Antarctic Marine Explorers Reveal First Hints Of Biological Change After Collapse Of Polar Ice Shelves

Once roofed by ice for millennia, a 10,000 square km portion of the Antarctic seabed represents a true frontier, one of Earth’s most pristine marine ecosystems, made suddenly accessible to exploration by the collapse of the Larsen A and B ice shelves, 12 and five years ago respectively. Now it has yielded secrets to some 52 marine explorers who accomplished the seabed’s first comprehensive biological survey during a 10-week expedition aboard the German research vessel Polarstern.

While their families at home in 14 countries were enjoying New Year’s dinners, experts on the powerful icebreaking research ship were logging finds from icy waters as deep as 850 meters off the Antarctic Peninsula – an area rapidly changing in fundamental ways. The recent report of the Intergovernmental Panel on Climate Change shows nowhere on Earth warming more quickly than this corner of Antarctica, a continent 1.5 times the size of continental USA.

The expedition forms part of the Census of Antarctic Marine Life (http://www.caml.aq), which has 13 upcoming voyages scheduled during International Polar Year, to be launched in Paris March 1. A project of the global Census of Marine Life (http://www.coml.org) collaboration, CAML is responsible for the synthesis of taxonomic data and supports the efforts of national programs the world over.

Says CAML leader Michael Stoddart of Australia: “What we learned from the Polarstern expedition is the tip of an iceberg, so to speak. Insights from this and CAML’s upcoming International Polar Year voyages will shed light on how climate variations affect ice-affiliated species living in this region.”

Leaving South Africa Nov 23, the research icebreaker Polarstern operated by the Alfred Wegener Institute for Polar and Marine Research criss-crossed the northwest Weddell Sea. The cruise included the Larsen A and B zones, an area about the size of Jamaica (or half the size of New Jersey, a third the size of Belgium. The voyage ended Jan. 30.

With sophisticated sampling and observation gear, including a camera-equipped, remotely-operated vehicle, experts on the Polarstern have returned with revealing photography of life on a seabed uncapped by the disintegration of Larsen A and B. The expedition uncovered a wealth of new insights and brilliant images of unfamiliar creatures among an estimated 1,000 species collected, several of which may prove new to science.

The Polarstern’s mission included charting the environmental impact of history’s largest known ice shelf collapses. Polarstern’s team set out to find what indigenous forms of marine life existed under Larsen A and B, and what new organisms now are opportunistically moving in, redefining the ecosystem.

“The breakup of these ice shelves opened up huge, near pristine portions of the ocean floor, sealed off from above for at least 5,000 years, and possibly up to 12,000 years in the case of Larsen B,” says Julian Gutt, a marine ecologist at Germany’s Alfred Wegener Institute for Polar and Marine Research and chief scientist on the Polarstern expedition.

“The collapse of the Larsen shelves may tell us about impacts of climate-induced changes on marine biodiversity and the functioning of the ecosystem. Until now, scientists have glimpsed life under Antarctica’s ice shelves only through drill holes. We were in the unique position to sample wherever we wanted in a marine ecosystem considered one of the least disturbed by humankind anywhere on the planet.”

“This knowledge of biodiversity is fundamental to understanding ecosystem functioning,” he adds. “The results of our efforts will advance our ability to predict the future of our biosphere in a changing environment.”

When Antarctic glaciers reach the coast of the continent, they begin to float and become ice shelves, from which icebergs calve. Since 1974, a total of 13,500 square km of ice shelves have disintegrated in the Antarctic Peninsula, a phenomenon linked to regional temperature increases in the past 50 years. Growing numbers of scientists worry that similar break-ups in other areas could lead to increases in ice flow and cause sea levels to rise.

Polarstern Discoveries and Insights

Larsen zone seafloor sediments were extremely varied, ranging from bedrock to pure mud. As a result, animals living on the sediment (epifauna) were highly varied as well, though far less abundant in the Larsen A and B areas – perhaps only 1% animal abundance compared to sea beds in the eastern part of the Weddell Sea.

In the relatively shallow waters of the Larsen zone, scientists were intrigued to find abundant deep sea lilies (members of a group called crinoids) and their relatives, sea cucumbers and sea urchins.

These species are more commonly found around 2,000 meters or so, able to adapt to life where resources far more scarce – conditions similar to those under an ice shelf.

Apparent newcomers found colonizing the Larsen zone include fast-growing, gelatinous sea squirts. The scientists found dense patches of sea squirts and say they were likely able to colonize the Larsen B area only after ice shelf broke in 2002.

Very slow-growing animals called glass sponges were discovered, with greatest densities in the Larsen A area, where life forms have had seven more years to re-colonize than Larsen B. The high number of juvenile forms of glass sponges observed probably indicates shifting species composition and abundance in the past 12 years.

Biodiversity in the Antarctic Peninsula

Among many hundreds of animal specimens collected on the voyage:

15 potential new amphipod (shrimp-like) species from 400 specimens. The star attraction is one of Antarctica’s biggest-ever amphipod crustaceans – nearly 10 cm long, larger than many similar species found in temperate climates; and
Four presumed new species of cnidarians (organisms related to coral, jelly fish and sea anemones). One is a potentially new sea anemone, co-existing on the back of a snail – their symbiotic relationship providing locomotion for one and protection for the other.

Extensive analyses will be conducted to prove whether or not candidate specimens are in fact new species. Confirmed new species will be logged in the Census of Marine Life OBIS (Ocean Biogeographic Information System) database and its Antarctic component SCAR-MarBIN (the Marine Biodiversity Information Network), which to date has recorded some 5,957 marine life forms, with an estimated 5,000 to 11,000 species yet to be discovered.

The remotely operated vehicle (ROV) used on Polarstern revealed less scouring damage than anticipated from icebergs that broke away from the Larsen shelves. In shallower depths to about 220 metres, the scientists found considerable richness of species variety.

“Iceberg disturbance was much more obvious north of the Larsen A and B areas where icebergs more typically run aground,” says Dr. Gutt. “In those outer areas, at depths of roughly 100 meters, we observed fresh ice scour marks everywhere and early stages of marine life re-colonization but no mature community. At around 200 meters depth we discovered a mosaic of life in different stages of re-colonization.”

Extreme clamdigging

A potentially far-reaching find by the Polarstern ROV: small clusters of dead clamshells littering an area on the dark ocean floor and pointing to the presence of a very rare “cold seep” – essentially a sea floor vent spewing methane and sulphide. Seeps can create a temporary habitat for animal life in otherwise barren, inhospitable terrain for many years before extinguishing, abruptly starving off the community.

The first-ever cold vent on Antarctica’s continental shelf was discovered at roughly 830 metres depth two years ago by a U.S. research team. The ROV located it and sampled the soil sediments, the first analysis of which revealed concentrated methane and sulphide. Clamshells found will be studied to determine their age and the life span of the colony.

In all, some 700 and 8,000 nautical miles were dedicated by the Polarstern and its helicopter crews respectively to recording the presence and behavious of marine mammals, which included Minke whales close to the pack ice edge and very rare beaked whale species near Elephant Island.

“It was surprising how fast such a new habitat was used and colonized by Minke whales in considerable densities,” says specialist Dr. Meike Scheidat of Germany. “They indicate that the ecosystem in the water column changed considerably.”

Fisheries investigations were carried out at islands west and north of the Antarctic Peninsula. The results of 85 hauls over 19 days show the biomass of two Antarctic cod species has increased since a survey in 2003 while stocks of Blackfin and Mackerel Icefish has decreased. The results will contribute to fish stock monitoring and assessment ongoing under the Convention on the Conservation of Antarctic Marine Living Resources (http://www.ccamlr.org).

Preliminary findings from the voyage will be confirmed by detailed analysis at the scientists’ home institutes over the next few years.

According to Dr. Stoddart, a significant consequence in the Antarctic Peninsula of rising temperatures is the slow decrease of sea ice and of the planktonic algae that grows underneath. These algae feeds krill, small shrimp-like creatures, and therefore represents the bottom rung on a marine food chain that eventually sustains the iconic large Antarctic species: penguins, whales and seals. An adult blue whale alone eats about 4 million individual krill per day.

“Algae is a source of abundant, high-quality winter food and is utterly central to the health of the whole ecosystem,” says Dr. Stoddart, adding that recent research by colleagues from the U.K. shows krill stocks decreasing significantly around the Antarctic Peninsula.

However, cautions Dr. Gutt: “Predicting the future of higher levels in the food chain, e.g. animals living at the sea-floor or fish, is very difficult. It is for example clear that in the Larsen zone a major biodiversity shift will happen and the unique under-ice shelf system will disappear in this limited area, but we have to analyze carefully our raw data to provide, as a first step, a basis for such predictions. Besides modeling, further observations and ecological field studies are necessary.”

“This is virgin geography. If we don’t find out what this area is like now following the collapse of the ice shelf, and what species are there, we won’t have any basis to know in 20 years’ time what has changed, and how global warming has altered the marine ecosystem,” says Gauthier Chapelle, outreach officer for the expedition and biologist at the Brussels-based International Polar Foundation.

Says Tarik Chekchak, Program Manager of the Cousteau Society: “The Southern Ocean spans 35 million square km – 10% of Earth’s ocean surface, and ice shelves cover 1.5 million square km of it. When Captain Cousteau explored Antarctica aboard the Calypso in 1972-73, the Larsen B ice shelf was 3,250 square km bigger and krill abundance in the Peninsula was much higher than today. The annual local temperature has risen 2.5 °C since the 1940’s.

“Impacts of these changes on the Southern Ocean ecosystem are substantial. Interplay between ocean circulation, sea ice extent, ice shelf cover and the iceberg’s mechanical action on the sea bed seem to determine the characteristics of some key planktonic and benthic communities. In a changing environment, the results of the CAML efforts are key to advancing our ability to understand our biosphere, inform public debate and allow decision-makers to lead us into a more sustainable future.”

`Killer algae' back, scientists discover

The "killer" is back.

Caulerpa brachypus, an exotic, highly invasive underwater vine known as "killer algae," has spread north to take over many deep Martin County coral reefs, scientists studying the algae said Wednesday.

The algae, which have been missing from Palm Beach County reefs since the 2004 hurricanes, have a reputation for smothering coral and forcing sea life to avoid normally thriving ecosystems.

Now scientists at Harbor Branch Oceanographic Institution have documented a resurgence -- this time covering local reefs more than ever.

"It's coming back with a vengeance," said Brian LaPointe, a Harbor Branch scientist. "This is the first time we've seen those reefs in Martin County covered with that much Caulerpa brachypus."

LaPointe and other scientists found the algae growing in the Indian River Lagoon in 2003, and at that time he feared the fast-spreading plants would take over that diverse environment like it did deep-sea corals.

But scientists discovered the pollution-loving algae could not tolerate bright conditions, so it thrived only in shady, deep coral reefs.

Plus, the lagoon algae and the blooms on Palm Beach and Martin county reefs were blown away with the winds from Hurricanes Frances and Jeanne in 2004 and Wilma in 2005.

But monitoring last summer, LaPointe and research assistant Chip Baumberger found the algae blooming in about 65 to 80 feet of water about halfway between the Jupiter and St. Lucie inlets, on a natural reef known locally as the "Loran Tower Ledge."

The algae also were spotted in small patches in the Indian River Lagoon and in 45 to 55 feet of water on other Martin County reefs.

It was also seen as far south as Deerfield Beach, LaPointe said. "We felt strongly it would come back," he said. "It was only a matter of time."

Scientists hope an artificial reef proposed near the San Onofre power plant will restore once-thriving kelp forests

The thinning kelp beds damaged by the San Onofre Nuclear Generating Station may flourish again when one of the country's biggest artificial kelp reefs is completed off the San Clemente coast near the power plant.
The 150-acre reef will be about one-half mile off San Clemente Beach, bounded by San Clemente Pier to the north and San Mateo Point to the south.
Marine biologists hope the $20 million man-made reef will spawn dense kelp forests, like those that once thrived near the power plant and were home to an abundance of sea life.
If it receives approval from the California Coastal Commission, the power plant's majority owner, Southern California Edison, could begin construction of the artificial reefs as early as next summer, said David Kay, the utility's environmental project manager.
“In Southern California, kelp forests are not all that abundant,” said Steve Schroeter, a University of California Santa Barbara marine biologist. “But they are valuable habitats, extremely diverse habitats. They have a high density of plants, algae, fish and invertebrates.”
The artificial kelp reef is part of a compensation package that Southern California Edison agreed to after a 1989 Coastal Commission report concluded that the power plant's operations degraded the ocean because they killed fish and thinned the kelp beds, which provide shelter for marine life.

Courtesy of Southern California Edison
Biologists found that pisasters flourished at the test reef, as did crabs, starfish, tunicate, surf perch, blacksmith, kelp bass, sand bass, lobsters and sheephead.The utility company always has disputed the findings but agreed to corrective measures.
“We maintain the impact was insignificant,” Kay said. “In 1990, the power plant set operating records, but the kelp forest was as large as had been recorded since the 1960s.”
Southern California Edison agreed to:
Build a 150-acre artificial kelp reef near the power plant. The project began with an experimental reef in 1999 and will finish with the proposed main reef. The total cost of the project is estimated at $22 million.
Restore wetlands, which are fish nurseries, at the San Dieguito Lagoon at a cost of $86 million. The lagoon is 33 miles south of the power plant. Work began in September.
Graphic:
Proposed kelp reef Build a white sea bass hatchery adjacent to the Encina Power Plant in Carlsbad with a goal of producing 300,000 fish to release into the ocean. White bass is popular among commercial and recreational anglers. The $5 million hatchery was built seven years ago.
San Onofre opened its first reactor in 1968, a second one in 1983 and a third in 1984. The first reactor was retired in 1992 and is being dismantled. The second and third reactors are in use.
The reactors cool down by sucking in ocean water. They then return it to the ocean in a continuous cycle.
The Coastal Commission report, using data collected between 1975 and 1988, found that the water that is sucked in is laced with fish, larvae and eggs, some of which are killed.

Courtesy of Southern California Edison
Blacksmiths made themselves at home at the $2 million, 22.4-acre experimental reef where the main reef would be built. In 1999, Southern California Edison built the test reef, which was studied from 2000 to 2004.When discharged, the water rushes out in huge volumes. When all three reactors were operating, that volume measured one square mile by 14 feet deep each day, the report said.
The discharge stirs up sand from the ocean floor, creating a cloudy plume that drifts southward to the San Onofre kelp reef. The plume, which is thick and wide enough to be seen on satellite images, blocks sunlight vital to kelp growth.
As a result, the kelp beds outside of San Onofre were reduced by about 180 acres, or 60 percent, the Coastal Commission study said.
“Part of the San Onofre kelp bed is bald,” said Schroeter, one of three UC Santa Barbara marine biologists tapped by the Coastal Commission to study the effectiveness of the experimental kelp reef.
“Kelp doesn't live to be that old. If there is no (production of young kelp) for three to six years, there will be nothing there,” Schroeter said.
The power plant also sucked in 45 tons of fish each year, killing at least 21 tons while releasing the rest, the study said.

Courtesy of Southern California Edison
A kelp crab rested on fronds at the test reef, which was made of 56 blocks of concrete or quarry. The test reef will count toward the 150 acres.Consequently, the population of fish and invertebrates that depend on kelp was significantly reduced. For instance, sheephead, barred sand bass and black surf perch were reduced by 200,000, or 70 percent.
Invertebrates such as snails and sea urchins were reduced 30 percent to 90 percent.
In 1991, the Coastal Commission required Southern California Edison to rectify the damage. The next eight years or so were filled with disputes over the extent of damage, proposals of remedies and environmental reviews.
In 1999, Southern California Edison built a $2 million, 22.4-acre experimental reef where the main reef would be built. The test reef, made of 56 blocks of concrete or quarry placed apart, will count toward the 150 acres.
The experimental reef was studied from 2000 to 2004 by Schroeter and two other UC Santa Barbara marine biologists, who were under contract with the Coastal Commission but whose work was funded by Southern California Edison.
The biologists found that kelp flourished there, as did crabs, starfish, tunicate, surf perch, blacksmith, kelp bass, sand bass, lobsters, pisasters and sheephead.
In 2005, Southern California Edison proposed the last phase of the artificial reef.
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It would be made of blocks of quarry rock from nearby Santa Catalina Island and would vary in shape and size. The rocks would be inserted into the gaps between the test reefs to form a massive reef.
Unlike the test reefs, which grew from spores that naturally drifted over from other kelp beds and from young lab-grown plants, the main reef will only use drifters because researchers found that they grew better, Kay said.
He expects a kelp canopy to appear in about two years and marine life to begin migrating from the surrounding test reefs within a year after that.
To compensate for the additional 30 acres of kelp beds damaged by the power plant and for the fish killed, Southern California Edison began restoring San Dieguito Lagoon in September and hopes to complete the work in three years. The $86 million project includes keeping the lagoon's inlet open, building earthen berms to control flooding along the San Dieguito River, constructing five nesting sites for the endangered California least tern and the Western snowy plover, and planting new salt marsh.

Four Antarctic Glaciers Key to Future Sea Levels, 'Vunerable to Small Changes in Ocean Temps'

Edinburgh, Scotland (Mar 15, 2007 19:00 EST) Scientists have identified four Antarctic glaciers that pose a threat to future sea levels using satellite observations, according to a study published in the journal Science.
Experts from the University of Edinburgh and University College London determined the effect that Antarctica and Greenland were having on global sea level in a comprehensive evaluation of the Earth’s ice sheets. They found that together these two ice-sheets were responsible for a sea level rise of 0.35 millimetres per year over the past decade – representing about 12 per cent of the current global trend.
However, despite recent attention that has focused on the importance of the Greenland ice sheet, the research shows that its glaciers are changing too erratically to establish a trend with confidence. In contrast, four major glaciers in East and West Antarctica were shown to be retreating in unison, raising concerns that global sea level could rapidly rise if the oceans continue to warm.

Dr. Andrew Shepherd, at the University of Edinburgh’s School of GeoSciences, said: "Our assessment confirms that just one type of glacier in Antarctica is retreating today – those that are seated in deep submarine basins and flow directly into the oceans. These glaciers are vulnerable to small changes in ocean temperature, such as those that have occurred over the 20th century, and those predicted for the 21st century. A rise of less than 0.5 ºC could have triggered the present imbalance."
Professor Duncan Wingham, at University College London, insists that the success of the research lies in the satellite instrumentation from which it is derived: "The extreme precision with which we can now make measurements of the Earth’s surface allows us to see the increasingly subtle changes within the ice sheets that will govern their future sea level contribution."

Discovery age continues

MARINE creatures are thriving by a hot volcanic vent in the Atlantic and in dark waters under thick Antarctic ice, boosting theories that planets other than Earth are suitable for life, scientists said yesterday.About 150 new types of fish were among 500 new marine species, including furry crabs and a lobster off Madagascar, found this year, according to researchers in the 70-nation Census of Marine Life.
Many species were found in places long thought too hostile for life – including by a vent spewing liquids at 407C and other habitats that were dark, cold or deep. Some places seemed as inhospitable as planets such as Mars or Venus.
"The age of discovery is not over," said Jesse Ausubel, a program manager at the US Sloan Foundation, which is a sponsor of the 10-year census. Finds "are provocative for NASA and for people who are interested in life in places other than Earth".
Among discoveries this year were shrimps, clams and bacteria living by the searing 407-degree vent on the floor of the Atlantic Ocean north of Ascension Island, the hottest sea vent documented and more than hot enough to melt lead.
"This is the most extreme environment and there is plenty of life around it," said Chris German, of Britain's Southampton Oceanography Centre and a leader of the Atlantic survey.
He said one big puzzle was how creatures coped with shifts in temperatures – water on the sea bed at 3000m was only 2C, yet many creatures withstood near-boiling temperatures of up to 80C from the thermal vent.
German said it was a bit like a person agreeing to live in a blistering sauna and be hosed at random with freezing water.
Scientists had not yet probed how hardy the microbes nearest the hottest part of the vent were – a type of bacteria called "Strain 121" found in the Pacific in 2003 holds the record by being able to withstand temperatures of 121C.
And another expedition found crustaceans, jellyfish and single-celled animals living in darkness in the Weddell Sea off Antarctica under ice 700m thick and 200km from open water. Most of those creatures were new to science.
"You can think of it as a cave, one of the remotest caves on Earth," Mr Ausubel said of findings by a robot camera.
"Wherever we've gone on Earth we've continued to find life," German said.
He said recent discoveries could be encouraging for the search for life elsewhere in the universe.
Some experts speculate that Jupiter's moon, Europa, could hide an ocean beneath its frozen surface and Mr Ausubel noted life has been found on Earth beside sub-sea methane seeps – Saturn's moon, Titan, also has methane. And NASA said last week it had found signs of liquid water on Mars.
Among other finds this year by the census, due for completion in 2010, was a Jurassic shrimp in the Coral Sea east of Australia and previously thought to have become extinct 50 million years ago.
The biggest new species was probably a 1.8kg rock lobster found off Madagascar. And a furry crab, also dubbed a yeti crab, was found in the waters off Easter Island.

U.N.: Number of Ocean 'Dead Zones' Rise

Scientists have found 200 "dead zones" in the world's oceans — places where pollution threatens fish, other marine life and the people who depend on them. The United Nations report Thursday showed a 34 percent jump in the number of such zones from just two years ago.
Pollution-fed algae, which deprives other living marine life of oxygen, is the cause of most of the world's dead zones that cover tens of thousands of square miles of waterways. Scientists chiefly blame fertilizer and other farm run-off, sewage and fossil-fuel burning.
Those contain an excess of nutrients, particularly phosphorous and nitrogen, that cause explosive blooms of tiny plants known as phytoplankton. When they die, they sink to the bottom, where they are eaten by bacteria that use up the oxygen in the water.
"The low levels of oxygen in the water make it difficult for fish, oysters and other marine creatures to survive as well as important habitats such as sea grass beds," U.N. officials said. "These areas are fast becoming major threats to fish stocks and thus to the people who depend upon fisheries for food and livelihoods."
By 2030, the world's rivers will pump 14 percent more nitrogen into seas and oceans than that found in the mid-1990s, according to new U.N. research released at a meeting in Beijing.
Researchers led by Robert Diaz, a marine scientist at Virginia's College of William and Mary, said they found new dead zones at the Archipelago Sea in Finland; Fosu Lagoon in Ghana; Pearl River estuary and Changjiang River in China; and Mersey River estuary in Britain.
Other new zones found were at the Elefsis Bay and Aegean Sea in Greece; Paracas Bay in Peru; Mondego River in Portugal; Montevideo Bay in Uruguay; and in the western Indian Ocean.
The United Nations marine experts said the number and size of oxygen-deprived zones has grown each decade since the 1970s.
Not all the dead zones persist year-round; some return seasonally, depending on winds that bring nutrient-rich water to the surface.
"It seems like a big jump in two years," said Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium, who was not part of the U.N. research. She said an important factor has been the huge increase in pollution from fast-developing countries.
Rabalais, who has studied the Gulf of Mexico's massive dead zone that is now the size of New Jersey, said marine creatures that swim fast enough can usually escape.
"The things that are left behind are the ones that usually can't survive," she said. When you consider the size of some of these areas, it's removing what's considered the essential habitat for fishes and crustaceans."
Other U.N. scientific findings released Thursday, however, raised hopes for the recovery of damaged coral reefs, which serve as the ocean's nurseries. It found that reefs bleached in the late 1990s by high surface sea temperatures are affected by how polluted the waters are.
"Coral reefs recovering faster are generally those living in marine protected areas and coastal waters where the levels of pollution, dredging and other kinds of human-induced disturbance are considered low," the U.N. said.

Scientists Discover Bacteria That Use Radiated Water as Food; 'A Completely Different World'

Researchers from Indiana University Bloomington and eight collaborating institutions report in this week's Science a self-sustaining community of bacteria that live in rocks 2.8 kilometers below Earth's surface. Think that's weird? The bacteria rely on radioactive uranium to convert water molecules to useable energy.
The discovery is a confirmed expansion of Earth's biosphere, the three-dimensional shell that encompasses all planetary life.
The research has less Earthly implications, however. It will likely fuel optimism that life exists in other deep subsurface environments, such as in groundwater beneath the permafrost on Mars.

"We know surprisingly little about the origin, evolution and limits for life on Earth," said IUB biogeochemist Lisa Pratt, who led IU Bloomington's contribution to the project. "Scientists are just beginning to study the diverse organisms living in the deepest parts of the ocean. The rocky crust on Earth is virtually unexplored at depths more than half a kilometer below the surface. The organisms we describe in this paper live in a completely different world than the one we know at the surface."
Bacteria living in groundwater or in other subsurface environments is not news. Until now, however, it was not known whether subterranean microorganisms were recent arrivals bound for extinction or whether they were permanent fixtures of an unlikely habitat. Also, many scientists have been skeptical of subsurface bacterial communities being completely disconnected from surface ecologies fed by the sun's light.
Pratt, Princeton University geomicrobiologist Tullis Onstatt and former graduate student Li-Hung Lin (the paper's lead author, now at National Taiwan University) and colleagues present evidence the bacterial communities are indeed permanent -- apparently millions of years old -- and depend not on sunlight but on radiation from uranium ores for their existence.
Coauthors of the present paper learned of a new water-filled fracture inside a South African gold mine near the Johannesburg metropolitan area and viewed it as an opportunity to study subsurface rock uncontaminated by human activities. Lin and others in the research team traveled to the mine and descended the hot, gas-choked shafts to study water slowly seeping from the crack.
The scientists sampled the flowing fracture water many times over 54 days to determine whether the community of microbes, if present, changed in composition and character, and to determine whether contamination had occurred. The researchers also examined the age of the fracture water and its chemical composition.
This fracture water contained hydrocarbons and hydrogen not likely to have been created through biological processes, but rather from decomposition of water exposed to radiation from uranium-bearing rocks.
High density DNA microarray analysis revealed a vast number of bacterial species present, but the samples were dominated by a single new species related to hydrothermal vent bacteria from the division Firmicutes. The ancient age of the fracture water and comparative DNA analysis of the bacterial genes suggests subsurface Firmicutes were removed from contact with their surface cousins anywhere from 3 million to 25 million years ago. The bacteria's rocky living space is a metamorphosed basalt that is about 2.7 billion years old. How surface-related Firmicutes and other species managed to colonize an area so deep within Earth's crust is a mystery.
Some surface Firmicutes species are known to consume sulfate and hydrogen as a way to get energy for growth. Other bacteria can then use the by-products of the Firmicutes as a source of food. The scientists found that the fracture Firmicutes are also able to consume sulfate. Firmicutes do not use radiation directly as a source of energy, however.
Radiation emanating from uranium minerals in or near the fracture allows for the formation of hydrogen gas from decomposition of water and formation of sulfate from decomposition of sulfur minerals. Hydrogen gas is highly energetic if it reacts with oxygen or other oxidants like sulfate, as the Hindenburg disaster demonstrated. Firmicutes are able to harvest energy from the reaction of hydrogen and sulfate, allowing other microbes in the fracture community to use the chemical waste from the Firmicutes as food.
In a way, Firmicutes serve the same function as photosynthetic organisms, such as plankton and trees at Earth's surface, that capture sunlight energy ultimately to the benefit of everything and everyone else. In the deep subsurface case, Firmicutes species are the producers, capturing the energy of radiation-borne hydrogen gas to support microbial communities.