Diazotrophs are the only organisms capable to use N2 gas dissolved in seawater and transform it into a bioavailable nitrogen (N) form (i.e. NH4+), by which they act as natural fertilizers for the open oceans, where N is often limiting productivity. Though N is not limiting for diazotrophs, other nutrients like iron (Fe) and phosphorus (P) have a strong influence on their growth and N2 fixing capabilities.
During my PhD I am developing a method to measure single cell nutrient uptake rates for C, N, P and Fe simultaneously with the use of nano-scale secondary-ion mass spectrometry (nanoSIMS). In addition we will combine this method with assays that indicate the physiological status of Diazotrophs related to P and Fe limitation within their marine environment.
By applying this approach in situ on multiple diazotrophic species from different challenging marine environments we will contribute to a better understanding on the role of diazotrophs within today’s global N, P and Fe cycles.