Direct and indirect effects of ionizing radiation on grazer–phytoplankton interactions. (May 2016)

• Record Type: Journal Article
• Authors: Nascimento, Francisco J.A.; Bradshaw, Clare
• Is Part Of: Journal of environmental radioactivity. Volume 155/156(2016:May)
• Page Start: 63
• Page End: 70
• Publication Date: 2016-05
• Subjects: Gamma radiation -- Carbon incorporation -- Daphnia magna -- Microalgae -- Food–web interactions; Radioactivity -- Periodicals; Radiation, Background -- Periodicals; Radioecology -- Periodicals; Radioactive pollution -- Periodicals; Environmental Pollutants -- Periodicals; Radioactive Pollutants -- Periodicals; Radioactivity -- Periodicals; Radioécologie -- Périodiques; Pollution radioactive -- Périodiques; Fond de rayonnement -- Périodiques; 539.752
• DOI: 10.1016/j.jenvrad.2016.02.007
• Languages: English
• ISSNs: 0265-931X

Abstract

Abstract: Risk assessment of exposure to radionuclides and radiation does not usually take into account the role of species interactions. We investigated how the transfer of carbon between a primary producer, Raphidocelis subcapitata, and a consumer, Daphnia magna, was affected by acute exposure to gamma radiation. In addition to unexposed controls, different treatments were used where: a) only D. magna (Z treatment); b) only R. subcapitata (P treatment) and c) both D. magna and R. subcapitata (ZP treatment) were exposed to one of three acute doses of gamma radiation (5, 50 and 100 Gy). We then compared differences among treatments for three endpoints: incorporation of carbon by D. magna, D. magna growth and R. subcapitata densities. Carbon incorporation was affected by which combination of species was irradiated and by the radiation dose. Densities of R. subcapitata at the end of the experiment were also affected by which species had been exposed to radiation. Carbon incorporation by D. magna was significantly lower in the Z treatment, indicating reduced grazing, an effect stronger with higher radiation doses, possibly due to direct effects of gamma radiation. Top-down indirect effects of this reduced grazing were also seen as R. subcapitata densities increased in the Z treatment due to decreased herbivory. The opposite pattern was observed in the P treatment where only R. subcapitata was exposed to gamma radiation, while the ZP treatment showed intermediate results for both endpoints. In the P treatments, carbon incorporation by D. magna was significantly higher than in the other treatments, suggesting a higher grazing pressure. This, together with direct effects of gamma radiation on R. subcapitata, probably significantly decreased phytoplankton densities in the P treatment. Our results highlight the importance of taking into account the role of species interactions when assessing the effects of exposure to gamma radiation in aquatic ecosystems. Highlights: Direct and indirect effects of γ-radiation on zoo- and phytoplankton were assessed. Bottom-up and top-down effects were seen depending on which species was irradiated. γ-radiation decreased grazing and C incorporation resulting in higher algal cell densities. When algae were irradiated, C-incorporation by Daphnia magna increased. Ecosystem-level effects of γ-radiation can be different to individual-level effects