Organisms living in aquatic ecosystems may experience high doses of natural UV radiation. UV radiation penetrates the water column down to several meters. The penetration depth differs depending on the contents of particles, dissolved matter or pollutants. The aim of this study was to establish the dose-response relationship of phenotypic changes caused by UV. A modification of the antioxidant defence was assessed by adding a methacrylate that was previously found to decrease the amount of glutathione in cells [1]. The zebrafish embryo test [2] was applied to score toxic effects of UVA and UVB. Embryos were treated with broadband UVA- and UVB radiation in the period including mid- to late blastula stage, i.e. until 5 hours postfertilisation. Broadband UVB radiation was approximately 1000 times more effective in inducing morphological lesions and embryo death than was UVA radiation. Combined exposure to hydroxyethylmethacrylate and UV increased the toxic effects of UVA and UVB on the embryos significantly. The amount of reduced glutathione was decreased as indicated by measuring the fluorescence from embryos incubated with monobromobimane. Reduced efficiency of the antioxidant system involving glutathione is a likely explanation of increased radiation efficiency in the presence of methacrylates. The finding that the relative sensitivity of zebrafish embryos to UVA is 1/1000 of the sensitivity to UVB is supported by similar observations in several other biological systems, including human skin. Pollutants may interact with UV- and visible radiation induced effects e.g. by weakening the antioxidant system as observed for methacrylates.

This work was partly supported by the Research Council of Norway through its Centres of Excellence funding scheme, project number 223268/F50.
[1] T. Christensen, E. Bruzell, Photochem. Photobiol. Sci., 2010, 9, 1597.
[2] OECD Test Guideline (TG) 236, Fish Embryo Acute Toxicity (FET) Test, 26 July 2013, http://www.oecd-ilibrary.org/environment/test-no-236-fish-embryo-acutetoxicity- fet-test_9789264203709-en

Relative Efficiency Of Ultraviolet Radiation A And B Combined With A Chemical Stressor On Zebrafish Embryos
Christensen T, Aleksandersen TB, Aleström P, Lyche JL, Bruzell EM.
9th European Zebrafish Meeting (9thEZM), Oslo, Norway June 28 – July 2, 2015. (A)