What controls the persistence of marine dissolved organic matter?

The major processes controlling the inventory of the largest reduced carbon reservoir in the ocean, dissolved organic matter (DOM), are unknown. The average radiocarbon age of marine DOM coupled with some evidence of a surface ocean photosynthetic source, have led us to conclude that this reservoir accumulates in the ocean on millennial timescales. Two overarching theories have been proposed for why DOM accumulates on these timescales. One theory considers that individual DOM compounds exist at too low of a concentration in the deep ocean to be efficiently utilized by heterotrophic bacteria. The other links the intrinsic chemical properties of DOM to its long term accumulation in the ocean. In order to determine the relative importance of these two mechanisms it is necessary to compare the chemical compositions of the more labile and more refractory components of DOM. In this talk I will discuss the approaches that we have been taking in my lab to better characterize marine DOM in an attempt to uncover the processes contributing to its long-term accumulation. The mechanisms responsible for transforming organic matter in the oxygenated water column could influence the subsequent processes that act to preserve compounds on geological timescales and are therefore relevant for understanding the pathways of CO2 sequestration in the marine environment.

Dr. Lihini Aluwihare is a Professor of Marine Chemistry and currently serves as Chair of the Scripps Institution of Oceanography (SIO) Department at UC San Diego. She earned her bachelor's degree from Mount Holyoke College in 1993, graduating with a double major in Chemistry and Philosophy. Dr. Aluwihare completed her PhD in Chemical Oceanography through the Woods Hole Oceanographic Institution–MIT Joint Program in Oceanography, where she was mentored by Dr. Dan Repeta.

Following her doctoral work, she conducted a brief postdoctoral fellowship at SIO with Professor Farooq Azam. Shortly after her arrival, she was offered a position as an Assistant Professor. Dr. Aluwihare has been a faculty member at SIO for the past 25 years.