Latitudinal variability in phosphate uptake in the Central Atlantic

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 194:283-294 (2000) - doi:10.3354/meps194283 Latitudinal variability in phosphate uptake in the Central Atlantic Mireia Cañellas*, Susana Agustí, Carlos M. Duarte** Instituto Mediterráneo de Estudios Avanzados (IMEDEA), CSIC-Universitat de Illes Balears, c/Miquel Marquès 21, 07190 Esporles (Illes Balears), Spain *Present address: Regidoria de Medi Ambient i Sostenibilitat, Ajuntament de Sabadell, C. del Sol 1-1, 08201 Sabadell, Spain **Corresponding author. E-mail: ieacdq@clust.uib.es ABSTRACT: The role of P in regulating planktonic production in Atlantic waters was assessed by the examination of the phosphate turnover time and uptake rate along a latitudinal transect across the Central Atlantic Ocean (27°N to 36°S). Phosphate uptake rates and the affinity for phosphate were higher for small (<0.8 µm) organisms, compared with those >0.8 µm. Phosphate uptake rates were relatively low, resulting in long phosphate turnover times (days), except in the surface waters south of 25°S, which were also characterized by the highest uptake rates and affinity for phosphate, and the smallest total P pools observed along the transect. The organisms were found to realize their maximal phosphate uptake rates at ambient phosphate concentrations, suggesting the adequacy of the P supply to support the requirements of organisms. These findings suggest that inorganic P was not limiting community production in most of the Central Atlantic, except for the area south of 25°S, where P uptake could possibly be limited by P supply. The long turnover times generally observed in the Central Atlantic Ocean are in agreement with previous observations in oceanic systems elsewhere, suggesting that the observation that P is unlikely to be a limiting resource for planktonic growth can be extrapolated to most of the open ocean. The combined rate of P excretion from planktonic organisms and their microbial grazers as dissolved organic phosphorus (DOP) represented 75% of the total phosphate uptake. This DOP does not reach a sufficient accumulation as to drive an important downward flux of DOP, which represents a loss of only 9% of the P inputs into the biogenic layer. Hence, the high P uptake rate of the planktonic community in the Central Atlantic provides P in excess to support primary production, leading to a release as DOP, which appears to be rapidly recycled in the biogenic layer, thereby maintaining an adequate P supply to fuel primary production. KEY WORDS: Phosphate · Uptake · Atlantic · Excretion · Turnover · Picoplankton · Microplankton Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 194. Publication date: March 17, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.