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Effects of varying growth irradiance and nitrogen sources on calcification and physiological performance of the coccolithophore Gephyrocapsa oceanica grown under nitrogen limitation
Author(s) -
Tong Shanying,
Hutchins David A.,
Fu Feixue,
Gao Kunshan
Publication year - 2016
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.10371
Subject(s) - coccolithophore , nitrogen , photosynthesis , light intensity , carbon fibers , chemistry , irradiance , environmental chemistry , total inorganic carbon , emiliania huxleyi , botany , phytoplankton , carbon dioxide , biology , ecology , nutrient , materials science , physics , organic chemistry , optics , quantum mechanics , composite number , composite material
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 sourcesN O 3 −andN 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 byN H 4 +relative toN O 3 −. There were no significant growth rate differences betweenN O 3 −‐ andN 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 byN H 4 +only at the highest light level. Non‐photochemical quenching (NPQ) increased with increasing light intensity, and was higher inN O 3 −rather than inN 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 ofN O 3 −byN 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.