Sensors for Monitoring Harmful Algae, Cyanobacteria and Their Toxins

2 I NTRODUCTION Harmful algal blooms (HABs) are a continued threat to economies and marine/freshwater and human health throughout the US, including coastal regions encompassing the Pacific, Gulf of Mexico, Southeast Atlantic, Northeast Atlantic, and the Great Lakes. While blooms of varying intensities are common, highly toxic events have great impact and thrust the issue into the public spotlight. A few recent notable events include: 1) in the summer of 2014, more than half a million Toledo, OH residents were restricted from using tap water for three days because microcystin levels were measured as high as 2.5 ug/L, more than twice the 1.0 ug/L threshold for human consumption recommended by the World Health Organization (T. Henry, August 3, 2014); 2) in 2015, a sustained domoic acid event along the entire US West coast cost California more than $48 million in lost income for the Dungeness crab industry (Brown 2016); and 3) in 2016, the first domoic acid event was recorded in Maine, with toxin levels five times higher than what is considered safe for human consumption and resulting in the recall of approximately five tons of shellfish (P. McGuire, posted October 6, 2016). Monitoring efforts and long-term data sets are invaluable for developing strategies for prevention and mitigation of events such as these (Kudela et al. 2015). These data serve to inform now- and forecasting networks towards NOAA’s mandate of developing an Ecological Forecasting Roadmap (EFR). In addition, the Harmful Algal Bloom and Hypoxia Research and Control Act (HABHRCA) calls for predictive capabilities through advancing our understanding of and abilities for HAB event detection, monitoring, and assessment. Anderson (1989) and Hallegraeff (1993) first outlined the rise in frequency, magnitude and geographical extent of HABs and their impacts during prior decades. Since then, continued long- term monitoring efforts on many levels (e.g. citizen scientists, tribal, NGOs, state and federally funded research) have confirmed this HAB expansion. While work is still needed towards the ultimate goal of predicting HAB events as a means of mitigating their impacts, seasonal periods of increased risk have been defined in some cases, which can serve to inform more efficient allocation of resources toward monitoring and research on triggers of bloom events. We are only beginning to understand how HAB events fit into the larger context of regional and global changes in climate and nutrient loadings (Sellner et al. 2003, Anderson et al. 2008, Hallegraeff 2010, Wells et al. 2015). Decades of research have identified many of the harmful species responsible for toxic blooms, however the physiological drivers of toxicity have not been fully elucidated. Moreover, the genetic controls on toxin production and their variability within and among species and strains are still largely unknown. This is compounded by underlying cryptic diversity within genera/species that can affect detection capabilities for monitoring purposes. On a broader scale, factors controlling bloom initiation, persistence, and decline are not fully known. The variables involved can be very complex and work synergistically, including availability of micro- and macronutrients, physical parameters (e.g. irradiance, salinity, temperature, pH), biological influences (e.g. bacteria, grazers), and diversity (e.g. species and strains) within blooms (see Lelong et al. 2012 for review). Several technologies exist or are in development for the detection of HAB species and their toxins (for review see Doucette and Kudela 2017). Instruments can be moored, mobile or handheld and scheduled for discreet sampling times or triggered remotely. Sampling can be passive or in response to fluorescence signatures that are broad (e.g. chlorophyll) or more group-specific (e.g. phycocyanin, phycoerythrin), while some sensors are coupled with imaging or genetic/toxin detection capabilities for more detailed species identification. The appropriateness of specific