This is one in a series on careers in science, technology, engineering and mathematics made possible with generous support from Arconic Foundation.
Looking through the cameras of a remote-controlled submarine, Nicholas Higgs can see the bottom of the ocean, far below. The camera’s light sweeps through the black water, illuminating a flat, silty seafloor. Suddenly the spotlight shines on a huge skeleton. Strange, alien-looking animals cover it. Higgs has found what he was looking for: a whale fall.
He normally works in England out of Plymouth University. A marine biologist, Higgs is deputy director of its Marine Institute.
More than 60 percent of Earth’s surface is deep underwater — so deep, the sun’s light can’t reach it. Huge mountains rise from the seafloor. Chasms deeper than the Grand Canyon shelter microbial life that must survive on what nothing else wants to eat. Animals live out their lives in near-freezing, pitch-black ecosystems.
Or so it seems. Scientists actually know very little about this part of our world, how it works and the creatures living here. “It’s the largest habitat on the planet,” Higgs says.
But to date, he notes, “We’ve explored less than five percent of it — less than one percent in extreme detail.”
Scientists who study the deep ocean are constantly learning new things and discovering surprises. They also face unique challenges working in such a remote and deep environment: darkness, near-freezing temperatures, extreme pressures and even the occasional curious whale. But by probing this mysterious undersea-scape, they can gain new insights into our planet, other species and the nature of life itself.
Whale falls and zombie worms
Imagine living on the bottom of the ocean. With no sunlight, plants cannot grow. Food is hard to find. So you swim around, scouting for edible bits in the seafloor mud. Then out of nowhere, a gigantic dead body cascades down from above.
Woohoo! It’s party time!
This is what scientists call a whale fall. As the carcass of a whale sinks to the sea floor, it becomes an instant feast for animals of the deep. So many come to dine that the whale’s body becomes a new ecosystem — one that can last for years, even decades.
The first to chow down are scavengers. These include sharks and slimy hagfish. They’ll dig into the rotting flesh. Then worms, shrimp and other invertebrates move in. They’ve come to pick up bits of meat and to nibble on the bones. Later, bacteria take over. They make energy from chemical reactions using a process called chemosynthesis (KEE-mo-SIN-the-sis). Finally, the whale’s skeleton becomes a structure within which some animals build their homes.
Higgs has studied all of these communities of creatures.
Sometimes scientists exploring the ocean floor will stumble across a whale carcass by accident. Other times, they find a dead whale that has washed ashore. They might tow it out to sea and sink it on purpose. Then they can study the organisms that come in to recycle the dead.
Higgs is part of a team that has cruised to a whale fall aboard a research ship. There, they drop an underwater robot overboard to study the carcass. The robot stays connected to the ship with a tether. Scientists steer the robot to the whale fall, then use the submersible’s cameras, sensors, robotic arm and other tools to investigate. Onboard vacuums can even suck up small sea creatures for study back on the boat or in the lab.
One creature found at whale falls particularly interests Higgs. It is a weird worm from the genus Osedax. These worms eat whale bones. But they don’t have mouths or digestive systems. Instead, they grow rootlike extensions into the bone and dissolve it. By studying marine fossils, Higgs and other scientists have learned that these “zombie worms” have been around at least 100 million years. Yet until 2004 they were unknown to science.
That’s one reason Higgs loves exploring the deep sea.
“It’s one of the last frontiers for discovery on the planet,” he says. “On the one hand, it’s a very difficult environment to study. But what that means is you’re usually finding new things when you go down there. The more samples you get, the more new species you find.”
Small but mighty
A portion of the seafloor may experience a whale fall only once in a blue moon. When it does, a feast follows. For the rest of the time, though, the only food that makes it that far down is the tough stuff that no other animal wants. These might be the material that forms crustacean shells or the cells of plant fibers.
“It can be really recalcitrant stuff,” says Doug Bartlett. “So you have to have superbugs down there to make use of it.” He should know. Bartlett is a deep sea microbiologist at the Scripps Institution of Oceanography at the University of California, San Diego.
He focuses on microbes in the hadal zone. It’s the deepest part of the ocean, found at the bottom of sea-floor trenches more than 6,000 meters (3.7 miles) deep. Microbes here subsist on food no other organisms can digest. They also must survive pressures as high as 1,125 kilogram-force/square centimeter (16,000 pounds per square inch) in near-freezing temperatures and total darkness.
Because deep ocean trenches are isolated from one another, the animals within each evolve to be unique. A trench is like an underwater island, with its own distinct species of crustaceans, jellies and microbes. In these trenches, scientists can see how evolution has played out in extreme conditions. “We’re learning about the outer boundaries in which life can exist,” Bartlett explains.
The conditions deep in a trench are too extreme for humans. So, like Higgs, Bartlett uses an underwater robot to collect samples of water, silt and marine organisms from the ocean floor. This remote-controlled device brings samples up to the ship for study. Larger animals like fish and invertebrates die before they reach the surface. They can’t survive the drop in pressure and rise in temperature. But some microbes can survive a trip to the surface. Bartlett keeps them in special dark, cold, pressurized containers. That way, he can continue to grow and study them while they’re alive.
Scientists hope that by studying these microbes they might discover something new that could be useful. This might be anything from a microbe that breaks down plastic to one that could be used to make new cancer-fighting drugs.
Learning how life survives in such extreme conditions also interests scientists who think about what life might exist on other worlds within our solar system. One example is Jupiter’s moon Europa. Scientists now believe it has a deep, watery ocean. “It may be decades before we get samples back from Europa,” Bartlett says. “But we can go to an ocean setting in a Europa-like environment on Earth and see what life is like there.”
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Waves down deep
You may have watched winds whipping up whitecaps on big lakes or the ocean. But where does all that energy go? Those winds don’t just stir up the water’s surface. It turns out that they create waves that can travel to the floor of even the deepest oceans.
These near-inertial (In-UR-shul) waves — ones that flow through the interior of the ocean — are what Kelly Pearson studies. She’s a physical oceanographer and PhD candidate at the University of Hawaii at Manoa.
On one research trip, she studied how water moves through the Samoan Passage. This is a gap between two underwater mountains north of the island nation of Samoa. Here, cold water from Antarctica flows along the ocean floor into the North Pacific. Researchers were excited to observe near-inertial waves more than 5,000 meters (3.1 miles) below the ocean’s surface. No one knew they could travel that deeply!
So what if they do? Near-inertial waves contribute to ocean mixing. When rain falls on the ocean’s surface, these waves help stir it into the salty water below. And as climate change warms the world’s oceans, understanding the movement of near-inertial waves could help scientists better predict how quickly that warm water will get mixed into the cold waters at the very bottom of the sea.
To study this phenomenon, Pearson joins other scientists on research cruises to the Samoan Passage. They travel to a remote part of the ocean, then drop long lines that sink to the bottom. They attach instruments that measure ocean qualities such as saltiness, temperature, pressure and water currents. On one trip, Pearson recalls, “when we were putting [the instrument] in, some whales came and started playing with the instrument, pushing it up and down the rope with their nose…We were like, ‘This is so cool! But also don’t break our instrument!’”
A cruise can last 30 to 40 days. Throughout, there is no cell-phone service. There also is no regular internet access.
It can be hard to be away that long from family, friends and news of the outside world. The scientists plan lots of activities so that they don’t get bored or lonely when they’re not working. There’s a cafeteria, a gym, a library and a movie room on the ship. On one cruise, the scientists held a ping-pong tournament and built themselves a hot tub to pass the time, Pearson says. “It’s a completely different world,” she notes.
Pearson continues learning new things about near inertial waves. Not only are they powerful enough to make it down to the seabed, but they also have enough energy left to “reflect” off the seafloor and start heading back up.
She has also found this takes a long time. According to her observations, some waves took three years to travel from the surface to the seafloor. She won’t be totally certain, however, until other scientists can confirm her results.
Like Higgs, Pearson loves the challenge and mystery of studying the deep sea. “It’s that unknown,” she says. “We don’t know what’s going on down there. There are three people who’ve gone down to the bottom of the ocean at Challenger Deep.” (This is a chasm nearly 11,000 meters [6.8 miles] deep at its lowest point in the Mariana Trench). Those people required special submersibles to do so. And that’s only one quarter as many people as have walked on the moon, she notes.
The deep ocean remains, she says, “one of the last elusive things.”
alien A non-native organism. (in astronomy) Life on or from a distant world.
Antarctica A continent mostly covered in ice, which sits in the southernmost part of the world.
bacteria (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).
carcass The body of a dead animal.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
chasm A great or deep gulf or fissure in the ground, such as a crevasse, gorge or breach. Or anything (or any event or situation) that would seem to present a struggle in your attempt to cross to the other side.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
chemical reaction A process that involves the rearrangement of the molecules or structure of a substance, as opposed to a change in physical form (as from a solid to a gas).
climate The weather conditions that typically exist in one area, in general, or over a long period.
climate change Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.
crustaceans Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.
current A fluid — such as of water or air — that moves in a recognizable direction.
digest (noun: digestion) To break down food into simple compounds that the body can absorb and use for growth. Some sewage-treatment plants harness microbes to digest — or degrade — wastes so that the breakdown products can be recycled for use elsewhere in the environment.
dissolve To turn a solid into a liquid and disperse it into that starting liquid. (For instance, sugar or salt crystals, which are solids, will dissolve into water. Now the crystals are gone and the solution is a fully dispersed mix of the liquid form of the sugar or salt in water.)
ecosystem A group of interacting living organisms — including microorganisms, plants and animals — and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).
Europa One of the moons of Jupiter and the sixth-closest satellite to the planet.
evolve (adj. evolving) To change gradually over generations, or a long period of time. In living organisms, the evolution usually involves random changes to genes that will then be passed along to an individual’s offspring. These can lead to new traits, such as altered coloration, new susceptibility to disease or protection from it, or different shaped features (such as legs, antennae, toes or internal organs).
fiber Something whose shape resembles a thread or filament. (in nutrition) Components of many fibrous plant-based foods. These so-called non-digestible fibers tend to come from cellulose, lignin, and pectin — all plant constituents that resist breakdown by the body’s digestive enzymes.
force Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.
genus (plural: genera) A group of closely related species. For example, the genus Canis — which is Latin for “dog” — includes all domestic breeds of dog and their closest wild relatives, including wolves, coyotes, jackals and dingoes.
Grand Canyon A natural canyon in northwest Arizona that formed as the Colorado River cut through the rock here over the past 5 million to 6 million years. The Grand Canyon is 446 kilometers (277 miles) long. Its depth varies. At its deepest point, the river is 1,829 vertical meters (6,000 feet) below the upper rim.
habitat The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.
hadal zone A term for the deepest and some of the most extreme undersea habitats on Earth. These regions tend to exist along seafloor trenches at depths of 6 to 11 kilometers (3.7 to 6.8 miles). The name for this environment comes from Hades, the name the ancient Greeks gave to the underworld and to its king.
hagfish Slimy, eel-shaped fish without hinging jaws, whose skeletons are made of bendy cartilage rather than hard bone, and with eyes far simpler than those of other fish. Like lampreys, they are considered to be “living fossils” similar to the early relatives of vertebrates that lived hundreds of millions of years ago.
insight A more an accurate and deep understanding of a situation that comes just by thinking about it, instead of working out a solution through experimentation.
internet An electronic communications network. It allows computers anywhere in the world to link into other networks to find information, download files and share data (including pictures).
invertebrate An animal lacking a backbone. About 90 percent of animal species are invertebrates.
jellies (in biology) These are gelatinous animals that drift in water (mostly seawater) or brackish (semi-salty) estuaries. For more than 500 million years, they have moved around the oceans by pumping pulses of water through their jelly-like tissue. Their body often has an umbrella-shaped bell. Trailing from around a central mouth may be many tentacles. Although jellies don’t have brains, they do have a nervous system which can sometimes detect light, movement or certain chemicals. Some members of this family, known as cnidarians, are known as jellyfish. In fact, none are true fish but related to hydras and corals.
Jupiter (in astronomy) The solar system’s largest planet, it has the shortest day length (10 hours). A gas giant, its low density indicates that this planet is composed of light elements, such as hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).
Mariana trench A deep, crescent-shaped canyon running along the Pacific Ocean floor east of the Philippines. It’s massive, some 2,550 kilometers (1,500 miles) long and 70 kilometers (43 miles) wide, on average. The trench marks where two of Earth’s tectonic plates are colliding, forcing one to dive beneath the other.
marine Having to do with the ocean world or environment.
microbe Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.
oceanography (adj. oceanographic ) The branch of science that deals with the physical and biological properties and phenomena of the oceans. People who work in this field are known as oceanographers.
organism Any living thing, from elephants and plants to bacteria and other types of single-celled life.
Pacific The largest of the world’s five oceans. It separates Asia and Australia to the west from North and South America to the east.
PhD (also known as a doctorate) A type of advanced degree offered by universities — typically after five or six years of study — for work that creates new knowledge. People qualify to begin this type of graduate study only after having first completed a college degree (a program that typically takes four years of study).
phenomenon Something that is surprising or unusual.
pressure Force applied uniformly over a surface, measured as force per unit of area.
recalcitrant An adjective that describes something that resists change or being controlled.
recycle To find new uses for something — or parts of something — that might otherwise be discarded, or treated as waste.
robot A machine that can sense its environment, process information and respond with specific actions. Some robots can act without any human input, while others are guided by a human.
Samoan Passage This is a gap separating two underwater mountains north of Samoa (an island nation directly east of northern Australia in the southern Pacific Ocean). Here, cold miles-deep water flows northward up from Antarctica and along the ocean floor into the Pacific.
scavenger A creature that feeds on dead or dying organic matter in its environment. Scavengers include vultures, raccoons, dung beetles and some types of flies.
sea An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
sensor A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly.
silt Very fine mineral particles or grains present in soil. They can be made of sand or other materials. Silt is formed by the erosion of rocks, and then usually is deposited elsewhere by wind, water or glaciers.
solar system The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
submarine A term for beneath the oceans. (in transportation) A ship designed to move through the oceans, totally submerged. Such ships — especially those used in research — are also known as submersibles.
unique Something that is unlike anything else; the only one of its kind.
wave A disturbance or variation that travels through space and matter in a regular, oscillating fashion.