Measurement of benthic invertebrates, zooplankton, stamp sands and metals from four beaches near Keweenaw Bay, Lake Superior in 2021

Between 1900 and 1932, a copper (Cu) mine operated near Gay, Michigan, along the shore of Lake Superior, discharged approximately 22.8 million metric tons of waste material known as ‘stamp sands’ (SS) to a nearby beach. This pile of SS has migrated via wind and rain along the beaches in northern Grand Traverse Bay and into Buffalo Reef, an important spawning area for Lake Trout and Lake Whitefish. During their first summer, these newly spawned fish consume benthic invertebrates and zooplankton in nearby beach habitats. SS contain elevated concentrations of metals (especially Cu) that are toxic to many invertebrate taxa, and studies have observed very few benthic taxa in areas with very high SS. Here, we sampled the invertebrate community from four beaches: one near Buffalo Reef with very high SS, one in southern Grand Traverse Bay with moderate SS, one in the nearby Little Traverse Bay with very little SS and a beach ~58 km away with no SS (Big Bay). We also re-sampled the benthos at some sites that had been sampled as part of an earlier study. Both benthic invertebrates (in August 2021) and zooplankton (in June and July 2021) were sampled along the transects at these four beaches. Sediment samples were collected at the same time as the benthic invertebrate sampling and used to quantify SS and 12 metals at each site (including Cu).