Manipulative whole-pond experiments to examine the ecosystem-level effects of pesticide applications

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In this study we will use whole-ecosystem experiments to examine the effects of a common chemical herbicide on aquatic communities. We do this in natural systems where we can explore how fertilizer inputs and predation interact with herbicide effects. Until recently, glyphosate (i.e. RoundUp and Vision), a chemical herbicide that is widely-used to control vegetation in forestry, agriculture, and on military installations, was considered by many to be a relatively benign herbicide. New research suggests that glyphosate may have greater negative environmental impacts than had previously been suspected. However, the results have been ambiguous, in large part because the experiments were carried out in small artificial systems that cannot capture all of the spatial, temporal and biological heterogeneity present in nature. We have the unique opportunity to establish a set of 36 experimental ponds at CFB Gagetown in southern New Brunswick to determine the effects of glyphosate in natural systems that capture all the complexity found in nature. We will conduct replicated experiments with all ponds separated into two halves by an impermeable curtain and treatments applied to one half while the other half is left untreated as a control. Treatments will include glyphosate at predicted (i.e. worst case scenario) and realistic environmental concentrations, alone and in combination with agricultural fertilizers and natural predators of amphibians. We will examine impacts of these treatments on a variety of aquatic organisms, including phytoplankton, macrophytes, and invertebrates, but the primary emphasis of this work will be on amphibians because of their unique developmental biology, physiology and potential as indicators of environmental stress. We will be testing to see if new glyphosate formulations, alone or in combination with fertilizers and predators, have effects on amphibian gene expression, hormone levels, fecundity, survival, sex ratios, disease prevalence, deformities, abundance and species richness. These results will be used by our partners, the Department of National Defence and Canadian Forest Service to develop watershed management plans.