Alexandria Niebergall and Weiyi Tang in the lab aboard the research vessel. Credit: Alex Niebergall


By Parker Brown, Communications Specialist

DURHAM, N.C. — This summer, PhD students advised by Nicolas Cassar participated in a NASA-funded research cruise in the Northern Pacific Ocean as part of the Export Processes in the Ocean from Remote Sensing (EXPORTS) project.

EXPORTS is a multi-institutional research initiative that seeks to develop a predictive understanding of the export and fate of global ocean net primary production and its implications for present and future climates. The students’ research project specifically looked at the role marine microbes play in drawing carbon dioxide out of the atmosphere.  
Duke Environment corresponded with PhD students Alexandria Niebergall and Weiyi Tang to discuss their experience on the EXPORTS research cruise, what sparked their interest in the field and how it will contribute to their own research moving forward.

1. How did you get involved in the EXPORTS project, what were your day-to-day scientific responsibilities, and what did you learn on this cruise?
Tang: I am a graduate student in Nicolas Cassar’s research group in the Division of Earth and Ocean Sciences. Cassar is one of the co-investigators in the project “Quantifying the carbon export potential of the marine microbial community: coupling of biogenic rates and fluxes with genomics” within the EXPORTS project.
I had the opportunity join the first EXPORTS cruise near Station P in the North Pacific this past summer. During the cruise, I worked with Alexandria Niebergall to measure net community production using equilibrator inlet mass spectrometer and collected molecular samples for determining the microbial community structure. We also measured the oxygen concentrations in seawater at different depths using Winkler titrations to calibrate the oxygen sensors equipped on various autonomous platforms like the Lagrangian float, Seaglider and Bio-Argo floats.
I hope to learn more about other research groups’ projects: the research questions, the methods used to answer the questions and how these projects contribute to the overall goal of EXPORTS.

Niebergall: I became interested in the EXPORTS project while I was working on my Duke Graduate School application and speaking with my adviser, Nicolas Cassar, about opportunities in his lab.

This project is especially exciting because it examines the role of the ocean's biological carbon pump in drawing carbon dioxide, a greenhouse gas, out of Earth's atmosphere. I knew that I was interested in studying ocean biogeochemistry for my PhD, and the EXPORTS project offers a unique and exciting opportunity to collaborate with researchers from all over the country to answer important questions about the ocean and Earth's climate. Overall, for the EXPORTS cruises, we are trying to learn how the microbial community in the surface ocean relates to Net Community Production and carbon export potential.
2. How will this research contribute to your dissertation?
Tang: My dissertation is not directly related to this research project. But this research provides a great opportunity for me to know more about how to apply multiple approaches to understand the export and fate of marine net primary production, which I have a strong interest in. This experience gives insights to construct my dissertation in a broad perspective.

Niebergall: This research will be a large part of my dissertation work. We have already started data analysis from this cruise and we are planning for future field work with the EXPORTS project.

3. What sparked your interest in that research area?
Tang: The role of ocean in Earth’s system and climate has been attractive to me. After learning that abundant and diverse groups of microbes exist in the ocean, I got interested in the functions of these microbes and how they participate in the marine carbon cycling and further affect the climate.

Niebergall: I have always been enamored with the ocean. As an undergraduate student at the University of California, Berkeley, I studied marine science, which primarily involved geochemistry and geology courses, and worked in an integrative biology lab studying marine invertebrates. This background gave me insight into the benefits of studying the ocean with an interdisciplinary approach. As an undergrad I also became interested in natural processes that affect Earth's climate, such as the carbon cycle. In graduate school, I am excited to study the ocean through the lens of increasing understanding of climate and climate change.

4. What has been the most enjoyable and/or rewarding aspect of the research cruise?
Tang: Communicating with great scientists and crew members has been really pleasant. It’s also exciting to see wonderful views on the ocean: sunrise, sunset, rainbows, dolphins and whales.

Niebergall: There is a lot to love about being out in the field. I woke up at 3 a.m. to start my shift in the lab so one of my favorite parts of the cruise was drinking coffee on the back deck of the ship and watching the sunrise. Because of our sampling schedule, sunrise was usually a peaceful time on the ship after the scientists on the night shift had finished sampling and before many of the day shift scientists were awake. For me, this was a great time to reflect (with a spectacular view!) before the day started and we began our rigorous sampling schedule.

It was also extremely rewarding, as a junior scientist at the beginning of my PhD, to be able to work alongside some phenomenal senior oceanographers who were working on a wide range of other projects for over a month. This is a very unique field opportunity and it was an incredible learning experience for me.