Selected metal(oid) concentrations in the liver and muscle of Clarias gariepinus and Schilbe intermedius: a dataset of the Tzaneen Dam populations in South Africa
This data comprise morphometric characteristics of Clarius gariepinus and Schilbe intermedius from Tzaneen Dam. The dam also presents metal(loid) concentrations recorded in the liver and muscle of these two species. It was hypothesized that since the catchment is not characterized by heavy industrial activities, metal(loid) concentration in the water, sediment, and fish tissues will be low. However, these results are showing that the bottom sediment and fish tissues have accumulated elevated concentrations. How the data was collected is clearly described under steps to reproduce.
Steps to reproduce
Water and sediment sampling Samples were collected from the inflow, middle and dam wall during high-flow (October to March) and low-flow (April to September) seasons between 2015 and 2016. Water variables i.e. dissolved oxygen (DO), pH, water temperature, salinity, total dissolved solids and electrical conductivity (EC) were determined in situ by means of a handheld multi parameter instrument (YSI model 54 Combometer). Water samples were collected using 1L polyethylene acid pre-treated sampling bottles and immediately kept in the fridge on site until metal analysis in the laboratory. Sediment were sampled using a friedlinger mud grab (225 cm3), put in 500 mL polyethylene acid pre-treated sampling bottles and immediately frozen until metal analysis in the laboratory. Fish sampling and processing Fish were collected using gillnets. The fish were carefully cut open ventrally and a portion of the liver, and a muscle tissue was cut out, wrapped with aluminium foil and kept in the freezer. Metal(loid)s analysis In the laboratory, the water was filtered through a 0.45 µm filter paper and acidified with analytical grade nitric acid (HNO3 65%). The solution was filtered again with a PTFE syringe filter. The water was made to the mark of 250 mL with deionised water kept and metal analysis was carried out using inductively coupled plasma-optical emission spectrophotometry (ICP-OES; Perkin Elmer, Optima 2100DV). For sediment, about 0.5 g of the sample was digested following USEPA 3052 protocol. Sediment samples were digested with nitric acid and hydrofluoric acid mixture (9HNO3 65%:3HF 40%) using microwave heated at 180ᵒC for 10 min and 100ᵒC for another 10 min at 600W. The rotor was cooled to room temperature. The vessel was then opened and the solution was transferred to the beakers. The solution was filtered through a 0.45 µm filter paper and PTFE syringe filter, respectively. Samples were then made to 250 mL mark with deionised water and kept in the fridge until elements analysis. Fish tissues were dried and digested using suprapur grade HNO3 and hydrogen peroxide (H2O2) (7HNO3 69%:1H2O2 30%) in a microwave digestive system. The solution was cooled to room temperature, filtered with 0.45µm filter paper and made to 250 mL mark with deionised water in a volumetric flask. All solutions, water, sediment and tissues were analysed using ICP-OES (Perkin Elmer, Optima 2100DV).