UV radiation and its effects on P-uptake in arctic diatoms

Abstract

Four years go by surprisingly fast, and I am very grateful to have had the privilege to pursue my research interests and be a part of the scientific environment. First of all, I would like to acknowledge my supervisors: Richard Bellerby, Dag O. Hessen and Truls Johannessen. I thank you for believing in me and offering scientific guidance and encouragement. Richard took me in as a master student 7 years ago, and I am very grateful for the opportunities you have given me. Dag has been my introduction to the field of ecological stoichiometry, and I am very grateful for your prompt and thorough feedbacks. Truls has been a continued supporter, and always finds time to read and comment on my work. I also wish to thank Tom Andersen, who was not an official supervisor, but has been instrumental to this thesis and has patiently taught me about statistics and the intricacies of R.I am also grateful to the research group here at GFI and BCCR for a positive working environment, and to the CEES group in Oslo for hosting me during the first year of my PhD. I wish to thank my fellow PhD-students, Anna and Siv, for friendship, countless coffee breaks and the joint arena to share our experiences of the trials of PhD-life. I also wish to thank my office-mate Emanuele, for the continued flow of amazing Italian desserts and cakes, and the occasional mathematical insight.My family and friends, here in Bergen, Oslo, Brigthon, Ål and Arendal are very important to me, and I thank you for being who you are and supporting me and what I do. I very much value the time I can spend with you, and look forward to much more of it in the months and years to come. Finally, I wish to thank my husband Erlend, who always lifts my spirits, and keeps me fed, sane and happy.

The fascinating diatom frustule—can it play a role for attenuation of UV radiation?

“…This agrees with varying effects of UV among cultured diatom species both with regard to response and sensitivity to UV (Karentz et al 1991;Davidson et al 1994;Waring et al 2006;Hessen et al 2012;Scholz et al 2014), even among species within a genus (Hargraves et al 1993). This has raised speculations as to why differences in UV effects vary more in diatoms than in other algal groups where the responses can often be correlated to cell size due to size-related effects on self-shading and UV-absorbing compounds (Waring et al 2006 and references herein).…”

“…In spite of the reported effects of UV radiation, some studies find no effect of UV on diatoms, or less effect than on flagellates (Villafañe et al 1995;Vernet 2000;Litchman and Neale 2005;Guihéneuf et al 2010;Hessen et al 2012: Wu et al 2012. So far, no explanation has been found for this difference.…”

“…As most UV radiation is not photosynthetically active, cell strategies would thus be expected to be either to avoid or tolerate UV radiation (Holzinger and Lütz 2006). A UV-induced effect is dependent on the level of UV, the duration of the exposure, the spectral composition of the light in the UV range, the sensitivity of the organism(s) investigated, physiological status, ambient nutrient conditions, and temperature (Buma et al 1996;Cullen and Lesser 1991;Litchman and Neale 2005;Hessen et al 2012). UV radiation harms cells through absorption by nucleic acids and proteins, hence inhibiting DNA translation, replication, and transcription (Buma et al 1995;Holzinger and Lütz 2006).…”

Estimating absorption coefficients of colored dissolved organic matter (CDOM) using a semi-analytical algorithm for southern Beaufort Sea waters: application to deriving concentrations of dissolved organic carbon from space

“…During ice-free seasons, this material covers the surface ocean and significantly reduces penetration of ultraviolet irradiation that influences marine organisms such as phytoplankton and bacteria (Judd et al, 2007;Leu et al, 2007;Bonilla et al, 2009;Hessen et al, 2012). In the context of the expansion of the hole in ozone layer at high northern latitudes (e.g., Wirth and Renger, 1996;Andersen and Knudsen, 2002), variability in CDOM absorption can impact the physiological status or acclimation/adaptation of marine organisms.…”

Increased nutrients from aeolian‐dust and riverine origin decrease the CO2‐sink capacity of coastal South Atlantic waters under UVR exposure

“…This can promote greater heterotrophy by increased community respiration (Martínez‐García et al ), thus altering the energy transfer to higher trophic levels (Tsagaraki et al ). On the other hand, it is known that current or enhanced levels of UVR inhibits the PP (Helbling et al ; Villafañe et al ), nutrient uptake (Hessen et al ), Φ PSII or DNA repair (Jeffrey et al ; Harrison et al ; Villafañe et al ); however, although the combined impact of both global change drivers is generally considered antagonistic (e.g., nutrients attenuate the harmful effect of UVR), recent results by Carrillo et al () and Harrison et al () evidence that nutrient inputs can also unmask the harmful UVR effects on planktonic responses.…”