Studies on the use of limestone to restore atlantic salmon habitat in acidified rivers

Abstract

Liming experiments were conducted using two approaches: Instream placements of limestone gravel and headwater lake neutralization with limestone powder. Instream gravel was ineffective at low temperatures and high flows, and required at least 100 tonnes for each m3.s−1of flow to achieve biologically useful pH increases. The Atlantic salmon showed positive responses, but only in the immediate vicinity of the limestone. Headwater lake liming produced high neutralization efficiencies, but, there were rapid fluctuations in river pH’s which resulted from the natural stratification and mixing cycles within the lakes, and from rapid flushing due to high runoff volumes. Inverse stratification under winter ice occasionally produced acidic surface layers and dramatic lowering of downstream pH’s. Positive responses were obtained from salmon in the lake’s outlet stream. The problems of environmental chemistry and logistics seriously limit the practicability of using limestone to mitigate the acidification of Atlantic salmon rivers. © 1984 Taylor & Francis Group, LLC.