Application of dolomite to forested catchments in Nova Scotia improves water quality - but more is needed to meet water quality targets

Populations of Atlantic salmon (Salmo salar) in Nova Scotia have plummeted in recent decades. One of the major threats for these populations is freshwater acidification, which has caused toxic water conditions including elevated stream water concentrations of toxic cationic aluminum (Ali). The only viable management option to reduce the threats of acidification to Atlantic salmon within the timeline needed to save the remaining populations is the addition of alkaline materials to waters or soils, via “liming.” While studies in Europe, the UK, and the northeastern USA show that stream water Ali concentrations decrease in response to terrestrial liming with positive impacts on fish communities, stream chemistry response to terrestrial liming in Nova Scotia has not yet been examined. Here we examine the response of stream water chemistry to terrestrial liming in two types of experimental treatments in Nova Scotia. Our results show that liming decreased streamwater Ali concentrations and increased dissolved calcium concentrations and pH levels. Untreated sites have water chemistry conditions that are toxic to Atlantic salmon, and although water chemistry was improved at treated sites, some parameters still do not meet thresholds for aquatic health, indicating that higher doses or repeated liming treatments are required. Results suggest that expansion of liming activities with higher liming doses may help avoid loss of the remaining wild salmon populations.