Harmful Algal Blooms (HABs)

Lake Basics & Water Quality

Protect people, pets, and the lake by recognizing HABs early, making smart choices, and sharing useful information with the right folks.

Rule of Thumb

When in doubt, stay out.

What Is a HAB?

A harmful algal bloom occurs when algae—often cyanobacteria (also called blue‑green algae)—grow rapidly and may produce toxins that can affect people, pets, and wildlife.

Important: You cannot tell whether toxins are present by sight alone.

Why Blooms Happen

  • Nutrients

    Elevated phosphorus and nitrogen from runoff, eroding soil, leaf litter, fertilizers, and failing septics.

  • Weather

    Warm temperatures, sun, and light winds that let surface waters stagnate.

  • Lake Physics

    Summer stratification and calm periods that hold algae near the surface.

Recognizing a Possible HAB (Plain‑Language Clues)

Appearance
  • "Pea soup" look
  • Green paint‑like streaks
  • Surface scums
  • Bluish‑green mats
  • Unusually turquoise, bright green, or brown‑green water
Texture
  • Slick or paint‑like when disturbed
  • Streaks may collect along wind‑blown shorelines
Odor
  • Earthy smell
  • Musty smell
  • Septic smell during heavy blooms
Rapid Change
  • Clear water in the morning
  • Scummy by afternoon
  • Especially during hot, calm days

Health & Exposure Basics

People:
Skin, eye, and throat irritation; stomach upset if swallowed; headaches. Severe symptoms are possible with high exposures.
Pets & Livestock:
Higher risk because they drink lake water and lick wet fur; can become ill quickly.
Fish:
Toxins concentrate most in organs. If a bloom is present, avoid harvesting. Otherwise, trim skin/fat, remove organs, and rinse fillets.
Drinking Water:
Never drink untreated lake water. Boiling does not remove algal toxins. Household filters may not remove them either.

Immediate Actions if Exposed

  1. Leave the water and rinse off with clean water as soon as possible.
  2. Do not let pets groom themselves; rinse them thoroughly.
  3. Watch for symptoms (people: rash, vomiting, headache; pets: drooling, weakness, seizures). Seek medical or veterinary care if symptoms occur.
  4. Do not cook with or boil bloom water.

Simple Decision Guide for Recreation

If you see scum, streaks, or paint‑like water:

Do not swim; keep pets/livestock away; avoid contact until conditions clear.

If water is greenish but no visible scum:

Use caution; avoid swallowing water; rinse after contact; keep sensitive individuals and pets out.

After a bloom subsides:

Wait for the water to look clear across the area and for cooler/windier conditions to persist before resuming normal use.

What to Record and Report

If you suspect a HAB, collect clear observations that help responders. Write down:

  • Date & time of observation
  • Location (lake name, nearest public access or landmark, shoreline description)
  • Extent (small cove, entire shoreline segment, whole bay, open water streaks)
  • Appearance & color (scum, streaks, paint‑like, pea soup; green/turquoise/brown‑green)
  • Weather (hot/calm, recent storm, strong sun, wind direction pushing material onto shore)
  • Any illnesses or pet exposures you're aware of

Share your report with your local health department, environmental agency, or lake association using their preferred channels. If public beaches or intakes could be affected, escalate promptly.

Common Myths—And Facts

Myth

"If I boil the water it's safe."

Fact

Some toxins survive boiling.

Myth

"If the water is clear there's no risk."

Fact

Toxin levels don't always match what you see.

Myth

"A home pitcher filter will fix it."

Fact

Many do not remove algal toxins.

Myth

"Winter/fall means no blooms."

Fact

Blooms can occur outside summer during warm spells or in shallow areas.

Prevention You Can Do Right Now

  • Keep leaves and grass clippings out of streets and ditches
  • Reduce fertilizer use; if needed, use low‑ or no‑phosphorus products and follow label rates
  • Stabilize bare soil and vegetate shorelines with native plants
  • Capture runoff with rain gardens, swales, barrels, and infiltration practices
  • Maintain septic systems on the recommended schedule
  • Clean, drain, and dry boats and gear to limit invasive species that can change bloom dynamics

Coordinating as a Community

  • Track simple weekly observations from consistent spots during warm seasons
  • Share updates with neighbors and your lake group; align on plain‑language advisories ("avoid contact in the cove near… until conditions clear")
  • Pair observations with nutrient‑reduction projects so each report leads to action

Bottom Line

See scum or paint‑like water? Stay out, keep pets out, rinse off, and report. Reduce nutrients to reduce bloom risk over time.

When in Doubt

STAY OUT

If you see scum, streaks, or unusual coloring, avoid contact and keep pets away until conditions clear.

Related Topics

Key Takeaways

  • You cannot tell if toxins are present by sight alone
  • Boiling water does NOT remove algal toxins
  • Pets are at higher risk—keep them away from suspicious water
  • Document and report suspected blooms with clear details
  • Prevention starts with reducing nutrient inputs to the lake

Who to Contact

Report suspected HABs to:

  • Local health department
  • Environmental agency
  • Lake association

For medical concerns: Contact your doctor or veterinarian immediately if symptoms develop after exposure.

Have Questions?

Connect with your local lake association or health department for guidance.

Contact Us