Phosphate oxygen isotopes within aquatic ecosystems: Global data synthesis and future research priorities

The oxygen isotope ratio of dissolved inorganic phosphate (δ18Op) represents a novel and potentially powerful stable isotope tracer for biogeochemical research. Analysis of δ18Op may offer new insights into the relative importance of different sources of phosphorus within natural ecosystems. Due to the isotope fractionations that occur alongside the metabolism of phosphorus, δ18Op could also be used to better understand the intracellular and extracellular reaction mechanisms that control phosphorus cycling. In this review focussed on aquatic ecosystems, we examine the theoretical basis to using stable oxygen isotopes within phosphorus research. We consider the methodological challenges involved in accurately determining δ18Op, given aquatic matrices in which potential sources of contaminant oxygen are ubiquitous. Finally, we synthesise the existing global data regarding δ18Op in aquatic ecosystems, concluding by identifying four key areas for future development of δ18Op research. Through this synthesis, we seek to stimulate broader interest in the use of δ18Op to address the significant research and management challenges that continue to surround the stewardship of phosphorus. •Oxygen isotope ratio in dissolved inorganic phosphate a novel stable isotope tracer.•Theoretical basis for application of this tracer in aquatic ecosystems reviewed.•Protocols for determining phosphate oxygen isotope ratio summarised.•Synthesis of global data from marine and freshwater ecosystems reported.•Priorities for future research in this rapidly evolving field identified.