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

The oxygen isotope ratio of dissolved inorganic phosphate (δ(18)Op) represents a novel and potentially powerful stable isotope tracer for biogeochemical research. Analysis of δ(18)Op 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, δ(18)Op 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 δ(18)Op, given aquatic matrices in which potential sources of contaminant oxygen are ubiquitous. Finally, we synthesise the existing global data regarding δ(18)Op in aquatic ecosystems, concluding by identifying four key areas for future development of δ(18)Op research. Through this synthesis, we seek to stimulate broader interest in the use of δ(18)Op to address the significant research and management challenges that continue to surround the stewardship of phosphorus.