Raphidiopsis (Cylindrospermopsis)

Raphidiopsis spp. · Phytoplankton

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NativePlanktonic cyanobacteria (in the water)Can produce toxins

Also called Cylindrospermopsis, Cylindrospermopsis raciborskii, Raphidiopsis raciborskii

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 Raphidiopsis (Cylindrospermopsis)

Under the microscope: thin, straight or coiled single filaments with a teardrop shaped heterocyst at one or both ends
Some forms have pointed ends and no heterocysts
Akinetes oval, near the ends of the filament
In the water: does not form surface scums; turns water a dull green or brownish

Similar species

Dolichospermum has heterocysts along the filament, not at the tips; Planktothrix and Limnothrix lack heterocysts.

Profile

Season	Late summer when water is warmest.
Starts	About 70 to 75 F and warmer
Light	Low light tolerant
Depth	Spread through the water column, no scums
How it spreads or reproduces	Filament breakage and akinetes
Habitat	Warm, nutrient rich, stable lakes, reservoirs and ponds; spreads mainly in the southern and central US.

Why it matters in a lake

Some strains produce cylindrospermopsin (mainly in Australia and Asia) or saxitoxins (mainly in South America); North American strains often test negative for both, but blooms should still be treated as potentially toxic. Not yet documented as an established bloom former in Idaho, Oregon or Wyoming, but it is spreading north and blooms are easy to miss because it stays mixed in the water.