Patterns of detrital biofilm metabolism in urban and nonurban stream environments when exposed to selected pharmaceuticals

Abstract

Contamination of streams with pharmaceuticals is increasingly common, yet research on impacts to aquatic ecosystems is relatively limited. Microorganisms are vital components in stream environments, making it important to identify consequences of their exposure to pharmaceuticals. My research objective was to study how selected pharmaceuticals impact detrital biofilm metabolism in urban and nonurban streams. First, biological oxygen demand (BOD) of red maple (Acer rubrum) biofilms was measured in an urban and a nonurban stream; BOD was greater at the urban site. Second, using a mesocosm study, BOD of biofilms on single-species and mixed-species leaf litter from the same sites was measured after exposure to two antimicrobial agents. Pharmaceuticals did not affect microbial respiration compared to controls, however, there were significant differences among some treatments at the nonurban site. Also, BOD of mixed-leaf biofilms was not different from that of single-species litter after exposure. An unexpected finding was the detection of climbazole in the nonurban stream, suggesting possible septic tank leakage from surrounding areas. Overall, results indicate that effects of pharmaceuticals on stream biofilms depend on the pharmaceutical mixture components and concentrations, as well as the substrates upon which biofilms grow.