FSU review shows molecular fingerprints of human impacts on global water systems

A Florida State University-led review shows how ultrahigh-resolution mass spectrometry can help researchers identify the molecular fingerprints of human activity in water systems around the world.

Mass spectrometry is a powerful analytical tool that lets researchers identify unknown compounds and determine the structure and chemical properties of molecules. Rob Spencer, the Verta Cox Professor of Oceanography in the Department of Earth, Ocean, and Atmospheric Science, has used ultrahigh-resolution mass spectrometry to investigate environmental changes for almost 20 years. He led a review of the technology featured as the cover article in the September issue of Nature Water.

“Our research aims to understand how organic matter within a water sample from anywhere in the world can tell us something about human-induced change in that aquatic environment,” Spencer said. “The security and stability of our water resources are important, and we found a new way to address these issues in ways we never thought possible. With the application of this technology, we’re seeing an almost diagnostic response to human activities at the molecular level.”

How it works: Molecular fingerprints

Dissolved organic matter, or DOM, is a complex mixture found in all global waters that plays many roles in the environment. It’s an energy source for aquatic life, affects drinking water treatment and plays an important role in major biogeochemical cycles. Understanding the composition of DOM is critical to distinguishing the roles it plays in the environment. Ultrahigh- and high-resolution mass spectrometry, or UHRMS, have transformed researchers’ ability to understand how human activities alter that mixture.

“By synthesizing what we’ve learned across many different aquatic systems, Rob and his colleagues highlight both the power and current limitations of UHRMS and help chart a path toward better identifying and understanding the molecular fingerprints of human impacts, combining aquatic biogeochemistry with cutting-edge analytical techniques to address fundamental questions about our changing planet,” said Mike Stukel, chair of the FSU Department of Earth, Ocean, and Atmospheric Science.

Research at the National High Magnetic Field Laboratory

At the National Science Foundation-funded, FSU-headquartered National High Magnetic Field Laboratory, researchers like Spencer combine mass spectrometry with high magnetic fields for a range of research applications at the lab’s Ion Cyclotron Resonance Facility. UHRMS differs from conventional mass spectrometry in its exceptional accuracy and precision, allowing researchers to examine tens of thousands of data points — in this case, organic markers and molecular formulas — that provide valuable diagnostic data.

“At FSU, we’re uniquely positioned to conduct this research thanks to the National MagLab’s facilities,” Spencer said. “When analyzing tens of thousands of molecular formulae in a sample, we might end up with 10 diagnostic markers in the Amazon River Basin that track land-use change, for example. Similar research in the Mississippi Basin found a small number of organic markers linked to agriculture, and it was noted that these molecular formulae were very similar to those from the Amazon. This ties big human impacts, like converting pristine lands to agricultural land, to molecular-level changes in our global water systems.”

Understanding human impacts and the global carbon cycle

Changes in DOM’s molecular composition can also reveal the effects of urbanization, fires, and overall changes in climate and precipitation patterns.

“One motivation for this review was to encourage researchers to make their data openly accessible so we can improve identification of these diagnostic indicators and organic markers in conjunction with different human impacts,” Spencer said. “Ultimately, that tells us how things will respond to changes downstream. It was really interesting to look across different temperate and tropical systems and see similar responses at the molecular level with common major human impacts.”

Another focus of the review was Arctic change, as the region is warming faster than anywhere else on Earth. Nearly two-thirds of all soil carbon on Earth is frozen in Arctic permafrost. As the region thaws, carbon that has been stored for thousands of years can enter the modern carbon cycle. By identifying organic markers linked to thawing permafrost, scientists can more confidently predict how this carbon will interact with the environment, whether it moves from long-term storage in soils to long-term ocean storage or is consumed by microbes and released into the atmosphere as carbon dioxide.

“In addition to advancing our understanding of the global carbon cycle, this work addresses societally important issues such as agriculture, urbanization, fire effects and climate change,” Stukel said. “Rob’s work also highlights the tremendous opportunities created by combining EOAS expertise with the world-class analytical capabilities of the National MagLab. This invited review reflects both his team’s leadership in aquatic biogeochemistry and their ability to help define where the field should go next.”

Collaborators and support

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This research was supported by the National Science Foundation, NASA, the Novo Nordisk Foundation and the National Institute of Food and Agriculture through the U.S. Department of Agriculture. Researchers from the University of Wisconsin-Madison and Colorado State University were co-authors on this study.

Visit the Department of Earth, Ocean, and Atmospheric Science website for more information about research conducted in the department. Visit the National High Magnetic Field Laboratory to learn more about how this facility supports groundbreaking research at FSU and beyond.