Researchers have developed numerous per- and polyfluoroalkyl substances (PFAS)-free aqueous film-forming foam (AFFF) formulations to replace PFAS-containing AFFF used for fire suppression. As part of the Department of Defense’s Strategic Environmental Research and Development Program (SERDP), we examined the direct lethal effects of seven PFAS-free AFFF and a PFAS-containing AFFF on 14 aquatic species using a series of lethal concentration (LC50) tests. We assessed the LC10, LC50, and LC90 values using log–logistic and logit analyses. Across all aquatic species tested, we discovered that exposure to at least one PFAS-free AFFF was more or as toxic as exposure to the PFAS-containing AFFF. For most cases, National Foam Avio F3 Green KHC 3% and Buckeye Platinum Plus C6MILSPEC 3% were the most and least toxic formulations, respectively. Moreover, we found consistency among results from multiple experiments using the same minnow species (Pimephales promelas) and among closely related taxa (e.g., daphnids, amphibians). Lastly, the LC50 values for AFFF formulations trended lower for tested marine species as compared to those of freshwater species. These results dramatically increase the current knowledge on the potentially toxic effects of AFFF but also highlight the need for additional research and the development of new PFAS-free AFFF that are more “ecologically friendly” than those containing persistent PFAS.

It is well-established that both resources and infectious disease can influence species invasions, but little is known regarding interactive effects of these two factors. We performed a series of experiments to understand how resources and parasites can jointly affect the ability of a freshwater invasive zooplankton to establish in a population of a native zooplankton. In a life history trial, we found that both species increased offspring production to the same degree as algal resources increased, suggesting that changes in resources would have similar effects on both species. In a microcosm experiment simulating an invasion, we found that the invasive species reached its highest densities when there was a combination of both high resources and the presence of a shared parasite, but not for each of these conditions alone (i.e., a significant resource x parasite interaction). This result can be explained by changes in native host population density; high resource levels initially led to an increase in the density of the native host, which caused larger epidemics when the parasite was present. This high infection prevalence caused a subsequent reduction in native host density, increasing available resources and allowing the invasive species to establish relatively dense populations. Thus, in this system, native communities with a combination of high resource levels and parasitism may be the most vulnerable to invasions. More generally, our results suggest that parasitism and resource availability can have interactive, non-additive effects on the outcome of invasions.

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