UV-B treated algae exhibiting different responses as a food source for Daphnia magna

Abstract

The response of green algae Scenedesmus quadricauda and Selenastrum capricornutum to different levels of UV-B radiation was studied. Daphnia magna, the next step in the food web, was fed with UV-B treated algae. UV-B radiation induced the synthesis of UV absorbing substances and photosynthetic pigments, enhanced the level of respiratory potential and suppressed growth of the treated algae. Biomass production in S. quadricauda was higher than in S. capricornutum, but the production of photosynthetic pigments and relative amounts of UV absorbing substances as well as respiratory potential were more pronounced in S. capricornutum. A short-term feeding experiment with D. magna showed that in general, females ingested higher numbers of cells of algae treated with a high UV-B dose, but the biomass of ingested algae did not differ significantly. The exception was S. capricornutum treated with a high UV-B dose; a lower biomass was ingested, probably reflecting the smaller UV-treated cells.