PS 27-123 - Embryonic exposure to copper sulfate can affect life history traits in Brachionus calyciflorus

Abstract: Dormant embryos represent an important long-term survival strategy for many aquatic microinvertebrates. Heavy metals such as copper tend to accumulate in aquatic systems, posing a threat to sediment egg banks. Here, we exposed the freshwater rotifer Brachionus calyciflorus diapausing eggs to copper to assess the effects of embryonic exposure on adult life history traits. First, the eggs were exposed to 3 concentrations of copper (CuSO4): the representative LC50 for active populations (0.18 mgL-1; based on a literature review); environmentally relevant concentrations in freshwaters of the USA (0.003 mgL-1) and Mexico (0.03 mgL-1); and a control (0 mgL-1) and hatching was quantified. After hatching in their respective treatments, one set of hatchlings from each treatment was placed in the control medium while another set was re-exposed to the same concentration as in the hatching treatment, totaling 9 treatments. Except for the 0.003 mgL-1 treatment, we found (1) a decreasing trend for lifespan and offspring production at higher copper concentrations, the control and the 0.003 mgL-1 treatments had the longest lifespan (mean + SD: 13.5 + 5.2 days) and offspring production per female (11.6 + 5.2 neonates); (2) treatments with 0.03 and 0.18 mgL-1 in a single exposure had a lifespan (7.4 + 5.1) and offspring production per female (5.5 + 4.4) lower than the first, and (3) treatments with 0.03 and 0.18 mg L-1 of re-exposure had the lowest averages for lifespan (2.0 + 2.0) and offspring production per female (1.0 + 1.0). These results indicate that copper exposure to resting egg banks may affect the future performance of active populations, and thereby affect the production of higher trophic levels.