Photosynthesis and photoinhibition at low temperatures: D1 turnover in Antarctic rhodophytes

Performing photosynthesis under high light but low temperature conditions poses the problem of slowed down enzymatic reactions and increased generation of reactive oxygen species. However, these are the abiotic conditions, macroalgae from Antarctica are usually exposed to during the Antarctic spring/summer season.

In our study the interactive effect of high light and low temperature was evaluated in laboratory and field experiments on endemic Antarctic rhodophytes.

During two expeditions to King George Island (summer 2007 and spring/ summer 2007/2008) we applied a combination of low water temperatures and high irradiances of photosynthetically active radiation (400-700 nm, PAR) to specimens of the Antarctic endemic red alga Palmaria decipiens (Reinsch) Ricker (1987) in order to test physiological responses of photosynthetic performance to the combined (stress-) factors.

In laboratory as well as in field experiments a marked interaction between low water temperatures (0 - 3 °C) and high light intensities was found. Samples taken will be analysed focussing on the generation and scavenging of reactive oxygen species, as well as the related damage and turnover of the reaction centre protein of photosystem II (D1). Moreover, changes in the abundance of D1 will be related to species-specific lipid composition and expression of psbA genes encoding for D1.

Additionally, our study is connected to the IPY initiative CLICOPEN. One major task in CLICOPEN is “to analyze and quantify effects of glacial melting and sediment import into coastal waters on terrestrial and near shore marine ecosystems along a latitudinal gradient along the Western coast of the Antarctic Peninsula.“ The substantial changes in underwater radiation conditions due to increased sediment loads require acclimation mechanisms of benthic primary producers to cope with reduced light availability, in order to maintain positive net photosynthetic carbon gains. As the central aspect of CLICOPEN is the increased freshwater impact due to increased glacier melting, we will address how salinity changes as an additional abiotic factor may influence D1 protein turnover and thus photosynthetic activity. Consequently, our study will add substantial baseline information on photosynthetic performance of the dominant benthic primary producers in this highly susceptible ecosystem.

Scientists

Kai Bischof
Dep. Marine Botany
University of Bremen

Christian Wiencke
Alfred Wegener Institute
Bremerhaven

Susanne Becker
Dep. Marine Botany
University of Bremen

Research areas

King George Island (62° S, 58° W), Dallmann Laboratory/ Base Jubany

Publications

Becker S, Quartino ML, Campana GL, Bucolo P, Wiencke C, Bischof K, (in press). The biology of an Antarctic rhodophyte, Palmaria decipiens: an overview of recent advances. Antarctic Sciences.

Becker S, Graeve M, Bischof K, 2010. Photosynthesis and lipid composition of the Antarctic endemic rhodophyte Palmaria decipiens: Effects of changing light and temperature levels. Polar Biology 33: 945-955.

Becker S, Walter B, Bischof K, 2009. Freezing tolerance and photosynthetic performance of polar seaweeds at low temperatures. Botanica Marina 52: 609-616.

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Research funding organisation

German Research Foundation

Project number: BI 772/ 7-1,2,3
Funding period: 2006 – 2009