title: SHORT- AND LONG-TERM EFFECTS OF ELEVATED CO2 ON PHOTOSYNTHESIS AND RESPIRATION IN THE MARINE MACROALGA HIZIKIA FUSIFORMIS (SARGASSACEAE, PHAEOPHYTA) GROWN AT LOW AND HIGH N SUPPLIES(1).
abstract: The short-term and long-term effects of elevated CO2 on photosynthesis and respiration were examined in cultures of the marine brown macroalga Hizikia fusiformis (Harv.) Okamura grown under ambient (375 μL · L(-1) ) and elevated (700 μL · L(-1) ) CO2 concentrations and at low and high N availability. Short-term exposure to CO2 enrichment stimulated photosynthesis, and this stimulation was maintained with prolonged growth at elevated CO2 , regardless of the N levels in culture, indicating no down-regulation of photosynthesis with prolonged growth at elevated CO2 . However, the photosynthetic rate of low-N-grown H. fusiformis was more responsive to CO2 enrichment than that of high-N-grown algae. Elevation of CO2 concentration increased the value of K1/2 (Ci) (the half-saturation constant) for photosynthesis, whereas high N supply lowered it. Neither short-term nor long-term CO2 enrichment had inhibitory effects on respiration rate, irrespective of the N supply, under which the algae were grown. Under high-N growth, the Q10 value of respiration was higher in the elevated-CO2 -grown algae than the ambient-CO2 -grown algae. Either short- or long-term exposure to CO2 enrichment decreased respiration as a proportion of gross photosynthesis (Pg) in low-N-grown H. fusiformis. It was proposed that in a future world of higher atmospheric CO2 concentration and simultaneous coastal eutrophication, the respiratory carbon flux would be more sensitive to changing temperature.
authors.affiliation: College of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006, China The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, ChinaState Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian 361005, ChinaCollege of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006, China.
authors.forename: Dinghui
authors.initials: D
authors.lastname: Zou
authors.affiliation: College of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006, China The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, ChinaState Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian 361005, ChinaCollege of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006, China.
authors.forename: Kunshan
authors.initials: K
authors.lastname: Gao
authors.affiliation: College of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006, China The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, ChinaState Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian 361005, ChinaCollege of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006, China.
authors.forename: Hanjin
authors.initials: H
authors.lastname: Luo
keywords: CO2; Hizikia fusiformis; brown algae; marine macroalgae; photosynthesis; respiration