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SHORT‐ AND LONG‐TERM EFFECTS OF ELEVATED CO 2 ON PHOTOSYNTHESIS AND RESPIRATION IN THE MARINE MACROALGA HIZIKIA FUSIFORMIS (SARGASSACEAE, PHAEOPHYTA) GROWN AT LOW AND HIGH N SUPPLIES 1
Author(s) -
Zou Dinghui,
Gao Kunshan,
Luo Hanjin
Publication year - 2011
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2010.00929.x
Subject(s) - photosynthesis , respiration , algae , biology , botany , zoology , respiration rate , eutrophication , carbon dioxide , environmental chemistry , ecology , nutrient , chemistry
The short‐term and long‐term effects of elevated CO 2 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 ) CO 2 concentrations and at low and high N availability. Short‐term exposure to CO 2 enrichment stimulated photosynthesis, and this stimulation was maintained with prolonged growth at elevated CO 2 , regardless of the N levels in culture, indicating no down‐regulation of photosynthesis with prolonged growth at elevated CO 2 . However, the photosynthetic rate of low‐N‐grown H. fusiformis was more responsive to CO 2 enrichment than that of high‐N‐grown algae. Elevation of CO 2 concentration increased the value of K 1/2 (Ci) (the half‐saturation constant) for photosynthesis, whereas high N supply lowered it. Neither short‐term nor long‐term CO 2 enrichment had inhibitory effects on respiration rate, irrespective of the N supply, under which the algae were grown. Under high‐N growth, the Q 10 value of respiration was higher in the elevated‐CO 2 ‐grown algae than the ambient‐CO 2 ‐grown algae. Either short‐ or long‐term exposure to CO 2 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 CO 2 concentration and simultaneous coastal eutrophication, the respiratory carbon flux would be more sensitive to changing temperature.