The impact of sewage effluents on the fecundity and survival of Eurytemora americana in a eutrophic estuary of Argentina

Abstract

The present study shows the results of laboratory experiments addressing the effects of different water qualities on E. americana's fecundity and survival. The study was carried out with cultured females, incubated under different water qualities and controlled conditions during ten days (7 ± 2 °C, 14 h light, salinity of 32 ± 2, Tetraselmis sp. and Nannochloropsis sp. as food). Four treatments were established: P = subsurface water from sewage plume of Bahía Blanca city, D = the dissolved phase of P, I = bottom water in the sewage discharge point of Bahía Blanca city, and C = water from the low-impacted area of Monte Hermoso, used as a control treatment. Egg production, number of nauplii, number of faecal pellets, survival and fertility-state of females were evaluated. The differences and relationships among copepod factors, environmental variables and pollutants levels (cadmium, lead, copper, zinc, chrome and ammonium-phosphate dissolved), were analysed among treatment using non-parametric multivariate analysis. The copepod factors showed a negative association with pollutants levels and the turbidity. No mortality was observed in C, P and D treatments, whereas 100% mortality was observed in treatment I. Females from C, showed the highest egg production (22.6 ± 6.5 egg/female.clutch), as well as gonads regeneration and a second egg laying. Egg production, number of nauplli and faecal pellets were similar for P and D treatments, but significantly lower than those registered in C. In P treatment, only 40% of females showed regeneration of their gonads for a second egg laying (12.4 ± 2.9 egg/female.clutch) and in D treatment, no female regenerated their gonads for a second egg laying (12.5 ± 3 egg/female.clutch). The results indicate that bioavailable contaminants from dissolved phase of sewage effluent reduce the fertility in Eurytemora americana, while the bottom water at the sewage discharge site is undoubtedly lethal for this species.