Diurnal photosynthetic response of the motile symbiotic benthic foraminiferan marginopora vertebralis

Sinutok, S; Hill, R; Doblin, MA; Ralph, PJ

Diurnal photosynthetic response of the motile symbiotic benthic foraminiferan marginopora vertebralis

Sinutok, S Hill, R

Doblin, MA

Ralph, PJ

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Publication Type:: Journal Article
Citation:: Marine Ecology Progress Series, 2013, 478 pp. 127 - 138
Issue Date:: 2013-03-25

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Field	Value	Language
dc.contributor.author	Sinutok, S	en_US
dc.contributor.author	Hill, R https://orcid.org/0000-0002-4623-1563	en_US
dc.contributor.author	Doblin, MA https://orcid.org/0000-0001-8750-3433	en_US
dc.contributor.author	Ralph, PJ https://orcid.org/0000-0002-3103-7346	en_US
dc.date.issued	2013-03-25	en_US
dc.identifier.citation	Marine Ecology Progress Series, 2013, 478 pp. 127 - 138	en_US
dc.identifier.issn	0171-8630	en_US
dc.identifier.uri	http://hdl.handle.net/10453/26285
dc.description.abstract	Movement of the symbiont-bearing foraminiferan Marginopora vertebralis and photo physiological response to diurnal fluctuations in irradiance were investigated in field and laboratory experiments. The abundance of M. vertebralis from both light-exposed and sheltered habitats was determined 5 times during the day, from pre-dawn to post-dusk. M. vertebralis abundance was significantly higher in sheltered compared to exposed habitats at midday under high irradiance, and this movement enabled the algal symbionts to avoid excessive photoinhibition. The diurnal changes in photosynthetic efficiency were not consistent with the typical midday solar maximum downregulation of photosystem II observed in other photoautotrophs and was likely due to the negatively phototactic capacity of the foraminifera. To confirm the light-dependent movement of foraminifera, individuals in exposed and sheltered habitats were exposed to the photosynthetic inhibitor 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) in the laboratory. The lack of movement in DCMU-exposed specimens confirmed light-dependent movement and subsequent disruption of signalling between the host foraminiferan and the algal symbionts. Analysis of chlorophyll and xanthophyll pigments, as well as symbiont density, indicated that under high irradiance, foraminiferal symbionts have the capacity to reduce light stress by activating photoprotective mechanisms. The negatively phototactic behaviour prevented chlorophyll degradation, symbiont loss and bleaching, suggesting that it is the primary mechanism for controlling light exposure in these foraminifera. This behaviour provides a competitive advantage over other sessile organisms in avoiding photoinhibition and bleaching by moving away from over-saturating irradiance, towards less damaging light fields. © Inter-Research 2013.	en_US
dc.relation.ispartof	Marine Ecology Progress Series	en_US
dc.relation.isbasedon	10.3354/meps10187	en_US
dc.subject.classification	Marine Biology & Hydrobiology	en_US
dc.title	Diurnal photosynthetic response of the motile symbiotic benthic foraminiferan marginopora vertebralis	en_US
dc.type	Journal Article
utslib.citation.volume	478	en_US
utslib.for	0602 Ecology	en_US
utslib.for	0405 Oceanography	en_US
utslib.for	0608 Zoology	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
utslib.copyright.status	closed_access
pubs.publication-status	Published	en_US
pubs.volume	478	en_US

Abstract:

Movement of the symbiont-bearing foraminiferan Marginopora vertebralis and photo physiological response to diurnal fluctuations in irradiance were investigated in field and laboratory experiments. The abundance of M. vertebralis from both light-exposed and sheltered habitats was determined 5 times during the day, from pre-dawn to post-dusk. M. vertebralis abundance was significantly higher in sheltered compared to exposed habitats at midday under high irradiance, and this movement enabled the algal symbionts to avoid excessive photoinhibition. The diurnal changes in photosynthetic efficiency were not consistent with the typical midday solar maximum downregulation of photosystem II observed in other photoautotrophs and was likely due to the negatively phototactic capacity of the foraminifera. To confirm the light-dependent movement of foraminifera, individuals in exposed and sheltered habitats were exposed to the photosynthetic inhibitor 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) in the laboratory. The lack of movement in DCMU-exposed specimens confirmed light-dependent movement and subsequent disruption of signalling between the host foraminiferan and the algal symbionts. Analysis of chlorophyll and xanthophyll pigments, as well as symbiont density, indicated that under high irradiance, foraminiferal symbionts have the capacity to reduce light stress by activating photoprotective mechanisms. The negatively phototactic behaviour prevented chlorophyll degradation, symbiont loss and bleaching, suggesting that it is the primary mechanism for controlling light exposure in these foraminifera. This behaviour provides a competitive advantage over other sessile organisms in avoiding photoinhibition and bleaching by moving away from over-saturating irradiance, towards less damaging light fields. © Inter-Research 2013.

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http://hdl.handle.net/10453/26285