Comparing primary production methods to better constrain historical, current and future rates

Understanding current primary production and carbon export rates to the deep ocean will provide insight into possible climate change scenarios, because carbon export is an important mechanism sequestering carbon from the surface and may change in the future. By using multiple methods, production rates can be better constrained. Each method has its own advantages, disadvantages, and assumptions. By pairing methods, biases can be taken into account for data interpretation. For example, removing phytoplankton from the environment could change the light levels and temperature of the water. In addition, phytoplankton can be affected by the sides of the incubation container. By including in situ methods, bottle effects are removed and integration times are lengthened. In situ methods have their own set of disadvantages; uncertainty is introduced with the gas exchange rate and if surface water mixes with deeper water. However, comparing methods is complicated since each measures a different fraction of production (e.g net community, net primary, gross production). We present simultaneous in situ (O₂/Ar, triple oxygen isotope), in vitro (¹³C, ¹⁵NO₃, ¹⁵NH₄, and ¹⁸O incubations) and satellite measurements of primary production from the subarctic northeast Pacific Ocean, Labrador Sea, Baffin Bay, and Canadian Arctic Archipelago. By comparing net community production (NCP; O₂/Ar) to gross production (¹⁸O incubation or triple oxygen isotope), we estimate ecosystem efficiency. Some methods have multiple ways the rates could be calculated, but by comparing methods it could be possible to select the best options. Our goal is to identify conditions where the methods have consistent differences so measurements can be converted between methods and so ecosystem efficiency can be determined. By finding a way of converting to a more relevant export term (NCP), a wealth of ¹⁴C and ¹³C data exists that could be used to determine historic, current and future export rates.