Effects of single Ca(OH)(2) doses on phosphorus concentration and macrophyte biomass of two boreal eutrophic lakes over 2 years

1. Two hardwater eutrophic lakes of central Alberta were subjected to singl e doses of Ca(OH)(2) (74 or 107 mg L-1). The effects of lime treatment on p hosphorus (P) precipitation, sediment P release, and macrophyte biomass wer e assessed for up to 2 years. 2. In both lakes, sediment P release was reduced to 16 and 27%, respectivel y, of pre-treatment values by the first winter following treatment. However , sediment P release returned to pre-treatment values during the following year. 3. In contrast to these short-term effects, macrophyte biomass decreased by as much as 80% after lime application and remained there for at least 2 ye ars. 4. Our results indicate that a single dose of Ca(OH)(2) may give short-term (< 1 year) control of P and long-term control (> 1 year) of macrophytes in hardwater eutrophic lakes of Alberta.