| Food web studies have shown that bioaccumulation of polychlorinated biphenyls (PCBs) from water into phytoplankton is on the scale of 102 to 106 fold. Any changes in the initial step will cascade up the food web. The biochemical characteristics of algae in the initial bioaccumulation step are critical to understanding PCB biomagnification. The amounts of biochemical constituents of algae can vary as a function of nutrient limitation. We hypothesized that the amount of PCBs accumulated by algae is a function of the degree of nutrient limitation of the algae. Three algal species, Ankistrodesmus falcatus, Aphanizomenon flos-aquae and Cyclotella meneghiniana were grown under unlimited conditions, and under nutrient limitation in semicontinuous cultures. Proteins, carbohydrates, lipids were measured. At steady state, the cultures were subjected to 24-h uptake experiments using 14C labeled hexachlorobiphenyl, a PCB. Si limited C. meneghiniana cells exposed to PCB for 24 hrs. took up significantly higher amounts than control cells, and those under N and P limitation. A. falcatus showed no difference among treatments and A. flos-aquae took up most under low P, less under low N and least under control. Any large variations in accumulation of PCBs in this initial step can cause large variations in PCB content of the top consumers in food webs that are a function of the degree of nutrient limitation at the base of the food web. We therefore have a stake in understanding these processes for the sake of humans, other fish consumers and for biodiversity. |
