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Zonal differences in phosphorus pools, turnover and deficiency across the tropical North Atlantic Ocean
Author(s) -
Sohm Jill A.,
Capone Douglas G.
Publication year - 2010
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2008gb003414
Subject(s) - trichodesmium , biogeochemical cycle , phosphorus , subtropics , tropical atlantic , oceanography , nutrient , environmental science , phosphorus deficiency , cycling , ecology , geology , biology , nitrogen , chemistry , geography , diazotroph , sea surface temperature , nitrogen fixation , organic chemistry , archaeology
The oceanic phosphorus (P) cycle is often overlooked in biogeochemical studies because it is dominated by geological processes. However, recent reports indicate that some oceanic regimes are P limited; thus an evaluation of the P pools and the biological cycling of P is warranted in these locations. The subtropical and tropical North Atlantic is one area proposed to be P deficient. A cruise across a wide swath of the tropical North Atlantic (∼25–60°W and 0–15°N) allowed us to investigate spatial differences in these parameters, including in waters influenced by the Amazon River plume. The majority of the total P pool was present as dissolved organic phosphorus (DOP, ∼80%), with soluble reactive phosphorus (SRP) and particulate organic phosphorus (POP) comprising much smaller fractions. Concentrations of both SRP and POP were elevated in areas influenced by the Amazon River, while DOP was not. The turnover time of the PO 4 3− pool was more rapid on the western side of the basin (<10 h) and slower to the east (>100 h). Fast turnover times are indicative of P deficiency, and the observed trend suggests an east to west increase in P deficiency in the tropical North Atlantic. The maximal PO 4 3− uptake rate (V max ) of Trichodesmium spp., a well‐studied nitrogen‐fixing cyanobacterium, also indicates higher P deficiency in the western compared to eastern basin. These data support the hypothesis that P could be an important nutrient limiting certain biological processes in the North Atlantic, although it may be spatially (as well as temporally) variable in this basin.