Changes in primary productivity and chlorophyll a in response to iron fertilization in the Southern Polar Frontal Zone

• DOI: 10.4319/lo.2002.47.5.1324
• Publication Date: 2010-06-30T20:24:51Z
• Authors: Frank Gervais; Ulf Riebesell; Maxim Y. Gorbunov
• Keywords: Bloom

EisenEx—the second in situ iron enrichment experiment the Southern Ocean—was performed Atlantic sector over 3 weeks November 2000 with overarching goal to test hypothesis that primary productivity Ocean is limited by availability austral spring. Underwater irradiance, chlorophyll a (Chl a), photochemical efficiency, and were measured inside outside of an iron‐enriched patch order quantify response phytoplankton fertilization. Chl concentration photosynthetic rate (14C uptake simulated incubations) pico‐, nano‐, microphytoplankton. Photochemical efficiency was studied fast repetition fluorometry xenon‐pulse amplitude modulated fluorometry. The high‐nutrient low‐chlorophyll waters Fe‐enriched characterized deep euphotic zones (63–72 m), low (48–56 mg m -2 ), (F v /F ~ 0.3), daily (130–220 C d -1 ). Between 70 90% found pico‐ nanophytoplankton. During induced bloom, F increased up ;0.55, reached maximum values 790 231 , respectively. As consequence, depth decreased ~41 m. Picophytoplankton biomass hardly changed. Nano‐ microphytoplankton increased. In first 2 experiment, when upper mixed layer mostly ≪40 m, highly correlated a. third week, much lower than predicted from a, probably because reduction capacity as consequence physical variability water column. These results provide unequivocal evidence supply central factor controlling Ocean, even if mixing ≫80