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Effects of increased CO2 and temperature on the growth and photosynthesis in the marine macroalga Gracilaria lemaneiformis from the coastal waters of South China

Liu, Lu, Zou, Dinghui, Jiang, Heng, Chen, Binbin, Zeng, Xiaopeng
Journal of applied phycology 2018 v.30 no.2 pp. 1271-1280
Gracilaria, acute exposure, carbon dioxide, carbon dioxide enrichment, carbon sequestration, carotenoids, chlorophyll, climate change, coastal water, macroalgae, photosynthesis, phycobiliprotein, seaweed culture, temperature, China
The marine red macroalga Gracilaria lemaneiformis (Gracilariales, Rhodophyta) is one of the most important species for seaweed cultivation along the coastal waters of South China. In this study, G. lemaneiformis was incubated under present-day (390 ppm) or predicted-year CO₂ levels (700 ppm), and under normal (20 °C) versus elevated temperatures (24 °C), to investigate possible effects of climate change conditions on the growth and photosynthesis. The chlorophyll a (Chl a), carotenoid (Car), and phycobiliprotein (PB) contents responded significantly to increased temperature under normal CO₂ and high CO₂ concentrations. However, CO₂ enrichment in the culture had no significant impact on Chl a and Car but decreased the PB contents in G. lemaneiformis. The growth rates of G. lemaneiformis were significantly improved by increasing temperature, especially under concurrent increasing CO₂ levels. Additionally, short-term exposure to high temperature stimulated the irradiance-saturated maximum photosynthetic rate (P ₘₐₓ), and this stimulation was preserved with exposure to the high temperature in long-term incubations, with such stimulation being much more pronounced under normal CO₂ concentrations than high CO₂ concentrations. Results suggest that increased temperature exerted more pronounced effects on the growth and photosynthesis of G. lemaneiformis than increased CO₂ concentrations did. We proposed that the sea cultivation of G. lemaneiformis would benefit from the ongoing climate change (increasing atmospheric CO₂ concentrations and sea surface temperatures) through enhanced growth and carbon sequestration.