Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 7 2 2010 10.5194/bg-7-695-2010 http://www.biogeosciences.net/7/695/2010/ http://www.biogeosciences.net/7/695/2010/bg-7-695-2010.html http://www.biogeosciences.net/7/695/2010/bg-7-695-2010.pdf 695 710 2010-02-19 Sargasso Sea phosphorus biogeochemistry: an important role for dissolved organic phosphorus (DOP) M. W. Lomas michael.lomas@bios.edu A. L. Burke D. A. Lomas D. W. Bell C. Shen S. T. Dyhrman J. W. Ammerman Bermuda Institute of Ocean Sciences, St. George's GE01, Bermuda Princeton University, Princeton Environmental Institute, Princeton, New Jersey, 08544, USA Woods Hole Oceanographic Institution, Biology Department, Woods Hole, Massachusetts, 02543, USA School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA current address: University of Rhode Island, Graduate School of Oceanography, Narragansett, RI 02882, USA Inorganic phosphorus (SRP) concentrations in the subtropical North Atlantic are some of the lowest in the global ocean and have been hypothesized to constrain primary production. Based upon data from several transect cruises in this region, it has been hypothesized that dissolved organic phosphorus (DOP) supports a significant fraction of primary production in the subtropical North Atlantic. In this study, a time-series of phosphorus biogeochemistry is presented for the Bermuda Atlantic Time-series Study site, including rates of phosphorus export. Most parameters have a seasonal pattern, although year-over-year variability in the seasonal pattern is substantial, likely due to differences in external forcing. Suspended particulate phosphorus exhibits a seasonal maximum during the spring bloom, despite the absence of a seasonal peak in SRP. However, DOP concentrations are at an annual maximum prior to the winter/spring bloom and decline over the course of the spring bloom while whole community alkaline phosphatase activities are highest. As a result of DOP bioavailability, the growth of particles during the spring bloom occurs in Redfield proportions, though particles exported from the euphotic zone show rapid and significant remineralization of phosphorus within the first 50 m below the euphotic zone. 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