Transgenic and cell wall-deficient Chlamydomonas reinhardtii food affects life history of Daphnia magna

The economical interest in the use of genetically modified microalgae (GMM) increases because of their potential for low-cost industrial mass cultivation, high productivity (e.g., biomass, lipids, and recombinant proteins), and short generation times. However, the unintentional release of GMMs to the environment might cause harmful biotic interactions affecting ecosystems. GMMs could invade natural ecosystems and could affect ecosystem services by biotic interactions with other species from the same trophic level, as well as organisms from higher trophic levels. So far, potential negative influences of GMMs on natural ecosystems have mainly been hypothesized and empirical studies are rare and usually consider only direct short-term effects on adult organisms. In analyzing life history effects on Daphnia magna fed with transgenic Chlamydomonas reinhardtii synthesizing and secreting recombinant human vascular endothelial growth factor VEGF-165 (VEGF), we found that neonate size, fecundity, and fitness were significantly influenced by the different C. reinhardtii food sources. Clear GMM specific effects on Daphnia resulted in lower fecundity and neonates were small in size but higher in numbers. These, especially, might be consequences of changes in behavior or metabolism in Daphnia induced by the growth-enhancing protein VEGF. The results indicate a measurable response of Daphnia life history, which can result in further effects on higher trophic levels such as planktivorous invertebrates or fish.