Increasing Aluminum Levels in Southwestern Nova Scotia Rivers

Abstract

Declines in Atlantic salmon populations in Nova Scotia (NS) may be linked with aluminum, a known toxin to aquatic organisms; however, aluminum trends in NS have not been assessed. Here we analyze water chemistry from 1980-2014 in 65 NS rivers and lakes; 35% have significantly increasing aluminum. We propose a new acidification recovery model, incorporating the effects of organic acids on chemical recovery in regions with high dissolved organic carbon (DOC). 67% of ionic aluminum (Ali) samples collected between April 2015 and July 2016 in two rivers were above 15 μg/L, the 5.0< pH <6.0 threshold for Atlantic salmon. Ali predictive equations were created using water chemistry parameters, and back-cast to >20-year water chemistry data; back-cast trends show increasing Ali in the spring/summer seasons. Following reductions in acid deposition, it appears that increased aluminum, a direct effect of acidification, poses a threat to aquatic life in regions with high DOC.