the ocean.

Credit: B. S. Halpern

BOSTON--Four years in the making, a groundbreaking new map of the state of the world's oceans was released today, and its message is stark: Human activity has left a mark on nearly every square kilometer of sea, severely compromising ecosystems in more than 40% of waters.

The map, presented here at the annual meeting of the American Association for the Advancement of Science (publisher of ScienceNOW)--and published tomorrow in Science--combines 17 anthropogenic stressors, including coastal runoff and pollution, warming water temperature due to human-induced climate change, oil rigs that damage the sea floor, and five different kinds of fishing. Hundreds of experts worked to weigh and compare the stressors, overlaying them on top of maps that the scientists built of various ecosystems, with data obtained from shipping maps, satellite imagery, and scientific buoys. Then marine scientists modeled how different ecosystems would be affected by the stressors, mapping so-called impact scores onto square-kilometer-sized parcels worldwide. The scores correspond to colored pixels on the new map.

Researchers don't know what the impact scores, which mostly ranged from 0 to 20, mean in terms of specific damage for different ecosystems. And without hard data sets, marine ecologists must rely on fuzzy terms such as "degraded" or "severe." But previous studies of devastated coral reefs provide some context. A 2003 paper (Science, 15 August 2003, p. 955) showed that certain coral reef ecosystems in the Caribbean Sea and off the coast of Australia had lost as much as half of their species since preindustrial times. This level of damage corresponds to an impact score of 13 or 14 in the current map, values found in wide swaths of orange on the map of the world's oceans.

Those figures are sobering, says marine ecologist Benjamin Halpern of the National Center for Ecological Analysis and Synthesis in Santa Barbara, California, who led the effort. The data suggest, for example, that ecosystems found in rocky reefs and on continental shelves "are being impacted even more" than coastal coral reefs, which get much more attention. But coral reefs are in bad shape themselves: The map indicates that nearly half of global reefs are experiencing serious, multiple impacts, including damage from fishing and ocean acidification.

"The takeaway message of the paper is that one needs to take into account the cumulative effects of different threats to the ocean," says Duke University marine ecologist Larry Crowder, who wasn't part of the effort. Still, although the map is a "bold attempt," Crowder notes that it is far from comprehensive. Some very severely threatened ecosystems, such as certain rare reefs, are too small to show up on the map, he notes, and other data, such as the cumulative impact of fishing historically, are simply not available. Scientists in the broader community will be able to update the various data sets that form the map, which could fill some of these gaps.

Related site

• The new map and Google Earth Layers

Ballast.
Adult round gobies hang out on lake bottoms, but larvae swim to the surface, where they might get sucked into ships.

Credit: David Jude/Center for Great Lakes and Aquatic Sciences

Researchers have suspected that the invasive round goby spread throughout the Great Lakes by hitching a ride in ballast water tanks of cargo ships. There was only one problem: The round goby lives on the bottom--below the intakes of ships--so it was hard to fathom how the fish could have hopscotched from one port to another. Now scientists have discovered that at night the fish's larvae rise to the surface, where they could be pumped into ballast tanks.

About 18 centimeters long, the round goby (Neogobius melanostomus) is an aggressive predator that eats the eggs of native fishes and chases them out of their habitat. The species was first spotted in the St. Clair River in 1990, and it presumably came to the United States in ballast water that cargo ships sucked up in the Black and Caspian seas.

But how did gobies get into the ballast tanks in the first place, and how were they able to spread so rapidly through the Great Lakes? Although the fish are bottom-dwellers, limnologist David Jude of the University of Michigan, Ann Arbor, who first noticed the goby in the United States, and his graduate student Stephen Hensler, observed that goby larvae in lab aquaria would occasionally swim up from the glass floor. That contradicted all the literature on round gobies, however, so Jude doubted it happened in the wild.

Then in 2002, Hensler found a few larval gobies, each less than a centimeter long, in the surface water of Lake Michigan. "It was a giant surprise," he recalls. In the following years, Hensler and Jude netted gobies in the surface water of Lake Erie as well. Although scarce in Lake Michigan, there were up to 80 larvae per 1000 cubic meters of water in Lake Erie, the pair reports in the current issue of the Journal of Great Lakes Research. The larvae only came up to the surface during the night, probably following the zooplankton that they eat, Hensler says.

Jude says that freighters could avoid spreading gobies by pumping water into their tanks only during the day. "A lot of the damage has been done already, but [round gobies] haven't colonized all the harbors yet," Jude says. "It might slow down their transmittal." It's not a perfect solution, because other alien species might make it into the ballast tanks during the day.

Fisheries biologist Philip Moy of the University of Wisconsin Sea Grant Institute in Manitowoc thinks a requirement for daytime-only ballasting is "not a likely prospect," because the carriers would probably consider it an economic hardship. Hensler notes other good news in the fight against Great Lakes invaders: Michigan recently enacted regulations that require oceangoing ships, the major source of new species introductions, to treat their ballast water to kill aquatic hitchhikers.

Related site

• Natural history of the round goby

Undulating ice.
Swelling and draining lakes beneath Antarctic ice raised and lowered the surface up to 9 meters (red and yellow lines), cracking the surface (inset).

Credit: H. Fricker et al.

Earlier this month, the Intergovernmental Panel on Climate Change (IPCC) declined to extrapolate the recent accelerated loss of glacial ice far into the future (ScienceNOW, 2 February). Too poorly understood, the IPCC authors said. Overly cautious, some scientists responded in very public complaints (Science, 9 February, p. 754). The accelerated ice loss--apparently driven by global warming--could raise sea level much faster than the IPCC was predicting, they said. Yet almost immediately, new findings have emerged to support the IPCC's conservative stance.

In a surprise development, glaciologists reported online last week in Science (10.1126/science.1138478) that two major outlet glaciers draining the Greenland ice sheet--Kangerdlugssuaq and Helheim--did a lively two-step in the first part of the decade. By gauging the elevation and flow speed of the glaciers using satellite data, Ian Howat of the University of Washington's Applied Physics Laboratory in Seattle and his colleagues found that Kangerdlugssuaq sped up abruptly in 2005, no doubt accelerating sea level rise just a bit. But then it fell back to near its earlier flow speed by the next year. Helheim gradually accelerated over several years, also sped up sharply in 2005, and then slowed abruptly to its original flow speed. Apparently, these glaciers were temporarily responding to the loss of some restraining ice at their lower ends, much as a river's flow would temporarily increase with the lowering of a dam.

Helen Fricker of Scripps Institution of Oceanography in San Diego, California, and her colleagues report another glaciological surprise in a paper published online today in Science. Fricker also presented the study this morning at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW) in San Francisco, California. Using a new satellite-based laser technique, the team discovered an unexpectedly active network of linked lakes beneath two ice streams--Whillans and Mercer--draining the West Antarctic Ice Sheet. Researchers knew of pools of meltwater at the base of Antarctic ice, but Fricker and her colleagues recorded the rising and falling of the surface by up to 9 meters over 14 patches of ice, the largest three spanning 120 to 500 square kilometers. Water that could lubricate the base of the ice and perhaps accelerate its flow was seeping from one subglacial lake to another in a matter of months, and in one case escaping to the sea. "We didn't know as much about the Antarctic ice sheet as we thought we did," says Fricker.

Glaciologist Richard Alley of Pennsylvania State University in State College agrees. "Lots of people were saying we [IPCC authors] should extrapolate into the future," he says, but "we dug our heels in at the IPCC and said we don't know enough to give an answer." Researchers will have to understand how and why glacier speeds can vary so much, he adds, before they can trust their models to forecast the fate of the ice sheets, much less sea level.

Related site

• National Snow and Ice Data Center

Glacial lubrication.
This is the first view of a channel cut out of the Antarctic continental shelf by high pressure "ice streams" that flow beneath the ice sheet.

Credit: NERC

The research vessel JCR has now dropped anchor at the Rothera research station on the Antarctic Peninsula, and the scientists are flying back home today via Punta Arenas, Chile. As they were pulling in, the researchers emailed ScienceNOW one last dispatch. Their first report which included images from the remote-controlled vehicle Isis under 3500 meters of water, the deepest dive ever in the Southern Ocean--focused on the Antarctica's geologic past. The second dispatch found evidence of a biological invasion in the making. The final word from the JCR concerns the future.

One of the most fearsome possible consequences of climate change is a major rise in sea levels. How high--and how fast--the seas will rise depends mostly on how much ice will slide off its perch on continental bedrock into the oceans. Scientists have had major difficulties figuring out what causes glaciers to break away from land because they don't have access to the bottom where the action is, says Rob Larter, a marine geophysicist with the British Antarctic Survey in Cambridge, U.K. "All proposed mechanisms for fast glacier flow require an ample supply of water at the ice bed," he wrote from the ship yesterday. Sonar imaging has revealed what look like meltwater channels beneath the Antarctic ice sheet. And last year, researchers spotted signs of water moving beneath the Antarctic ice sheet in satellite data (ScienceNOW, 19 April 2006).

Why is it so hard to study the base of ice sheets? The ice sheet is up to 4 kilometers thick, which hampers the use of seismic and other geophysical probes. Only a handful of very expensive holes have ever been drilled into the bed. There is a good view, however: 10,000 years ago, glaciers retreated rapidly from some parts of the continental shelf around Antarctica, leaving the former ice sheet bed "perfectly preserved," Larter says, albeit under 500 meters of water. So Isis visited the bottom of the ice sheet's leading edge last week for a first-hand look.

The images sent up provide the first views of "ice streams" flowing beneath the Antarctic glaciers into the ocean. The meltwater has flowed long and fast enough to cut channels into the bedrock, says Larter. "What we have found is one piece of the machinery that operates in large ice sheets, which puts us one step nearer being able to reliably model how they behave." With a single image, all models of ice flow that do not include subglacial water can now be ruled out. (Most models do, however). The implications for predicting sea level changes will take some time to sort out, Larter says.

Expect to hear more from the JCR cruise later this year as the scientists piece together their cache of data. But for now, it's time to get used to life on land once again.

Related sites

• The JCR home page

Net decrease.
Trawling for big cod has led to slim pickings, researchers say.

Credit: Jeffrey L. Rotman / CORBIS

For Atlantic cod, overfishing is the bad gift that keeps on giving. Once a mainstay of fishing fleets, cod began to thin out in the 1960s. Today, their numbers--and the fish themselves--remain small, despite a moratorium on fishing established in 1993. Now, a study of the Gulf of St. Lawrence in Canada might explain why. Researchers report that because the largest and fastest-growing fish were harvested, cod have evolved to grow slowly--an adaptation that haunts them to this day.

The average size of young adult cod has decreased by about 20% in the last 3 decades. Lab experiments have shown that harvesting mainly large fish will cause average size to shrink (ScienceNOW, 5 July 2004). But in the wild, other factors can also influence size, such as temperature and population density.

To control for these variables, Douglas Swain, a fisheries biologist at the Gulf Fisheries Center in Moncton, Canada, and colleagues looked back over data on fishing intensity, cod population, fish size, and environmental variables from 1977 to 1997. Temperatures were warm, which should have stimulated growth, and prey was abundant. So why didn't the cod recover to full size? The team found that the change in average length of 4-year-old cod correlated with the size selection exerted on their parents--which suggests that younger generations inherited their small size from small parents, because larger fish had been caught. This makes sense, Swain says; slow-growing fish would have an advantage, as they have a greater chance of reproducing before they're caught in nets.

"It is the best demonstration that the growth rates of fish themselves have been reduced in this stock," says David Conover of Stony Brook University in New York. "This nails it." But not everyone is convinced. "I am a real skeptic of this result," says Ray Hilborn of the University of Washington, Seattle. Hilborn has analyzed 73 fish stocks and found no relationship between fishing intensity and growth rate. Swain says that the impact could vary depending on fishing methods and the nature of the fish stock. Although the strong selection pressure of fishing can quickly slow down growth rate, he says, it will likely take much longer for nature to speed it up again.

Related site

• More about cod

Hold please.
A call from Alvin to the International Space Station (inset) created buzz--and a bit of static--today.

Credit: WHOI / NASA

What did the oceanographer say to the astronaut? Scientists got a chance to find out today, as a researcher on board the Alvin submersible placed a 253-kilometer long-distance call to the International Space Station. The call--the first from deep sea to space--doesn't break any new scientific ground, but it could pave the way for future interplanetary communication.

The idea for the chat originated quite a while ago from a conversation between astronaut Suni Williams, who is now in the middle of a 6-month stint on the space station, and her sister, Dina Pandya, a Web designer at the Woods Hole Oceanographic Institute (WHOI) in Massachusetts. Both liked the notion of having Williams talk with the Alvin crew, especially given the similar challenges of sea and space exploration.

The technical details for making such a call have been in place for years. The three-person crew aboard the Alvin--submerged 2.5 kilometers below the East Pacific--communicates to the surface ship Atlantis via acoustic transponders, a type of underwater telephone. The phone on Atlantis is in turn connected to a satellite phone, which can buzz anyone on shore. To complete the sea-to-space link, scientists merely needed to have Atlantis call the NASA Johnson Space Center in Houston, where a high-powered dish transmitter speaks directly with the space station.

The hard part turned out to be coordinating Williams' schedule with that of Alvin crewmember Tim Shank, a WHOI biologist. Science and engineering operations take priority, and sea surface conditions determine whether the submersible deploys as scheduled. Still, Michael Carlowicz, WHOI communications coordinator for the call, said Shank was "giddy" when he learned of the plan before he left for sea.

The call itself went smoothly. After exchanging greetings, Williams noted that the space station was currently hovering over the coast of Chili and Argentina. "We're looking at the ocean hoping you're having a good time down there," she said. Later, Williams asked if Shank had any interest in switching jobs. "I'd love to see what it's like on the ocean floor," she said. "How about coming up here for awhile?" To which Shank replied: "Anytime."

And what of the phone bill? It's not as astronomical as you'd expect. Shank says that the bulk of cost for the approximately 30-minute call comes from using the Iridium satellite, which runs 22 cents per minute. Getting the researchers to their respective locations, he says, was the expensive part.

The record for a long-distance call still belongs to the Apollo astronauts, who reached out and touched Houston from 384,400 kilometers away. Nevertheless, "it's very exciting to the have the space program and the seafloor program directly talking to each other in this basic way," says ocean seismologist Maya Tolstoy of the Lamont-Doherty Earth Observatory in New York. "There is so much that can be learned at the seafloor that is directly applicable to space exploration, and in particular looking for life elsewhere in our solar system."

Astrobiologists too are enthused about today's chat. "Anytime that you can communicate with people off of the planet and when you have to do it through three different media: water, air, and vacuum--it's an astonishing accomplishment," says astrobiologist Richard Shand of Northern Arizona University in Flagstaff. Such conversations between astronomers and Earth-bound scientists, he says, are critical in the search for possible life elsewhere in the solar system.

Not bad, for what still amounts--in cosmic terms--to a local call.

Related sites

• More on the call
• More on Alvin
• More on the space station

Sea junk.
Objects lost in the ocean can traverse the Subarctic Gyre for years.

Credit: (map) Ebbsmeyer et al., Eos 88, 1 (2007); (flotsam) Dave Ingraham

Shoes, toys, and other flotsam in the North Pacific can float as many as 13,000 kilometers, only to wind up 3 years later exactly where they started. The surprising finding comes thanks to the most realistic simulation to date of the Subarctic Gyre, a current that traces a circular path between North America and Asia. The analysis sheds new light on the complex movements of the ocean, which affect transportation, climate change, and other key environmental issues.

Every ocean hosts one or more gyres, created by Earth's rotation and prevailing winds. Little is known about the exact paths and power of these gyres, so Curtis Ebbesmeyer, a retired oceanographer based in Seattle, Washington, and collaborators created a model of the Subarctic Gyre. As a reality check, the team predicted trajectories of small objects caught in the gyre, such as plastic toys and Nike sandals--the kind of junk that has washed up in droves every so often on coastlines.

Drifting roughly 11 centimeters per second, the hypothetical flotsam took 2 to 4 years to circle the gyre. The team then compared those estimates to real-world observations. In 1992, for example, 29,000 toys on a cargo ship en route from Hong Kong to Washington state fell overboard in the North Pacific. Since then, beachcombers in Sitka, Alaska, have reported finding some of the lost toys at about 3-year intervals.

Ebbesmeyer says that the new model of the Subarctic Gyre will allow oceanographers to better understand the navigation of sealife, such as the migration routes of salmon. In addition, he says, the findings--published 2 January in Eos--show that buoyant junk keeps on drifting and poses a long-term hazard to seabirds and other creatures that might ingest it. "You lose something in the ocean, and it doesn't disappear," Ebbesmeyer says.

The model could also help researchers track oil spills and harmful algal blooms, notes oceanographer Nandita Sarkar of Old Dominion University in Norfolk, Virginia. "A study like this can be really helpful," she says.

Related sites

• More on gyres and ocean currents
• Beachcombers and the junk they find

Homebound.
Small as a human fingernail, a larval cardinalfish uses its nose to smell its way home.

Credit: Gabriele Gerlach

Once spawned, reef fish larvae are at the mercy of the ocean's currents, which propel them far from their birthplaces. At least that was the theory. New evidence, however, indicates that some reef fish species recognize the odor of their natal reef and use it to sniff their way home. This behavior may help explain the incredible biodiversity of fish seen on the ocean's reefs.

Biologists have had a tough time explaining how reef fish have become so biodiverse, considering that larval dispersal should scatter relatives far from each other. New species form when populations become isolated from one another and develop their own genetic identities over time. In order for this to occur, the subpopulation must have enough genetically similar members--such as close relatives--who can interbreed.

Biologists Gabriele Gerlach and Jelle Atema of the Marine Biological Laboratory in Woods Hole, Massachusetts, wondered if these fish were somehow able to find their way back to home reefs and their closest kin. Drawing on previous studies, which showed that juvenile salmon "imprint" on odors associated with their native streams, the team tested the homing ability of three species of reef fish living on five closely spaced reefs of Australia's Great Barrier Reef. The researchers captured late-stage larval fish of each species, including the spiny damselfish and a cardinalfish, that were either freshly settled, or about to settle, at various reef sites. Using a specially constructed flume, they then exposed each fish to water samples from the different reefs and compared how long it spent in water from its home reef versus that of the other reefs.

Two species showed clear preferences for their home waters, spending, on average, roughly twice as much time there compared with water from "foreign" reefs. The findings suggest that odors--not yet identified--could guide larvae either to reefs in general or to their home reef. Returning to their home reef allows these fish to keep their population genetically isolated from other populations on different reefs, thus contributing to the overall diversity of tropical reef fish, the researchers report online this week in the Proceedings of the National Academy of Sciences.

Biologist Timothy Tricas, of the University of Hawaii, Manoa, applauds the study for "showing for the first time that larval fish can chemically distinguish--very likely by olfaction--between waters of their settlement reefs and adjacent areas." It seems larval reef fish are "anything but passive drifters with currents," he adds.

Related sites

• Video of flume experiment (link at bottom of page)
• Gerlach's Web page, with more on larval reef fish project
• On the sense of smell in fish

Deadly cargo.
Rivers delivering sediments and nutrients into the Gulf of Mexico. Dark green and black patches near the shore indicate blooms of marine plants.

Credit: SeaWiFS Project, NASA Goddard, and ORBIMAGE

The number of oxygen-starved "dead zones" in global marine waters has jumped by more than a third in the last 2 years, according to a United Nations Environment Programme (UNEP) report released last week. The latest figures reveal some 200 dead zones worldwide, up from 149 since 2004. The affected waters are robbed of fish, oysters, sea grasses, and other marine life, damaging food supplies for millions of people worldwide, the report warns.

Dead zones form when microscopic marine plants called phytoplankton explode in number. When the phytoplankton die, bacteria feast on them and consume vast amounts of dissolved oxygen. The resulting oxygen depletion--or hypoxia--kills fish, oysters, sea grasses, and other marine life. Although phytoplankton are the backbone of marine food chains and their populations naturally wax and wane, abnormally large "blooms" have been on the rise since the 1970s. According to the UNEP report, this has been due to skyrocketing marine levels of nutrients such as phosphorus and nitrogen from fertilizers, sewage, animal wastes, and other sources.

Marine biologist Robert Diaz of the Virginia Institute of Marine Sciences in Williamsburg compiled much of the findings on dead zones from exhaustive reviews of scientific journals around the world. Better scientific reporting in recent years likely accounts for some of the apparent increase in the phenomenon, he says; "however, there's no mistaking the consistent upward trend over the last 50 years." It is difficult to estimate the total area affected worldwide, but he believes the total is "on the order of" 300,000 square kilometers. About 80% of the zones occur every summer and autumn, he says. Some, such as the Baltic Sea's 80,000-square-kilometer zone, even persist year-round.

The situation may well worsen. The UNEP report projects that the volume of nitrogen alone dumped by rivers into the oceans will climb 14% by 2030, compared to mid-1990s levels. However, not all dead zones are linked to human activities, says paleoceanographer Kjell Nordberg of Göteborg University in Sweden. His historical and geological studies indicate that natural changes in climate and ocean conditions have caused oxygen depletion in some North Sea estuaries and fjords. Not all hope is lost, however. In some areas where sewage discharge and agricultural practices are implicated, regulations to curb the impacts have helped improve oxygen levels over the last few years, Nordberg says.

Related sites

• 2004 UNEP report
• More on dead zones

Weather, or not?
The El Niños of 1997 and 2002 were centered in different parts of the Pacific, leading to vastly different consequences for India's monsoons.

Credit: NASA

Monsoons are critical to India's farmers. If the rains don't come, there can be serious consequences for the country's agriculture-driven economy. Predicting the severity of a drought has been a tricky business, but a new study suggests that the key to better forecasts depends on a detailed understanding of a warming of the Pacific Ocean, called El Niño.

Over the past 132 years, every Indian drought has come in an El Niño year. But not every El Niño has been accompanied by a drought. In 1997, a predicted drought never materialized. Worse, in both 2002 and 2004, unexpected and severe droughts surprised a completely unprepared country.

It turns out the devil is in the details. Many previous forecasts used an average of sea-surface temperatures to gauge the strength of El Niño events and predicted that the rains would vary in direct proportion. By focusing on the recent years where this relationship failed, a team led by meteorologist Martin Hoerling of the National Oceanic and Atmospheric Administration discovered that the key is determining exactly where in the Pacific the sea-surface warming is strongest. Using rainfall records dating back to 1871, the researchers found that the most severe droughts occurred when the warmest water was further east, closer to the international dateline. When the hottest spot was closer to the coast of South America in the central or western Pacific, droughts were weaker or nonexistent. The findings matched the predictions of three climate models, the team reports today in Science.

Hoerling's group suspects the correlation can be attributed to the differences in baseline sea-surface temperatures. In the cooler eastern Pacific waters, more warming has to occur to boost temperatures past a threshold before there is an effect on rain in India. But in the western Pacific where sea-surface temperatures are among the warmest in the world, less additional warming is needed before rainfall in India is increased. So western El Niños are not apt to produce a serious drought.

"It's strong work, but I think its applicability is suspect," says climate scientist Peter Webster of the Georgia Institute of Technology in Atlanta. One problem is that forecasting precisely where the warmest waters will be during an El Niño is well beyond current capabilities, he says. And scientists only get their first hint of an El Niño in April. "Even if the forecast were perfect, you wouldn't get much lead time" to prepare for a drought, says Webster. Still, he says, it's a step in the right direction.

Related sites

• NOAA's El Niño site
• Indian monsoon forecasting
• India Meteorological Department

Nasty neighbor.
Algae releases carbon that fuels coral-killing bacteria.

Credit: Jennifer Smith

Corals just can't win. Global warming, sewage, over-fishing, and other human activities all damage reefs. Now, two of corals' fellow ocean dwellers--algae and bacteria--appear to be in cahoots to destroy coral populations further.

Algae are often found growing where corals once lived. Most researchers supposed that the algae simply moved in once corals were already dead or dying. But a recent study (Science, 24 February 2006) revealed that organic carbon--which often leaks out of some plants and algae--promotes microbial activity that kills coral.

To elucidate a possible connection between algae, microbes, and corals, marine ecologist Jennifer Smith of the University of California, Santa Barbara, and colleagues brought samples of coral and algae back to the lab from the Central Pacific. The team placed corals in tubs, half of which also contained algae. A filter separated the algae from the coral; it was fine enough to block bacteria and viruses, but large enough to allow passage of dissolved compounds.

Within 2 days, all the corals with algae neighbors turned white and died, while all the solo corals survived. Near the dying corals' surface, oxygen levels had plummeted, and the energy molecule ATP spiked--both signs of microbial activity. When the researchers performed the same experiments and added a broad-spectrum antibiotic to the tubs, none of the corals died. "We got the clearest results I've ever seen," says Smith. The organic carbon released by algae appears to be traveling through the filter and fostering bacteria, she says. Bacteria in turn suffocate the corals by using up the dissolved oxygen at their surface.

The researchers repeated their experiments on several different combinations of 10 coral genera and seven algae genera. Over 95% of corals suffered to some degree from being near algae, the team reports online 5 June in Ecology Letters. As more corals die, Smith says, there is more room for algae to settle and grow (algae can't grow effectively over living coral). "It can spin quickly into [a] positive feedback loop," says Smith.

The fact that the same results were observed with various genera of coral and algae "provide[s] an inkling that this could be fairly general" in many ocean habitats, says marine ecologist Drew Harvell of Cornell University in Ithaca, New York. But marine ecologist John Bruno of the University of North Carolina at Chapel Hill questions how often this really happens in coral reefs. "You always have algae next to corals, and corals aren't just dropping dead all the time," he notes.

Related sites

• Watch documentaries on coral reef threats
• Threats to corals