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Abstract

All photosynthetic organisms endeavor to balance
energy supply with demand. For sea-ice diatoms, as
with all marine photoautotrophs, light is the most
important factor for determining growth and carbonfixation
rates. Light varies from extremely low to
often relatively high irradiances within the sea-ice
environment, meaning that sea-ice algae require
moderate physiological plasticity that is necessary for
rapid light acclimation and photoprotection. This
study investigated photoprotective mechanisms
employed by bottom Antarctic sea-ice algae in
response to relatively high irradiances to understand
how they acclimate to the environmental conditions
presented during early spring, as the light climate
begins to intensify and snow and sea-ice thinning
commences. The sea-ice microalgae displayed high
photosynthetic plasticity to increased irradiance, with
a rapid decline in photochemical efficiency that was
completely reversible when placed under low light.
Similarly, the photoprotective xanthophyll pigment
diatoxanthin (Dt) was immediately activated but
reversed during recovery under low light. The xanthophyll
inhibitor dithiothreitol (DTT) and state transition
inhibitor sodium fluoride (NaF) were used in
under-ice in situ incubations and revealed that nonphotochemical
quenching (NPQ) via xanthophyllcycle
activation was the preferred method for light
acclimation and photoprotection by bottom sea-ice
algae. This study showed that bottom sea-ice algae
from the east Antarctic possess a high level of plasticity
in their light-acclimation capabilities and identified
the xanthophyll cycle as a critical mechanism in
photoprotection and the preferred means

Item Type:	Article
Authors/Creators:	Petrou, K and Hill, R and Doblin, MA and McMinn, A
Keywords:	chl a fluorescence;fast induction curves (FICs);sea-ice microalgae;xanthophyll cycle
Journal or Publication Title:	Journal of Phycology
DOI / ID Number:	https://doi.org/10.1111/j.1529-8817.2010.00944.x
Additional Information:	The definitive published version is available online at: http://onlinelibrary.wiley.com/
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