The cells clear first. The toxin stays behind.
Discolored water is what the public sees. What closes a bed, empties a beach or reaches a hospital is chemistry, on its own timetable.
Toxicity does not follow from a bloom being there, and a toxic bloom need not be visible. So bloom management runs on assays, and a system that takes the biomass down alone has done half the job.
Three toxin families carry most of the public health and regulatory pressure. They behave differently, are measured differently, and close different things.
Brevetoxin — the one you breathe
Florida red tide, Karenia brevis, turns its toxin into an air quality problem. Wave action aerosolizes brevetoxins and onshore wind carries them inland. The clinical literature describes an apparently reversible upper-respiratory syndrome — coughing, throat irritation, chest tightness — and a markedly harder version in people with asthma.
Fleming and colleagues record asthmatic participants reporting symptoms for up to at least five days after a single one-hour beach exposure. A closure window is set around that group.
A beach where some visitors start coughing empties, and stays empty long after the aerosol has gone. That drives the tourism losses on the Florida record.
Domoic acid — the one with no antidote
Pseudo-nitzschia blooms produce domoic acid, which causes amnesic shellfish poisoning. At low doses that means nausea, vomiting and diarrhea. At higher doses, seizures, coma, irreversible short-term memory loss and death, with elderly people at highest risk.
There is no antidote. And cooking or freezing does not destroy it, so no step downstream of harvest makes contaminated tissue safe.
That is why a shellfish closure holds after the water has cleared, and why the 2015 West Coast event cost $97.5 million in Dungeness crab landings and roughly $40 million more in razor-clam tourism, against a bloom most people never saw.
Microcystin — the one in the tap
Cyanobacterial blooms in fresh and brackish water produce microcystins, of which microcystin-LR is the most studied. WHO sets the provisional drinking-water guideline at one microgram per liter for lifetime exposure and twelve for the short term, meaning the fortnight a utility takes to get treatment back under control. Applying the wrong one closes a supply that did not need closing. Human poisoning presents primarily as liver damage and gastrointestinal illness.
Toledo, Ohio, is the case the field cites. In 2014 a Lake Erie bloom contaminated the municipal supply. A city recovers its water system faster than its confidence in it.
What this changes about treatment
The closure order is written against the assay.
Biomass is the visible target.
Reopening a bed, lifting an advisory, restarting an intake: each is decided by a public health authority on assay data. Water color has no standing in that room.
So toxin work is governed at the source term, in the seconds before a discharge can form. Nothing waits aboard for a laboratory: the duty moves water through at a design rate near 5,000 gallons a minute and hands it back a few meters from the intake, and no bay is impounded. A toxin mission runs to a tighter envelope and more conservative settings, and the inline instruments are authorized to cut the oxidant or stop the intake on their own.
That costs throughput. Nobody can assay every parcel of a moving stream before it leaves. Instead, the oxidant stops before the water does, an outside laboratory confirms the stable end products no instrument can see, independent scientists are on the same feed, and you can halt an active deployment yourself on any suspected infraction until it is cleared.
The physics, the agency trials and the Florida permit
Bubbles below about a micron hold a charge and disperse instead of collecting at the surface, and their measured gain in gas transfer is in the peer-reviewed record. That science is uncontested, and none of it belongs to this group.
In 2018 NOAA's coastal science centers reported an ozone nanobubble system clearing algae from an eight-acre Florida pond inside two days, with reoxygenation held and no apparent harm to the life in the water. A separate ballast-water evaluation two years later found no statistically significant adverse residual toxicity downstream. Different equipment, different partners. Those releases say the approach is workable, and nothing about a SeaBreather hull.
The field record is one permit. Florida DEP granted Alarivean, Inc. permit FLOA00062 in September 2024, under Chapter 403 of the Florida Statutes and on a five-year window, to trial an ozonated-seawater craft against red tide with live Karenia brevis above 100,000 cells per liter as the gate. The Sarasota Bay Estuary Program and START logged it independently. The estuary program supported the application on technical grounds, took no funding for it, and has asked to hold the instruments when open-water measurements are taken.
Alarivean also completed the term of a Cooperative Research and Development Agreement with NOAA, entered through AMURI, and work under it with Dr Peter Moeller established that this treatment neutralizes toxins by taking apart the structure that makes them toxic, so nothing precipitates or has to be collected afterward. The term is finished. There is no CRADA in force today. Dr Moeller advises the program in a personal capacity and still checks the verification work. CRADAs are private instruments, none of them published, so this is the company's account of its own research; a research agreement stops well short of an approval, and a completed one shorter still.
That CRADA was organized around one nanobubble generator the program no longer uses. Later work has run with Arizona State University, the Middle East Desalination Research Center and more, at facilities that suit the scale being tested next.
Two things stay open. Whether the bubbles themselves generate hydroxyl radicals is argued in the literature, so no plan assumes they do. And nobody has published an open-water result for this class of treatment, the licensee included. The pond and the ballast tank are what exists. A calibration phase produces a number on your own water, on a bounded area, against parameters agreed before it starts.
Where these figures come from
- NOAA Fisheries — Hitting us where it hurts: the untold story of harmful algal blooms.
- WHO — Microcystins in drinking water, background document.
- California Department of Public Health — Domoic acid fact sheet.
- Peer-reviewed respiratory and toxicology literature — aerosolized brevetoxin exposure, PMC.
- NOAA National Centers for Coastal Ocean Science — Nanobubble technology validated for remediation of harmful freshwater algal blooms, 26 September 2018.
- NOAA National Centers for Coastal Ocean Science — Nanobubble ozone technology shown to safely eliminate invasive species in ballast water, 1 July 2020.
- Chae, Kim, Kim & Fortner — Reactive oxygen species generation from nanobubbles, ACS ES&T Engineering, 2023.
- Sarasota Bay Estuary Program and START (Solutions To Avoid Red Tide) — public documentation of FDEP permit FLOA00062, 2024.
Asked in the first meeting
Assays, cooking, and what can be guaranteed
Is a bloom dangerous even when the water looks normal?
It can be. Toxin concentration and cell count are related but not interchangeable, and shellfish tissue holds toxin after the water has cleared.
Closures are decided on assay results, so verification is by assay. A bay that looks clean and assays badly is the report you get.
Does cooking make contaminated shellfish safe?
No. Domoic acid is not destroyed by cooking or freezing, and there is no antidote for amnesic shellfish poisoning.
Closures exist because there is no downstream fix once toxin is in the tissue. Prevention in the water is the only lever left.
Can HABslayer guarantee a toxin level in my water?
No. Not before a calibration phase has run on that specific water.
Committed up front: the method, the standard the discharged water is held to, the measurement interval and the report format. Everything numeric follows the measurement. The pass-or-fail thresholds for calibration are written down before the work starts.
For the public health desk
Which species, and which assay do you run?
The organisms your monitoring program finds, the toxin panel you test against, and who signs a closure order in your jurisdiction. Those three decide what a bloom program can be held to on your coast.