The turnover of organic nitrogen is a key process in maintaining marine productivity. In coastal regions, remineralization associated with the enhanced export of organic matter can lead to the accumulation of reduced nitrogen, notably at the primary nitrite maximum. Particle remineralization likely alters the surrounding water in other ways, by adding dissolved organic matter (DOM) that can contribute to nutrient cycling and microbial productivity. An investigation of the dissolved metabolites accumulating at these depths may reveal the role of DOM in driving the microbial ecology of this environment. Here, we measured nutrients, particulate organic matter, bacterial abundance, microbial dynamics via 16S rRNA sequencing and metabolites via solid phase extracted non-targeted metabolomics across multiple Lagrangian-based research cruises within the California Current Ecosystem Long Term Ecological Research program. We observe depth-dependent and diel trends in in-situ nitrite and ammonium concentrations, which we used as proxies to isolate the potential impact of particle remineralization on extracellular metabolite composition by mining non-targeted metabolomics datasets that showed similar trends. Molecular networking conjoined with in-silico annotation tools revealed metabolites and compound classes enriched in nitrogen and sulfur unique to these depths of elevated nitrite and ammonium. Microbe-metabolite correlations further yield information towards understanding the metabolic processes occurring in the water column at elevated recycled nitrogen concentrations.

Primary Presenter: Ralph Torres, University of California, San Diego (rrtorres@ucsd.edu)

Authors:

Ralph Riley Torres, Scripps Institution of Oceanography  (rrtorres@ucsd.edu)

Daniel Petras, University of Tuebingen  (daniel.petras@uni-tuebingen.de)

Sarah Schwenck, Scripps Institution of Oceanography  (sschwenc@ucsd.edu)

Sara Rivera, University of Michigan  (sarariv@umich.edu)

Abzer Shah, University of Tuebingen  (abzer.kelmina@gmail.com)

Andrew Allen, Scripps Institution of Oceanography / J. Craig Venter Institute  (aallen@ucsd.edu)

Pieter Dorrestein, University of California San Diego  (pdorrestein@health.ucsd.edu)

Lihini Aluwihare, Scripps Institution of Oceanography  (laluwihare@ucsd.edu)