Reproduction, growth and chemical composition of Ulva sp. in response to different light treatments

laurie.c.hofmann [ at ]


In this study, Ulva sp. collected on Helgoland were subjected to one of four light treatments consisting of different light colour and daylength: 24h blue light, 24h white light, 16h blue light and 16h white light. All algae were kept in a temperature controlled dark room on Helgoland at 15 °C. Over the course of 44 days growth rate, photosynthesis (via oxygen spot optodes) and reproductive area were measured. At the end of the experiment the antioxidant activity of extracts from the algae was measured using the ABTS radical decolourization assay. In addition chlorophyll and carotenoid concentration were analysed for all treatments. The aim was to identify conditions with minimal reproduction and maximal growth and antioxidant activity. These parameters were of interested for potential applications of Ulva in the development of alternative packaging material. White light treatments had higher growth rates than blue light (12.6 and 10.6 % d-1 vs. 4.17 and 2.69 % d-1). However this is likely due to differences in light intensity rather than colour. Similarly, reproduction only occurred in white light treatments and irrespective of daylength. Since the algae grown in white light also were biggest, this trend is also not necessarily attributable to light colour and more likely a consequence of size. Antioxidant activity was highest in algae grown under 24h-BL. While this is also at least partially a consequence of light intensity, light colour also seems to play a role. Pigment content followed a similar trend with treatments under low light intensity (blue light) containing more pigments than those under high intensity (white) light. The 24h white light treatment was an exception to this and did not differ significantly from treatments under blue light. The implication of light colour and intensity, both daily and short term, for algal physiology in general and algae in this study in particular are reviewed. Potential strategies to manipulate antioxidants in the context of commercial applications such as biodegradable, sustainable packaging are discussed.

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Schwoerbel, J. (2019): Reproduction, growth and chemical composition of Ulva sp. in response to different light treatments Master thesis,

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