PS 27-129 - Exposure to copper concentrations on dormant population of the freshwater rotifer Brachionus calyciflorus

Abstract: In the El Paso (USA)\Cuidad Juarez (MX) border region there is contamination of local waterbodies by heavy metals, such as copper, because of industrial activities. Rotifers have been used as bioindicators of environmental pollution, including heavy metals. Cyclical parthenogenetic rotifers produce diapausing eggs to withstand harsh environmental conditions. Most toxicological studies have determined the impact of heavy metals on active populations, while relatively little is known about how they affect dormant populations. We hypothesized that high copper concentrations would negatively affect diapausing egg hatching. To test this, we exposed diapausing eggs of Brachionus calyciflorus to 5 concentrations of copper (CuSO4), including a control (0.0 mg/L), one environmentally relevant concentration (0.03 mg/L), the average LC50 for active populations reported in the literature (0.18 mg/L), and regulatory-relevant concentrations (0.003 and 4 mg/L, EPA-USA and NOM-Mexico, respectively). Preliminary results showed that the number of viable offspring was up to 79% lower at higher concentrations of copper (0.18 mg/L and 4 mg/L) than in the other treatments. This can be explained by the significantly higher proportion of failed hatchings (5 - 30%) and deaths after hatching (51 - 82 %) in the 0.18 mg/L and 4 mg/L treatments, compared to other treatments ( < 1% and 2%, respectively). Results indicate that at some regulatory levels, rotifer populations will be negatively impacted which could be translated to higher trophic levels.