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Day length as a key factor moderating the response of coccolithophore growth to elevated pCO 2

Day length as a key factor moderating the response of coccolithophore growth to elevated pCO 2
Day length as a key factor moderating the response of coccolithophore growth to elevated pCO 2

The fate of coccolithophores in the future oceans remains uncertain, in part due to key factors having not been standardized across experiments. A potentially moderating role for differences in day length (photoperiod) remains largely unexplored. We therefore cultured four different geographical isolates of the species Emiliania huxleyi, as well as two additional species, Gephyrocapsa oceanica (tropical) and Coccolithus braarudii (temperate), to test for interactive effects of pCO 2 with the light : dark (L : D) cycle. We confirmed a general regulatory effect of photoperiod on the pCO 2 response, whereby growth and particulate inorganic carbon and particulate organic carbon (PIC : POC) ratios were reduced with elevated pCO 2 under 14 : 10 h L : D, but these reductions were dampened under continuous (24 h) light. The dynamics underpinning this pattern generally differed for the temperate vs. tropical isolates. Reductions in PIC : POC with elevated pCO 2 for tropical taxa were largely through reduced calcification and enhanced photosynthesis under 14 : 10 h L : D, with differences dampened under continuous light. In contrast, reduced PIC : POC for temperate strains reflected increases of photosynthesis that outpaced increases in calcification rates under 14 : 10 h L : D, with both responses again dampened under continuous light. A multivariate analysis of 35 past studies of E. huxleyi further demonstrated that differences in photoperiod account for as much as 40% (strain B11/92) to 55% (strain NZEH) of the variance in reported pCO 2 -induced reductions to growth but not PIC : POC. Our study thus highlights a critical role for day length in moderating the effect of ocean acidification on coccolithophore growth and consequently how this response may play out across latitudes and seasons in future oceans.

0024-3590
1284-1296
Bretherton, Laura
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Poulton, Alex J.
14bf64a7-d617-4913-b882-e8495543e717
Lawson, Tracy
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Rukminasari, Nita
4485fbdf-2e96-4015-8948-eec08ff35165
Balestreri, Cecilia
f8a1457c-3cae-40aa-b29b-9b900937dc6b
Schroeder, Declan
c3e25db4-5af2-4792-8eda-bd3c94ad03ba
Moore, C. Mark
7ec80b7b-bedc-4dd5-8924-0f5d01927b12
Suggett, David J.
9100a791-1264-40e4-9403-8491190c3430
Bretherton, Laura
55484deb-d72d-4605-aa1b-d899e3197933
Poulton, Alex J.
14bf64a7-d617-4913-b882-e8495543e717
Lawson, Tracy
6b62f544-1615-4620-b2f2-a3ce846495b7
Rukminasari, Nita
4485fbdf-2e96-4015-8948-eec08ff35165
Balestreri, Cecilia
f8a1457c-3cae-40aa-b29b-9b900937dc6b
Schroeder, Declan
c3e25db4-5af2-4792-8eda-bd3c94ad03ba
Moore, C. Mark
7ec80b7b-bedc-4dd5-8924-0f5d01927b12
Suggett, David J.
9100a791-1264-40e4-9403-8491190c3430

Bretherton, Laura, Poulton, Alex J., Lawson, Tracy, Rukminasari, Nita, Balestreri, Cecilia, Schroeder, Declan, Moore, C. Mark and Suggett, David J. (2019) Day length as a key factor moderating the response of coccolithophore growth to elevated pCO 2. Limnology and Oceanography, 64 (3), 1284-1296. (doi:10.1002/lno.11115).

Record type: Article

Abstract

The fate of coccolithophores in the future oceans remains uncertain, in part due to key factors having not been standardized across experiments. A potentially moderating role for differences in day length (photoperiod) remains largely unexplored. We therefore cultured four different geographical isolates of the species Emiliania huxleyi, as well as two additional species, Gephyrocapsa oceanica (tropical) and Coccolithus braarudii (temperate), to test for interactive effects of pCO 2 with the light : dark (L : D) cycle. We confirmed a general regulatory effect of photoperiod on the pCO 2 response, whereby growth and particulate inorganic carbon and particulate organic carbon (PIC : POC) ratios were reduced with elevated pCO 2 under 14 : 10 h L : D, but these reductions were dampened under continuous (24 h) light. The dynamics underpinning this pattern generally differed for the temperate vs. tropical isolates. Reductions in PIC : POC with elevated pCO 2 for tropical taxa were largely through reduced calcification and enhanced photosynthesis under 14 : 10 h L : D, with differences dampened under continuous light. In contrast, reduced PIC : POC for temperate strains reflected increases of photosynthesis that outpaced increases in calcification rates under 14 : 10 h L : D, with both responses again dampened under continuous light. A multivariate analysis of 35 past studies of E. huxleyi further demonstrated that differences in photoperiod account for as much as 40% (strain B11/92) to 55% (strain NZEH) of the variance in reported pCO 2 -induced reductions to growth but not PIC : POC. Our study thus highlights a critical role for day length in moderating the effect of ocean acidification on coccolithophore growth and consequently how this response may play out across latitudes and seasons in future oceans.

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Accepted/In Press date: 11 December 2018
e-pub ahead of print date: 15 January 2019
Published date: 1 May 2019

Identifiers

Local EPrints ID: 431442
URI: http://eprints.soton.ac.uk/id/eprint/431442
ISSN: 0024-3590
PURE UUID: 0ed83ead-c6c4-401e-a20c-d2aa5d33b967
ORCID for C. Mark Moore: ORCID iD orcid.org/0000-0002-9541-6046

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Date deposited: 03 Jun 2019 16:30
Last modified: 26 Nov 2021 02:42

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Contributors

Author: Laura Bretherton
Author: Alex J. Poulton
Author: Tracy Lawson
Author: Nita Rukminasari
Author: Cecilia Balestreri
Author: Declan Schroeder
Author: C. Mark Moore ORCID iD
Author: David J. Suggett

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