Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation
<p>Marine phytoplankton such as bloom-forming, calcite-producing coccolithophores, are naturally exposed to solar ultraviolet radiation (UVR, 280–400 nm) in the ocean's upper mixed layers. Nevertheless, the effects of increasing carbon dioxide (<span class="inline-formu...
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doaj-fbac148fa96d4db2bb58374ec9c623a12020-11-25T00:41:53ZengCopernicus PublicationsBiogeosciences1726-41701726-41892019-01-011656157210.5194/bg-16-561-2019Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiationS. Tong0S. Tong1D. A. Hutchins2K. Gao3State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, ChinaCollege of Life Science, Ludong University, Yantai, ChinaDepartment of Biological Sciences, University of Southern California, Los Angeles, California, USAState Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China<p>Marine phytoplankton such as bloom-forming, calcite-producing coccolithophores, are naturally exposed to solar ultraviolet radiation (UVR, 280–400 nm) in the ocean's upper mixed layers. Nevertheless, the effects of increasing carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>)-induced ocean acidification and warming have rarely been investigated in the presence of UVR. We examined calcification and photosynthetic carbon fixation performance in the most cosmopolitan coccolithophorid, <i>Emiliania huxleyi</i>, grown under high (1000 <span class="inline-formula">µ</span>atm, HC; pH<span class="inline-formula"><sub>T</sub></span>: 7.70) and low (400 <span class="inline-formula">µ</span>atm, LC; pH<span class="inline-formula"><sub>T</sub></span>: 8.02) <span class="inline-formula">CO<sub>2</sub></span> levels, at 15 <span class="inline-formula"><sup>∘</sup></span>C, 20 <span class="inline-formula"><sup>∘</sup></span>C and 24 <span class="inline-formula"><sup>∘</sup></span>C with or without UVR. The HC treatment did not affect photosynthetic carbon fixation at 15 <span class="inline-formula"><sup>∘</sup></span>C, but significantly enhanced it with increasing temperature. Exposure to UVR inhibited photosynthesis, with higher inhibition by UVA (320–395 nm) than UVB (295–320 nm), except in the HC and 24 <span class="inline-formula"><sup>∘</sup></span>C-grown cells, in which UVB caused more inhibition than UVA. A reduced thickness of the coccolith layer in the HC-grown cells appeared to be responsible for the UV-induced inhibition, and an increased repair rate of UVA-derived damage in the HC–high-temperature grown cells could be responsible for lowered UVA-induced inhibition. While calcification was reduced with elevated <span class="inline-formula">CO<sub>2</sub></span> concentration, exposure to UVB or UVA affected the process differentially, with the former inhibiting it and the latter enhancing it. UVA-induced stimulation of calcification was higher in the HC-grown cells at 15 and 20 <span class="inline-formula"><sup>∘</sup></span>C, whereas at 24 <span class="inline-formula"><sup>∘</sup></span>C observed enhancement was not significant. The calcification to photosynthesis ratio (Cal <span class="inline-formula">∕</span> Pho ratio) was lower in the HC treatment, and increasing temperature also lowered the value. However, at 20 and 24 <span class="inline-formula"><sup>∘</sup></span>C, exposure to UVR significantly increased the Cal <span class="inline-formula">∕</span> Pho ratio, especially in HC-grown cells, by up to 100 %. This implies that UVR can counteract the negative effects of the “greenhouse” treatment on the Cal <span class="inline-formula">∕</span> Pho ratio; hence, UVR may be a key stressor when considering the impacts of future greenhouse conditions on <i>E. huxleyi</i>.</p>https://www.biogeosciences.net/16/561/2019/bg-16-561-2019.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
S. Tong S. Tong D. A. Hutchins K. Gao |
spellingShingle |
S. Tong S. Tong D. A. Hutchins K. Gao Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation Biogeosciences |
author_facet |
S. Tong S. Tong D. A. Hutchins K. Gao |
author_sort |
S. Tong |
title |
Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation |
title_short |
Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation |
title_full |
Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation |
title_fullStr |
Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation |
title_full_unstemmed |
Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation |
title_sort |
physiological and biochemical responses of <i>emiliania huxleyi</i> to ocean acidification and warming are modulated by uv radiation |
publisher |
Copernicus Publications |
series |
Biogeosciences |
issn |
1726-4170 1726-4189 |
publishDate |
2019-01-01 |
description |
<p>Marine phytoplankton such as bloom-forming, calcite-producing
coccolithophores, are naturally exposed to solar ultraviolet radiation (UVR,
280–400 nm) in the ocean's upper mixed layers. Nevertheless, the effects of
increasing carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>)-induced ocean acidification and warming have rarely
been investigated in the presence of UVR. We examined calcification and
photosynthetic carbon fixation performance in the most cosmopolitan
coccolithophorid, <i>Emiliania huxleyi</i>, grown under high
(1000 <span class="inline-formula">µ</span>atm, HC; pH<span class="inline-formula"><sub>T</sub></span>: 7.70) and low (400 <span class="inline-formula">µ</span>atm,
LC; pH<span class="inline-formula"><sub>T</sub></span>: 8.02) <span class="inline-formula">CO<sub>2</sub></span> levels, at 15 <span class="inline-formula"><sup>∘</sup></span>C,
20 <span class="inline-formula"><sup>∘</sup></span>C and 24 <span class="inline-formula"><sup>∘</sup></span>C with or without UVR. The HC
treatment did not affect photosynthetic carbon fixation at 15 <span class="inline-formula"><sup>∘</sup></span>C,
but significantly enhanced it with increasing temperature. Exposure to UVR
inhibited photosynthesis, with higher inhibition by UVA (320–395 nm) than
UVB (295–320 nm), except in the HC and 24 <span class="inline-formula"><sup>∘</sup></span>C-grown cells, in which
UVB caused more inhibition than UVA. A reduced thickness of the coccolith layer
in the HC-grown cells appeared to be responsible for the UV-induced
inhibition, and an increased repair rate of UVA-derived damage in the
HC–high-temperature grown cells could be responsible for lowered UVA-induced inhibition.
While calcification was reduced with elevated <span class="inline-formula">CO<sub>2</sub></span> concentration,
exposure to UVB or UVA affected the process differentially, with the former
inhibiting it and the latter enhancing it. UVA-induced stimulation of calcification was
higher in the HC-grown cells at 15 and 20 <span class="inline-formula"><sup>∘</sup></span>C, whereas at
24 <span class="inline-formula"><sup>∘</sup></span>C observed enhancement was not significant. The calcification
to photosynthesis ratio (Cal <span class="inline-formula">∕</span> Pho ratio) was lower in the HC treatment,
and increasing temperature also lowered the value. However, at 20 and
24 <span class="inline-formula"><sup>∘</sup></span>C, exposure to UVR significantly increased the Cal <span class="inline-formula">∕</span> Pho
ratio, especially in HC-grown cells, by up to 100 %. This implies that
UVR can counteract the negative effects of the “greenhouse” treatment on
the Cal <span class="inline-formula">∕</span> Pho ratio; hence, UVR may be a key stressor when considering the
impacts of future greenhouse conditions on <i>E. huxleyi</i>.</p> |
url |
https://www.biogeosciences.net/16/561/2019/bg-16-561-2019.pdf |
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