2008, by the American Society of Limnology and Oceanography, Inc. Relative influence of nitrogen and phosphorus availability on phytoplankton physiology and productivity in the oligotrophic sub-tropical North Atlantic Ocean

• Main Authors: C. Mark Moore, Matthew M. Mills, Rebecca Langlois, Angela Milne, Eric P. Achterberg, Julie La Roche, Richard J. Geider
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.227.6731; http://www.aslo.org/lo/toc/vol_53/issue_1/0291.pdf

Nutrient addition bioassay experiments were performed in the low-nutrient, low-chlorophyll oligotrophic subtropical North Atlantic Ocean to investigate the influence of nitrogen (N), phosphorus (P), and/or iron (Fe) on phytoplankton physiology and the limitation of primary productivity or picophytoplankton biomass. Additions of N alone resulted in 1.5–2 fold increases in primary productivity and chlorophyll after 48 h, with larger (,threefold) increases observed for the addition of P in combination with N (NP). Measurements of cellular chlorophyll contents permitted evaluation of the physiological response of the photosynthetic apparatus to N and P additions in three picophytoplankton groups. In both Prochlorococcus and the picoeukaryotes, cellular chlorophyll increased by similar amounts in N and NP treatments relative to all other treatments, suggesting that pigment synthesis was N limited. In contrast, the increase of cellular chlorophyll was greater in NP than in N treatments in Synechococcus,suggestiveof NP co-limitation. Relative increases in cellular nucleic acid were also only observed in Synechococcus for NP treatments, indicating co-limitation of net nucleic acid synthesis. A lack of response to relief of nutrient stress for the