UWM Research Profile Magazine - What lies beneath

The floor beneath the frigid waters of Yellowstone Lake, whose surface is commonly frozen from December to June, is covered with many geothermal features similar to those that have made its namesake park famous—steaming geysers, boiling hot springs, and bubbling mud pots.

UWM researchers uncover secrets below the surface of the calm waters of Yellowstone Lake.

By
Kelly Kizer Whitt

Photos from the UWM WATER Institute, unless noted. Click on photos for larger images.

n the northwest corner of Wyoming, high in the Rocky Mountains, lies the majestic Yellowstone National Park. Visitors from around the globe flock here by the thousands every summer to gape in wonder at the steaming geysers, boiling hot springs, bubbling mud pots, and accompanying wildlife. Out on peaceful Yellowstone Lake a handful of UWM researchers are exploring these same types of features—but under the water. This aqueous world of geothermal formations and its resident creatures may even provide insight into the beginnings of life on Earth and other planets.

America’s first national park and the lake that bears its name rest partly upon the caldera of the largest volcanic eruption known. About 1.2 million years ago and again 650,000 years ago a giant volcano exploded, forming a crater from the collapsed magma chamber. The northern half of Yellowstone Lake sits within the boundary of this volcanic depression, and its cold, quiet waters belie the seething activity of what lies beneath.

Because of the high water temperature near the hydrothermal vents and safety guidelines for diving in high-altitude lakes, WATER Institute divers go no more than 30 feet down, in this lake that averages a depth of 140 feet and reaches a maximum depth 320 feet. For deeper observations, the WATER Institute uses a 200-pound underwater remotely operated vehicle (ROV), owned and operated by Eastern Oceanics. Although smaller than the one used to discover the Titanic, it has many sophisticated features and is highly portable.

The UWM researchers, part of the Great Lakes WATER Institute, are studying the 136-square-mile, up to 400-feet-deep lake that houses hundreds of hydrothermal vents, spires, craters, domes, and faults, many of which are home to peculiar creatures. “When you stand at the boardwalk in West Thumb and follow the line of fumaroles (vents for volcanic steam and gases) all the way to the lake, you can easily imagine how one could find those structures underwater,” says Carmen Aguilar, UWM’s principal investigator of a study on life in extreme environments, funded by a three-year grant from the National Science Foundation. “Once you visualize that, you start wondering about the activity underwater. What kind of bacteria and other organisms are present in this extreme environment, what are the conditions that allow different organisms to take advantage of this environment . . . and so the passion begins.”

Aguilar’s forages into the wilds of Yellowstone are a long way from her home country of Mexico, but the setting is not far from her heart. “I had a great biology teacher in high school who allowed me to ask questions and search for answers in different topics; she even took me one day to her classes at the university and I loved it,” she says. “I was always interested in water and organisms that live in different lakes and the ocean.” Aguilar has been to Yellowstone Lake for experiments about 10 times now, and three to four undergraduate summer students usually assist the lead investigators on the excursions. Being a role model is important to Aguilar, who says that “it is uncommon to see many women in these fields of science,” and women of Hispanic backgrounds are particularly scarce.

UWM researchers and student interns began their annual summer pilgrimages to Yellowstone Lake in 1983 and quickly uncovered evidence that the lake floor is not that much different from the topography of the park’s dry land. Underwater fissures, or faults, are a result of much of the geologic activity. Craters were found clustered along these faults, with some of the depressions as large as a football field. Scientists believe that hydrothermal explosions are responsible for these circular, steep-walled formations.

Above: During calm days on Yellowstone Lake, the team searches for bubble fields, marking the area for further exploration with the ROV. Below: Bubbling vent on the floor of the lake.

Researchers suspect that dome-like structures found under the lake are the precursor to the exploded craters. These domes are regions where gas vents have become choked shut with sediment, causing the underlying pressure to push the lake floor upward into a bulge. One dome that measures 100 feet wide at its base and 100 feet tall has been nicknamed the “Matterhorn.”

Some of the underwater features show evidence of volatility. “The resurgent domes on the outlet of the lake at LeHardy Rapids have probably shown the greatest change over a large area,” says Aguilar’s colleague Val Klump, a UWM senior scientist and one of the original researchers at Yellowstone Lake. “The individual springs, gas fumaroles, et cetera, within the lake may wax and wane.” Klump has even seen changes on the lake floor from one visit to the next. “There was a period of a couple years following some rather large seismic activity in the lake basin in which we could not find a deep, yet very small canyon near Stevenson Island. Did it temporarily fill in via slumping?” he wonders. “We do not really know, but it certainly seemed to disappear.”

Another curious feature the researchers have revealed are clusters of spires—tall columns of extinct hydrothermal vent conduits consisting primarily of silica, protruding from the floor. In 1997, the UWM team explored a whole crop of the trunk-like features in the Bridge Bay area of the lake, some of them standing in only 45 feet of water. In 1996, these structures were found through acoustic surveys made by National Park Service archaeologists. Many of them are arrayed in long rows, such as the “Avenue of Spires,” and can reach about 10 feet in height.

The discovery of these amazing underwater features has been due in large part to the use of a Remotely Operated Vehicle, or ROV, which allows scientists to delve into previously inaccessible locations. At more than 7,000 feet above sea level, Yellowstone Lake is the largest high-altitude lake in North America, “and is extremely hazardous to work on because of the extreme cold water and the very sudden, violent storms and winds that can come over the mountains,” Klump says. Some of the on-site research was originally done through scuba diving, which has its own dangers. The pressure change from going underwater to a high altitude puts a diver at increased risk of decompression sickness. Even though the average lake temperature is perilously cold, some of the underwater vents are much hotter than those on the land, so divers must also be careful to avoid associated hot-water blasts. A few of the more shallow vents are still visited by scientists in scuba gear, but the ROV has been essential in exploring deeper regions.

Some of the spires in Bridge Bay have reached 20 feet in height. Picture from the bottom of Mary Bay showing the “yellow brick road,” a dense mat of photosynthetic and chemosynthetic bacteria. The growth of bacteria occurs along a fissure that lets minerals seep to the surface.

The 200-pound underwater roving device, is operated by subcontractor Dave Lovalvo from Eastern Oceanics. Although smaller than the one used to discover the Titanic, it has many sophisticated features and is highly portable. “During the past several years, we have designed, built, and deployed water and sediment sampling systems using an ROV,” Aguilar explains. The ROV gives the researchers access to even the deepest vents in Yellowstone Lake. Ability to sample the water chemistry and microbial populations in the hot vents of the Yellowstone geothermal ecosystem, Aguilar says, “is critical for conducting microbiological and geochemical analyses aimed at determining the metabolic processes promoting life in the habitats and tolerances of the organisms to extreme conditions.

Through X-ray and electron microscopic observation and analysis, UWM researchers have found the spires to consist mainly of amorphous silica, with diatoms present on the outside of the structures. The diatoms are tiny planktonic organisms with exoskeletons of silica. “The hydrothermal waters in the park are often near saturation in dissolved silica,” says Klump, and therefore are excellent breeding grounds for the formation of the spires. A dried spire sample appears similar to a sponge made of sandstone. The outer surface is dark brown with bacteria, algae, sponges, and other life forms growing on it, but its interior is white. The spire sample consists of a network of interconnecting tunnels for funneling vent water. All the spires collected so far seem to have been formed up to 12,000 years ago and are no longer considered active.

The ROV’s telescoping arm sampling a hydrothermal vent.
At right: Water and sediment samples collected by the ROV.

Aguilar has studied the conditions that allow for bacteria, such as those likely to have lived on the active spires, to find a habitat. “Geothermally heated water percolating through the volcanic chamber becomes enriched in carbonate, silicate, and chloride, with some locations additionally rich in methane, iron, and sulfide,” she explains, and these elements are capable of sustaining various microbes. Some of the varieties of life found at the vents include different types of bacteria, living (and occasionally boiled) leeches, snails, and sponges, and sometimes fish. “Bacteria present in the vent areas can be mesophiles, thermophiles, or hyperthermophiles, depending on their tolerance to temperature,” Aguilar says. Mesophiles are microorganisms that grow optimally in waters between approximately 200C and 450C; thermophiles generally grow in temperatures between 450C and 800C; and hyperthermophiles grow optimally at above 800C. “Within these bacteria there are some that oxidize sulfur and iron, and utilize several minerals available in the hydrothermal vent fluid.”

“The minerals drive everything,” says Senior Scientist Russell Cuhel as he loads another sample into an analyzer at the WATER Institute facility in Milwaukee. “The sulfur and iron that both feed the bacteria and form part of the physical structure of developing spires are particularly elusive. We have to take a significant component of our laboratory to Yellowstone, and that allows us to sample, measure, and analyze our samples hours after they were collected.

Top: Hot vents deep beneath the lake’s surface are illuminated by the lights of the ROV. Bottom: Underwater structures from West Thumb; the orange color is iron oxide and the dark color is manganese oxide.

“It is challenging to measure the life that thrives on these ephemeral energy sources. These measurements are made every year and adding new ones each season, a consistent picture of life in extreme environments is emerging.”

The ROV has captured freshwater creatures swirling around the vents like little whirlpools. The bacteria embedded in the formations attract hungry water fleas and snails, which in turn bring the next step up on the food chain: leeches. One vent, dubbed the “Trout Jacuzzi,” has brought in native cutthroat trout, which normally prefer cooler waters near the surface of the lake. The vents seem to release an unusually high amount of arsenic and mercury into the water, which has been shown in large concentrations in the trout and even in the bears and other animals that eat the trout.

“The interaction of biology with geothermal and geochemical energy may be more ancient than any other ecology,” Aguilar says, and it therefore provides insight into the evolution of life on Earth and possibly other planets. Bacteria and other life that thrives at high temperatures “can be a link to ancient organisms and can be a key to the earthly evolution and development of life,” Aguilar explains. “One of the theories is that life arose under reducing conditions with high temperatures, similar to the hydrothermal vent systems that are currently found on Earth. These high-temperature systems are relevant to understanding extreme environments on Earth, as well as other planets and moons in our solar system.”

“The young Earth’s hydrothermal systems would have started to be present after the surface of the planet had cooled enough to sustain liquid water,” Aguilar says. “Evidence of hydrothermal systems also existed early in the history of Mars.” Continued explorations at Yellowstone have Aguilar and her colleagues excited about how their research contributes to a broader understanding of life in the universe.

Left: An exploded view of the spire collected from Yellowstone Lake. The spire was cut with a Water-Jet Saw (at KLH Industries, Germantown Wis). UWM researchers have found the spires from the floor of Yellowstone Lake to consist mainly of amorphous silica, with diatoms—tiny planktonic organisms with exoskeletons of silica, shown at right—present on the outside of the structures. Diatom photos from U.S. Geological Survey.

“Successful sampling of microbiota from shallow, freshwater hydrothermal systems with high temperature and elevated, sometimes toxic mineral content will provide an additional model for understanding biogenesis and evolution under primitive Earth conditions,” she says. “Many of the appealing features of two primary theories of early life— that of hot, reducing conditions and shallow, atmospherically influenced pools—are melded in the Yellowstone hydrothermal vent ecosystem.”

The UWM researchers are just beginning to find the pieces of the puzzle that make up Yellowstone Lake’s shadowy floor. With each return trip they are able to better complete the picture of its fascinating geologic features, the life that finds a home there, and how it relates to the evolution of life in our solar system.

Many of the images in this article appear in Yellowstone Lake: Join the Expedition!, a 56-page book documenting in text and pictures the exploration of Yellowstone Lake by UWM researchers since 1983. For information about the book or to order, contact Elizabeth Trendel at the WATER Institute (eat@uwm.edu or (414) 382-1700) or visit www.amazon.com.