Biofilms can be used as a biomonitoring tool to determine metal bioavailability in streams affected by mining and other anthropogenic activities. Surface water and biofilm were sampled over two years from rivers located in the vicinity of a mine located in a Nordic ecosystem (Nunavik, Quebec). Biofilm metal content (Cd, Cu, and Ni) as well as a variety of physicochemical properties were determined to examine relationships between metal accumulation and water quality. Among the three metals of interest, copper and nickel had the highest levels of accumulation and cadmium had the lowest. When considering the exposure levels, nickel was the most abundant metal in our sampling sites. Both exposure and accumulation levels were consistent over time. Biofilm metal content was highly correlated to the ambient free metal ion concentration for sites of circumneutral pHs for all three metals. When the surface water pH was below 6, biofilm metal content was much lower than at other sites with similar aqueous metal concentrations of exposure. This apparent protective effect of decreasing pH can be explained by proton competition with dissolved metals for uptake binding sites at the surface of the organisms within the biofilm as described by the Biotic Ligand Model principles. The relationships obtained for Cd and Cu were overlapping those observed in previous publications, indicating strong similarities in metal accumulation processes in biofilms over very large geographical areas. Although more data are needed for Ni, our results show that biofilms represent a promising metal biomonitoring tool.

Nunavik (Northern Quebec, Canada) is experiencing a mining boom. While several studies have been conducted in the region in relation to climate change, the effects of mining have received much less attention. In this study, we explored the use of biofilms in natural streams as an indicator of potential stress on living organisms caused by metal contamination from nickel mining activities. More specifically, we assessed diatom assemblages and the presence of teratologies (morphologic abnormalities) as a response to metals in streams located in close proximity to mining sites. Metal concentrations (as well as other cations), anions and pH values varied markedly among stations. Different diatom assemblage structures (four biotypes, i.e., groups of samples with similar diatom species composition) were observed depending on the level and the type of contamination. The frequency of diatom teratologies was higher in metal contaminated sites. The present study lays the foundation for bioassessment of metal contamination in low Arctic streams using diatom-based approaches, and will serve as a point in time reference for future evaluation of ecosystems degradation or recovery in Nunavik.

Arabidopsis thaliana (L.) Heynh. has emerged as the dominant plant species used in molecular genetics and functional genomics. Although it possesses several attributes of model organisms, the ease with which it can be transformed genetically is a paramount factor that has led to its widespread application as a tool for functional genomics. Progress made in the late 1990s has relieved users of the need to use a vacuum chamber for transformation, substituting its function with a surfactant known as Silwet L-77, to facilitate access to ovules by bacterial solution. Here, we evaluate the substitution of Silwet L-77 by XIAMETER OFX-0309. We demonstrate that transformation efficiency can be increased by an average of 3-fold (and up to 10-fold) solely by replacing Silwet L-77 with XIAMETER OFX-0309. Because downstream selection of transgenic plants, in either soil or Petri dishes, can be long and tedious, this substitution represents a significant reduction of time and materials required to retrieve transgenic lines.