Ocean reflux
Corrosive seawater burps up temporarily
IN DEEP WATER: Cold water, in blue, indicates where researchers measured a corrosive upwelling from the deep.Image courtesy of Dana Greeley and Simone Alin of PMEL
Seawater with the potentially shell-disrupting chemistry predicted for the open ocean after 2050 has already surfaced along North America’s West Coast, scientists report.
In spring 2007, the corrosive, deep water rose temporarily to the Pacific surface some 40 kilometers roughly west of the California-Oregon border, says Richard Feely of the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle. Elsewhere on the continental shelf, corrosive water rolled up but didn’t surge all the way to the surface, Feely and his colleagues report in an upcoming Science.
Deeper water normally swells upward at this time of year. But so much carbon dioxide — from natural and human-related processes — had dissolved in the water that the upwelling had a pH around 7.7. Surface water in the region typically has a pH of between 8.0 and 8.3 (a pH below 7 is acidic).
Gloomy estimates hadn’t predicted such a pH drop at the ocean surface until the second half of the century, Feely says. “This means that ocean acidification may be seriously impacting marine life on our continental shelf right now,” he says.
Feely blames human releases of greenhouse gas for creating the conditions that led to the upwelling. Deeper water naturally dips closer to acidity and carbonate scarcity, and human additions of carbon dioxide have expanded this zone upward.
“I was expecting that upwelling systems would be the first place where corrosive waters would reach the surface, but I hadn't really thought we were already there,” says Corinne Le Quéré of the University of East Anglia, in Norwich, England, after hearing about the work.
"What this study will really do is to point at where the biologists should come and study the impact of ocean acidification," says Le Quéré.
Just what the slosh of unusually low pH meant to the sea creatures isn’t clear, says Victoria Fabry of California State University, San Marcos. Lab tests, including her work on free-swimming pteropod snails, suggest that many species in shallower waters fail to make proper calcium carbonate shells and skeletons in lowered pH waters, where carbonate is scarce. Mussels, oysters and other commercial species could be at risk. So might fish, such as juvenile salmon that fatten up on pteropods and other calcifying nuggets.
Feely and his colleagues discovered the extent of the upwelling during a research cruise last May and June. The research team sampled water along a series of paths sticking out from the shore like teeth on a somewhat splayed comb. The cruise data can’t tell them how the water moved along the coast in later days or months, but Feely says he’s seen signs that it rolled down toward San Francisco Bay.
Some colder water normally rises toward the sea surface along the coast at this time of year, says coauthor Christopher Sabine, also of NOAA’s Seattle lab. Spring and summer wind patterns nudge surface waters westward, drawing up water from 150 to 200 meters below the surface.
With the industrial age, extra carbon dioxide wafts into the atmosphere and gets picked up by the sea. The oceans now take up 30 million metric tons of carbon dioxide a day, Sabine says. The extra dose makes the pH decline in the water column more dramatic so lower pH water is closer to the surface, where the upwelling originates.
“The water it’s grabbing is now corrosive, and it wasn’t before,” he says.
The California report looks like only the second report of low-carbonate, or undersaturated, water on any sea surface, says Toby Tyrrell of the National Oceanography Centre at the University of Southampton in England. He and his colleagues reported the first, in the Baltic Sea, but he notes that the chemistry there is different because the brackish sea ranks between freshwater and open-ocean in salinity.
Other regions with water dynamics similar to those off the California coast might have their own corrosive upwellings, Fabry says. Waters along the eastern edges of oceans, such as those off South America or Africa, now need surveying.
Penguins wash up closer to equator in Brazil
RIO DE JANEIRO, Brazil - Penguins from frigid waters near the bottom of the world are washing up closer to the equator than ever before, Brazilian wildlife authorities said Wednesday.
Adelson Cerqueira Silva of the federal environmental agency said that about 300 penguins have been found dead or alive in recent days along the coast of Bahia state, better known for sunbathers in bikinis than for seabirds native to Antarctica and Patagonia.
Its capital of Salvador is roughly 600 miles (1,000 kilometers) closer to the equator than Miami is and temperatures in the current Southern Hemisphere winter are in the mid-70s (low 20s centigrade).
"This is unheard of. There have even been reports of penguins washing up as far as Aracaju," Silva said, referring to a beachside state capital even closer to the equator.
Silva said biologists believe stronger-than-usual ocean currents have pulled the birds north. Others have suggested the increase might be due to overfishing near Patagonia and Antarctica that has forced the penguins to swim further in search of food.
Silva said the environmental authority was receiving hundreds of phone calls reporting penguin sightings.
"We're telling people if the penguins don't appear to be injured or sick to leave them alone so they can swim back," Silva said in telephone interview from the Bahia state capital of Salvador.
Rescued penguins have swamped a triage center for rescued birds, and Silva said about 90 of the birds found alive have since died.
Penguins have been sweeping up on Brazilian shores in ever greater numbers this year, for reasons that are not entirely clear.
While penguins commonly wash up as far north as Rio de Janeiro state in July and August - hundreds have done so this year. Bahia is roughly 750 miles (1,200 kilometers) northeast of Rio.
P. Dee Boersma, a conservation biologist at the University of Washington who works with penguins in Argentina, said that while she has heard of penguins occasionally washing up as far north as Bahia, the numbers washing up this year are extremely high.
"The last time that you got a lot of penguins was in 2000, mostly in Rio but some further north. That year the sea surface temperature was a degree lower than the 30 year average so the penguins just keep swimming in search of food without noticing where they're going," said Boersma in a telephone interview from Seattle.
She also said overfishing near Patagonia and Antarctica could be a factor. In the past decade, penguins have had to swim an average of 40 miles (60 kilometers) further north to find food, Boersma said.
The majority of penguins turning up are baby birds that have just left the nest and are least able to outswim the strong ocean currents.
Not-OK Coral
Full review of status finds a quarter of reef-building species in peril
TOUGH TIMES Porites pukoensis coral (top left, close-up of polyps each some 2 millimeters in diameter when expanded) now ranks as critically endangered. Corals are beset by invading species such as the crown of thorns starfish (lower left, in the Philippines) and Drupella gastropods (damage on Acropora coral in Australia's Great Barrier Reef).D. Potts; S. Livingstone; C. Page
At least a quarter of the planet’s reef-building corals face a noticeable risk of extinction, according to the first large scale review of hundreds of species.
Out of 845 known species of warm-water corals, 231 meet the criteria for listing in worrisome categories on the international IUCN Red List of Threatened Species, says marine biologist Kent Carpenter of Old Dominion University in Norfolk, Va.
The troubled species fall into the vulnerable, endangered or critically endangered categories on the Red List, which is maintained by the conservation group International Union for Conservation of Nature and Natural Resources.
If the coral species keep declining, coasts could lose the storm protection and other ecological benefits healthy reefs provide, Carpenter warns. Reef breakdown would have “huge economic effects on food security for hundreds of millions of people dependent on reef fish,” Carpenter and 38 co-authors conclude in a paper to be published in Science that appeared online July 10.
“The Carpenter paper has some scary conclusions,” says marine biologist Jenny Waddell of the National Oceanic and Atmospheric Administration’s reef programs in Silver Spring, Md. She points out that the new paper’s proportion of corals in trouble exceeds the threatened portion of most other big groups of land animals except amphibians.
Carpenter says the new roll of threatened reef corals will be added to the IUCN’s list, increasing 20-fold the number of corals the group tracks.
Monitoring of marine species has lagged compared with terrestrial species, he says. Out of some 40,000 total species the IUCN had evaluated up to now, only 1,400 species live in the sea.
To catch up, the IUCN and environmental group Conservation International fund the Global Marine Species Assessment to review major groups of creatures. For a year and a half, Carpenter has led an international team of marine biologists working through the known species that build classic shallow-water reefs.
Skimpy information kept the researchers from evaluating 141 coral species. For the others, the biologists worked out trends in population growth or decline.
Reports on shrinking areas of reefs have long indicated trouble for corals, but “we brought a new dimension,” Carpenter says. At the final tally of 231 imperiled species, “everyone’s jaw absolutely dropped.”
Two main kinds of miseries beset the corals, Carpenter says.
Climate change is taking a toll as warming sea water raises the risks of disease and coral bleaching (when corals lose their symbiotic algae and thus face nutrient shortages).
Abundant local threats also hammer corals. Sediments erode into the sea from frenetic development booms along coasts, and boats drag anchors over reefs, smashing structures that took hundreds of years to build.
“If we can control local threats, it will buy us some time,” says Andrew Baker of the University of Miami. “But ultimately corals will face some pretty tough challenges due to high temperatures and acidity.”
That worldwide process of ocean acidification is already altering surface water chemistry as those waters absorb excess carbon dioxide from the atmosphere. Though seawater is not acid now and isn’t expected to become so, the shift could disrupt ecosystems. “The new species analysis’ methods didn’t address this threat,” comments Maoz Fine of Bar-Ilan University in Ramat-Gan, Israel, so it “may require a category updating very soon.”
In the audit’s regional view, Caribbean reefs have the largest proportion of corals in the most threatened categories, the paper shows. “I used to dive in the Caribbean — the reefs were gorgeous,” Carpenter says. “Now, to use a technical term repeated frequently around here, they’re toast.”
Caribbean reef vulnerability also showed up in a NOAA report co-edited by Waddell and released July 7 at the International Coral Reef Symposium in Fort Lauderdale, Fla. Every three years, the NOAA reef research program presents a status report on the reef communities off the continental coast and U.S.-related islands.
The 2008 report found 69 percent of Pacific reefs in good or excellent condition but only 25 percent of Caribbean and Atlantic ones ranking that high.
Disturbing as both reports are, Carpenter calls for action, saying “there is hope.”
Under Ice
Expedition yields first evidence of explosive volcanism on Arctic seafloor
ASH DRIFTS: Layers of volcanic ash (samples shown in inset) blanket the Arctic seafloor 4,000 meters down. The ash is evidence of an explosive eruption, long thought impossible at those depths.Reves-Sohn et al.; A. Soule and C. Willis/WHOI
A two-week cruise on an icebreaker to the top of the world last summer gave scientists a look at the aftermath of an event once thought impossible: a violent volcanic eruption on the deep-sea floor.
In 1999, a global network of seismic instruments detected the largest swarm of earthquakes ever to occur along the planet’s system of mid-ocean ridges, where tectonic plates spread to form new ocean crust. Several aspects of the recorded vibrations suggested that the quakes were generated by volcanic activity, says Robert A. Reves-Sohn, a geophysicist at the Woods Hole Oceanographic Institution in Massachusetts.
However, he notes, many scientists have doubted that explosive volcanism can take place at the 4,000-plus-meter depth where these quakes occurred because the immense pressure of overlying water prevents seawater from flashing into steam, a major driving force for such eruptions.
The source of the quakes was the Gakkel Ridge, a mid-ocean ridge that runs along the bottom of the Arctic Ocean. Sonar scans at a stretch of the ridge about 500 kilometers from the North Pole revealed several distinctive volcanic features, says Reves-Sohn. The largest of these undersea features, which usually have flat tops scarred with prominent central craters, are about 2 kilometers across and a few hundred meters tall.
Images gathered by a remotely operated vehicle show that the ocean floor is blanketed by layers of loose volcanic ash up to 10 centimeters thick. This material is piled on top of rocks and other high-standing features on the ocean floor, a sign that the jagged, glassy particles of ash — each typically measuring no more than a couple of millimeters across — gently rained down upon the ocean floor rather than sweeping down the flanks of the undersea volcanoes, Reves-Sohn says.
He and his colleagues don’t know the full extent of the volcanic deposits, but they did find ash in all parts of the 5-by-10-kilometer area that they surveyed, they report in the June 23 Nature.
The size and shape of the larger particles hint that one of the area’s undersea volcanoes spewed 1-kilometer-tall fountains of lava during an explosive eruption. When that molten material hit the near-freezing seawater, it quickly chilled into golf-ball-size chunks and then fractured into tiny bits that rained to the seafloor, Reves-Sohn speculates. Many of the ash bits are jagged, thin, Christmas-ornament-like fragments of glass, a testament to the violence of the eruption and the bubbles contained in the molten material.