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Research report 1: The effect of temperature on the photophysiology of four picophytoplankton species

Vries, P. de and Kulk, G. and Visser, R.J.W. and Buma, A.G.J. (2012) Research report 1: The effect of temperature on the photophysiology of four picophytoplankton species. Master's Thesis / Essay, Biology.

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Rising seawater temperatures and increased stratification that are associated with global warming are expected to cause changes in the picophytoplankton community. In this study, the picophytoplankton species P. marinus, Synechococcus sp., Ostreococcus sp., and P. calceolata were cultured at 16, 20, and 24 °C to study the effect of temperature on their photophysiology. Photosynthetic parameters were assessed by measurements of growth, pigmentation, absorption spectra, electron transport rates, and 14C incorporation. In addition, the recovery of photosystem II (PSII) after exposure to high photosynthetic active radiation (PAR) and ultraviolet radiation (UVR) was assessed. Results showed that, maximum growth rates were generally found at higher temperatures. The activity of the xanthophyll pigment cycle was most effective at 24 °C. Temperature did not have an effect on the photosynthetic parameters of Ostreococcus sp.. For both P. marinus and P. calceolata, photosynthetic parameters were highest at 16 °C. In addition, P. calceolata showed photoinhibition at all three temperatures. Ostreococcus sp. showed the lowest sensitivity to UVR, whereas P. calceolata was most sensitive. P. marinus suffered from PSII damage caused by UVR, but not beyond repair. Overall, rising seawater temperatures will have a positive effect on the growth rates, xanthophyll pigment cycle activity and the electron transport rate in picophytoplankton, but will have little effect on D1 photorepair From this study, it can be concluded that all four species benefit from rising temperatures. However, this benefit could be nullified: stronger thermoclines and upper layer mixing due to rising sea water temperatures cause more frequent exposure to excessive (UV) irradiances. Furthermore, temperature induced stratification eventually causes nutrient depletion. This can cause a shift to smaller species, and eventually changes in carbon fixation and ocean species communities.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:52
Last Modified: 15 Feb 2018 07:52

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