Downing, J. A.. Iowa State University, 515-294-7874
Osenberg, C. A.. University of Florida, osenberg@zoo.ufl.edu
Sarnelle, O. Michigan State University, sarnelle@lifesci.lscf.ucsb.edu

 
MARINE PHYTOPLANKTON GROWTH LIMITATION VARIES WITH N:P STOICHIOMETRY: A META-ANALYSIS OF NUTRIENT ENRICHMENT EXPERIMENTS
 
N:P stoichiometry of marine ecosystems suggests that nitrogen should be most prevalent in coastal regions or in areas polluted by low N:P freshwater inputs, while limitation by P, Si or Fe should be strongest in unpolluted, open oceans. Marine nutrient bioassay experiments implicated nitrogen, phosphorus, silica, iron etc. as factors limiting phytoplankton growth. We quantified limitation across a large number of studies as the per-unit growth rate of phytoplankton directly attributable to addition of specific nutrients and made meta-analytic comparisons. When data were restricted to reliable time ranges (2-7 day duration), meta-analysis indicated that phosphorus enrichment usually had little impact on phytoplankton growth, while enrichments of nitrogen and iron increased phytoplankton growth by 0.1 to 0.3/day. However, nutrient limitation due to N, P and Fe varied significantly among sites. As expected from stoichiometric patterns, nitrogen limitation was greatest in nearshore, nutrient-polluted, and temperate environments, while phosphorus and iron limitation were strongest in open ocean, unpolluted, and tropical ecosystems, or those receiving pollutants with high N:P ratios. Because phosphorus enrichment studies have been most often performed in relatively polluted coastal waters, its possible role in limiting primary production in unpolluted oceanic systems may have been underestimated.
 
Day: Tuesday, Feb. 2
Time: 02:30 - 02:45pm
Location: Sweeney Center
 
Code: SS49TU0230S