Feedbacks between phytoplankton and nutrient cycles in a warming ocean

Climate warming increasingly drives changes in large-scale ocean physics and biogeochemistry, and affects the kinetics of biological reactions. Together these factors govern phytoplankton productivity, thereby shaping the responses of ocean carbon and nutrient cycles to global change. Here we bring together results from experimental, observational and modelling studies to highlight how interactive feedbacks between warming and nutrient limitation can affect the responses of biogeochemically critical marine primary producers. The availability of many bioactive elements in seawater will be altered markedly in the future, thereby shifting resource deficiencies. These modifications to nutrient limitation when compounded by concurrent warming can change phytoplankton optimum growth temperatures and elemental use efficiencies in group-specific and nutrient-specific ways. The biogeochemical impacts of these nutrient and warming interactions reflect a distinction between the thermal reactivity of major cellular structural elements like nitrogen (N) and catalytic micronutrients like iron (Fe). Integrating the mechanistic feedbacks between warming, nutrient availability and primary productivity into Earth system models is necessary to improve confidence in projections of ocean biogeochemical cycle transformations in a changing climate. Nutrient limitation of marine primary producers will change in complex ways as anthropogenic warming continues, altering global biogeochemical cycles, according to a synthesis of recent studies.