Prymnesium parvum effects on green algae, cladocerans and fish in field and laboratory studies.

Prymnesium parvum, commonly named “golden algae,” has severely impacted fisheries in Texas, USA and other parts of the world. This study explored the environmental conditions during fish kills in Texas inland waters known to trigger P. parvum bloom formation and ecological impacts on a fish model, Pimephales promelas, a model green algae competitor, Pseudokirchinella subcapitata and a model cladoceran predator, Daphnia magna. Prymnesium parvum reduced D. magna survival and reproduction in laboratory and field studies, providing the first evidence of P. parvum impacts on cladocera. Nutrient treatment of N:P = 20 in the field decreased aquatic toxicity of P. parvum to cladocerans and fish. Whereas a potential relationship was observed between lower P. parvum related toxicity to fish, lower bacteria densities and fewer observations of P. parvum swarming behavior in laboratory studies, future studies are needed to understand the relationships among environmental conditions, grazing pressure, mixotrophy and toxin production.