Evaluation of Plankton Communities to Support the Delisting of Waukegan Harbor, Illinois as a Great Lakes Area of Concern (Aoc)

Several decades of industrial contamination at Waukegan Harbor, IL, USA in southwestern Lake Michigan lead to the existence of three superfund sites and its listing as a Great Lakes Area of Concern (AOC). After extensive remediation efforts, evaluations are underway toward the removal of the six Beneficial Use Impairments (BUIs) to delist Waukegan Harbor as an AOC. To address the “Degradation of Phytoplankton and Zooplankton Populations” BUI, plankton samples and physiochemical data were collected semi-monthly in 2017 to compare the Waukegan Harbor AOC to a nearby reference site, North Point Marina, and nearshore lake locations outside of each harbor. Water samples were collected on three separate occasions to perform water toxicity tests to help elucidate potential contamination effects on plankton communities. Both zooplankton and phytoplankton communities were dominated by relatively few taxa and any patchiness in their distribution was highly influential on our multivariate community statistics. Seasonal changes during the study also influenced plankton communities at these sites and confounded statistical analyses and interpretation. Global ANOSIM tests revealed significant differences between the plankton communities of the AOC and non-AOC reference. However, zooplankton communities were not different when accounting for seasonal changes. Chronic toxicity tests on waters collected from both harbors and nearshores sites concluded that none of the waters were toxic and contamination was not the likely cause of plankton community differences between the AOC and non-AOC. Our study demonstrates the difficulty in evaluating the “Degradation of Phytoplankton and Zooplankton Populations” BUI in Great lakes AOCs. However, combining community analyses with water toxicity testing provided sufficient evidence to propose the removal of this BUI at the Waukegan harbor AOC.