Two measurements; one of them closes a tap

In 2014 about 500,000 people around Toledo woke to advice not to drink from the tap. That advisory came from a toxin measured inside a treatment plant. Nothing visible on the lake produced it.

The seasonal index is a different instrument doing a different job. It counts biomass across a bloom's peak 30 days, and this year NOAA puts the forecast at 3.5 with a range of 3 to 4.5, where 3 to 5 is moderate. A good number, honestly labeled. Simply not the one a duty engineer needs at four in the morning.

The World Health Organization is unusually direct about where to look. Microcystins are the most commonly reported cyanobacterial toxins worldwide, drinking water is the most likely route of exposure, and averaged concentrations may underestimate the risk at a particular site, so the place to sample is the place the water is actually used. It also says the main driver is nutrients from farm runoff and wastewater, and that controlling those is the primary long-term management option.

So a reasonably healthy version of this water is not a lake without cyanobacteria in it. It is one where an intake is governed by a toxin concentration, measured where the water is drawn, on a cadence somebody outside the utility can check.

What work in the water then does to that concentration is a question about a given intake. Alarivean has not yet published open-water data for HABslayer; a paid pilot, with no obligation to subscribe, or the calibration phase of a full program, where payment waits on the committed outcomes, measures it in the client's own water.

NOAA's western Lake Erie forecast of 25 June 2026, including the line about size and toxicity: https://coastalscience.noaa.gov/news/moderate-harmful-algal-bloom-predicted-for-western-lake-erie-in-summer-2026/ The World Health Organization's background document on microcystins: https://cdn.who.int/media/docs/default-source/wash-documents/wash-chemicals/microcystins-background-201223.pdf The Toledo figures, via NOAA Fisheries: https://www.fisheries.noaa.gov/west-coast/science-data/hitting-us-where-it-hurts-untold-story-harmful-algal-blooms