Rivers, including the Rio Grande, receive discharges from urban, agricultural, and industrial areas where emerging contaminants of concern, such as pharmaceuticals and personal care products (PPCPs), have been found. PPCPs may affect life span, fecundity, or behaviors of aquatic organisms. Basal members of aquatic food webs such as rotifers and microcrustaceans may be exposed with these toxicants, resulting in decreases in their abundances and thus negatively impacting populations of their predators. Here we determined water quality near a discharge point source and investigated impacts of PPCPs. Long-term, integrative organic samplers (POCIS) were left in situ for about one month near a wastewater treatment plant that discharges into the river. Once PPCPs were identified, three pharmaceuticals were selected to conduct acute toxicity (LC50) assessment and to observe any changes in population growth, fecundity, and/or behavior during long-term exposures at sublethal concentrations in the riverine rotifer Plationus patulus.
Results/Conclusions
Over 40 PPCPs, including carbamazepine, erythromycin, gemfibrozil, ofloxacin, sulfamethoxazole, and trimethoprim were detected at ng concentrations in the river. The LC50 for P. patulus exposed to erythromycin for 48 h was 39.5 mg/L, 821.8 mg/L for ofloxacin, and 170.3 mg/L for trimethoprim (Probit analysis, p=0.001). These compounds caused negative population growth rates (r) and reduced fecundity (Ro) as well as inhibited egg eclosion and increased egg detachment at sublethal concentrations during chronic exposures. Negative effects similar to those observed during exposures of the three individual PPCPs were seen when P. patulus was exposed to a mixture of them. This study provided evidence that PPCPs are in detectable levels in the Rio Grande, the main source of water in Sunland Park, NM and El Paso, TX. The results indicate that antibiotics such as erythromycin, ofloxacin, trimethoprim, and a mixture of these compounds caused negative effects to one of the basal components of the food web, the rotifer P. patulus. The presence of these compounds and their continuous discharges represent a latent risk to the populations of aquatic species that depend on the Rio Grande to survive and thrive.