Table shows minimum and maximum concentrations, and the year of the maximum for each lake and element between 1925 and 2015. Lakes ST and WM show the highest ranges of elemental concentrations, followed by SL, CR, AR and TF. Generally, the elemental concentrations of FH, BL, PL and OR are the lowest of all ten lakes. Profiles from Lake FH and its neighboring Lake BL (Online Resource 1: Figs. S1, S5, and, S6) show a remarkable resemblance, not only in behavior but also in concentration. This holds true for the pairs SL-CR and ST-WM, albeit with less similarity. Regarding single elements, noticeably high concentration peaks are present for As in Lake TF in ca.