Profiles, On-Campus Profiles, Features

Isotopes, Nitrogen, and Oceans: BC Professor’s Lab Provides Unique Insight Into Ocean Chemistry

When a cargo ship carrying fertilizer sank into the Red Sea on March 2, reporters sought out expert insight from none other than Xingchen Wang, professor of earth and environmental sciences at Boston

“It was carrying 21,000 tons of fertilizer,” Wang said. “That’s a nutrient enrichment experiment here in the ocean. The same mechanism happened eight million years ago and dumped nutrients into the ocean.”

Wang seeks to understand the ocean’s current and past biogeochemical cycles through the Wang Stable Isotope Biochemistry Lab, which he leads at BC.

“My interest spans the entire range of Earth history, nutrient cycling, and exploring the ocean and how it affects the climate system,” Wang said. 

The lab specifically examines the isotopic composition of natural samples collected from oceans at two facilities in Devlin Hall and 245 Beacon St. 

Wang said the lab’s technology makes it unique—the Devlin facility is a “clean lab,” specifically designed with HEPA filters and water filtration systems to minimize contaminants. 

“It’s clean air, clean water, and then that’s how we make very good measurements about the ocean,” Wang said. 

Through experiments performed in the Center for Isotope Geochemistry, the goal of the lab is to analyze nitrogen in minuscule quantities.

The center houses an isotope ratio mass spectrometer, an instrument capable of performing analysis on liquid or solid samples. While liquids are aerosolized to be examined, solids samples need to be broken down and diffused.

“There’s a very high power laser and the laser can just blast a solid particle and kind of blast out particles, and those particles get swept up into a gas stream,” said Andrew Lonero, assistant director for the Center for Isotope Geochemistry.

The ability to analyze solid samples is particularly useful for Wang’s lab research, which inspects coral and fossils from the ocean.

“Then we can say something about nitrogen cycling or nutrient cycling,” Wang said. “It’s connected to the climate system. More nutrients encourage more phytoplankton growth, and then that will increase so-called ocean productivity that can increase the uptake of CO2 in the atmosphere into the ocean.” 

In 2020, Wang co-authored a research article centered around his work and the role of the Southern Ocean in moderating carbon dioxide levels in the atmosphere.

“During the Ice Age, you could increase the phytoplankton growth in that region and then the more phytoplankton growth means more carbon uptake from the atmosphere and more storage of CO2 in the deep ocean, and as a result, lower CO2 in the atmosphere,” Wang said. “That was the hypothesis proposed 40, 30 years ago.”

Wang and other researchers worked to prove this hypothesis by gathering coral samples from the region and dating them through isotope measurements. Their research discovered phytoplankton growth was more efficient about 20,000 years ago.

“The nutrient status or the future uptake of the carbon in the Southern Ocean area is also going to influence the remaining CO2 concentration in the atmosphere,” Wang said. 

The lab is currently researching ocean dead zones, which are areas in which the water contains little oxygen, Wang said.

“These dead zones pretty much didn’t exist until like eight million years ago, and the reason this didn’t exist eight million years ago is because there was less nutrients in this area, or in the global ocean in general,” Wang said. “Less nutrients in the ocean means less phytoplankton productivity. Less phytoplankton activity means less oxygen consumption. So the nutrient cycling is also closely tracking to the oceans’ oxygen content.” 

But while this transition eight million years ago occurred naturally, Wang said the fertilizer recently released by the cargo ship in the Red Sea could have significant ecosystem implications.

“You will cause phytoplankton growth because algae grows and then there’s a lot of corals in the area that people are concerned about because corals don’t like algae blooms,” Wang said. “One message I was trying to convey to the reporter is if we could salvage the boat before the fertilizer leaks out, we could still avoid ecosystem disaster.” 

Six PhD students also currently work at the lab with Wang, pursuing their own research interests involving oceans, waterways, and nutrient cycles. Many of them have also been able to travel for their research. 

Heather Donnelly, a third-year PhD student, researches nitrogen cycling in coral and how humans have altered nitrogen cycling. Donnelly’s research has taken her to the Gulf of Mexico to collect samples. 

“It was a five-day long cruise aboard the research vessel or RV pelican,” Donnelly said. “We take these big like CTD—which is conductivity temperature-depth—this big giant thing with a bunch of tubes on it. They throw it down to the bottom of the ocean. They get the depth and temperature from each place that we go to.” 

Another PhD student, Kameko Landry, recently returned from a 68-day voyage to Antarctica. 

“My job was to collect the nitrogen samples on board for the water column nitrogen,” Landry said. “I worked these 16-hour shifts, and to collect water column samples, you have to send down these big rosettes. And so it’s called the CTD Niskin rosette, and it has 36 big 10-liter bottles on it, and they go down open.” 

Landry said the samples collected have the power to supplement her research as well as the research of her peers.

“The overall purpose of this cruise was to basically quantify the biogeochemical cycling in the Amundsen Sea, which is a pretty understudied region,” she said.

Both Donnelly and Landry said working in the lab is an interesting experience because of the new perspectives it offers.

“I have labmates that [study] the past million years,” Donnelly said. “Getting to see what they do has been very interesting for me just because I think on smaller timescales and into the future, and they think on longer timescales to the future. So it’s interesting how we can use nitrogen isotopes for both those things.” 

Landry said having Wang as a mentor has helped her grow. 

“Personally, I came in not really familiar with biogeochemistry very much other than a few classes,” Landry said. “And he’s just always been really supportive in the way of encouraging me to become more independent as a researcher.”

Wang said the questions and ideas of his students often provide insight that changes the trajectory of his projects.

“I feel very lucky to have excellent students in our lab, as well as postdocs,” Wang said. “Intellectually, it’s very stimulating to work with a lot of smart students.”

April 7, 2024