NSF Award
2318985
Ocean productivity depends on nitrogen availability. The atmosphere is 78% nitrogen gas, but this form of nitrogen is unusable to most organisms. Nitrogen gas dissolves in the ocean and is converted, or fixed, into more reactive forms through nitrogen fixation. Reactive nitrogen inputs to the oceans are reversed through denitrification, which converts reactive nitrogen to nitrogen gas. Measuring the balance between nitrogen fixation and denitrification is challenging because the rates of these processes are small relative to the large inventory of nitrogen gas. Also, biological and physical processes both impact the nitrogen gas inventory. The researchers will develop a new method to measure three noble gases (neon, argon, and krypton), which are not impacted by biological processes, as well as nitrogen gas. They will use this method to quantify the fixed nitrogen balance: the rate of fixed nitrogen production minus fixed nitrogen loss. This method has many applications, including identifying nutrient management strategies to support healthy coastal ecosystems. The work will benefit society by generating new research infrastructure, educational materials, and a diverse workforce. The researchers will develop technology to measure the fixed nitrogen balance. They will prepare a college and high school course module about nutrient pollution in Connecticut. The module will describe how humans have identified harms of pollutants and developed solutions through legislation. The work will support an early-career female investigator, a female graduate student, and an early-career Hispanic lab manager.<br/><br/>The researchers seek to improve the reliability of widely used incubation techniques for determining benthic fixed nitrogen production/removal (the nitrogen/argon technique and nitrogen isotope pairing technique) by incorporating measurements of multiple noble gases into existing protocols. They will identify under which conditions physical perturbations can impact the calculated nitrogen fluxes and develop quantitative methods to correct for these effects. Additionally, the researchers will develop and demonstrate a new method for measuring net biological nitrogen fluxes at the ecosystem scale through in situ measurements, which will enable monitoring of fixed nitrogen removal and production in dynamic coastal systems. Improved tools for constraining biological nitrogen fluxes will help to resolve recent questions regarding the fixed nitrogen balance in coastal systems and improve scientific understanding of the capacity of coastal systems to attenuate eutrophication. The researchers will develop a high-precision, high-throughput method for noble gas analysis that is adapted from existing commercially available instrumentation and share the method with the scientific community. This work will enable other researchers to apply noble gas measurements to address a wide range of biogeochemical research questions.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
