Algaecidal effects of tryptoline, tryptamine, and other microbial metabolites on target and non-target cyanobacteria and freshwater indicator organisms

Cyanobacterial harmful algal blooms (cyanoHABs) are a growing global concern due to their negative impacts on freshwater ecosystems. To control HABs, researchers are developing short- and long-term mitigation strategies by exploiting natural, bacterial-derived products as targeted chemical control reagents to reduce the severity of HABs. In this study, we further characterized the cyanocidal and ecotoxicological properties of tryptoline and tryptamine against bloom-forming cyanobacterial strains using liquid assays and lawn studies. Results from these experiments indicate that tryptoline and tryptamine, elicit higher algaecidal activity against a range of freshwater cyanobacteria. In addition, tryptoline was more toxic to the cyanobacteria strains compared to tryptamine as it was more recalcitrant to degradation than tryptamine. Acute and chronic testing of the Ceriodaphnia dubia and Pimephales promelas imply that the high hazard of tryptoline does not provide a margin of safety to avoid non-targets effects. In contrast, tryptamine was a moderate to high hazard to non-targets. Results from these studies collectively provide data on the feasibility of bacterial-derived algaecides with regards to multi-treatment regimens, bloom densities, and effects on non-target organisms, which is critical for field testing evaluations towards a short-term chemical mitigation strategy. Future works aim to characterize the algaecidal efficacy of novel bacteria and other bacterial-derived secondary metabolites.

Primary Presenter: Forrest Lefler, University of Florida (flefler@ufl.edu)

Authors:

Brianna Fernando, US Army Engineer Research and Development Center Environmental Laboratory  (brianna.m.fernando@erdc.dren.mil)

Forrest Lefler, University of Florida  (flefler@ufl.edu)

Alan Kennedy, US Army Engineer Research and Development Center Environmental Laboratory  (alan.j.kennedy@usace.army.mil)

David Berthold, University of Florida  (Dberthold@ufl.edu)

Lauren May, US Army Engineer Research and Development Center Environmental Laboratory  (Lauren.R.May@usace.army.mil)

H. Dail Laughinghouse IV, University of Florida  (hlaughinghouse@ufl.edu)

Karl Indest, US Army Engineer Research and Development Center Environmental Laboratory  (karl.j.indest@erdc.dren.mil)