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Marine Ecology Progress Series

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MEPS 589:33-44 (2018)  -  DOI:

Responses of the diatom Asterionellopsis glacialis to increasing sea water CO2 concentrations and turbulence

Francesca Gallo1,*, Kai G. Schulz2, Eduardo B. Azevedo1, João Madruga1, Joana Barcelos e Ramos

1Institute for Agricultural and Environmental Research and Technology of the Azores, University of Azores, Rua do Capitão d’Ávila, Pico da Urze 970-0042 Angra do Heroísmo, Açores, Portugal
2Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia
*Corresponding author:

ABSTRACT: Greenhouse gas emissions, such as carbon dioxide (CO2), lead to enhanced atmospheric and surface ocean temperatures. At the same time, CO2 equilibrates between the atmosphere and the surface ocean, resulting in lower seawater pH. The changes in physical and chemical properties of the ocean potentially affect marine primary producers in various ways. A number of researches have addressed the effects of ocean acidification on marine phytoplankton. However, phytoplankton responses to combined effects are still poorly understood. Here, we chose the cosmopolitan chain-forming diatom Asterionellopsis glacialis to assess the combined effect of ocean acidification and carbonation (~420 to 2800 µatm) and water motion on its physiological rates. At current CO2 levels, we observed an increase in growth rates of A. glacialis accompanied by a prevalence of longer chains (>6 cells) under enhanced water motion. However, at increasing CO2 levels (up to ~2800 µatm) and decreasing pH values, enhanced water motion significantly decreased growth rates, chain length and organic matter production of A. glacialis. Thus, our study suggests that even though A. glacialis benefited from enhanced water motion at present CO2 concentration, at higher CO2 levels, the more unstable environment magnified the stress caused by acidification. If in the future the ocean surface layer will be more frequently exposed to storm and wind events, then phytoplankton communities might be more sensitive to lower pH, with potential consequences for community composition and productivity.

KEY WORDS: Phytoplankton · Climate change · Growth rate · Ocean acidification · CO2 · Water motion

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Cite this article as: Gallo F, Schulz KG, Azevedo EB, Madruga J, Barcelos e Ramos J (2018) Responses of the diatom Asterionellopsis glacialis to increasing sea water CO2 concentrations and turbulence. Mar Ecol Prog Ser 589:33-44.

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