MEPS 567:41-56 (2017)  -  DOI: https://doi.org/10.3354/meps12033

Nitrogen nutritional condition affects the response of energy metabolism in diatoms to elevated carbon dioxide

Haizheng Hong1,2, Dongmei Li1, Wenfang Lin1, Weiying Li1, Dalin Shi1,2,*

1State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian 361102, PR China
2Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Xiamen University, Xiamen, Fujian 361102, PR China
*Corresponding author:

ABSTRACT: Marine phytoplankton are expected to benefit from enhanced carbon dioxide (CO2), attributable largely to down-regulation of the CO2 concentrating mechanism (CCM) which saves energy resources for other cellular processes. However, the nitrogen (N) nutritional condition (N-replete vs. N-limiting) of phytoplankton may affect the responses of their intracellular metabolic processes to elevated CO2. We cultured the model diatoms Thalassiosira pseudonana, Phaeodactylum tricornutum, and Thalassiosira weissflogii at ambient and elevated CO2 levels under N-replete and N-limiting conditions. Key metabolic processes, including light harvesting, C fixation, photorespiration, respiration, and N assimilation, were assessed systematically and then incorporated into an energy budget to compare the effects of CO2 on the metabolic pathways and the consequent changes in photosynthesis and C fixation as a result of energy reallocation under the different N nutritional conditions. Under the N-replete condition, down-regulation of the CCM at high CO2 was the primary contributor to increased photosynthesis rates of the diatoms. Under N-limiting conditions, elevated CO2 significantly affected the photosynthetic photon flux and respiration, in addition to CCM down-regulation and declines in photorespiration, resulting in an increase of the C:N ratio in all 3 diatom species. In T. pseudonana and T. weissflogii, the elevated C:N ratio was driven largely by an increased cellular C quota, whereas in P. tricornutum it resulted primarily from a decreased cellular N quota. The N-limited diatoms therefore could fix more C per unit of N in response to elevated CO2, which could potentially provide a negative feedback to the ongoing increase in atmospheric CO2


KEY WORDS: Ocean acidification · N-limitation · Energy budget · C:N ratio · Diatoms


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Cite this article as: Hong H, Li D, Lin W, Li W, Shi D (2017) Nitrogen nutritional condition affects the response of energy metabolism in diatoms to elevated carbon dioxide. Mar Ecol Prog Ser 567:41-56. https://doi.org/10.3354/meps12033

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