The ocean offshore remains a mystery, but increasingly, as the federal government seeks energy and military security, the deep sea is coming under intense scrutiny. Congress would like to locate, size and claim untapped sources of fuel beneath the sea floor, the Department of Energy is exploring the potential for forestalling global warming by injecting captured carbon dioxide into the seabed or deep in ocean waters, and the U.S. Navy is hoping to employ low frequency sonar throughout vast swaths of ocean to detect stealth submarines. But for all the possibilities inherent in the poorly explored and understood deep seas, major risks and uncertainties lie in the ocean depths as well. The science surrounding these proposals for incursions into the sea is not fully developed. Aggressive efforts to exploit ocean resources threaten to alter, perhaps irrevocably, the finely-tuned chemical balances of the deep sea, with grave peril to animal and plant populations that dwell within it.

A Source of Energy
One fifth of all U.S. domestic oil supplies and more than a quarter of the country's natural gas comes from offshore sources. Significant reserves remain untapped. While many environmentalists are urging conservation and efficiency both to reduce dependence on oil imports and to limit greenhouse gas emissions, many from the oil and gas industry are interested primarily in reducing imports.

With a federal prohibition on new oil and gas development for much of the U.S. coastal waters in place for two decades, and state rules further impeding new offshore oil and gas projects, Congress is considering measures that will pave the way to re-opening these ocean frontiers.

"States have used the [Coastal Zone Management Act] to stall or halt offshore development on public lands by taking advantage of loosely worded passages within the statute and regulations that enmesh offshore lessees in a never-ending loop of permit approvals and appeals," complained Tom Fry, president of the National Ocean Industries Association, in testimony before the U.S. Commission on Ocean Policy in 2001.

The energy bill now under consideration in Congress includes a provision calling for an inventory of offshore oil and gas reserves held in the nation's outer continental shelf. The provision is in the Senate version but has been deleted from the House version.

There is reason, according to the provision's supporters, to do such an inventory. According to Senator Pete Domenici, R-New Mexico, chair of the Senate Energy Committee, new surveys doubled estimates of natural gas reserves in the Gulf of Mexico. In this bill, the Department of the Interior would survey all areas of the continental shelf containing possible oil and gas reserves, including areas off the coast of Alaska, California, Florida and New England where Congress previously had passed drilling moratoria.

Those who oppose the inventory charge it is a thinly veiled precursor to increased oil and gas exploration and drilling in offshore waters. The California State Lands Commission in August passed a resolution opposing the inventory, for example, arguing that "the intent behind an oil and gas reserves study is to promote future offshore oil and gas development, undermining current offshore drilling moratoria and also compromising the State of California's role under the federal Coastal Zone Management Act, in the leasing, exploration or development of Outer Continental Shelf lands."

Not only is the administration seeking to identify additional offshore oil and gas reserves in U.S. territorial waters, it is also working to extend those territorial waters. The UN Convention on the Law of the Sea gives nations jurisdiction over the seabed and ocean waters 200 nautical miles from shore. It also contains a provision allowing nations to extend jurisdiction over the seabed along their continental shelves out to 350 miles. The federal government is now mapping the edge of the continental shelf off New England and Alaska to determine how far beyond 200 miles jurisdiction could extend.

The United States has not ratified the Law of the Sea Treaty. In an interesting case of oil industry multilateralism, oil and gas companies are strongly encouraging ratification of the treaty. "The Senate needs to ratify this treaty immediately," says Fry.

The anticipated payoff is billions of dollars worth of oil, natural gas, and methane. Indeed, Fry says at stake is the preservation of "our strong economy and high standard of living."

However, the U.S. and global environmental future is also at stake. Will the United States, the largest emitter of greenhouse gases, continue on the perilous path of fossil fuel dependence, or will it seek to reduce carbon dioxide emissions through greater efficiency and alternative energy sources? Will invocations of "our high standard of living" succeed in legitimizing increased threats to the sea and to marine ecosystems from noise pollution created by increased seismic exploration and ship traffic, and from oil spills and leakage?

Each year, 29 million gallons of oil wash into the sea as a result of human activity, 85 percent leaking from cars, lawn-mowers and recreational watercraft. While only 15 percent is spilled from oil tankers or drilling rigs, the results are not inconsequential. Thirty years ago, a barge spilled 175,000 gallons of fuel into Buzzards Bay off Cape Cod, Massachusetts. The oil that drifted ashore has disappeared from the surface, but two inches down, it remains as concentrated as it was three decades prior.

A Sink for Carbon Dioxide
At the dawn of the industrial age, atmospheric levels of carbon dioxide were 280 parts per million (ppm). Today, they are 370 ppm and are projected to rise to 550 ppm by 2100. The global warming effect just of levels of 450 ppm threatens to bleach out coral reefs, substantially alter the circulation of the oceans and melt the Antarctic ice sheet.

One obvious way to begin to address this problem is to reduce the use of fossil fuels that generate emissions of carbon dioxide -- the leading greenhouse gas -- but as time goes on without the necessary reductions, the Department of Energy is seriously investigating the possibility of capturing and burying the carbon dioxide.

The Sleipner natural gas field lies in the North Sea, approximately 150 miles off the coast of Norway. The gas contains 9 percent carbon dioxide, far over the 2.5 percent threshold for marketability. A chemical plant on site extracts the excess, which is pumped into a sandstone aquifer 3,300 feet below the seafloor. Each year, the company extracting the gas, Stratoil, buries one million tons of carbon dioxide, or 3 percent of Norway's carbon dioxide emissions, into the aquifer. Doing so is not inexpensive -- the equipment cost $80 million -- but Norway's $38 per ton carbon tax (the same type of tax the Clinton administration proposed and then backed away from a decade ago) meant that the investment was paid off in less than two years (through savings on the carbon tax Stratoil hasn't had to pay).

Unresolved, however, are questions about the physical, geological and ecological impacts of the practice. Will carbon dioxide leak from the reservoirs? How will the integrity of the rock capping the aquifers hold up in the presence of carbon dioxide? How are microbial communities living in the rock affected? A seismic survey of the sandstone aquifer beneath the Sleipner field has identified the bubble of injected carbon dioxide; the International Energy Agency Greenhouse Gas Research and Development program, which is monitoring the field, expects that future surveys will reveal if it travels, and where.

The Sleipner field is an ongoing experiment on the effects of compressing and injecting carbon dioxide in the seabed. It is a critical experiment, since researchers believe that saline aquifers under the seafloor, and beneath dry land as well (where U.S. researchers have identified 35 potential reservoirs), could hold between 400 and 10,000 gigatons of carbon (GtC), more than enough capacity to contain anthropogenic carbon dioxide emissions for decades to come. (Worldwide emissions are 7 GtC per year.)

Other possibilities, with many more unknowns and uncertainties, include injecting carbon dioxide directly into seawater. Earth's oceans may contain an even larger capacity to absorb and retain carbon dioxide emissions than saline aquifers below the seafloor or the continents, a capacity on the order of thousands of GtC. The sea itself already contains 40,000 GtC (versus 750 GtC in the atmosphere). Carbon dioxide emissions which would double atmospheric concentrations if injected in the ocean would only increase ocean concentrations by less than 2 percent.

But while it may seem small, a 2 percent increase in oceanic carbon dioxide may nonetheless have enormous environmental consequences. It would significantly alter the pH of seawater, increasing its acidity, rendering it inhospitable to entire communities of deep-sea dwellers. Deep-sea organisms with low metabolic rates, adapted to an environment that has been stable for thousands of years, would have difficulty buffering or compensating for the sudden change. They would be less able to absorb oxygen and synthesize protein, with deleterious effects on their metabolism, growth and reproduction.

In addition, their shells and skeletons might dissolve. Increasing amounts of carbon dioxide entering surface waters may have produced a 10 percent decrease in limestone production on coral reefs in the last 100 years. If present emissions continue, reef limestone production may drop another 20 percent in the next 100 years, more than enough to halt the growth of coral reefs.

At this point, there is no baseline of information against which to measure the impact of pumping massive amounts of carbon dioxide into the deep sea. The communities of deep-sea organisms have not been identified. Not knowing what and how many species live in the deep water, it is impossible to say how many would be affected, to catalog the ecological implications or to project how wiping out entire communities may alter marine biochemical cycles.

In addition, injecting carbon dioxide into seawater may not work. The closer to the sea surface the carbon dioxide is injected, the more quickly it will rise and outgas back into the atmosphere. Below 3,000 feet, the water is dense and cold, and doesn't mix as quickly with the surface. At this depth, carbon dioxide injected into the Atlantic will return to the surface in about 300 years. Below 9,000 feet, the carbon dioxide might remain in the sea for several thousand years, although the cost and feasibility of getting it there remains prohibitive, and the ecological consequences are by and large unknown.

Sonar -- Security for the Homeland
Yet another threat to the inhabitants of the deep seas comes from the U.S. Navy, which is seeking to deploy high-intensity, low-frequency active sonar (LFA) throughout the world's oceans. Each system, towed from a ship, deploys an array of 18 loudspeakers, each beaming 215 decibels (dB) of sound at low-frequency throughout the sea. Noise emanating from each speaker is equivalent to standing on a runway next to a jet fighter taking off. Where the sound converges, further away from the source, the noise level rises to 235 dB, one hundred times louder. A hundred miles from the source, the sound may still be as loud as 160 dB, loud enough to cause permanent hearing damage in humans.

Ship engines and propellers (160 to 190 dB), and seismic airguns from oil exploration (250 dB), are already making the sea a noisy place, and the introduction of active sonar compounds the problem. Marine mammals depend on sound to survive -- to identify feeding grounds, to communicate and find mates, and to follow migration routes.

Whales strand coincident with U.S. and NATO testing of active sonar: 12 in Greece, 16 in the Bahamas, 14 on the Canary Islands. Tissue damage found in the ears of the Bahama whales provided the smoking gun linking sonar to whale deaths. In addition, in the Bahamas, the entire local population of beaked whales, about 35 whales, disappeared from the area, suggesting that in addition to those whales that stranded, others may have died at sea or been forced permanently from their home.

Noise in the sea can interrupt whales as they search for mates or track food. Male fin whales sing a low-frequency song, 185 dB, to call females. Since neither fin nor blue whales come together in groups to breed, their reproduction may be diminished if other noises in the sea mask their mating calls. Sound waves at 130 to 150 dB have caused humpbacks to stop singing.

Low frequency sonar damages fish as well, rupturing their swim bladders, causing hemorrhaging in their eyes and reducing their abilities to sense sound. Human divers, 90 miles away from the source of the sonar, have experienced vibrations in their lungs, head, and arms, as well as numbness.

The Navy disputes that deployment of LFA will pose a serious risk to marine mammals. Its environmental impact statement concluded that deploying LFA would only affect a small number of marine mammals and "have no more than a negligible impact on marine mammal stocks."

But environmental groups say the environmental impact statement was flawed.

"The study failed to answer the most basic questions about [the] controversial system," charges the Natural Resources Defense Council (NRDC). "How will LFA affect the long-term health and behavior of whales, dolphins and hundreds of other species? Taking place as it does over an enormous geographic area, what effect might it have on marine populations?"

The Navy sought and received a permit from the National Marine Fisheries Service, allowing LFA to kill 12 percent of marine mammal stocks, many already on the endangered species list. NRDC has been engaged in ongoing litigation to block deployment of LFA, so far successfully.

In addition to contesting the lawsuits, the Pentagon's response has been to seek broad exemptions from the Marine Mammal Protection Act (MMPA), as well as other environmental protection laws. According to an NRDC analysis, "The Department's proposed exemption is exceptionally broad in all its elements, which, working in combination, could render the MMPA's protections for marine mammals virtually meaningless." According to NRDC, the exemption would give the Pentagon complete authority to invoke the exemption, without even a requirement to report to Congress.

Into the deep
Evidence is increasingly accumulating of the long-term and serious impacts of exploiting coastal waters for energy and for fish, and discharging sewage and nitrogen from farm fields and cities in coastal waters. Now, powerful interests are moving out into the deep water, again to exploit the sea as a source of energy, a sink for waste and a site for the deployment of advanced military technologies -- all with uncertain and possibly deleterious consequences. It's become a vital public policy issue that, to date, is missing only the public.

Deborah Cramer is the author of a natural history of the sea, Great Waters: An Atlantic Passage.