Scientists initially thought the chemical composition of seawater was constant. In the late 20th century, however, indirect evidence revealed that seawater chemistry has changed systematically at particular time periods during the past 550 million years. Knowing how the oceans and climate changed previously gives scientists insights into how it might change in the future.

Weldeghebriel aims to understand what caused these changes. He believes they could be a result of variations in the rate of seafloor spreading and fluctuations in hydrothermal vents, which release ions that react with the existing seawater.

To substantiate this idea, Weldeghebriel and his advisor, Tim Lowenstein, analyze marine halite, a mineral that traps and preserves seawater during its formation. They have collected more than 150 halite samples from different locations and time periods dating back as far as 550 million years.

To study the contents of these samples, they use a state-of-the-art Laser Ablation Inductively Coupled Plasma Mass Spectrometer. First, a laser beam drills through a halite sample and evaporates the seawater inside (that’s the “laser ablation” part). The contents are then transported to a mass spectrometer, which analyzes the masses of individual elements and isotopes.

This allows for analysis of minor and trace elements in seawater in addition to the major elements. Minor elements comprise between 0.1 percent and 1 percent of a solution; trace elements make up less than 0.1 percent. Major elements comprise the rest.

Weldeghebriel’s research, which he presented at the Northeastern Section meeting of the Geological Society of America in 2018, is important because previous interpretations were based on analysis of major elements only. His new data has allowed him to narrow down other interpretations and bring forth hard evidence toward his interpretation.

While growing up in northeastern Africa, Weldeghebriel became infatuated with geology. He was still in high school when a group of geologists came to display minerals in the annual Eritrea Festival.

“When I saw these beautiful crystals and different colored rocks, it was in my mind,” he says.

At the Eritrea Institute of Technology, he graduated at the top of his class, winning a college gold medal. When Weldeghebriel reached out to Lowenstein about graduate studies, Lowenstein was impressed.

“He knew a lot about the subject material before he came here,” says Lowenstein, a distinguished professor of geological sciences. “I took him very seriously from the moment we emailed one another.”

After graduate school, Weldeghebriel is considering going into industry to work on Potash, minerals useful for agriculture. Later, he hopes to go on to become a professor. In Eritrea, Weldeghebriel says, there are limited resources because it is a developing country with economic inefficiencies and shortages. This limited him in his undergraduate research, as he only had the resources to do basic analyses.

“In America, there is a lot of opportunity,” he says. “I get one of the biggest opportunities coming here, because I can do whatever I want to do.”

“It’s one of the more extreme environments that I work on,” says Kulp, an assistant professor of geological sciences at Binghamton University since 2011. “Mono Lake has a pH of 9.7, and it’s so full of dissolved minerals that when you stick your hand in the water, it feels soapy. It’s a closed basin lake, so water flows in from the Sierras, but the only way it leaves is through evaporation, which concentrates all these metalloids in the basin. It’s a naturally arsenic-rich ecosystem that supports a very healthy population of bacteria.”

For years, scientists have known about bacteria that survive without oxygen, getting their energy by metabolizing compounds such as sulfate, nitrate and iron oxides. Kulp has pushed that knowledge further, studying the biogeochemical cycles of arsenic and antimony for a clearer understanding of microbiologically mediated reactions and their broader implications.

“I like the idea of discovering new ways life can exist that we didn’t realize before,” says Kulp, who came to Binghamton after years as a research microbiologist for the U.S. Geological Survey. “That’s the most exciting part, and a fair amount of my work has been funded by NASA, which is interested in ways life can exist outside the usual metabolic processes. So I study a lot of bacteria, not just in environmentally relevant aquifers and fresh-water ecosystems, but in some of the more extreme environments on Earth, places where there aren’t a lot of things that can survive.”

Along with his research at Mono Lake, Kulp’s work has taken him to arsenic-contaminated aquifers in Taiwan and California and the Stibnite Mine in central Idaho. That has become the main site for his current work, breaking ground in the study of bacteria that use antimony compounds in place of oxygen.

“There are some scientists who wave a flag to say, ‘Hey, look at me,’” says John F. Stolz, director of the Center for Environmental Research and Education at Duquesne University. “Tom doesn’t do that. He’s quiet, unassuming, meticulous and very attentive to detail. But he does great science, and he’s contributing some very significant findings about life on Earth — and maybe even beyond.”

For decades, geologists have looked at these water droplets — called fluid inclusions — and wondered whether microbes could be extracted from them. Fluid inclusions have been found inside salt crystals ranging in age from thousands to hundreds of millions years old.

But there has always been a question about whether the organisms cultured from salt crystals are genuinely ancient material or whether they are modern-day contaminants, said Tim Lowenstein, professor of geological sciences and environmental studies at Binghamton.

Lowenstein and Binghamton colleague J. Koji Lum, professor of anthropology and of biological sciences, believe they have resolved this doubt. And they’ve received $400,000 from the National Science Foundation to support further research on the topic.

Lowenstein’s team, which has been pursuing this problem for years, began by examining the fluid inclusions under a microscope. “Not only did we find bacteria, we found several types of algae as well,” he said. “The algae actually may be the food on which the bacteria survive for tens of thousands of years.”

When Lum got involved, the researchers began to wonder about the DNA of the organisms they were finding. “You have a little trapped ecosystem,” Lum said. “Some of these guys are feeding on other ones trapped in this space. The things that aren’t alive in there, their DNA is still preserved.”

Lum’s graduate student Krithivas Sankaranarayanan reviewed existing literature on ancient DNA and helped to develop a protocol for use with Lowenstein’s samples.

“We have these samples going back from the present to over 100,000 years in one exact location,” Lum said, his voice rising with excitement. “So Tim can look at the salinity and reconstruct ancient climates.

“Now we’re looking at the DNA from bacteria, the algae, the fungi and what was living in those waters and how those things changed over time. We have a view of all the different organisms that were in the lakes at the time these inclusions were formed.”

The researchers sequence the DNA and culture the bacteria they find. Then it’s time to think big. Lum’s most optimistic view of the project goes like this: “It’s possible that we can observe organisms evolving and see how they’re reacting to climate change over geologic time.”

The samples Lowenstein works with are drawn from Death Valley and Saline Valley in California as well as from sites in Michigan, Kansas and Italy. Temperatures at these locations may have reached 130 degrees Fahrenheit in the past, and the pockets of water trapped inside the rocks are generally very salty.

The environment may sound harsh — in fact, it’s among the most extreme on Earth — but the creatures that survive there are tough. “These are some of the hardiest beasts on the planet,” Lum said. And the conditions inside these water droplets are ideally suited to preserving DNA.

“They’re like time capsules,” Lowenstein agreed.

Radio: Lowenstein speaks to EarthSky about his research

Video: Lum and Lowenstein talk about this project