Contents lists available at ScienceDirect Harmful Algae journal homepage: www.elsevier.com/locate/hal Science meets policy: A framework for determining impairment designation criteria for large waterbodies affected by cyanobacterial harmful algal blooms Timothy W. Davis a, ⁎ , Richard Stumpf b , George S. Bullerjahn a , Robert Michael L. McKay a , Justin D. Chaffin c,e , Thomas B. Bridgeman d , Christopher Winslow c,e a Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio, 43403, USA b National Oceanic and Atmospheric Administration, National Centers for Coastal Ocean Science, Silver Spring, MD, 20910, USA c F.T. Stone Laboratory, The Ohio State University, 878 Bayview Ave. P.O. Box 119, Put-In-Bay, OH, 43456, USA d Department of Environmental Sciences and Lake Erie Center, University of Toledo, Toledo, OH, 43606, USA e Ohio Sea Grant College Program, The Ohio State University, 1314 Kinnear Rd., Research Area 100, Columbus, OH, 43212, USA ARTICLE INFO Keywords: Impairment Cyanobacteria Harmful algal blooms Remote sensing Clean Water Act ABSTRACT Toxic cyanobacterial harmful algal blooms (cyanoHABs) are one of the most significant threats to the security of Earth’s surface freshwaters. In the United States, the Federal Water Pollution Control Act of 1972 (i.e., the Clean Water Act) requires that states report any waterbody that fails to meet applicable water quality standards. The problem is that for fresh waters impacted by cyanoHABs, no scientifically-based framework exists for making this designation. This study describes the development of a data-based framework using the Ohio waters of western Lake Erie as an exemplar for large lakes impacted by cyanoHABs. To address this designation for Ohio’s open waters, the Ohio Environmental Protection Agency (EPA) assembled a group of academic, state and federal scientists to develop a framework that would determine the criteria for Ohio EPA to consider in deciding on a recreation use impairment designation due to cyanoHAB presence. Typically, the metrics are derived from on- lake monitoring programs, but for large, dynamic lakes such as Lake Erie, using criteria based on discrete samples is problematic. However, significant advances in remote sensing allows for the estimation of cyanoHAB biomass of an entire lake. Through multiple years of validation, we developed a framework to determine lake- specific criteria for designating a waterbody as impaired by cyanoHABs on an annual basis. While the criteria reported in this manuscript are specific to Ohio’s open waters, the framework used to determine them can be applied to any large lake where long-term monitoring data and satellite imagery are available. 1. Global impacts of toxic cyanobacterial harmful algal blooms The security of Earth’s surface freshwaters is under assault from multiple stressors. One of the most prevalent concerns is increased anthropogenic nutrient (nitrogen and phosphorus) pollution, which has allowed toxic cyanobacterial harmful algal blooms (cyanoHABs) to expand in recent decades (Bullerjahn et al., 2016; Harke et al., 2016; Paerl et al., 2016). These recurring events afflict many of Earth's most socio-economically important waterbodies that serve the drinking water needs of millions of people. Indeed, in the last two decades, drinking water advisories have been issued for major cities situated on large lakes in China (Wuxi; Qin et al., 2010), the United States (Toledo, OH; Steffen et al., 2017) and Africa (Kisumu, Kenya; reported in Sitoki et al., 2012) due to cyanoHAB toxins. Recently, in June 2018, elevated microcystin toxins produced by cyanoHABs resulted in a ‘do not drink’ advisory issued for Salem, Oregon’s capital city (City of Salem, 2018). The reality is that many cities must actively treat for both cyanobacteria and toxins for several months of the year, thus increasing costs to water users and eroding consumer confidence in public water utilities (Baum et al., 2016; Larson, 2017). Within the United States, a 2007 national lake assessment (NLA) conducted by the US Environmental Protection Agency found that of the 1161 lakes sampled, cyanobacteria were present in 98% of all lakes and dominated in 76% of them (Loftin et al., 2016). Furthermore, po- tential microcystin-producing cyanobacteria were found in 95% of samples where cyanobacteria were present and detectable levels of microcystins were found in 32% of those samples. Loftin et al. (2016) also found that using the World Health Organization (WHO) metrics for https://doi.org/10.1016/j.hal.2018.11.016 Received 1 August 2018; Received in revised form 26 November 2018; Accepted 27 November 2018 ⁎ Corresponding author. E-mail address: timdavi@bgsu.edu (T.W. Davis). Harmful Algae 81 (2019) 59–64 Available online 10 December 2018 1568-9883/ © 2018 Elsevier B.V. All rights reserved. T