Spatiotemporal and teratological analyses of diatom assemblages from sediments contaminated with industrial effluents in the St. Lawrence River near Cornwall (Ontario, Canada)

Throughout the twentieth century, waterfront industries in Cornwall (Ontario, Canada) discharged significant quantities of mercury (Hg) and other industrial effluents to the St. Lawrence River (SLR), which accumulated in downstream sediments and currently persist in some nearshore areas. While a great deal of research has investigated the bioavailability and movement of this legacy Hg up the food web, considerably less is understood about its impacts on the algae that live on these contaminated sediments. This study examined diatom (Bacillariophyceae) responses to present-day and historical sedimentary contamination on the SLR at Cornwall. Surface sediments collected from contaminated zones and upstream reference sites were analyzed alongside a dated sediment core from a contaminated area to evaluate the diatom community assemblage shifts and cell deformations (teratologies) in response to elevated concentrations of sedimentary Hg and other contaminants. Results suggest that elevated sedimentary metal concentrations have a small but significant effect on diatom community assemblage structure and incidence of teratologies. However, it appears that excess nutrient loading from waterfront industry was historically a more important driver of diatom assemblage structure than other industrial effluents.

Automated summary

This study examined the effects of sedimentary contamination on diatoms in Cornwall, Canada. The results suggest that elevated metal concentrations in sediments have a small but significant impact on diatom community structure and cell deformations. However, historical excess nutrient loading appears to be a more important driver of diatom assemblage structure.