Dissolved organic phosphorus (DOP) is critical for supporting primary production in key regions such as the western North Atlantic, but the production, composition, and bioavailability of DOP remain poorly constrained.  Leveraging a new method (Hull and Ruttenberg 2022), samples from the North Atlantic and North Pacific were screened for DOP molecular weight distribution and subjected to enzyme hydrolysis to determine the fraction of bioavailable phosphomonoester (PME) and phosphodiester (PDE).  The distribution of total DOP into molecular weight size fractions of <500Da, 500-1000Da, 1-100kDa, and >100 kDa varied across surface environments. Differences in molecular weight distribution were most striking for DOP recovered in the smallest fraction (<500Da), which was dominated by bioavailable PME and PDE compounds. Recovery of DOP in the <500Da fraction ranged from non-detectable in the lowest phosphate (P) environment to the dominant size fraction (>60% of total DOP) in comparatively higher P environments.   These patterns may be driven by changes in phytoplankton DOP production and microbial DOP hydrolysis as a function of P physiology. Moving forward we are examining these dynamics with experimental work to track the expression of P metabolism pathways and production and consumption processes.  Together, this combination of approaches is providing new insight into the heterogeneity of DOP and the processes that control DOP cycling.

Primary Presenter: Sonya Dyhrman, Columbia University (sdyhrman@ldeo.columbia.edu)

Authors:

Sonya Dyhrman, Department of Earth and Environmental Science and Lamont-Doherty Earth Observatory, Columbia University  (sdyhrman@ldeo.columbia.edu)

Kathleen Ruttenberg, Department of Oceanography, SOEST, University of Hawaii at Manoa  (kcr@hawaii.edu)

Danielle Hull, Department of Oceanography, SOEST, University of Hawaii at Manoa  (dhull@hawaii.edu)

Sheean Haley, Lamont-Doherty Earth Observatory, Columbia University  (shaley@ldeo.columbia.edu)