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Marine Ecology Progress Series

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MEPS 466:57-67 (2012)  -  DOI:

Carbon dioxide regulation of nitrogen and phosphorus in four species of marine phytoplankton

John R. Reinfelder*

Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901-8551, USA

ABSTRACT: The concentration of carbon dioxide in seawater may affect phytoplankton physiology and ecology and their role in marine biogeochemical cycles. In order to assess the effects of CO2 on the elemental composition of marine phytoplankon, carbon, nitrogen, and phosphorus quotas were measured in 4 species of marine phytoplankton acclimated to 150 to 1500 ppm CO2 (5 to 50 µM) in semi-continuous cultures. Nitrogen quotas declined steeply with increasing CO2 in the centric diatoms Thalassiosira pseudonana and T. weissflogii acclimated to 150 to 380 ppm (5 to 13 µM), but more slowly as the CO2 increased from 380 to 1500 ppm (13 to 50 µM). Nitrogen demand varied little with CO2 in the pennate diatom Phaeodactylum tricornutum, but was positively correlated with CO2 over the range of 150 to 770 ppm in the prymnesiophyte Isochrysis galbana. Based on the nitrogen−CO2 trends in centric diatoms, relief from carbon−nitrogen co-limitation could lead to 2-fold larger cells as CO2 increases from 150 to 380 ppm, but only 15% larger cells from 380 to 770 ppm CO2. Phosphorus quotas in the 3 diatoms decreased as CO2 increased from 150 to 380 ppm. As previously observed in these and other species, C:N, C:P, and N:P ratios increased with increasing CO2, but the present results show that much of this variation was due to differences in nitrogen and phosphorus rather than carbon quotas. Marine phytoplankton could provide a negative feedback against increasing CO2 over the pCO2 range of 150 to 380 ppm by supporting larger cells or higher biomass, but would support a smaller carbon sink as atmospheric CO2 rises above 380 ppm.

KEY WORDS: Nitrogen · Phosphorus · Carbon dioxide · Phytoplankton

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Cite this article as: Reinfelder JR (2012) Carbon dioxide regulation of nitrogen and phosphorus in four species of marine phytoplankton. Mar Ecol Prog Ser 466:57-67.

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