Ecotoxicity of binary mixtures of Microcystis aeruginosa and insecticides to Daphnia pulex

Ecotoxicity of binary mixtures of Microcystis aeruginosa and insecticides to Daphnia pulex

Harmful bluegreen algae such as cyanobacteria can have large impacts on aquatic ecosystems and ponds. Often, these cyanobacteria are not the only form of toxic stress present. In our recent paper, we study how cyanobacteria together with insecticides  used in crop protection can impact the model organism Daphnia. The results show that cyanobacteria and insecticides together can have significant effects on the reproduction of the daphnid. Depending on the type of insecticide used, these effects are  larger, smaller or equal to our expectations.

Scientific abstract

In Aquatic ecosystems, mixtures of chemical and natural stressors can occur which may significantly complicate risk assessment approaches. Here, we show that effects of binary combinations of four different insecticides and Microcystis aeruginosa, a toxic cyanobacteria, on Daphnia pulex exhibited distinct interaction patterns. Combinations with chlorpyrifos and tetradifon caused non-interactive effects, tebufenpyrad caused an antagonistic interaction and fenoyxcarb yielded patterns that depended on the reference model used (i.e. synergistic with independent action, additive with concentration addition). Our results demonstrate that interactive effects cannot be generalised across different insecticides, not even for those targeting the same biological pathway (i.e. tebufenpyrad and tetradifon both target oxidative phosphorylation). Also, the concentration addition reference model provided conservative predictions of effects in all investigated combinations for risk assessment. These predictions could, in absence of a full mechanistic understanding, provide a meaningful solution for managing water quality in systems impacted by both insecticides and cyanobacterial blooms.

Full reference

Asselman J, Janssen CR, Smagghe G, De Schamphelaere KAC. 2014. Ecotoxicity of binary mixtures of Microcystis aeruginosa and insecticides to Daphnia pulex. Environ Pollut 188, 56-63. DOI: 10.1016/j.envpol.2014.01.018