The stoichiometry coupling of carbon, nitrogen, and phosphorus cycles is a fundamental component of ecosystems and biogeochemical cycles. However, several competing hypotheses have been proposed invoking unique biochemical mechanism and associated environmental drivers to describe CNP variation. To test each biochemical mechanism, we used phytoplankton culture experiments, omics’, and the global Bio-GO-SHIP campaign measuring ecosystem CNP. First, we examined Synechococcus cell chemistry using laboratory chemostats and mass spectrometry proteomics. Here, we found that nutrient stress accounted for most CNP variability and induced tradeoffs between nutrient acquisition and ribosomes. There was a significant impact of temperature on ribosome and heat-shock proteins leading to minor stoichiometric changes. Ecosystem variation in CNP supported the culture experiments. Multiple dimensions of nutrient stress were important for CNP in low latitude ecosystems. Concurrent metagenomes separated each elemental stress type and revealed that interactions between nutrient supply rate and N vs. P stress is critical for hemispheric and regional CNP variability. In contrast, sea-surface temperature was important for CNP under nutrient replete and possibly high temperature conditions. Future climate projections suggest that CP and NP will increase at high latitudes but are uncertain at low latitudes due to unconstrained changes to nutrient stress. Our observations suggest a systematic biochemical regulation of elemental stoichiometry among ocean ecosystems, but future changes are uncertain.

Primary Presenter: Adam Martiny, University of California, Irvine (amartiny@uci.edu)

Authors:

Nathan Garcia, University of California Irvine  (n8garcia@gmail.com)

Mak Saito, WHOI  (msaito@whoi.edu)

Adam Fagan, University of California Irvine  (afagan@uci.edu)

Catherine Garcia, University of Hawii  (cathy.garcia@hawaii.edu)

Tatsuro Tanioka,   (tatsurobkkuk@gmail.com)