The toxicological effects of Perfluorooctane sulfonate (PFOS) on a freshwater gastropod, Physa pomilia, and a parthenogenetic decapod, Procambarus fallax f. virginalis
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Perfluorinated compounds (PFCs) are a class of synthetic chemicals that have recently become of increased interest and concern due to their ability to biomagnify through food webs. Perfluorinated compounds, in general, are persistent in the environment and some are carcinogenic. One specific PFC, perflurooctane sulfonate (PFOS), has gained increased attention because it is slightly toxic to aquatic organisms and has been detected in tissues of a wide variety of animals from all over the world including remote species such as polar bears. Like other PFCs, PFOS is highly resistant to chemical, biological, and thermal breakdown, and has high water solubility and low volatility; all of which indicate that PFOS can be both mobile and persistent in the environment. Like many PFAAs, PFOS was a key ingredient in Aqueous Film Forming Foams (AFFF) to fight hydrocarbon-fueled fires on fire-fighting training facilities common to airports and air force bases. Despite the fact that PFCs like PFOS have been detected in many habitats, the fate, biotransport mechanism, and overall ecotoxicology of PFCs are highly uncertain. While there are some data on environmental concentrations and toxicity to organisms, there is a general lack of toxicity data for many aquatic taxa. Despite initial heavy use on U.S. Air Force Bases, there is now growing concern of PFCs as they emerge as important contaminants on a global scale, especially at Barksdale Air Force Base (BAFB) in Shreveport, Louisiana. Of particular concern is whether PFCs from BAFB have now entered surface water and, if so, whether concentrations are high enough to potentially cause human or ecological effects. The research presented here is part of a larger project to develop and implement a comprehensive approach for characterizing PFC contamination and estimating potential human and ecological risk focused on BAFB. The specific research presented here focused on further characterizing the toxicity of PFOS to several aquatic organisms, which represent taxa observed at BAFB. The goal was to determine dose-response relationships as well as species sensitivity to PFOS to ultimately support upcoming environmental risk assessments. Specifically, we conducted acute and chronic (full life cycle) toxicity tests to a model freshwater gastropod (Physa pomilia) and acute and sub-chronic toxicity tests to a new model organism, the marbled crayfish. Physa pomilia are excellent laboratory organisms and can make up a large portion of biomass in the aquatic ecosystem. Like many freshwater gastropods, this species can be readily collected from local habitats, has a short generation time, and is relatively easy to culture in the lab. We conducted several experiments to characterize toxicity of PFOS to P. pomilia including (1) a 96-hour acute toxicity study on adults, (2) a sub-chronic toxicity study on adults, (3) a full-life cycle study, and (4) a behavioral assay. Next, we characterized PFOS toxicity to the marbled crayfish, Procambarus fallax f. virginalis, which is a subspecies of Procambarus fallax. The marmorkreb is unique because it is the first known parthenogenetic decapod; offspring produced by individuals are genetically identical. To determine PFOS toxicity to the marmorkreb we conducted several studies that included (1) an acute juvenile study, (2) a sub-chronic juvenile study, and (3) a juvenile study in which animals were raised under two different densities. The last study was performed because the role of social interaction among crayfish is important due to their display of aggression toward conspecifics. The specific goals for this laboratory project on Physa pomilia and Procambarus fallax f. virginalis were to characterize the ecotoxicity of PFOS in two species that represent environmentally relevant taxa. Because the overall toxicity of PFOS varies considerably among taxa, our hope was to add toxicity data that could then be used to build an updated species sensitivity distribution (SSD) to inform future ecological risk assessments.