| Abstract
| - Acidification of Norwegian surface waters, as indicatedby elevated concentrations of sulfate and a correspondingreduction in acid neutralizing capacity and pH, is aresult of emission and subsequent deposition of sulfurand nitrogen compounds. Episodic sea-salt deposition duringsevere weather conditions may increase the effects ofacidification by mobilizing more toxic aluminum during suchepisodes. Changes in climatic conditions may increasethe frequency and strength of storms along the coast thusinteracting with acidification effects on chemistry andbiota. We found that the North Atlantic Oscillation (NAO)is linked to sea-salt deposition and sea-salt induced waterchemistry effects in five rivers. Particularly, toxic levelsof aluminum in all rivers were significantly correlated withhigher NAO index values. Further, temporal trends werestudied by comparing tendencies for selected statisticalindices (i.e. frequency distributions) with time. The selectedindices exhibited strong correlations between the NAOindex, sea-salt deposition and river data such as chloride,pH and inorganic monomeric aluminum, pointing at theinfluence of North Atlantic climate variability on waterchemistry and water toxicity. The potentially toxic effectsof sea-salt deposition in rivers seem to be reduced asthe acidification is reduced. This suggests that sea-saltepisodes have to increase in strength in order to give thesame potential negative biological effects in the future,if acid deposition is further reduced. More extreme winterprecipitation events have been predicted in the northwestof Europe as a result of climate change. If this change willbe associated with more severe sea-salt episodes is yetunknown.
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