Prymnesium (golden algae)

Prymnesium parvum · Phytoplankton

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NativePlanktonic algae (in the water)Can produce toxins

Also called Prymnesium parvum, Golden alga, golden algae, Texas golden algae

Can produce toxins

Only a lab test shows whether a bloom is toxic. Keep people, pets and livestock out of discolored or scummy water until it is tested.

How to identify Prymnesium (golden algae)

Under the microscope: small, oval golden yellow cell with two flagella and a short, stiff haptonema between them
Two golden plastids along the sides
In the water: blooms turn water yellowish, golden or tea colored and can foam
Dying fish gasping at the surface or bleeding from the gills is often the first sign

Similar species

Ochromonas and other golden flagellates lack the haptonema; Cryptomonas has a groove and no haptonema.

Profile

Season	Often cool season blooms from late fall through spring.
Starts	Cool water; favors salty, hard water
Light	Moderate light
Depth	Throughout the water column
How it spreads or reproduces	Cell division and resting cysts
Habitat	Brackish or high salt, hard water lakes and reservoirs, especially in dry western areas with evaporation and high conductivity.

Why it matters in a lake

Produces prymnesins, toxins that damage fish gills and cause large fish kills. Blooms are not considered a public health threat and no harm to people or livestock has been shown, although this has not been fully studied. Confirmed in Wyoming and Washington but not yet documented in Idaho or Oregon.