Watershed was a significant predictor variable in the PFOS model ( χ 2 [df] = 11.63 [4], p = 0.0203) (Table S4 ), and while pairwise contrasts of watersheds were generally not significant (with the exception of the marginally significant Lake Ontario/Lake Superior contrast; p = 0.0577), modeled PFOS concentrations increased from west to east: Lake Superior < Lake Michigan ≅ Lake Huron < Lake Erie < Lake Ontario (Table 1 ; Figure 3 and Figure S6 ).
Mean PFOS concentrations showed a clear trend of biomagnification across a generalized Great Lakes food web (i.e., an estimated difference of two orders of magnitude between primary producers and apex predators), whereas concentration estimates of the long‐chain PFCAs reflected life history differences rather than dietary patterns.
Modeled temporal trends of PFOS in biota were highly significant but non‐linear, and may be correlated with industrial production, the timeline of compound phase‐out, food web shifts, and lake‐specific conditions.