LAUSR

Cigarette butts are a prevalent form of litter containing numerous toxic chemicals. Because cigarette butts are frequently deposited on the ground and carried into water bodies, greater understanding of the toxic effects of cigarette butts in aquatic ecosystems is needed. We examined the toxicity of cigarette butts to algal growth and diatom health—especially pertinent because of the strong ecological role of these organisms. We modified the agar-based nutrient-diffusing substrate method by using cigarette butt leachate (at 10, 5, 2.5, and 1.25 butts/l concentrations), a whole cigarette butt, and a plain agar control. After incubating for 10 days in a small stream, the biofilms from the diffusing substrates were assessed for algal biomass and diatom health (chloroplast intactness and size of lipid bodies in two abundant species of Navicula). There were no significant differences among the cigarette butt treatments for algal biomass or diatom health; hence, evidence of toxic effects was not found. Other studies have demonstrated cigarette butt leachate toxicity to fish and aquatic invertebrates, but these studies were done in closed systems. In contrast, in open stream ecosystems, effluent may be quickly diluted and carried away by water flow, and the complex chemical environment of streams likely includes leachate from a variety of riparian leaves that fell into the stream (i.e., algae are naturally exposed to low concentrations of a wide variety of secondary chemicals). Our results do not preclude the finding of toxicity of cigarette butt effluent to algae, including diatoms, in standard toxicity tests.