Deep-sea Mining May Pose Serious Threat To Fragile Marine Ecosystems, According To Study

Mining of massive sulphide deposits near "black smokers"--undersea hydrothermal vent systems that spew 350-degree Celsius water into the frigid deep-sea environment, and support sulphur-loving bacteria and bizarre worm and clam species--could smother and contaminate these communities, which some biologists argue may represent the origins of life on earth.

"We need to act now to establish scientific and legal methods to protect these sensitive ecosystems and minimize the potential environmental impact of this industry," says lead author Jochen Halfar, an assistant professor of earth sciences at U of T Mississauga. "Imposing regulations after operations begin would prove very difficult, and some of the governments in the jurisdictions targeted by this industry have a poor record of mining oversight. The prospects for regulation of underwater mining are not good."

A Canadian-based company is currently planning the world's first commercial undersea exploration for high-grade gold and copper. They are targeting an area known as the Manus backarc basin off the coast of Papua New Guinea. The active hydrothermal vents in these areas occur where new oceanic crust is formed through undersea volcanic activity. Until the late 1970s, scientists had assumed that life required sunlight, but the discovery of these vent communities showed that life could exist on thermal and chemical energy. Since oceans have existed, more or less, since the beginning of Earth's history, these deep sea hydrothermal vents could be the most ancient sites of life on Earth. Yet the vents are not only of scientific interest, since the organisms may have pharmaceutical and biotechnological applications.

Mining companies first turned their attention to the oceans in the 1970s, and interest grew in manganese nodules that exist on the surface of the ocean floor. However, high projected costs and the regulatory restrictions on deep sea mining in international waters through the United Nations Convention on the Law of the Sea (UNCLOS) have currently put those projects on hold. In particular, says Halfar, restrictions by the International Seabed Authority--which overseas environmental protection and demands that profits from mining in international waters be shared with developing nations--redirected prospecting and exploration of the seafloor into areas under national jurisdiction, where regulations are often weaker or non-existent.

"The demand for metals is growing rapidly, and along with the sharp rise in metal prices, we have seen the depletion of metal-rich terrestrial mines," says Halfar. "For mining companies and their investors, undersea mining offers high concentrations of ore at relatively low production costs."

The mining operations will use a strip-mining approach to remove deposits within the top 20 metres of the seafloor, using remotely operated underwater mine cutters and a hydraulic pump system to transfer roughly two million tons of ore per year to the surface. These strips would be located approximately 500 meters to two kilometres from the active vents, but Halfar argues that the cutting and pumping process will disgorge considerable amounts of fine sediment into the water column--a serious problem for vent organisms that feed by filtering the water in their habitat.

The process will also raise the concentrated nutrients from the deep sea to the relatively nutrient-poor surface waters of the ocean, causing algal blooms and potentially contaminating waters that support Papua New Guinea's commercial fishing industry, as well as local subsistence fishers. Depending on ocean currents, these nutrients could drift widely, disrupting the food chain and potentially damaging ecosystems that lie within other countries' economic zones or in international waters. This poses additional problems, because while a state has the right to exploit its own resources, international environmental law decrees that it cannot damage the environment beyond its boundaries.

While studies of proposed undersea manganese mining in the equatorial region of the Pacific found the risks to outweigh the benefits, says Halfar, there have been no independent impact assessment studies of the proposed massive sulphide mining sites. "Over 250 active and fossil deposits have already been found. And the company operating in Papua New Guinea has already staked claims off the coast of Tonga and Fiji," he says. "If this first attempt at mining proves successful, it's like letting the genie out of the bottle."

The study appears in the May 18 issue of the journal Science, and is co-authored by Rodney Fujita, a marine ecologist with U.S.-based Environmental Defense.