Seminar: Lihini Aluwihare

Tuesday, May 31, 2022 - 12:00pm

Lihini Aluwihare

Professor, Scripps Institution of Oceanography

The old and the new: Two tales of marine dissolved organic matter (DOM)

The 600 Gt C marine dissolved organic matter (DOM) reservoir facilitates ecosystem interactions, nutrient regeneration, and carbon and nutrient sequestration. As new analytical methods come on line, we learn more about the identities of the molecules that facilitate each of these processes. 

In this talk, I will describe some of the different analytical approaches we are taking to elucidate the dissolved organic currencies involved in maintaining ecosystem interactions and modulating global carbon cycling. In one example I will describe our work isolating radiocarbon-depleted DOM for chemical characterization and radiocarbon fractionation. Our work suggests that certain chemical features are dominant in recalcitrant DOM. In the second example, I will discuss our work with the more labile DOM components in the California Current Ecosystem. We are developing non-targeted approaches to provide a more comprehensive picture of the labile molecules that may underpin phytoplankton-bacterial interactions.

Lihini Aluwihare, a chemical oceanographer, was born in Sri Lanka and lived in Zambia and England before moving to the United States for college and post-graduate studies. Arriving at Scripps Institution of Oceanography at UC San Diego in 2000, she studies the cycling of carbon and nitrogen in the oceans using light isotope tools and organic matter chemical characterization.

As a marine geochemist, her work revolves around trying to read the messages encoded in molecules that maintain microbial life, facilitate ecosystem interactions, and contribute to long-term carbon and nutrient storage. While her research focuses mainly on naturally occurring molecules, her tools also enable her to examine the human fingerprint in aquatic environments through detection of anthropogenic organic compounds. Currently, her lab is interested in many projects including: the cycling of nitrogen in the eastern North Pacific Ocean, including in low oxygen environments, and its sensitivity to natural and anthropogenic climate change; the cycling of the longest-lived organic compounds in marine environments; biotic and abiotic transformations of organic compounds that result in organic matter accumulation in aquatic environments, including in coral reef environments and high elevation lakes; the microbial-metabolite “interactome” in surface aquatic environments that maintains or disrupts microbial ecosystem interactions, including the role of marine toxins; the fate of anthropogenic organic compounds in the coastal ocean; and quantifying carbon flux through the microbial food web. A common theme that underpins her work is her commitment to developing new analytical tools and research frameworks to examine a particular scientific question from a different perspective.

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