The Effects of Pharmaceuticals and Personal Care Products (PPCPs) on Predator-Prey Dynamics

Abstract

Predators impact community structure and stability by altering the abundance, distribution, and behavior of their prey and through the cascading effects that these changes have on other trophic levels. However, the effects of predators on food-web dynamics may be changing and becoming less predictable as ecosystems become increasingly polluted by anthropogenically-produced chemicals. This research investigates how an emerging class of contaminants – pharmaceuticals and personal care products (PPCPs) – can influence predator-prey interactions by interfering with predator consumptive (i.e. prey consumption) and non-consumptive (i.e. prey behavior) effects on prey. Specifically, a predator consumption experiment was conducted to assess how three common PPCPs – caffeine, DEET, and triclosan – affect mosquito fish predation on mosquito larvae, and an oviposition experiment was performed to determine how these three PPCPs influence the effects of predator cues (mosquito fish cues) on mosquito egg raft deposition, larval abundance, and adult emergence. I demonstrate how all three PPCPs, individually and combined as a mixture, reduced mosquito predator consumption rates. The presence of predator cues reduced mosquito oviposition and larval abundance for all PPCP treatments except for DEET. Predator cues reduced mosquito adult emergence across PPCP treatments, however, mosquitoes that were exposed to caffeine did not emerge as adults even in the absence of predator cues. This study shows that the effects of PPCPs and mosquito predators together cannot be predicted by their individual effects on mosquitoes, and it addresses the need to investigate the complex interactions between biologically active PPCPs and biological cues on contaminated communities.