The giant gelatinous predator moves silently through cold, dark waters, propelled by a pair of expanding and contracting swimming bells. Its rope-like body is actually a colony of almost a thousand individual subsections, each performing a specific task. Some provide propulsion, others, reproductive functions; but most specialize in capturing and devouring prey. When hunting, these sections deploy thousands of slender, stinging tentacles to capture drifting krill, copepods, small fish, and other jellies. Almost anything blundering into this deadly net of tentacles soon finds itself stuffed into the nearest waiting mouth. Longer even than the blue whale, individual specimens have been found measuring over 130 feet in length.
This is the siphonophore Praya dubia, and it makes its home in the cold, black waters of the Monterey Submarine Canyon in California’s Monterey Bay. Here, starting just a few hundred yards from shore, the coastal seafloor plunges into the underwater equivalent of the Grand Canyon, stretching 60 miles out to sea. Steep, rocky walls and soft sediment beds make up the deepest submarine canyon on the west coast of the contiguous United States — and one of the largest in the world. While its exact origin is still unknown, the canyon is believed to be 20–30 million years old, produced through tectonic processes between the shifting North American and Pacific plates, continually gouged and deepened by underwater landslides. The canyon system stretches over six miles across and digs almost two and a half miles deep into the ocean floor.
In the ocean’s surface waters, life occurs in abundance. There algae, phytoplankton and other plants convert sunlight into food and provide the base of the ocean’s food web. This area, known as the photic zone, extends downward to the maximum depth of sunlight penetration. But at only 500 feet down, 99% of the sunlight has been absorbed by seawater, leaving the waters below icy cold and pitch black. In a world far too dark for photosynthesis, canyon creatures like Praya must live without the rich algal blooms and flourishing plant life found in the surface waters, depending solely on their ability to make a meal of their neighbors or on nourishment drifting down from the photic zone above. Crushing pressures average three tons per square inch and oxygen levels are about one sixth of surface levels. While life here is not as abundant as in the nutrient-rich waters above, the deep-sea canyon is home to many diverse organisms, forming a complex web of life that scientists are only beginning to understand.
The privately funded Monterey Bay Aquarium Research Institute (MBARI) has been studying the geological wonder at its doorstep since 1987. “Monterey Canyon is the most heavily studied deep-sea area in the world, without a doubt,” says Dr. George Matsumoto, education and research specialist at MBARI. In its 13 years of research, MBARI has made over 3,000 dives in the canyon using remotely operated, camera-equipped vehicles, or ROVs. The ROV Ventana, which has been diving almost daily in Monterey since 1988, can reach a depth of over 6,000 feet, while the updated Tiburon launched in 1997 can reach over 13,000 feet. Altogether, MBARI ROVs, which are operated from aboard deep-sea research vessels, have logged almost 9,000 hours of video of the previously inaccessible environment.
Dr. Kevin Raskoff, a research fellow at MBARI, estimates that hundreds of jelly species live in Monterey Canyon, many unidentified. They include pulsing medusas with the traditional umbrella jelly shape, beautiful comb jellies that move through the waters using vibrating cilia, and the ropelike siphonophores such as Praya. One of his favorites, a large medusa called Solmissus, is especially easy to study, thanks to its transparent gut. “We’ve been able to do a lot of interesting research on what they eat without having to collect them,” says Raskoff. “We can just drive the ROV around, look right into their stomach and see what they’ve had for dinner.” Solmissus also has a stealthy manner of hunting other jellies. It swims with its tentacles pushed out in front or to the side instead of dangling underneath, allowing it to hide behind its own tentacles and nab unsuspecting prey. Research with submersible ROVs has opened the world of the jellyfish to scientists, allowing them to observe these creatures in their natural environment. “Previous research has pretty much ignored gelatinous animals,” says Raskoff, explaining that their soft bodies were often destroyed in nets during classic oceanographic research.
The canyon’s depths can also support fish. One resident, the deep-sea anglerfish, has evolved strange behaviors — and an equally strange appearance — to survive its nutrient-poor environment. “They are fascinating fish,” says Steven Webster, senior marine biologist at the Monterey Bay Aquarium. “They have a bioluminescent lure on their forehead that attracts their prey.” Adult anglers hover in darkness over 1,000 feet below the surface. Since their sit-and-wait hunting technique requires little swimming, the angler’s body does not need strong, energy-consuming muscles or a streamlined shape. Instead, their bodies consist almost entirely of a giant mouth filled with long, pointed teeth and an expandable stomach that allows them to consume prey nearly as large as themselves. Anglers have also developed an interesting mating strategy. “The big fish that you see is the female,” says Webster, “and the male is tiny and parasitic, basically a little sack of sperm embedded in the body wall of the female — which makes it a lot easier finding a mate down there in the dark!” Female anglers have been seen with as many as eleven males attached.
Anglers are only one of many deep-sea creatures to use bioluminescence, a process that works in a similar fashion to a glow-stick’s. In general, these creatures mix a light-producing chemical known as a luciferin with a catalyst called a luciferase, creating a chemical reaction that produces light. While only a few land organisms emit their own light, an estimated 90% of deep-sea creatures are bioluminescent. The giant red mysid, a deep-sea crustacean, temporarily blinds its predators by producing a bright blue luminescence to help it escape. Similarly, the small jelly Colobonema is believed to use bioluminescence in its 32 tentacles, which can drop off to distract predators. Many species of mid-water fish and cephalopods use bioluminescence on their bellies to blend in with the faint light filtering down from the surface, camouflaging them from predators lurking below. Other species like the lanternfish use special light-producing organs called photophores to produce species-specific light patterns, helping them to find a mate in the dark waters.
An important part of MBARI’s work is developing the tools and technology needed to explore the deep oceans and the creatures within them. In many ways, it is easier to communicate with a satellite in outer space, which can be solar powered and can transmit data through electromagnetic waves, than with a similar research tool in the deep sea, where it has limited battery life and cannot send data through the virtually opaque waters. But even the ROVs, as advanced as they are, have their drawbacks, including their size, roughly that of a small car. “They’re big, they’ve got lights on them, they’re noisy, and they’re slow,” Matsumoto explains, “which means that everything we see down there are the things that can’t see us, can’t hear us, can’t feel us, and are too slow to get away from us. We’re missing a huge part of the picture.” He pulls out a picture of a lancet, a three-foot-long fish with a muscular, streamlined body. “The last two months they’ve been washing up on the beaches all up and down California, [but] we don’t know anything about them. We assume they’re important predators down there because their mouths are huge and filled up with teeth. But nobody’s ever seen one live in the field. That’s also true with things like the giant squid. This is a big animal. It’s a dominant predator. We’ve never seen it [in the field].”
Outside Monterey Canyon, the deep sea remains even more mysterious, but researchers worldwide are slowly learning more about it. This May, a team of researchers from four marine science institutions traveled 75 miles off the coast of Monterey on the first extensive expedition to explore the Davidson Seamount. Underwater volcanoes known as seamounts are scattered throughout the world’s oceans and are believed to be biological hotspots, providing a variety of deep-sea habitat on their rocky surfaces and making surface waters above more productive. Davidson, the largest in a chain of seamounts along the California coast, is 25 miles long and rises over 7,800 feet above the seafloor, yet is still 4,000 feet below the ocean’s surface. Dr. Andrew DeVogelaere, marine scientist at the Monterey Bay National Marine Sanctuary, acted as chief scientist and co-principal investigator for the expedition, which included geologists, marine biologists, educators, and resource managers. “It’s a unique bump offshore, a very dramatic geologic feature that had people curious ever since it was originally mapped. Though nobody had looked at it very carefully, people had an intuitive feel that it was an important spot,” he said.
The expedition team spent eight days exploring Davidson with the ROV Tiburon — charting maps, logging video, and collecting samples. They saw an unidentified “mystery mollusk” with beautiful wing-like fins that seemed to fly through the water, and big spider-like crustaceans walking across the bottom. “Whenever we came up the seamount, it was like a surprise package,” says DeVogelaere. “It was very exciting for us just to see these strange creatures.” Atop the ridges were clusters of feathery bamboo coral, giant white sponges as big as garage doors, and deep-sea corals towering over 12 feet high. “Typically when you go diving you think of these corals as groundcover,” says Dr. Randall Kochevar, science communications manager at the Monterey Bay Aquarium. “What we were seeing on Davidson were trees. We were driving [the ROV] through a forest.”
One of the main objectives of the Davidson expedition was to determine whether the seamount deserves to be included in the Monterey Bay National Marine Sanctuary. The sanctuary, which will celebrate its tenth anniversary in September, encompasses 276 miles of shoreline, stretching from Rocky Point just seven miles north of the Golden Gate Bridge, to Cambria Rock in San Luis Obispo County, and extends an average distance of 30 miles from shore, covering 5,322 square miles of open ocean. “We know a fair amount about kelp forest, the continental shelf, rocky shores, and we have a lot of these areas protected within sanctuaries,” says DeVogelaere. “But in no sanctuary is a seamount protected anywhere in the ocean.” The sanctuary’s management plan is currently being reviewed by the National Marine Sanctuary Program to make sure it still fulfills its mission of conservation and protection. Policy makers can use data collected from the expedition to determine whether to redraw the borders to include Davidson and other seamounts, protecting them from activities such as oil drilling and mineral exploration, dredging and dumping.
As remote as it is, the Davidson Seamount is not untouched by human activity. The expedition found litter scattered on the seamount’s slopes, all well preserved in the cold, dark waters. “What I found interesting but also disconcerting in our ROV surveys,” says DeVogelaere, “was that, as we were going up the sides of the Davidson Seamount, essentially looking at places on the earth that nobody has ever looked at before, we did come across things like beer cans, a 40-year-old milk bottle, a broom, a curtain, a newspaper. And it sort of makes you stop and think. A place that if it were drained would surely be a national monument of some kind, people don’t even know it’s there and they’re just dumping their stuff off right above it.”
Trash also makes its way down into Monterey Canyon, along with pesticides and other chemicals. Although some contaminants are dumped directly into the oceans either on purpose or by accident, the majority come from non-point source pollution –– urban and agricultural runoff washing down storm-drains, into rivers, and out to sea. “Exxon Valdez was a terrible tragedy, but that amount of oil gets into the oceans often,” says Matsumoto. “Every time there’s a rain after six months without rain, you can get easily that much oil coming into the ocean, just off the streets. Everything you put in the street, every time you wash your car, every time you mow your lawn, everything that goes into the gutters that gets rinsed out by the next rains, all of that dumps into the oceans and is untreated and unfiltered.”
Although deep-sea habitats are still relatively undisturbed, they will come under increasing pressure by the same forces affecting land. For example, the deep sea is currently being considered by the US Department of Energy as a dumping ground for the greenhouse gas carbon dioxide (CO2) created by the burning of fossil fuels. In theory, liquid carbon dioxide could be pumped into the deep sea where, under the extreme pressure and low temperatures, it would turn into a solid lake of carbon dioxide hydrate on the ocean floor. Because the ocean can actually absorb a great deal more CO2 than it currently contains, a solid carbon dioxide lake would slowly dissipate into the seawater. It’s all very neat in computer models and controlled laboratory tests, but in preliminary field experiments, the liquid CO2 has behaved unpredictably. It sometimes reacts violently with seawater and sediments in the ocean floor, may or may not form a solid, and absorbs vast amounts of seawater, causing the carbon dioxide lake to become much larger than expected. Says Matsumoto, “The biologists are interested in this because, of course, if you put a solid lake of CO2 on the ocean floor, whatever is on the ocean floor is going to be buried under carbon dioxide and isn’t going to do very well.”
In many ways, life as we know it depends on the oceans. Each year, humans harvest 100 million metric tons of food from the sea. Scientists are researching antibiotics, antiviral agents, and other pharmaceuticals that can be extracted from deep-sea sponges and soft corals. The oceans also help regulate earth’s climate. They distribute heat from the equator to the poles, play a vital role in the water cycle that brings rain to the continents, and produce half of the oxygen in our atmosphere. The deep sea also contains a huge diversity of life. Based on the immense size of the habitat and the variety of organisms found there so far, it may even contain a majority of the earth’s species. But most of the ocean, the largest biome on the planet, has never been seen.
“Ninety-five percent of the living space on earth is in the deep sea,” says the Monterey Bay Aquarium’s Webster. “It’s mysterious. We know practically nothing about it. We’ve explored only one percent of it so far, worldwide. And when you realize the way water circulates through the oceans and the oceans interact with the atmosphere and it’s all intertwined, you realize it’s all connected. It’s something that’s said so often it becomes trite, but it’s true. Basically, life would not exist on earth without the oceans.”
