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Beneath the seafloor, there is an ecosystem of microbes living in the oceanic crust, independent of sunlight. Here, the seafloor of McMurdo Sound in Antarctica. NSF/USAP photo by Steve Clabuesch

If you were to hit the seafloor and continue to travel down, you’d run into an ecosystem unlike any other on earth. Beneath several hundred meters of seafloor sediment is the Earth’s crust: thick layers of lava rock running with cracks that cover around 70% of the planet’s surface. Seawater flows through the cracks, and this system of rock-bound rivulets is enormous: it’s the largest aquifer on earth, containing 4% of global ocean volume, says Mark Lever, an ecologist who studies anaerobic (no-oxygen) carbon cycling at Aarhus University in Denmark.

The sub-seafloor crust may also be the largest ecosystem on earth, according to a new study by Lever, published this month in Science. For seven years, he incubated 3.5 million-year old basalt rock collected from 565 meters below the ocean floor–the depth of nearly two stacked Eiffel towers–and found living microbes. These microbes live far away from the thriving bacterial communities at mid-ocean ridges, and survive by slowly churning sulfur and other minerals into energy.

But just how big is this chemically-fueled ecosystem that survives entirely without oxygen? If the results from his sample, collected from below the seafloor off the coast of Washington state, are similar to those found across the planet, then diverse microbial communities could survive throughout the ocean’s crust, covering two-thirds of the earth’s surface and potentially going miles deep.

The sub-seafloor crust has plenty of space and energy-rich minerals–a welcoming potential habitat for a large microbial community–“but we have no idea what the ecosystem looks like,” says Julie Huber, a microbial oceanographer at the Marine Biological Laboratory in Woods Hole, Massachusetts. “Mark’s evidence would point to it being a very different world.”

Microbes that get their energy from minerals, rather than from sunlight, are far from rare. The most well known of these so-called chemoautotrophic or chemosynthetic bacteria are those found at hydrothermal vents in the deep sea. Some of these bacteria live symbiotically with giant tubeworms, mussels and clams, providing chemically-produced energy to these larger organisms as they “breathe” the sulfur-rich water erupting from the vent–not unlike how plants convert sunlight into energy at the surface. Chemosynthetic microbes are also found in the rotting and oxygen-poor muck of salt marshes, mangroves and seagrass beds—“any place you’ve got stinky black mud, you can have chemoautotrophy,” says Chuck Fisher, a deep-sea biologist at Pennsylvania State University in College Park.

But what makes Lever’s sub-seafloor microbes different is that they don’t use any oxygen at all. The symbiotic bacteria at hydrothermal vents are often described as “life without sunlight,” but they still rely on sunlight indirectly by using sun-produced oxygen in the chemical reaction to generate energy. Chemosynthetic microbes in salt marshes feed on decomposing plants and animals, which got their energy from sunlight. Even deep-sea sediment is accumulated from an assortment of dead animals, plants, microbes and fecal pellets that relies on light energy.

The oceanic crust microbes, on the other hand, rely entirely on non-oxygen-containing molecules derived from rock and completely removed from photosynthesis, such as sulfate, carbon dioxide and hydrogen. “In that sense it’s a parallel universe, in that it runs on a different type of energy,” says Lever. These molecules provide a lot less energy than oxygen, creating a sort of microbial slow food movement. So instead of dividing and growing quickly like many oxygen-based bacteria, Fisher suspects that microbes in the Earth’s crust may divide once every hundred or thousand years.

A hydrothermal vent, covered with tube worms, spews black sulfur smoke on the Juan de Fuca Ridge. The oceanic crust microbes were collected hundreds of meters under the seafloor beneath this same ridge. Photo via University of Washington; NOAA/OAR/OER

But just because they’re slow doesn’t mean they’re uncommon. “There are lots of data that there is a large, very productive biosphere under the surface,” says Fisher.

In addition, microbial population sizes in different areas of the crust may vary greatly, Huber notes. Through her studies on the fluid found between the cracks in the crust,  she says that in some areas the fluid contains about the same number of microbes as standard deep-sea water collected at ocean depths of 4,000 meters (2.5 miles): around 10,000 microbial cells per milliliter. In other regions, such as at the Juan de Fuca Ridge in the Pacific Ocean where Lever found his microbes, there are fewer cells, around 8,000 microbes per milliliter. And in other regions, such as in non-oxygenated fluid deep in hydrothermal vents, there can be around 10 times more.

It’s not just the number of microbes that vary depending on location–it’s possible that different microbial species are found in different types of crust. “Different types of rock and different types of chemistry should result in different types of microbes,” says Andreas Teske, a deep-sea microbial ecologist at the University of North Carolina at Chapel Hill and co-author on Lever’s paper. The Juan de Fuca Ridge is a relatively hot area bursting with new rock, which tends to be made of more reactive minerals and thus able to provide more energy. Other parts of the crust are older, composed of different minerals, and cooler. And, in some regions, oxygenated water reaches down to the cracks.

It’s this infiltrating seawater that keeps this sub-seafloor ecosystem from existing on a completely separate plane from our oxygenated one. “The crust plays a significant role in influencing the chemical composition of the ocean and the atmosphere, ultimately influencing [nutrient] cycles on earth,” says Lever. Some of the compounds created by oceanic crust microbes from rock are water soluble, and will eventually enter the ocean. Sulfur, for example, is present in magma—but after the microbes use it for energy, it’s converted to sulfate. Then it dissolves and becomes an important nutrient in the ocean food chain.

Lever’s find of a microbial community in the crust could catalyze the scientific community to answer these questions. For example, what kinds of microbes are found where, do they interact through interconnected cracks in the rock, and what role do they play in mineral and nutrient cycling? In some ways, it’s very basic exploratory work. “A lot of what we do on the seafloor is similar to what we’re doing on Mars right now,” says Huber. “Controlling [NASA’s Mars Rover] Curiosity is very similar to operating an ROV under the ocean.”

  Learn more about the deep sea from the Smithsonian’s Ocean Portal.

Tadpole shrimp eggs can remain dormant for years, then burst into life when elusive desert rains arrive. Photo by Flickr user theloushe

As Easter draws near, we begin to notice signs of nature’s very own annual resurrection event. Warming weather begins “breeding lilacs out of the dead land,” as T.S. Elliot noted, and “stirring dull roots with spring rain.” Where a black and white wintery landscape just stood, now technicolor crocus buds peak through the earth and green shoots brighten up the azalea bushes.

Aside from this grand show of rebirth, however, nature offers several cases of even more overtly stunning resurrections. From frozen animals jumping back into action during spring thaws to life blooming from seemingly desolate desert sands, these creatures put a new spin on nature’s capacity for revival.

Resurrection fern

A resurrection fern, before and after watering. Photo by Flickr user Gardening in a Minute

As its name suggests, during a drought the resurrection fern shrivels up and appears dead, but with a little water the plant will burst back into vibrant life. It can morph from a crackled, desiccated brown into a lush, vibrant green in just 24 hours.

The fern doesn’t actually die, but it can lose up to 97 percent of its water content during an extreme dry spell. In comparison, other plants will usually crumble into dust if they lose more than 10 percent of their water content. Resurrection ferns achieve this feat by synthesizing proteins called dehydrins, which allow their cell walls to fold and reverse back to juicy fullness later.

Resurrection ferns are found as far north as New York and as far west as Texas. The ferns needs another plant to cling to in order to grow, and in the south it’s often found dramatically blanketing oak trees. A fallen oak branch covered in resurrection ferns are common features in southern gardens, though the ferns have also turned up in more uncanny locales: in 1997, astronauts took resurrection fern specimens onto the Space Shuttle Discovery to study how the plant resurrects in zero gravity. As investigators write (PDF), the fern “proved to be a hardy space traveler and exhibited regeneration patterns unaltered by its orbital adventure.” This earned it the title of “first fern in space.” 

Brine shrimp, clam shrimp and tadpole shrimp 

In the deserts of the western U.S., from seemingly life-barren rocks and sands, life blooms by just adding a little rain water. So-called ephemeral pools or “potholes” form tiny ecosystems ranging from just a few millimeters across to several meters deep. The ponds can reach up to 140 degrees Fahrenheit in the summer sun or drop below freezing during winter nights. They can evaporate nearly as quickly as they appeared, or linger on for days or weeks. As such, the animals that live there all have special adaptations for allowing them to thrive in these extreme conditions.

Ephemeral desert ponds in New Mexico. Photo: J. N. Stuart

Some of the potholes’ most captivating critters include brine shrimp (of sea monkey fame!), clam shrimp and tadpole shrimp. These crustaceans practice a peculiar form of drought tolerance: In a process known as cryptobiosis, they can lose up to 92 percent of their body water, then pop back into fully-functional action within an hour of a new rain’s arrival. To do this, the tiny animals keep their neural command center hydrated but use sugar molecules instead of water to keep the rest of their cells intact throughout the drought. Like resurrection ferns, brine shrimp, too, have been taken into space–they were successfully hatched even after being carried outside of the spacecraft. 

Most of these animals only live for about ten days, allowing them to complete their entire life cycle (hopefully) before their pool dries up. Their dried eggs are triggered to hatch not only when they’re hydrated again but also when oxygen content, temperature, salinity and other factors are just right. Some researchers, such as this zoologist quoted in a 1955 newspaper article, think that the eggs can remain dormant for several centuries and still hatch when conditions are right.

Wood frogs 

Some amphibians undergo their own sort of extreme hibernation in order to survive freezing winter temperatures. This suspended animation-like state allows them to slow down or stop their life processes–including breathing and heartbeat–just to the brink of death, but not quite. Wood frogs, for example, may encounter freezing conditions on the forest floor in winter. Their bodies may contain 50 to 60 percent ice, their breathing completely stops and their heartbeat is undetectable. They may stay like this for days, or even weeks. 

They achieve this through a specially evolved biological trick. When the frogs encounter the first signs of freezing, their bodies pull moisture away from its central organs, padding them in a layer of water which then turns into ice. Before it freezes, the frog also floods its circulatory system with sugar molecules, which act as an antifreeze. When conditions warm up again, they can make a complete recovery within a day, which researchers call “spontaneous resumption of function.” Here, Robert Krulwich explains the process: 

As seen through these examples, some creatures really do come back from the brink of death to thrive!

Footage from Brazil’s “spider rain.” Photo: TV45000

The Northeast may be prone to blizzards this time of year, but in Brazil it’s raining spiders. In a video that’s covered the Internet like an immense web, a local photographer captures images of thousands of spiders shimmying up and down silk threads attached to telephone pole wires. The footage gives the distinct impression of a shower–or perhaps light snow–of spiders sprinkling down on the shocked residents below.

Erick Reis, a 20-year-old web designer in Santo Antonio da Platina, a town about 250 miles west of Sao Paulo, captured the striking video that has since accumulated more than 2 million YouTube views over the course of the week.  “I was shooting an engagement party for some friends of mine and I saw the spiders when I was leaving, now in the late afternoon,” he explained to TV450000, which posted the video. “I’ve never seen anything like it before.”

According to biologist Marta Fischer of the Pontifical Catholic University of Parana, however, the phenomenon is not so strange. ”This type of spider is known to be quite social,” she said. “They are usually in trees during the day and in the late afternoon and early evening construct sort of giant sheets of webs, in order to trap insects.”

Scientists have described around 40,000 species of spiders around the world, but only a handful of them are social. These 23 species are scattered around the world and sometimes swarm, like ants or bees. Females often outnumber males 10 to 1 in colonies that can exceed 50,000 individuals.

Around Sao Paulo and its neighboring cities, she said, it’s not an unusual site to see a sky speckled by spiders. The species, Anelosimus eximius, can be found from Panama to Argentina and lives in colonies sometimes comprised of thousands of individuals. Each spider is around the size of a pencil eraser. As Examiner reports, the species’ webs can stretch from the ground up to tree canopies or human constructions 65 feet high.

If strong winds come along, the web may detach from its anchors, carrying the spiders and their ruined home to new sites where they appear to “rain down.” Catching rides on the wind–en mass–was likely what happened in Santo Antonio da Platina. While the humans gawked below, the flustered spiders were simply trying to pull themselves together after an unexpected journey from some forest or park.

Before North American readers breathe a sigh of relief that this isn’t happening a bit closer to home, however, it’s worth noting that similar colonies live in Texas. In Lake Tawakoni State Park, just east of Dallas, Guatemalan long-jawed spiders construct enormous webs covering up to 600 foot stretches. The spiders build the huge webs in less than two weeks. Researchers think the spiders achieve such sudden engineering feats thanks to their “remarkable reproductive capabilities and ability to disperse by ballooning,” according to A Field Guide of Scorpions and Spiders of Texas.

So far, Dallas residents haven’t reported massive sheets of webs and their arachnid residents “ballooning” into backyards. But, as witnessed by residents of Santo Antonio da Platina,  stranger things have happened. 

The Glaucus atlanticus sea slug, or blue dragon, feeds on toxins from much larger species. Taro Taylor / Getty Images

This tiny creature has gotten a fair bit of attention lately because of one simple reason: It’s absolutely crazy-looking. At first glance, it resembles a Pokémon or character from Final Fantasy more closely than a real biological animal. But the Glaucus atlanticus sea slug—commonly  known as the blue sea slug or blue dragon—is indeed a genuine species. And if you swim in the right places off of South Africa, Mozambique or Australia, you just might find one floating upside down, riding the surface tension of the water’s surface.

The species has a number of specialized adaptations that allow it to engage in a surprisingly aggressive behavior: preying on creatures much bigger than itself. The blue dragon, typically just an inch long, frequently feeds on Portuguese man o’ wars, which have tentacles that average 30 feet. A gas-filled sac in the stomach allows the small slug to float, and a muscular foot structure is used to cling to the surface. Then, if it floats by a man o’ war or other cnidarian, the blue dragon locks onto the larger creature’s tentacles and consumes the toxic nematocyst cells that the man o’ war uses to immobilize fish.

The slug is immune to the toxins and collects them in special sacs within the cerata—the finger-like branches at the end of its appendages—to deploy later on. Because the man o’ war’s venom is concentrated in the tiny fingers, blue dragons can actually have more powerful stings than the much larger creatures from which they took the poisons. So, if you float by a blue dragon sometime soon: look, but don’t touch.

A microbiologist collects a manure sample. Image courtesy of the USDA.

Hog farmers have a lot to worry about, such as fluctuating pork prices and sick pigs. Now they have a new concern: barn explosions. The culprit appears to be a strange new foam that has begun growing on the pools of liquid manure beneath large pig farms. The foam traps methane, a flammable gas that, when ignited, can cause catastrophic blowups. One explosion last September in Iowa leveled an entire barn, killing some 1,500 pigs and injuring one worker.

On big farms in the Midwest, pigs spend the latter part of their lives in large, low buildings called finishing barns. These barns have slotted floors and sit atop eight-foot-deep concrete pits. When the pigs defecate and urinate, the waste falls between the slats and into the pit, forming an underground manure lagoon. Once a year, the farmers empty these pits and sell the manure as fertilizer. This model has been used in the Midwest for the past 30 or 40 years, says Larry Jacobson, an agricultural engineer at the University of Minnesota.

In 2009, Jacobson and other agriculture experts began to hear reports of a mysterious foam growing on swine manure ponds. “Sometimes it would be enough that it would come up through the slats,” he says. To get rid of the foam, some farmers poured water on it. Others used machines to break it up. That’s when the explosions began.

Why these explosions happen is well understood. As manure ferments, it releases methane gas, which bubbles to the surface of the pit. Normally this methane doesn’t pose a risk. The gas seeps out of the pit, and the barn’s ventilation fans carry it away. But when thick, gelatinous foam covers a manure lagoon, the methane can’t rise. The foam acts like a sponge, Jacobsen says, soaking up the gas. Jacobsen and his colleagues have collected foam samples that are 60 percent methane by volume. When a farmer disturbs the foam by agitating the manure or emptying the pit, the methane gets released all at once. In barns without adequate ventilation, the concentration of methane can quickly reach the explosive range, between 5 percent and 15 percent. A spark from a fan motor or a burning cigarette can ignite the gas. An explosion in southeastern Minnesota raised a barn roof several feet in the air and blew the hog farmer, who was on his way out, 30 or 40 feet from the door.

For the past three years, Jacobson and his colleagues at the University of Minnesota and the University of Iowa have been trying to figure out why the foam forms. The slimy stuff appears to be the byproduct of bacteria. But the researchers don’t yet know which strain or why these foam-producing bacteria suddenly appeared. The researchers are in the midst of conducting DNA analyses to try to identify the microbes, comparing foamy manure with non-foamy samples.

One explanation may be dietary changes. About five years ago, pig farmers began mixing distillers grains, a fermented byproduct of the ethanol production process, into their pig feed. Distillers grains are much cheaper than traditional feed. But that can’t be the only factor, Jacobson says. Today, nearly everyone feeds their pigs distillers grains, but only a quarter of the swine barns grow foam.

Jacobson and his colleagues have identified a few additives that seem to help eliminate the foam. But those fixes are just “band-aids” Jacobson says. What he really wants is a way to prevent the foam from forming.

Want to see what the foam looks like? Check out this YouTube video, and prepare to be disgusted.