ASSESSING THE IMPACTS OF ACIDIFICATION ON ATLANTIC SALMON (SALMO-SALAR) - A SIMPLE-MODEL OF STREAM CHEMISTRY

We developed a model that simulates the effects of changes in sulphate (SO42-) deposition on the chemistry of naturally organic-rich streams , linked this chemical model to a model of Atlantic salmon (Salmo sala r) production (Korman et al. 1994. Can. J. Fish. Aquat. Sci. 51: 662-6 80), and assessed its performance on three acidified streams in southw est Nova Scotia. The chemical model closely tracked current chemistry by estimating the charge density required for charge balance on each s ampling date. Calculated charge densities were generally low (1-3 mu e quiv./mg dissolved organic carbon (DOC)), inversely related to DOG, an d positively related to pH. Predictions df minimum pH and salmon smelt output were relatively insensitive to the assumed F-factor (watershed neutralization of deposited acidity) in the parameter range most like ly for the three streams. The model permits rapid impact assessment of acid deposition scenarios with a modest amount of input data (acid-ne utralizing capacity, pH, SO42-, and DOG, ideally sampled weekly) while retaining natural cycles and processes.