Interactive effects of nutrient and light availability on the performance of Saccharina latissima

Christian.Wiencke [ at ]


Marine macroalgae are important marine costal primary producers and of high importance for ecosystem functions. Cold-temperate to Arctic rocky shores are dominated by brown algae of the order Laminariales. S. latissima, a species of this order, shows a wide geographic distribution, and therefore seems to have a high capacity for climatic adaptation. Climate change led to a warming of the upper 75m of the ocean by 0,11 °C from 1971 till 2010 on a global scale. We can already observe a reduction of the sea ice cover and glacier volume which is leading to a rise in the sea level. For the Arctic the IPCC 2013 report, forecast a nearly ice-free ocean before mid-century. This can lead to a change in light conditions in coastal ecosystems. Thus abiotic factors light and temperature are affected by global climate change. This will influence the distribution patterns of organisms. In the Arctic there is a seasonal fluctuation of the dissolved inorganic nitrogen (DIN) concentration in the water. Levels of DIN are generally highest in the winter and spring, falling to lower levels in summer, which limits kelp growth. In the natural environment organism are seldom confronted with only a single stress factor, but rather with a combination of different abiotic and biotic factors. Therefore, this thesis investigates the effect of multiple stress factors, as a combination of high photosynthetic active radiation (PAR), low PAR and nutrient limitation at 2°C, 7°C and 12°C, on the physiological performance of Saccharina latissima from Spitsbergen. Growth and photosynthetic performance were analysed. PCR primer were designed and tested for selected genes of interest (GOIs), to investigate the molecular processes by the performance of a quantitative real time PCR (qRT-PCR). After an exposure time of two weeks high PAR had a significant positive effect on the growth performance of the sporophytes. 2°C reduced the growth of S.latissima significantly. The photosynthetic performance was mostly affected at 2°C, high PAR and nutrient limitation. In general the loss of nutrients reduced the acclimation potential to high PAR and led to photoinhibition at low PAR conditions. Primer testing resulted in detection of the transcript of the photosystem II D1 protein. As it was the only detectable GOI, no real time PCR was set up. The results of this thesis suggest that nitrogen limitation in S. latissima seems to lead to a reduction of the biomolecule levels II in the cell. As the acclimation in S. latissima to high PAR is contributed to an up-regulation of diverse photosystem proteins, a loss of the synthesis potential would explain the different potential of acclimation of the high PAR treatment with and without nutrient supply. Low temperatures are additional stress because of the reduced activity of the enzymes of the Calvin-Cycle. In regard to possible changes in coastal ecosystems the data of this work suggest that Saccharina latissima from Spitsbergen is able to acclimate to rising irradiance conditions, but this potential is highly influenced by the adequate supply of nutrients. Higher temperatures, seem to affect the acclimation potential in a positive way. The molecular approach of this thesis points out, that it is essential for further qPCR investigations to improve of cDNA synthesis protocol.

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Grohmann, A. (2014): Interactive effects of nutrient and light availability on the performance of Saccharina latissima , Master thesis,

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