Population responses of the freshwater rotifer Plationus patulus to Pharmaceuticals and Personal Care Products (PPCPs) from impacted and unimpacted populations

Background/Question/Methods

Pharmaceutical and Personal Care Products (PPCPs) are chemicals of emerging concern that have been detected in many of our nation’s waterways. The Rio Grande is an important system to the United States and to Mexico, including the El Paso/Ciudad Juárez metroplex where it serves as the main source of drinking and irrigation water. The river receives pollutants from industrial, urban and agricultural effluents that likely include PPCPs. Little is known about PPCPs in the Rio Grande and even less is understood about their impacts on aquatic life. We used the rotifer Plationus patulus, a basal member of aquatic food webs, to test acute and chronic toxicity of 3 selected PPCPs (caffeine, triclosan, acetamidophenol). LC50 tests (48hr) were used to determine acute toxicity. While chronic toxicity was assessed using a 6-d life cycle test in which the population growth rate (r) was calculated over a range of concentrations.  Two populations of P. patulus were tested. One from a highly impacted site (EP: Rio Grande, downstream El Paso, TX) and the other from a remote site that is likely to be unimpacted by PPCPs (BB: in Mexico, south of Big Bend National Park, TX).

Results/Conclusions

Acute toxicity tests showed that the LC50 values were high compared with field concentrations reported in the literature. The BB population showed a higher tolerance to acetamidophenol (BB: 319 mg/L; EP: 121 mg/L) and LC50s for caffeine were similar (BB: 423 mg/L; EP: 435 mg/L). However, the BB population did show lower tolerance to triclosan (BB: 0.130 mg/L; EP 0.317 mg/L). During chronic exposures, even low concentrations of acetamidophenol (10-20 mg/L) resulted in the production of unviable eggs (E.G., BB:0% in control vs. 58% in treatments) and thus negative growth rates for both populations. Triclosan exposure resulted in immobility (0% in control vs. 42% in treatments) starting on day three in the BB population only. GLMM analysis of responses showed significant differences in growth rates among treatments for acetamidophenol (F=20.96, p<0.0001 for days 3-6), caffeine (F=6.63, p<0.0185 for days 4-6), and triclosan (F=10.06, p<0.0001 for days 4-6) for the BB population. Further statistical analysis will be done to determine whether populations respond differently to these compounds. Our results provide insight into how these compounds impact aquatic invertebrate communities and provide data for resource managers to more effectively protect our water resources.