Exploring the Dark Depths of the Oceans

Researchers seek to know the extent of life on Earth.

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By Marlene Cimons, National Science Foundation

Humans and other creatures that live in the Light World thrive in an abundance of sun and oxygen. In the Dark World, however, microbes flourish on something else entirely, although scientists don’t know for sure yet exactly what it is.

The Light World, of course, is the Earth and the few hundred meters of ocean where sunlight still penetrates. The Dark World, on the other hand, is the mysterious deep biosphere beneath the oceans where life does not entirely depend on solar energy and photosynthesis.

“In the Light World, we use oxygen, either making or consuming it, but in the Dark World, what you breathe might be very different,” says Katrina J. Edwards, professor of biological and earth sciences at the University of Southern California. “You might have organisms that eat sulfur and respire oxygen. They might breathe iron. Microbes can do all these complicated things, but they are very difficult to study in the dark.”

Researchers at the Center for Dark Energy Biosphere Investigations, which Edwards directs, are trying to change this.

Nearly half of the total biomass on earth resides in sub-surface habitats that include mines, aquifers, soils on the continents and sediments and rocks below the ocean floor. This massive area is what Edwards and her team will study at three sites under the ocean, North Pond in the mid- Atlantic, Juan de Fuca in the eastern Pacific, and South Pacific Gyre. The expedition will drill holes, seeking to discover how life exists in sediment and rock below the ocean’s bottom.

“We want to learn several things, primarily what is the extent of life on Earth?” she says.  “We haven’t yet found the bottom of our biosphere on Earth. We probably all would agree that life doesn’t penetrate to the Earth’s core, but how far does it go? What are the extremes that life can handle in temperature and pressure? What kind of microbes are where, and why? Microbial life in the dark ocean is very different than here in the Light World. Who knows what kinds of products they are producing?”

One of the team’s major objectives is to understand the influence of the biosphere on the rest of the planet.  “What does it mean to have this rich microbial world in the dark biosphere?” she says. “What impact does it have on Earth’s system as a whole? We won’t know until we examine it.”

The center is a National Science Foundation Science and Technology Center, which NSF supports with $5 million annually over five years. Its research partners include the University of Alaska Fairbanks, University of California at Santa Cruz, the University of Hawaii at Manoa, Pacific Northwest National Laboratory, the University of Rhode Island, Lawrence Berkeley National Laboratory, the Japan Agency for Marine Earth Science Technology, Harvard University, the University of Bremen, among other universities and research centers. In addition to conducting basic research, the schools are developing a number of programs and activities geared to students and the public.

“We have a huge education and outreach program getting the word out to school groups and the general public, trying to make them aware of the dark parts of the ocean,” Edwards says.  “For example, we have a program that uses robotics for children—miniature robots you can use in a pool or the shower, or the ocean, with the same kind of cool technology we use for the robots in the bottom of the ocean.”

The center relies heavily on new technology—tools, instruments and other equipment—with important potential applications outside the study of the biosphere, Edwards says.

“We’ve just created a microbial ‘logger,’ which you can send into a hole where it will scan and find hotspots of microbial activity,” she says. “Ultimately, it could have incredible use in the pharmaceutical industry, in plant inspections, for example, to ensure the facility’s cleanliness, or in the food industry, for example, restaurant inspections. Think about the recent e coli outbreak, and imagine using this scanner.  This is the type of tool that could help nail down the hotspot.”