Cyanobacteria in Ponds & Lakes

Cyanobacteria identification of some of the common species found in and around lakes and ponds. Analyzing samples of potential cyanobacteria under microscope is the best way to confirm if you have a harmful algal bloom.

A type of blue-green algae, is found in damp soil and in shallow water as plankton. Dolichospermum can be found as a colony or as single cells. Dolichospermum will cause blooms during summer months or months with increased temperatures. Dolichospermum (anabaena) produces a green paint like film at the water surface.

Dolichospermum under microscope

Dolichospermum bacteria form cells that resemble beads or barrels. These cells connect end to end creating filaments that look like a pearl necklace. These filaments can either be straight, curved or form a spiral. Filaments may include heterocysts, cells that fix nitrogen. The heterocysts are larger than the normal cells and lack color. They are irregularly dispersed in the colonies.

Under a microscope, dolichospermum is similar in appearance to nostoc.

Is dolichospermum harmful?

Dolichospermum can produce a number of cyanotoxins. These toxins include microcystin, anatoxin, cylindrospermopsin, and saxitoxin.

A type of blue-green algae, is a single cell, but can form colonies with hundreds of cells. When the colonies form, they float to the surface of the water. When cells collect on the surface of the water, this is referred to as a "bloom." Microcystis aeruginosa is found in freshwater with high nutrient levels.

Microcystis blooms usually peak during the warmest months of the year. Growth drops off in the water column in cooler weather. Cells can lay dormant in bottom sediment for extended periods of time.

Microcystis under microscope

Each cell is spherical or ovoidal in shape, but the colonies can vary in appearance.

Is microcystis harmful?

Microcystis can be harmful as it has the potential to produce cyanotoxins, including microcystin and anatoxin. These toxins can pose risks to human health and aquatic life when present in high concentrations.

Even if there is not a current microcystis bloom, scums that have dried along shorelines can still be a threat. These microcystis cells may still contain high concentrations of microcystin for several months after drying. The toxins can dissolve back into the water.

Microcystis bloom

A type of blue-green algae, can be found in soil or floating in calm water. Colonies of nostoc form green jelly-like blobs.

Nostoc under microscope

Within the colonies, spherical cells are linked in chains and held together in a gelatinous structure. Similar to Anabaena, Nostoc has heterocysts that fixate nitrogen.

Is nostoc harmful?

Nostoc can produce the cyanotoxin called microcystin.

Oscillatoria is a filamentous cyanobacteria or blue-green algae, which is found in freshwater. This type of bloom is a benthic cyanobacteria. It forms mats which grow in the sediments of lakes and ponds. Oscillatoria can be found in tangled mats or as one cell.

Oscillatoria under microscope

Oscillatoria are dark green filaments which are unbranched. These filaments consist of a series of cells which look like stacked coins. Oscillatoria moves through water by secreting mucilage to push itself in the opposite direction.

Other similar types of cyanobacteria include phormidium, planktothrix, and limnoraphis.

Is oscillatoria harmful?

Oscillatoria can produce the cyanotoxins microcystin and anatoxin.

A type of blue-green algae, found in freshwater streams, ponds and lakes. Phormidium can be found in tangled mats or free-floating in water.

Phormidium under microscope

Phormidium consists of a fine, smooth filament. The connected cells are square shaped. The end of the cell is tapered.

Is Phormidium harmful?

Phormidium can produce the cyanobacteria toxin anatoxin .