General Instructions

Observations should be made at the same location once per week. Observations must be made between 10:00 AM and 3:00 PM. At that time the algae have had a chance to rise from lower in the water column, but cells are not yet likely to have ruptured from the heat of mid-day. All observations submitted and approved will be posted on the Vermont Department of Health cyanobacteria tracker. Anyone providing reports should include information on the extent and type of algae and plant growth, the color of the water, and rate the algae intensity. The rating scale runs from one (a, b, c, or d) to three, with one being clear water with little to no cyanobacteria present and three being a cyanobacteria bloom in progress.

For category 2 and 3 conditions, three digital photographs should be submitted via the online form. Remember to avoid direct contact if the bloom is well developed.

Category 1a: No cyanobacteria present - clear water

Any organisms floating in water column are clear (e.g. insect ‘skins’) rather than green. Leafy or grass-like plants (including duckweed) may be present. Foam may be present.

Objects sitting lower in the water column are clearly visible (red arrow indicates water surface)
Overall appearance of water is clear

Category 1b - No cyanobacteria present - brown and turbid conditions

Brown turbid low visibility through water column

Brown and cloudy does not indicate presence of cyanobacteria

Category 1c - No cyanobacteria present - other plant material

Other material that doesn't count as cyanobacteria might include:

  • Long strands that tangle around paddles or boat hooks
  • Small bright mustard yellow (pollen) or grass green (duckweed) particles
  • Algae attached to rocks or the lake bottom.
Green dots are duckweed; stringy algae are not cyanobacteria
From a distance duckweed may look like green algae or cyanobacteria
Stringy algae attached to the bottom are not cyanobacteria
Duckweed up close

Category 1d - Little cyanobacteria present - Generally safe conditions

Green floating balls may be visible, but only on close inspection and in densities so low that they do not impair recreational enjoyment of the water. There are no surface or near shore accumulations of cyanobacteria.

Water appears perfectly clear
But close inspection shows some cyanobacteria present

Category 2: Cyanobacteria present, but at less than ‘bloom’ levels - Low alert conditions

Numerous green balls (pinhead size or larger) floating in water column, but not accumulated at water surface. Possible small (smaller than a softball) patches of algae accumulation. Open water color not green. Possible narrow band of cyanobacteria accumulation at shoreline.

Some cyanobacteria in water but not a uniform layer
Open water not green.
Band of cyanobacteria at shoreline

Category 3: Cyanobacteria bloom in progress - High alert conditions

Extensive surface scum on water – color may range from green to electric blue (not yellow/pollen). Usually accompanied by a thick accumulation at shoreline. Open water appears green.

Continuous layer of cyanobacteria at the surface - not stringy
Thick surface scum present
Open water surface green to turquoise