Variables affecting temporal trends Current
An analysis of covariance showed no relationship between the concentrations of POPs and lipids, indicating that lipid normalization was not justified statistically (Hebert and Keenleyside, 1995). There was also no theoretical justification. Accumulation of dietary POPs should be unrelated to lipid concentrations, in contrast to waterborne POPs transferred directly to gill lipids by equilibrium partitioning (Borgmann and Whittle, 1991). As well, comparisons among years of lipid-normalized POP concentrations in lake trout were confounded by age because rates of lipid accumulation changed in response to changes in food web structure following alewife die-offs (Borgmann and Whittle, 1991).