Effects of varying growth irradiance and nitrogen sources on calcification and physiological performance of the coccolithophore Gephyrocapsa oceanica grown under nitrogen limitation. (29th July 2016)

• Record Type: Journal Article
• Authors: Tong, Shanying; Hutchins, David A.; Fu, Feixue; Gao, Kunshan
• Is Part Of: Limnology and oceanography. Volume 61:Number 6(2016)
• Page Start: 2234
• Page End: 2242
• Publication Date: 2016-07-29
• Subjects: Limnology -- Periodicals; Oceanography -- Periodicals; Océanographie; Limnologie; Limnology; Oceanography; Computer network resources; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); Periodicals; 551.4805
• DOI: 10.1002/lno.10371
• Languages: English
• ISSNs: 0024-3590

Abstract

Abstract: Gephyrocapsa oceanica is a widespread species of coccolithophore that has a significant impact on the global carbon cycle through photosynthesis and calcium carbonate precipitation. We investigated combined effects of light (50 μ mol m −2 s −1, 190 μ mol m −2 s −1, and 400 μ mol m −2 s −1 ) and the nitrogen sources N O 3 − and N H 4 + on its physiological performance under nitrogen‐limited conditions. The specific growth rate was highest at the mid‐range light level of 190 μ mol m −2 s −1, where it was further accelerated by N H 4 + relative to N O 3 − . There were no significant growth rate differences between N O 3 − ‐ and N H 4 + ‐grown cells at the two light levels either above or below this optimum irradiance. Cellular particulate organic carbon (POC) and nitrogen (PON) content were not significantly affected by different light intensities and nitrogen sources. However, both the cellular particulate inorganic carbon (PIC) content and the PIC to POC ratio were greatly decreased by increased light levels, and were further decreased by N H 4 + only at the highest light level. Non‐photochemical quenching (NPQ) increased with increasing light intensity, and was higher in N O 3 − rather than in N H 4 + ‐grown cells at medium and high light intensities. Our results demonstrate that under low, relatively realistic oceanic nitrogen concentrations, increasing light intensity and the replacement of N O 3 − by N H 4 + would have a significant negative effect on the calcification of the coccolithophore G. oceanica . If these findings are also applicable to other coccolithophore species, the future ocean carbon cycle may be greatly affected.