Mercury, carbon and nitrogen isotope ratios in seven Great Lake fish species from 1975 to 2021

Atmospheric mercury (Hg) deposition, which has been declining in North America since 1985, is the preeminent delivery pathway to the Great Lakes, making them sentinels for tracking shifts in atmospheric deposition. Lake productivity is changing as a result of reductions in phosphorus inputs and habitat shifts in productivity due to invasive mussels. This has altered Hg cycling and energetic coupling within the Lakes. Seven fish species were analyzed for bulk carbon, nitrogen, and Hg isotope ratios and amino acid-specific nitrogen isotopes ratios in fish from the U.S. Environmental Protection Agency Great Lake Fish Monitoring and Surveillance Program archives (1975 – 2021) and the 1994 Lake Michigan Mass Balance to reconstruct the energetic- and Hg-source spatial and temporal trends within each lake. Data for the following fish species are included in this dataset: alewife, bloater, chub, coho salmon, lake trout, rainbow smelt, walleye.