The imbalance of new and export production in the western Antarctic Peninsula, a potentially leaky ecosystem

To quantify the balance between new production and vertical nitrogen export of sinking particles, we measured nitrate uptake, net nitrate drawdown, O-2/Ar-based net community production, sediment trap flux, and Th-234 export at a coastal site near Palmer Station, Antarctica, during the phytoplankton growing season from October 2012 to March 2013. We also measured nitrate uptake and Th-234 export throughout the northern western Antarctic Peninsula (WAP) region on a cruise in January 2013. We used a nonsteady state Th-234 equation with temporally varying upwelling rates and an irradiance-based phytoplankton production model to correct our export and new production estimates in the complex coastal site near Palmer Station. Results unequivocally showed that nitrate uptake and net community production were significantly greater than the sinking particle export on region-wide spatial scales and season-long temporal scales. At our coastal site, new production (10517.4mgNm(-2)d(-1), meanstandard error) was 5.3 times greater than vertical nitrogen export (20.42.4mgNm(-2)d(-1)). On the January cruise in the northern WAP, new production (47.914.4mgNm(-2)d(-1)) was 2.4 times greater than export (19.9 +/- 1.4mgNm(-2)d(-1)). Much of this imbalance can be attributed to diffusive losses of particulate nitrogen from the surface ocean due to diapycnal mixing, indicative of a leaky WAP ecosystem. If these diffusive losses are common in other systems where new production exceeds export, it may be necessary to revise current estimates of the ocean's biological pump.