Carbon Dynamics in Aquatic Ecosystems in Response to Elevated Atmospheric CO2 and Altered Nutrients Availability

Aquatic ecosystems will experience altered inorganic carbon, nitrogen and phosphorous availability in the future due to elevated atmospheric CO2, stronger stratification and anthropogenic activities. Despite its importance in modulating global carbon cycles, how carbon dynamics in aquatic ecosystem response to the future global change remains largely unknown. Here we performed a chemostat experiment to study how equilibrium carbon dynamics response to elevated CO2 and altered N, P availability. Our results show that elevated CO2 led to enhanced photosynthetic carbon uptake and dissolved organic carbon (DOC) production. DOC occupied larger percentage in total organic carbon production in high CO2 environment. N addition stimulated biomass carbon accumulation. Collectively, in the future, high CO2 and low nutrient availability lead to high C: nutrient ratio in both biomass and dissolved organic carbon. It indicates a possible change in nutrient limitation and increase in recalcitrant dissolved organic carbon as long term carbon sequestration. Total carbon consumption remains unclear and will depend on the net effects of depleted nutrients and elevated CO2