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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 11 | Copyright
Biogeosciences, 15, 3409-3420, 2018
https://doi.org/10.5194/bg-15-3409-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 11 Jun 2018

Research article | 11 Jun 2018

Ocean acidification and nutrient limitation synergistically reduce growth and photosynthetic performances of a green tide alga Ulva linza

Guang Gao1,2,3, John Beardall4, Menglin Bao1, Can Wang1, Wangwang Ren2, and Juntian Xu1,2 Guang Gao et al.
  • 1Jiangsu Key Laboratory of Marine Bioresources and Environment, Huaihai Institute of Technology, Lianyungang, 222005, China
  • 2Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Lianyungang 222005, China
  • 3State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China
  • 4School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia

Abstract. Large-scale green tides have been invading the coastal zones of the western Yellow Sea annually since 2008. Meanwhile, oceans are becoming more acidic due to continuous absorption of anthropogenic carbon dioxide, and intensive seaweed cultivation in Chinese coastal areas is leading to severe regional nutrient limitation. However, little is known about the combined effects of global and local stressors on the eco-physiology of bloom-forming algae. We cultured Ulva linza for 9–16 days under two levels of pCO2 (400 and 1000µatm) and four treatments of nutrients (nutrient repletion, N limitation, P limitation, and N–P limitation) to investigate the physiological responses of this green tide alga to the combination of ocean acidification and nutrient limitation. For both sporelings and adult plants, elevated pCO2 did not affect the growth rate when cultured under nutrient-replete conditions but reduced it under P limitation; N or P limitations by themselves reduced growth rate. P limitation resulted in a larger inhibition in growth for sporelings compared to adult plants. Sporelings under P limitation did not reach the mature stage after 16 days of culture while those under P repletion became mature by day 11. Elevated pCO2 reduced net photosynthetic rate for all nutrient treatments but increased nitrate reductase activity and soluble protein content under P-replete conditions. N or P limitation reduced nitrate reductase activity and soluble protein content. These findings indicate that ocean acidification and nutrient limitation would synergistically reduce the growth of Ulva species and may thus hinder the occurrence of green tides in a future ocean environment.

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We investigated the physiological responses of a green tide alga to the combination of ocean acidification and nutrient limitation. Elevated pCO2 did not affect the growth rate when cultured under nutrient replete conditions but reduced it under P limitation. P limitation resulted in a larger inhibition in growth for sporelings compared to adult plants. These findings indicate that ocean acidification and nutrient limitation may hinder the occurrence of green tides in future ocean environment.
We investigated the physiological responses of a green tide alga to the combination of ocean...
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