Smoked cigarette butts (CBs) are a pervasive source of litter wherever humans intersect with the natural environment. Previous studies have shown that when smoked CBs are introduced to aquatic environments, the toxins that have accumulated in the filters leach into the liquid forming cigarette butt leachate (CBL). It is possible that CBL influences and complicates mortality rates, behaviors, and predator-prey interactions of organisms that live in those environments. The rockpool ecosystem on the James River (Richmond, Virginia) is a good model for the potential damage that CBs can do in aquatic environments.
After a pilot experiment, CBL proved toxic to snails even at concentrations of less than one CB per liter. In the presence of crayfish, snails flee the water to avoid predation. Snails exhibit the same fleeing behavior when exposed to water in which crayfish had eaten conspecific snails. Because fleeing will remove the snails from the toxic CBL solution, we hypothesized that the combination of CBL and predation cue would improve the survivorship of the snails exposed to the CBL. This hypothesis was tested through field surveys of CB locations and a laboratory procedure crossing three levels of CBL concentration and the presence of a predation cue.
Results/Conclusions
Analysis of the coordinates collected from the visual surveys of the CBs revealed hotspots of anthropogenic pollution. Results of the laboratory experiment revealed that predator-prey interactions are able to alter the toxic effects of CBL in snails. By altering normal behavior, the predator cue kept the snails out of the toxic CBL and marginally decreased mortality rates in snails exposed to the pollutant. However, the interaction may not be as clear as we hypothesized due to the fact that the snails desiccate when they are out of water for extended periods of time. CBL and predator cue increased the number of egg sacks produced by the snails. This research shows that CBL and other anthropogenic pollutants are capable of directly and indirectly affecting mortality and fecundity rates in nontarget organisms. Further research is needed to understand the underlying complexities of the effects of CBL on the ecosystems where they have been introduced.