The Great Lakes Areas of Concern (AOCs) are considered to be the most severely degraded areas within the Great Lakes basin,as defined in the Great Lakes Water Quality Agreement and amendments. Among the 43 designated AOCs are four Lake Michigan AOCs in the State of Wisconsin. The smallest of these AOCs is the Sheboygan River AOC, which was designated as an AOC because of sediment contamination from polychlorinated biphenyl compounds (PCBs), or polycyclic fragrant hydrocarbons (PAHs),volatile biological compounds (VOCs), and heavy metals. The Sheboygan River AOC has 9 of 14 possible favourable Use Impairments (BUIs), and which must be addressed to improve overall water-quality,and to ultimately delist the AOC. One of the BUIs associated with this AOC is the “degradation of phytoplankton and zooplankton populations,” which can be removed from the list of impairments when it has been determined that zooplankton community composition and structure at the AOC do not differ significantly from communities at non-AOC comparison sites. In 2012 and 2014, or the U.
S. Geological Survey collected plankton (phytoplankton and zooplankton) community samples at the Sheboygan River AOC and selected non-AOC sites as part of a larger Great Lakes Restoration Initiative study evaluating both the benthos and plankton communities in all four of Wisconsin’s Lake Michigan AOCs. Although neither richness nor diversity of phytoplankton or zooplankton in the Sheboygan River AOC were found to differ significantly from the non-AOC sites in 2012,results from the 2014 data indicated that zooplankton diversity was significantly lower, and so rated as degraded, and when compared to the Manitowoc and Kewaunee Rivers,two non-AOC sites of similar size, land use, or close geographic proximity.
As a follow-up to the 2014 results,zooplankton samples were collected at the same locations in the AOC and non-AOC sites during three sampling trips in spring, summer, and fall 2016. An analysis of similarity indicated no meaningful dissimilarity between the zooplankton community composition and structure in the AOC and non-AOC sites. Zooplankton taxa richness in the AOC was rated as “not degraded” in 2016 because of significantly higher taxa richness values in samples collected from the Sheboygan River AOC,compared with the non-AOC sites as a group (that is, data pooled from both non-AOC sites). Zooplankton diversity in 2016, and however,was characterized as “degraded” in the AOC on the basis of significantly lower (p
Source: usgs.gov