Letter to the Editor

Dear Editor,

TWO YEARS AGO OUR ARTICLE, “NEARSHORE CONDITIONS in the Great Lakes national parks: A baseline water quality and toxicological assessment” was published in the Park Science 2015–2016 Winter edition (volume 32, number 2). In this piece we presented a summary of nearshore conditions in five Great Lakes coastal park units and related our results to interim water quality criteria identified by the Environmental Protection Agency for dissolved oxygen, chlorophyll a, dissolved inorganic nitrogen, dissolved inorganic phosphorus, and water clarity (table 2 in the publication). In addition, we assessed sediment quality based on regional and national ecological criteria. We noted that based on the water criteria, conditions at National Park Service (NPS) sites were rated “good” for each of these parameters and sediment quality was generally within published thresholds for ecological health.

Shortly after our publication, the EPA published a broader report summarizing results from the 2010 National Coastal Condition Assessment (NCCA; EPA 2015), and presented water and sediment quality criteria specific to Great Lakes coastal waters. The new water criteria addressed total phosphorus, chlorophyll a, water clarity as Secchi depth, and bottom dissolved oxygen. Based on the new water criteria, all of the NPS sites received “good” ratings for bottom dissolved oxygen, and a majority of NPS sites received “good” ratings for total phosphorus and chlorophyll a (figs. 1 and 2). However, far fewer NPS sites received “good” ratings for water clarity; in fact all sites at Pictured Rocks and Indiana Dunes and a majority of sites at Apostle Islands and Sleeping Bear Dunes received “fair” or “poor” ratings for water clarity. Such low ratings, often in park waters prized for their water clarity, may indicate emerging water clarity concerns in these parks, but may also reflect weather or hydrodynamic conditions at the time of sampling, site locations in more turbid coastal embayments, or other factors. It is worth noting that a majority of NPS sites still received an overall Water Quality Index rating of “good,” and no NPS sites received an overall Water Quality Index rating of “poor.”

The thresholds for ecological quality associated with the new sediment quality index (sediment toxicity and sediment contaminants) did not change following the 2010 NCCA report (EPA 2015). However, one aspect of sediment quality not evaluated in our original article was the Oligochaete Trophic Index, an indicator of organic enrichment in the sediments. Less than half of the NPS sites sampled for sediment quality had oligo
chaetes present, and although several sites were rated “poor” or “fair” for organic enrichment based on the Oligochaete Trophic Index, these results did not correlate strongly with the measured percentage of total organic carbon in the sediments, making them difficult to interpret. Finally, fish tissue contaminant burdens were assessed in the EPA (2015) report against the whole-body tissue concentrations for lowest observed adverse effects level. Our previous article assessed fish tissue concentrations against the more stringent criteria for human health used by Canada and the United States under the Great Lakes Water Quality Agreement General Objective 9. While there is no widespread exceedance of human health criteria, legacy contaminants continue to be measured in the majority of fish tissues.

Overall, this analysis provides a more nuanced view of water quality conditions in Great Lakes national parks and suggests that several parks would benefit from additional monitoring and assessment related to water clarity—particularly in light of recent broad-scale changes in water clarity throughout the Great Lakes region (Yousef et al. 2017). Complete results from the 2010 National Coastal Condition Assessment, including sites within NPS units and the broader Great Lakes region, are accessible at https://www.epa.gov/national-aquatic-resource-surveys/national-coastal-condition-assessment-2010-results.

References

US Environmental Protection Agency (EPA). Office of Water and Office of Research and Development. December 2015. National Coastal Condition Assessment 2010. EPA 841-R-15-006. Washington, DC, USA. http://www.epa.gov/national-aquatic-resource-surveys/ncca.

Yousef, F., R. Shuchman, M. Sayers, G. Fahnenstiel, and A. Henareh. 2017. Water clarity of the Upper Great Lakes: Tracking changes between 1998–2012. Journal of Great Lakes Research 43(2):239–247.

Sincerely,

Brenda Moraska LaFrancois, William O. Hobbs, and Eva DiDonato

Last updated: April 12, 2018