Ecotoxicological effects on the coral endosymbiont Symbiodiniaceae of organic UV-filter chemicals

Abstract: Coral bleaching causes the disappearance of unique ecosystems supporting thousands of different species. The corals health depends on its relationship with its endosymbiont, the zooxanthellate Symbiodiniaceae. This mutualistic relationship can be disrupted by anthropogenic chemical pollution by inducing physiologically stress in Symbiodiniaceae. This thesis investigates the effects of organic ultraviolet filter chemical in Symbiodiniaceae of four genera (Fugacium, Effrenium, Symbiodinium, Breviolum), with regards to their growth and photophysiological performance. Six Symbiodiniaceae strains were exposed to a mixture of the most commonly observed UV-filter at five different concentrations. The cells growth during exposure was followed with spectrophotometry optical density measures and flow cytometry cell counts. The photophysiological performance of Symbiodiniaceae cells in presence of UV-filter chemicals was obtained using chlorophyll fluorometry. This experiment revealed strain-specific sensitivity to UV-filter chemicals, where Symbiodiniaceae strains 421 and 4013 showed highest sensitivity on cell growth. A difference in photophysical performance of Symbiodiniaceae exposed to UV-filter chemicals was observed. The ecotoxicological effects observed in Symbiodiniaceae from UV-filter chemical exposure could indicate a contribution to the disruption of the mutualistic relationship between the coral host and Symbiodiniaceae.