hydrothermal vent

Living With Deep-Sea Mining

Deep-sea mining has been coming for the better part of 50 years. In the mid-1960s, polymetallic nodule fields — compact masses of minerals at the bottom of the Pacific and Indian Oceans — were explored as economically viable sources of manganese, nickel, copper, and cobalt. Due to technological limitations and the vagaries of the commodities market, however, the industry never took off and deep-sea mining remained a pipe dream for the remainder of the twentieth century.

tracker_finalIn the last ten years, innovations in underwater robotics and deep-submergence technology, along with an increased demand for the materials essential to smartphones, tablets, and other personal electronics, has led to a resurgence in new mining ventures and benthic prospecting in both national waters and the high seas. Though polymetallic nodule fields were the original targets for early mining campaigns, the first mining will occur in deep-sea hydrothermal vents —  ecosystems that, until 1977, we didn’t even know existed.

Deep-sea hydrothermal vents form when seawater, under enormous pressure, percolates through the earth’s crust and comes in contact with a source of intense heat, most often in the form of magma. This superheated seawater is expelled through the vent, similar to a terrestrial geyser, as chemically-enriched vent effluent. That chemical enrichment is what makes vents so appealing, both to biologists who study the creatures that thrive near them, and to mining companies.

Vibrant communities of vent-endemic organisms form around the plume and drink from its chemical cocktail, deriving energy through a process called chemosynthesis. This process, which relies upon a partnership between multicellular host organisms and unicellular symbiotic bacteria (or archaea), is one of only a handful of feeding strategies on this planet that are independent of the sun. In general, the deep sea is a world of profound food limitations. Hydrothermal vents exist as oases in the submarine desert, providing abundant food to organisms that can exploit it.

The same process that creates the energy-rich vent fluid also enriches that fluid with valuable metals drawn from deep within the earth. As effluent exits the ground, it contacts cold seawater, and those metals are forced out of the solution and deposited on the walls of the growing vent chimney. Under the right conditions, a field of hydrothermal vents can form a massive ore body, rich in gold, copper, zinc, silver, nickel, and other valuable metals, as well as rare earth elements.

Known as seafloor massive sulfides, these potential prospects are among the richest ore bodies in the world. Free of the layers of soil and rock that surface miners must excavate —  at great expense —  to access underground minerals, seafloor massive sulfides would be easy to exploit were it not for the tons of seawater pressing down on them.

Between the islands of New Britain and New Ireland, Papua New Guinea, lies Solwara 1, a hydrothermal vent field 1,600 meters below the surface of the Bismarck Sea. As the first deep-sea mining prospect to be licensed for extraction, sometime between 2017 and 2018, three massive underwater robots will descend upon it and, over the course of several years, extract the copper-rich ore. The company in charge, Nautilus Minerals, argues that this process can be done sustainably, with minimal disturbance to the surrounding seafloor.

And they might be right.

Deep-sea hydrothermal vents, especially those in Papua New Guinea’s territorial seas, are exceptionally dynamic ecosystems, experiencing natural, occasionally catastrophic disturbance on a decadal time scale. Whether a mining event exceeds the natural disturbance of a hydrothermal vent ecosystem is one of many unknowns of this largely unexplored venture. Even though hydrothermal vents have received a significant proportion of research focus since their discovery, the vast majority of vents almost certainly have yet to be discovered. Of the 521 known hydrothermal vents around the world, almost a fifth now fall within a mining exploration lease.

Deep-sea mining is among the first of a new kind of emergent global industry, where science and conservation have a decades-long advantage. Historically, new industries emerge to exploit newly discovered resources. They disrupt the surrounding environment, and only then does conservation science come in to quantify loss and inform recovery and future management. Because deep-sea mining had such a long lead-up to actual production, we have almost 40 years of data about deep-sea hydrothermal vents. This presents us with a rare opportunity to establish environmental and biodiversity baselines at the prospective site and within connected communities, before the first mining tool crawls across the seafloor.

Within a biogeographic province — an area in which vent systems share the same fauna — vents are generally well-connected, with species distributing recruits to distant fields, producing a pool of genetic diversity which extends beyond a single vent. Identifying and establishing refuges, or vent fields where mining cannot occur, may be adequate to preserve the overall biodiversity of the biogeographic province and act as a source for later recruits if the mine site recovers. In the rare circumstances where we’ve been fortunate enough to observe a vent system recover after volcanic eruptions decimate the community, this has been the case.

We have a reasonably good grasp of the diversity and connectivity of some of the most abundant species that inhabit the vents of Solwara 1 and the broader western Pacific. Snails, mussels, shrimp, and squat lobsters dominate western Pacific hydrothermal vent ecosystems. Preliminary studies suggest that these species are relatively resilient to even catastrophic disturbance.

But when it comes to deep-sea mining, the most abundant species aren’t the only species of concern and vent ecosystems aren’t the only ecosystems affected. Hydrothermal vents, particularly in the western Pacific, are biodiversity hotspots, possessing a host of rare species that, though they are not the primary shapers of the vent ecosystem, may still play a critical role within the vent community. Many of these species have yet to be described.

Surrounding every hydrothermal vent is a halo of fauna that, though not endemic to hydrothermal vents, aggregate around them due to the prodigious amount of food available. While vent-endemic organisms have evolved to be resilient to frequent and occasionally catastrophic disturbance, these other organisms have not. Halo fauna are deep-sea generalists, adapted to an environment that is vast and stable. Where hydrothermal vent communities may be resilient to the environmental insult of deep-sea mining, any level of disturbance will likely exceed the resilience of the halo community.

With mining imminent, it is nearly impossible to fully characterize a threatened vent community. Understanding how these ecologic features fit together, at least generally if not specifically, is essential to understanding and mitigating the impacts of deep-sea mining. The broader question is: How important are rare species and halo fauna to a hydrothermal vent ecosystem and how much can the deep sea afford to lose?

Andrew David Thaler is a deep-sea ecologist and population geneticist. He earned a PhD in Marine Science and Conservation from Duke University, and he is currently a visiting scientist at the Virginia Institute of Marine Science. Thaler also runs the conservation website Southern Fried Science.