Pharmaceuticals and personal care products alter growth and function in lentic biofilms

Environmental context Pharmaceuticals and personal care products are routinely found in waters discharged from treatment plants and in surrounding aquatic ecosystems. Despite the widespread occurrence of these biologically active agents, there is limited understanding of their potential effects on key ecosystem processes such as primary production, ecosystem respiration and algal growth. This paper examines the effects of five common pharmaceuticals on the rates of these fundamental processes. Abstract Pharmaceutical diffusing substrates were used to study in situ responses of aquatic biofilms in an urbanised lentic ecosystem to five pharmaceutical and personal care products (PPCPs; caffeine, cimetidine, ciprofloxacin, diphenhydramine and metformin). The pharmaceutical diffusing substrates consisted of porous biofilm substrates placed atop a mass of agar amended with 2.5mM of the PPCP compound of interest. Over 21 days, biofilms growing on the substrata were exposed to slow diffusion of the PPCP through the agar and porous substrate. Algal biomass was suppressed by exposure to diphenhydramine (-81%) and ciprofloxacin (-50%). Gross primary production was completely suppressed by diphenhydramine exposure but stimulated by caffeine (+39%) and cimetidine (+46%). For heterotroph biofilms, community respiration was suppressed by exposure to diphenhydramine (-24%). To characterise PPCP exposure, rates of diffusion from the pharmaceutical diffusing substrates were measured at 10, 20 and 30 degrees C. Diffusion was Fickian for all compounds and all temperatures. Diffusion coefficients, D, were in the range 1.5x10(-10) to 1.1x10(-9)m(2)s(-1). From diffusion data, average release rates over 21 days were typically 30-50ngmin(-1)cm(-2) at 20 degrees C. The results show that PPCPs can dramatically affect rates of key ecological processes, and the relationship between release rate and ambient concentration of PPCPs is discussed.