What are toxic algae, and how dangerous are they really?

In this episode of AquaDiary, Ally breaks down the health risks of harmful algal blooms (HABs), including cyanotoxins like microcystin, how exposure can affect people and pets, why dogs can die within hours, what the health advisory limits are federally and by state, what toxic blooms mean for lakes and drinking water systems, how to find out if your state is monitoring for cyanotoxins, how to see if you're being exposed to toxins in your drinking water, and why public awareness still lags behind the science. She also explores emerging research into possible long-term neurological risks, including whether certain algae toxins may one day be linked to diseases like Alzheimer’s.

Topics covered: toxic algae, mattoon water crisis, harmful algal blooms (HABs), cyanobacteria, cyanotoxins, microcystin, anatoxin-a, BMAA, algae toxins, dog deaths from algae blooms, toxic lake water, harmful algal bloom health risks, cyanotoxins in drinking water, algae blooms and pets, lake water safety, tap water contamination, public health, water treatment, health advisories, emerging research, and environmental science.

References:

• Caller, T.A., et al. (2009). A cluster of amyotrophic lateral sclerosis in New Hampshire:

• A possible role for toxic cyanobacteria blooms. Amyotrophic Lateral Sclerosis, 10(Suppl. 2), 101–108.

• Cox, P.A., et al. (2016). Chronic exposure to BMAA may trigger Alzheimer's-like pathology in primates. Proceedings of the Royal Society B.

• Durden, W.N., et al. (2025). Alzheimer's disease signatures in the brain transcriptome of estuarine dolphins. Communications Biology, 8(1), 1400.

• Environmental Working Group. Tap water database — does your state monitor microcystin https://www.ewg.org/tapwater

• Garamszegi, S.P., et al. (2023). Detection of BMAA in postmortem olfactory bulbs of Alzheimer's disease patients. Toxicology Reports, 10, 392–400.

• IPM Newsroom. (2025, September 5). What to know about algal blooms after Mattoon's water crisis.
• NPR Illinois. (2025, September 15). Toxic bacteria shut down Mattoon's water supply.
• U.S. Environmental Protection Agency. (2015). Health advisory for microcystins (0.3 µg/L children; 1.6 µg/L adults). https://www.epa.gov
• World Health Organization. Guidelines for drinking-water quality. [Microcystin-LR guideline: 1.0 µg/L]

Links:

• EWG Tap Water Database (microcystin by state): https://www.ewg.org/tapwater
• NY HABs Tracker (harmful algal bloom advisories): https://www.dec.ny.gov/chemical/77118.html
• Find your Annual Drinking Water Report: Search [your town name] + 'annual drinking water report' or https://www.epa.gov/ccr
• Water filter — tested for microcystin removal (Berkey): https://amzn.to/4t25nPY
• Microcystin regulations by state: https://static.ewg.org/reports/2019/microcystin/img/EWG_Microcystins-StateReg_C02.pdf

In 2014, a harmful algae bloom shut off drinking water for nearly half a million people in Toledo, Ohio. The city spent 65 million dollars responding. They've invested half a billion dollars in upgrades since. And every summer, the blooms come back.

Harmful algal blooms are getting worse. And the reason why is more complicated than most people realize, and more alarming than most officials or lake managers are admitting.

In this episode, environmental scientist and host Ally breaks down the full science of toxic algae blooms to help you think like a scientist, including the ancient biology behind them, how phosphorus fuels toxic growth, how lake stratification and turnover distribute nutrients through the water column, and why new peer reviewed research suggests that even lakes with reduced pollution are still experiencing blooms.

This is the science behind the headlines, explained.

References:

• Nürnberg GK. (2025). Importance of considering internal phosphorus loading during climate change. Lake and Reservoir Management, 41:3, 165–179.
• Jane SF et al. (2023). Longer duration of seasonal stratification contributes to widespread increases in lake hypoxia and anoxia. Global Change Biology, 29(4), 1009–1023.
• Harrison JW et al. (2025). Hypolimnetic photosynthesis precedes a Microcystis bloom in a temperate, oligo-mesotrophic reservoir. Lake and Reservoir Management, 41:194–209.
• Meyers K et al. (2025). National forecasting of cyanobacterial harmful algal bloom events: a 3-year model evaluation. Lake and Reservoir Management.
• Chaffin JD et al. (2023). Microcystin congeners in Lake Erie follow the seasonal pattern of nitrogen availability. Harmful Algae, 127, 102466.
• Taranu ZE et al. (2014). Nitrogen forms influence microcystin concentration and composition via changes in cyanobacterial community structure. PLOS ONE.
• NOAA/NCCOS ongoing research: Evaluating the Effects of Nitrogen Form and Concentration on Toxin Phenotypes of Microcystis. coastalscience.noaa.gov
• CDC MMWR report: McCarty CL et al. (2016). Community Needs Assessment After Microcystin Toxin Contamination of a Municipal Water Supply — Lucas County, Ohio. MMWR, 65(35):925–929.
• Schopf JW. The Fossil Record of Cyanobacteria. In: Whitton BA, editor. Ecology of Cyanobacteria II. Springer; 2012. — 3.5 billion year stromatolite evidence
• Gueneli N et al. (2024). Oldest thylakoids in fossil cells directly evidence oxygenic photosynthesis. Nature. — 2.1 billion year undisputed confirmed fossil
• CNN. (August 3, 2014). 400,000 in Toledo, Ohio, water scare await test results. CNN.com
• Circle of Blue. (2015). The Toledo Water Crisis, One Year Later. circleofblue.org
• The Statehouse News Bureau. (August 2, 2024). A decade ago, Toledo lost access to its water. statenews.org
• University of Toledo. (July 15, 2024). 10 Years After Water Crisis, UToledo Researchers Remain Committed to Protecting Region's Drinking Water.
• Chaffin JD, Westrick JA, Reitz LA, Bridgeman TB. (2023). Microcystin congeners in Lake Erie follow the seasonal pattern of nitrogen availability. Harmful Algae, 127, 102466. DOI: 10.1016/j.hal.2023.102466. — nitrogen availability influences microcystin congener composition and therefore bloom toxicity; more toxic forms dominate late season as nitrogen depletes
• Lisboa, MS, RL Schneider, LG Rudstam, MT Walter. 2025. Groundwater phosphorus contributions comparable to tributaries in a large, mesotrophic, polymictic lake. Science of the Total Environment. 1008:180978. doi.org/10.1016/j.scitotenv.2025.180978

Beach closures after rain aren't random. They're the result of a stormwater and sewer system that was never designed to handle what we're asking it to do — and in hundreds of American cities, including many in New York State, that system is sending raw sewage and dozens of chemicals directly into lakes and rivers when it downpours.

In this episode, environmental scientist Ally breaks down how stormwater runoff works, what combined sewer systems are and why they overflow, what the New York State Sewage Pollution Right to Know Law means for you, and why your lake looks and smells different after a heavy storm - scientific facts, articles, and research - all in plain English.

Topics covered: stormwater runoff, combined sewer overflows, CSOs, impervious surfaces, water pollution, beach closures, New York water quality, drinking water safety, lake pollution, SPDES permits, green infrastructure.