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- Title
Responses of the large centric diatom <italic>Coscinodiscus</italic> sp. to interactions between warming, elevated CO<sub>2</sub>, and nitrate availability.
- Authors
Qu, Pingping; Fu, Feixue; Hutchins, David A.
- Abstract
Abstract: Marine ecosystems are facing multiple anthropogenic global changes, including ocean acidification, warming, and reduced nutrient supplies. Together, these will challenge phytoplankton including large centric diatoms such as <italic>Coscinodiscus</italic> sp., a group that is important to ocean food webs and carbon export. We investigated the interactive effects of warming, elevated CO2, and nitrate availability on <italic>Coscinodiscus</italic> growth, elemental stoichiometry, and Fe and C uptake rates in a four‐treatment factorial experiment combining two CO2 levels (∼400 ppm and 800 ppm) and two temperatures (16°C and 20°C) across seven nitrate concentrations (1–100 <italic>μ</italic>mol L−1). Higher temperatures led to higher maximum growth rates (<italic>μ</italic>max), but also higher half‐saturation constants for nitrate (<italic>K</italic>1/2), while elevated CO2 increased <italic>K</italic>1/2 only at the warmer temperature. Lower <italic>μ</italic>max/<italic>K</italic>1/2 ratios under warming and rising CO2 indicated a higher nitrate requirement at these conditions. High temperature decreased cellular P and Si contents and consequently increased N : P and C : Si ratios, especially at ambient CO2. Fe : C uptake ratios responded positively to lower nitrate levels, lower CO2, and warming. Significant interactions between nitrate availability and temperature or CO2 were observed for specific growth rates, chlorophyll <italic>a</italic> and Si contents, Fe : C, N : P, and Si : C, while temperature and CO2 interactions were only significant for <italic>μ</italic>max/<italic>K</italic>1/2 and cellular P content. The mutual interactions among CO2 concentrations, temperature, and nitrate supply may all affect future growth, physiology, and carbon export by <italic>Coscinodiscus</italic> sp., however, in general warming and nitrate availability appear to be more influential than CO2.
- Subjects
CENTRALES; MARINE ecology; OCEAN acidification; NITRATE content of water; ANTHROPOGENIC effects on nature
- Publication
Limnology & Oceanography, 2018, Vol 63, Issue 3, p1407
- ISSN
0024-3590
- Publication type
Article
- DOI
10.1002/lno.10781