Transcriptional effects of metal-rich acid drainage water from the abandoned Løkken Mine on Atlantic salmon (Salmo salar) smolt

ABSTRACT

Runoff of metals represents one of the major environmental challenges related to historic and ongoing mining activity. In this study, transcriptomics (direct RNA sequencing [RNA-seq] and reverse-transcription quantitative polymerase chain reaction [RT-qPCR]) was used to predict toxicity of metal-rich acid mine drainage (AMD) water collected in the abandoned copper (Cu) mine called Løkken Mine on Atlantic salmon liver and kidney, the main target organs of Cu-induced toxicity in fish. Smolts were exposed to control and diluted AMD water, which contains a mixture of metals but is especially enriched with Cu, at 4 concentrations in freshwater (FW) for 96 h, and then were transferred to and kept in seawater (SW) for another 24 h. Significant accumulation of Cu was observed in the gills, but not liver and kidney tissues, after 96 h of exposure. Short-term exposure to metal-rich ADM (high exposure group) significantly upregulated 3201 transcripts and downregulated 3782 transcripts in liver. The strongest effect attributed to exposure was observed on the KEGG pathway “protein processing in endoplasmic reticulum,” followed by “steroid biosynthesis.” Gene ontology (GO) analysis suggested that exposure predominantly affected “protein folding,” possibly by disrupting disulfide bonds as a result of endoplasmic-reticulum-generated stress, and “sterol biosynthetic processes.” Transfer to uncontaminated SW for 24 h amended the transcription of several genes, suggesting a transient effect of treatment on some mechanisms. In conclusion, the data show that trace metals in AMD from abandoned pyrite mines might disturb molecular mechanisms linked to protein folding in Atlantic salmon smolt endoplasmic reticulum.

Supplementary data

Supplemental data for this article can be accessed at the publisher’s website

Funding

This experiment was approved by the Norwegian Animal Research Authority (NARA), 57272/2012. Funding for the experimental and analytical work was provided by NIVA and NIFES. The authors thank Hui-shan Tung and Synnøve Winterthun (NIFES) for analytical help.

Additional information

Funding

This experiment was approved by the Norwegian Animal Research Authority (NARA), 57272/2012. Funding for the experimental and analytical work was provided by NIVA and NIFES. The authors thank Hui-shan Tung and Synnøve Winterthun (NIFES) for analytical help.