RESUMO
In present study the effect of iron (Fe) and manganese (Mn) contamination was assessed by modeling a freshwater food web of water, zooplankton (Daphnia pulex), and zebrafish (Danio rerio) under laboratory conditions. Metals were added to the rearing media of D. pulex, and enriched zooplankton was fed to zebrafish in a feeding trial. The elemental analysis of rearing water, zooplankton, and fish revealed significant difference in the treatments compared to the control. In D. pulex the Mn level increased almost in parallel with the dose of supplementation, as well as the Fe level differed statistically. A negative influence of the supplementation on the fish growth was observed: specific growth rate (SGR%) and weight gain (WG) decreased in Fe and Mn containing treatments. The redundancy analysis (RDA) of concentration data showed strong correlation between the rearing water and D. pulex, as well as the prey organism of Fe- and Mn-enriched D. pulex and the predator organism of D. rerio. The bioconcentration factors (BCF) calculated for water to zooplankton further proved the relationship between the Fe and Mn dosage applied in the treatments and measured in D. pulex. Trophic transfer factor (TTF) results also indicate that significant retention of the metals occurred in D. rerio individuals, however, in a much lower extent than in the water to zooplankton stage. Our study suggests that Fe and Mn significantly accumulate in the lower part of the trophic chain and retention is effective through the digestive track of zebrafish, yet no biomagnification occurs. Graphical abstract.
Assuntos
Daphnia , Peixe-Zebra , Animais , Ferro , Manganês , ZooplânctonRESUMO
Many oxbows are contaminated by Fe and Mn as a consequence of the elemental concentration of sediment and water originating from the Upper Tisza Region of Hungary. The phenomenon is partly caused by anthropogenic activities and mainly due to the geochemical characteristics of the region. The effects of Fe and Mn on the aquatic ecosystem of these wetlands were investigated in a model experiments in this study. Survival, individual body weight and the elemental concentrations of organs were determined in common carp (Cyprinus carpio) juveniles reared in Fe and Mn contaminated media (treatment 1: Fe 0.57 mg L-1, Mn 0.29 mg L-1, treatment 2: Fe 0.57 mg L-1, Mn 0.625 mg L-1, treatment 3: Fe 1.50 mg L-1, Mn 0.29 mg L-1, treatment 4: Fe 1.50 mg L-1, Mn 0.625 mg L-1 and control: Fe 0.005 mg L-1, Mn 0.003 mg L-1), for rearing time of 49 days. The treatment with Fe and Mn did not have any effect on the survival data and individual body weight in the levels tested. The highest concentration of Fe and Mn was found in the liver and brain of carp juveniles, while the lowest concentration of these elements occurred in the muscular tissue and gills. The treatment where Fe and Mn were applied in the highest concentrations resulted in a statistically higher level of these elements in the brain, grills and muscle tissues. The treatment where only Mn was present in the highest concentration caused increased level of Mn only in the liver. We found metal accumulation in almost every organ; however, the applied concentrations and exposure time did not affect the survival and average body weight of carp juveniles.