Hydrothermal Vents

Mysterious empires of the deep ocean

Volcanoes traditionally conjure visions of Mount St. Helens-like behemoths erupting with lava flowing ominously down a mountainside. But not all volcanoes are on land nor are they always destructive. Hydrothermal vents are underwater volcanoes that play an important role in the ocean's temperature, chemistry and circulation patterns, and they contain extremely valuable resources sought by scientists, governments and private industry, creating debate about whether the riches are worth great risk.
Life at 7,000 Feet
Although hydrothermal vents likely began forming millions of years ago, scientists became aware of them only 34 years ago. Found on seabeds at depths of 7,000 feet, hydrothermal vents are often nestled among vast underwater mountain ranges. They form when the earth's tectonic plates shift, creating cracks in the ocean floor and allowing geysers of rich mineral water to escape.

Although most of the deep ocean where hydrothermal vents are found is sparsely populated, they are teeming with minerals and organisms. Since their discovery, more than 1,300 previously unknown species have been identified at vent sites, and even more new creatures are found with each visit.

The food web in the ecosystems of hydrothermal vents is 300 to 500 times more concentrated than that of the surrounding waters. It is based not on photosynthesis (which requires light) but on bacteria that use the energy found in hydrogen sulfide, a chemical poisonous to most animals. Because the water from the hydrothermal vents is so rich in hydrogen sulfide, the bacteria are able to form dense masses in and around the hot water vents. Despite their microscopic size, the bacteria are the primary producers in the food web and support a wide variety of other marine life including tubeworms, giant clams, shrimp, mussels and lobsters.
What Lies Beneath
While the marine life of a hydrothermal vent is enough to keep anyone riveted, what really catches the attention of many on the surface are the potential riches to be found. Pound for pound, seafloor ore has more gold, zinc and silver than land deposits do. In 2009 Nautilus Minerals, a Canada-based seafloor-mining company, estimated there are thousands of vent systems under the sea, creating the potential for an annual yield of "several billion tons of copper" alone. Copper is a key component in construction, power generation and transmission, industrial machinery, transportation, heating and cooling systems, electronics, plumbing and telecommunications. Other minerals found in hydrothermal vents include nickel, cobalt and rarer minerals such as tellurium, which is used in the manufacturing of computers, CDs, DVDs and batteries.

The Alvin submersible vehicle on board the R/V Atlantis in preparation
for a hydrothermal vent exploration in 2000

But the value of hydrothermal vents extends beyond the minerals. Scientists have also discovered in hydrothermal vents microbes found nowhere else on earth that may hold the key to the development of new drugs, industrial processes and other products. Scientists believe the microbes are as economically valuable as the vents' minerals because they are sources of enzymes used in DNA fingerprinting, detergents and the enhancement of oil flow from old wells. The microbes also produce bioactive compounds that may have pharmaceutical applications in cures for cancer and other diseases.

Even more fascinating, hydrothermal vents demonstrate accelerated biological and geological processes that far exceed what scientists believed possible. Taken together, the benefits of mining the riches of hydrothermal vents are proving hard to resist.

Mining Hydrothermal Vents
The mining, in fact, has already begun. Nautilus Minerals has a major seabed sulfide-mining project under way in the waters of Papua New Guinea. Canada, New Zealand and Australia have also set up mining operations at hydrothermal vent sites off their coasts.

But the most ambitious and expensive deep-sea mining project proposed to date belongs to China. After using remotely operated underwater vehicles (ROVs) to explore vents throughout the world, the Chinese government submitted plans to the International Seabed Authority (ISA) in May 2010 to mine the hydrothermal vents around an underwater ridge in the Indian Ocean near Madagascar. The selected vents lie at a depth more than 5,000 feet below the surface, and the intended harvest is mineral-rich ore.
Environmental Impacts of Deep-Sea Mining

Zoarcid fish and mussels at a vent site

Despite the expected benefits derived from gathering what lies beneath the ocean floor, some environmentalists are concerned about deep-sea mining. At 7,000 feet there is little margin for error. As we've seen before, equipment failure, engineering miscalculations and unforeseen accidents can have devastating consequences. The fear is that without proper monitoring and responsible mining protocols, hydrothermal vents and surrounding ocean ecosystems may be damaged.

But because of the vents' remote locations, it's hard to say exactly what damage will be done. Some experts predict that removing a sizeable portion of the seafloor could cause a major disturbance. Deep-sea mining may release toxic plumes of sediment from mining machinery, degrading or killing the seabed's filter-feeding organisms vital to the vent food chain. Such plumes might also block out light at shallower depths, hindering the development of plankton, also vital to the food chain. Deep-sea mining could reopen naturally closed vents and release sulfur and methane compounds toxic to surrounding ecosystems. Some predict the mining could cause suboceanic landslides, while others fear the equipment will produce enough noise and vibration in the floor-to-surface water column to disrupt the lives of marine mammals that live there. As conservationist Charles Clover said, "The potential for conflict between commerce and conservation is huge."

On the other end of the controversy, some of the most ardent proponents of deep-sea mining are the scientists themselves. Some believe that if done responsibly the information and resources gleaned outweigh potential problems. Many scientists argue that hydrothermal vent ecosystems do not appear to be fragile. For millennia they have withstood enormous natural impacts and are periodically decimated. Yet they rebuild within only a few years, proving great resilience.
The Debate Continues
While advocates and opponents argue the implications of exploration, at this point the greatest obstacle to deep-sea mining is cost, as a single operation can run hundreds of millions of dollars per year. But as land-based mineral ores become increasingly scarce and the quest for new drugs escalates, there is no doubt the ocean floor will be targeted for mining. Although we can hope, it remains to be seen whether this technological treasure hunt will be undertaken with respect for environmental conservation and sustainability.
For More Information
Read "Who's Minding the Mining?"

© Alert Diver — Summer 2011