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Harmful Algal Blooms (HABs)

Some species of cyanobacteria produce metabolites¹ that are toxic to many animal species, including humans and dogs. There four most notable cyanotoxins are:

• anatoxin, a neurotoxin, often occurring due to Anabaena flos-aquae blooms;
• cylindrospermopsin is a hepatotoxin, meaning it affects liver function; it is typically produced by strains of Aphanizomenon or Dolichospermum;
• microcystin, another hepatotoxin, is produce by the Microcystis clade in many freshwater lakes;
• saxitoxin, also a neurotoxin, can be produced by various species of Dolichospermum, Aphanizomenon, and Cylindrospermopsis among other algae and bacteria.

Not only are these compounds toxic, they do not denature when boiled, and are difficult to filter or destroy. Many water treatment plants whose source waters have experienced HABs will install ozone (O₃) systems. The ozone is highly oxidative, severing carbon-carbon bonds to break down stable compounds like cyanotoxins that are otherwise very stable.

Cyanobacteria are one of the oldest organisms on Earth, and can be found in the oceans and on every continent. Originating billions of years ago, they are likely the oldest photosynthesizers, and so are responsible for driving up the oxygen content of the atmosphere in the early life of the planet. The various genera exhibit a number of superpowers, including nitrogen-fixation, rapid vertical migration through the water column, and the ability to form akinetes, a sort of hibernation state for the cell that allows it to overwinter, surviving with little nutrients or energy resources (light, temperature, nitrogen, etc.).

These unique characteristics mean it can be difficult to detect cyanobacteria blooms - the mats of algae may descend for a time, growing below the epilimnion, only to arise later - and they can persist through a wide range of environments. Further, the presence of a bloom alone does not mean toxins will be present; often the cyanobacterial colonies can bloom with little to no toxin being released into the waters. Conversely, the lack of a visible bloom does not mean there aren’t toxins being generated by submerged or benthic colonies. However, we do have a few tools for tracking them effectively, understanding the risk of a toxic event, and uncovering the mechanisms that control their responses to different conditions.

• Vertical profilers
• Satellite data; refer to CyAN pubs for band info, details
• Tracking populations & nutrient levels through grab samples

Data-driven Predictions

The Dashboard

• Add a GIF of a screen recording of dashboard charts & usage

The online HAB dashboard is the centralized location for all of the datasets and predictions discussed above. Upon loading, the user has a navigation pane along the side of the screen, overlaid onto a map of the latest chlorophyll-a concentrations in the waterbody. The sidebar shows the latest estimates of HAB risk level for the waterbody, with tabs that explore the empirical data contributing to those predictions (weather records, water sample analyses, algal population levels, streamgage readings, etc.). This gives an immediate measure of risk, along with the history of the risk predictions, so that stakeholders can determine the trend of risks over time and contrast it with trends in environmental variables.

Some customers are able to deploy vertical profilers in their waterbodies, providing persistent, depth-

Additional satellite layers are available, such as the Cyanobacterial Assessment Network (CyAN) estimate of cell counts for cyanobacteria. This layer was developed by scientists at the EPA and NASA (link) [FIX], and utilizes the multispectral data available from the Sentinel-3 mission to detect phycocyanin in surface waters. In particular, the Ocean and Land Color Instrument has 21 spectral bands that were selected for monitoring ecosystems, agriculture, and waters; one of these bands ()

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