Rates of nitrogen fixation in surface waters by stable-isotope mass spectrometry during the AMT programme cruise AMT20 (JC053).

This dataset consists of measurements of whole community nitrogen fixation rates and particulate organic nitrogen concentrations from samples collected during the Atlantic Meridional Transect programme cruise 20 (AMT20 JC053) between 12th October 2010 and 25th November 2010. Nitrogen fixation, in which dinitrogen gas (N2) is converted by diazotrophic microorganisms to ammonium (NH4+), represents a potentially important source of nitrogen in nutrient poor regions of the Atlantic Ocean. Incubations using 15N-N2 additions were performed in order to quantify nitrogen fixation rates in surface waters of the Atlantic, assess the differences between traditional methodology and a recently published method (Mohr et al 2010) and investigate the impact of ocean acidification on nitrogen fixation rates.