Harmful algal blooms (HABs) are large growths of cyanobacteria that may change the water color or form surface scums and occur in lakes, reservoirs, ponds, and less frequently in streams. Cyanobacteria can produce deadly toxins that are harmful to human, livestock, and pet health. These tiny plant-like bacteria produce toxins that can attack the kidneys, liver, reproductive and nervous systems, and irritate the skin. Animals and swimmers, which often ingest surface waters, are at particular risk.
Cyanobacteria blooms tend to take two forms:
- HABs can be suspended throughout the water column. Blooms forming in the water column can look like “pea soup,” green clumps or globules, green mats, or grass clippings.
- HABs can form a thick surface scum. These scums develop when the cyanobacteria begin to die and cannot control their buoyancy. These scums can be especially toxic. These HABs are often described as looking like “spilled paint” or streaks on the water surface and may change color (green, white, blue, red, purple, brown) over time.