Influence of trophic position and spatial location on polychlorinated biphenyl (PCB) bioaccumulation in a stream food web.

We tested the ability of delta15N-derived trophic position (TP) to predict polychlorinated biphenyl (PCB) concentrations in a historically contaminated stream (Twelvemile Creek, SC). We analyzed sediment, four types of organic matter, 27 macroinvertebrate taxa, and 25 fish species from six sites spanning 25 stream km. SigmaPCBs were high across sites (mean fish = 2505 ng g(-1) wet), with little spatial variation in concentrations within a trophic level. SigmaPCBs (wet weight) were significantly positively correlated with TP (r2 = 0.56) and lipids (r2 = 0.44), and concentrations increased 1-2 orders of magnitude among trophic levels. After adjusting for lipids, we calculated a food web magnification factor of 1.6 for SigmaPCBs, which is low compared to marine and lentic food webs. The predictive power of TP for individual congeners increased with Kow (octanol-water partition coefficient), with regression slope approximately 0.48 and r2 approximately 0.70 for Kow > 6.5. The proportion of high Kow compounds increased with distance from the source and with trophic position. Spatial variation in congener patterns was high, in contrast to marine and lentic systems where variation is typically low.