Marine N2 Fixation, Global Change and the Future

Long-term environmental changes, including those caused by climate change, are dynamic processes and, in the sea, multiple physical and chemical factors are changing over time which can affect the physiologies, distributions and activities of marine diazotrophs in positive and negative ways. As a result of the increases in atmospheric CO2 concentrations, surface ocean temperatures and dissolved CO2 concentrations are increasing while pH is decreasing. The concentrations of inorganic nutrients, metals and dust in surface waters due to amplified atmospheric deposition as well as runoff are also increasing. At broader scales, ocean circulation may be affected which in turn will affect the nutrient cycles, distribution of species including diazotrophs and the food webs associated with them in the global ocean.