Resource Availability Modulates Effects of Fluorine Free Firefighting Foams.

Fluorine-free foam (F3) alternatives that lack per- and polyfluoroalkyl substances (PFAS) are rapidly being adopted for firefighting operations and will be entering ecosystems. Despite this, little is known about their impact on freshwater communities. This knowledge gap is concerning for zooplankton, which are highly sensitive to F3 exposure and serve a keystone role as phytoplankton grazers and prey items for fish and invertebrates. Additionally, it is unknown how resource availability, which widely fluctuates in nature, influences the toxicity of F3s to zooplankton. Using varying algae feeding levels, we investigated how exposure to two F3s, National Foam Avio F3 Green KHC 3% (Avio) and Bio-Ex ECOPOL A 3% FFF (ECOPOL), impacts life history tradeoffs in a freshwater zooplankton, Daphnia magna. At high food levels, sublethal exposure to F3s caused earlier onset of reproduction and increased growth with no apparent tradeoffs, consistent with cases of fecundity compensation or hormesis. In contrast, when no food was provided, individuals exposed to Avio starved earlier, indicating an energetic cost of toxic exposure. This work shows F3s can substantially alter the life history of D. magna, possibly leading to altered freshwater community dynamics and trophic cascades. Additionally, this work highlights that toxic responses, and therefore ecological consequences, can vary based on food availability.