The relationship between cellular protein content and selenium accumulation in freshwater micro-algae

In algal cells, an apparent threshold ceiling for selenium incorporation into amino acids suggests that protein content may determine the amount of selenium accumulated in these organisms at the base of the food web. The amount of selenium taken up at the base of the food web directly impacts bioaccumulation and subsequent toxicity observed in higher trophic level organisms. In this research, the protein content of four different Chlorophyta species (Parachlorella kessleri, Chlorella vulgaris, Raphidocelis subcapitata, and Tetradesmus obliquus) was determined during the different phases of algal growth (lag, exponential and stationary), and for R. subcapitata grown under different lighting intensities. Results from tissue analysis for selenium and protein following exposure to 40 µg/L showed no relationship between protein and selenium accumulation in the exponential phase, but a strong relationship in the stationary phase for P. kessleri, C. vulgaris, and R. subcapitata, as well as under different lighting intensities for R. subcapitata. These results suggest that considering protein content in site-specific primary producers is important in predicting bioaccumulation of selenium in higher trophic levels.