Developing As and Cu Tissue Residue Thresholds to Attain the Good Ecological Status of Rivers in Mining Areas

Abstract

The study was performed on residue-effects datasets from polluted and unpolluted sites in the Nalón River basin (northern Spain). The effects were measured in terms of alteration of field macroinvertebrate communities, and measured as ecological status scores, and number of families and abundance of Ephemeroptera, Plecoptera and Trichoptera (EPT). Non-linear regression models of the field-measured tissue residues in 10 taxa related to the ecological status of the macroinvertebrate communities were used to derive effective tissue residues (ERs). These were estimated for the good/moderate boundary defined by the ecological quality ratio (EQRs) score and for the 50% reduction of EQR and EPT metrics. As, Cu, Hg and Se ERs were calculated for several macroinvertebrate taxa with different feeding styles. The ER dataset allowed us to estimate As and Cu hazardous concentrations (HC), using species sensitivity distribution models, and were interpreted as community thresholds. Further studies for Hg and Se are needed to complete the database required for HC estimation. The reliability and differences of the several thresholds were tested in a risk assessment using a tissue-residue approach (TRA) conducted with field organisms from Cauxa Creek, a tributary from the same basin exposed to high levels of metals in the sediments due to gold mining activities. This risk assessment identified that As and Cu tissue residues satisfactorily explained the reduction in the ecological status of the macroinvertebrate assemblages. Our results indicate that TRA can help in setting future environmental quality standards for the protection of aquatic biota. Graphical Abstract

Toxicogenomics of the Freshwater Oligochaete, Tubifex tubifex (Annelida, Clitellata), in Acute Water-Only Exposure to Arsenic

“…These results demonstrate that the LR 50 and ER 50 calculated from acute water-only exposure can give, with caution, a good approximation to the tissue residues after sediment chronic exposure. The results are also comparable with a field approach for the estimation of tissue residues of ER 50 for aquatic Microdrile oligochaetes (ER 50 = 509–570 μg g −1 dw: [ 7 ]) related to the 50% reduction in the river macroinvertebrate ecological status. Interestingly, that range of ER 50 values from field aquatic oligochaete worms overlaps, or is very close to, the ER 50 values estimated in the present study for mortality and autotomy after 72 h and 96 h exposure.…”

“…In fact, arsenic appears in high concentrations in groundwater from geological sources, causing chronic health disorders [ 5 ]. Arsenic pollution in sediments and bioaccumulation has been demonstrated as one of the main causes of toxicity [ 3 ], and of the alteration of the ecological status in rivers affected by mining activities [ 6 , 7 ]. Integrating chemical analysis with biological endpoints can help in the monitoring and protection of aquatic ecosystems.…”