Studies of the isotopic composition of Nitrogen in various species yield insights on the dynamics of biogeochemical processes and recent results suggest that within the North Pacific Ocean, long-term nitrogen isotope chronologies are indicating a marked ecosystem state change raising questions as to whether the signal indicates a trophic decline resultant from overfishing by humans that has shifted the entire trophic structure of the oceanic food web and/or an increase in nitrogen fixation linked to climate-coupled changes in the environment.
This grant supports acquisition of a gas source stable isotope ratio mass spectrometer (SIRMS), a laser optical cavity ring down mass spectrometer (LCOS), materials to construct a compressor system for filling air tanks with a range of N2O concentrations and isotopic compositions, and a gas chromatography nitrogen (GC-N) compound specific isotope analysis system capable of improved amino acid ä15N values. The equipment will foster investigator research focused on global nitrogen cycling in the oceans and aquatic systems with targeted studies of the stable isotopic composition of Nitrogen in Nitrous Oxide (N2O), a greenhouse gas and within amino acids recovered from aquatic and marine organism tissues. The requested equipment will replace an aging SIRMS at Michigan State, the LCOS will allow comparative studies of the value and precision of laser-based isotopic analysis versus traditional SIRMS analysis and the PI will prepare and make available to the broader community a suite of N isotopic standards needed for LCOS measurements.