Spatial-temporal patterns of perfluoroalkyl substances in the biota of the Laurentian Great Lakes: A meta-analysis.

To better understand the dynamics of per- and polyfluoroalkyl substances (PFAS) in complex freshwater ecosystems, we performed a systematic meta-analysis of PFAS distributions and spatiotemporal variance in biota of the Laurentian Great Lakes watersheds. We reviewed 50 publications that contained 2489 records (primarily of fish and birds) spanning 42 years of biological sampling. Using this dataset, we built generalized additive models for six compounds-perfluorooctanesulfonic acid (PFOS) and five perfluoroalkyl carboxylic acids (PFCAs)-routinely detected in biological tissues. Estimated concentrations of PFOS, the dominant compound in biota, increased along a lake gradient from west (Lake Superior) to east (Lake Ontario), and PFCA levels also varied across the lakes. 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. In the eastern lakes, biotic PFOS concentrations were highly variable through time, spanning one to two orders of magnitude, and model estimates generally declined following industrial phase-out of the compound. In the western lakes, PFOS levels did not demonstrate substantial changes from lower baseline concentrations. PFOS, but not PFCA, levels biomagnified from primary producers to apex predators across the Great Lakes. Model output indicated that eggs, blood, and liver samples were consistently the most contaminated tissues. Our review also revealed several data constraints in the literature revolving around lake coverage, taxonomic biases, and methodological inconsistencies. Addressing these data gaps will maximize the inferential ability of future synthetic studies of PFAS.