Babin, J . , and E. E. Prepas. 1985. Modelling winter oxygen depletion rates in ice-covered temperate zone lakes in Canada. Can. J. Fish. Aquat. Sci. 42: 239-249.Winter oxygen depletion rates (WODR) ( g~~-m -' -d -' ) were determined for 13 lakes in central Alberta during the winter of 1982-83. ABthough dissolved oxygen decreased in alf lakes for the first 3.5 mo after freeze-up, the decreases were nonlinear. The highest WODR were observed just after freeze-up. The noniinear WODR were significantly correlated with two estimates of lake productivity (i.e. total phosphorus and chlorophyll a, P < 0.85) but were not significantly correlated with msrphometry (e.g. mean depth). When the WODRfrom the Albertan lakes were treated as linear, to enable a comparison with other studies, correlations were found between WODR and morphometry, and WODR and estimates of summer produdivity. These relationships were significantly different from observations by previous investigators who worked on ice-covered lakes in two other regions. When data from other ice-covered fakes were combined with this study, WODR were best predicted from a combination of mean summer TB (TP,, in mgam-'1 in the euphotic zone and mean depth (t in m):The above equation permits the prediction of WODR for a greater range of lake types than previQ~$ models.Les taux d'appauvrissement hivernal en oxygene (TAHO) (g ~~. m -~-j o u r -' ) ont Ct6 quantifiees dans 13 lacs du centre de IfAlberta pendant O'hiver de 1982-83. La concentration dfoxyg$ne dissous a baissC pendant Bes premiers 3,s mo apres le gel dans tous les lacs, mais ces diminutions nf6taient pas lineaires. Le taux ie plus klevC a kt6 observe juste a p r h le gel. Les TAHO non Binkaires etaient en correlation significative avec deux estimations de B a productivitk lacustre (c.-A-el. D e phosphore total et le shlorophyfle a, P < 0,05) mais non avec la morphometrie (par ex. la profondeur moyenne). Une comparaison des TAHO des lacs albertains, considkrCs %inkaires, avec ceux tires d'autses etudes a rkv6l6 des cors6lations entre Bes TAHO et la morphomktrie et les TAHO et !a productivitk estivale. Ces relations ktaient significativement diffgrentes des observations effectuees par d'autres chercheurs qui ont ktudi6 des lacs gel& de deux autres regions. On a obtenu une meifleure prediction des TAHO en combinant la proderctivitc5 msyenne totale en Cte (PTetc en rng. m2) dans la zone euphotique et la profondeur moyenne (2 en m), a Ifaide des donnees de Bf6trode et des donn6es recueislies dans dfautres lacs gel&. L1Cquation ainsi obtenue : permet %a prediction du TAM0 dans une plus grande varietk de lacs que les mod&%es prkcedents.

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1. Whole‐lake experiments were conducted in two hardwater lakes (Halfmoon and Figure Eight) in Alberta, Canada, to investigate the effectiveness of repeated lime (slaked lime: Ca(OH)2 and/or calcite: CaCO3) treatments (5–78 mg L–1) for up to 7 years. 2. Randomized intervention analysis of intersystem differences between the experimental and three reference lakes demonstrated a decline in euphotic total phosphorus and chlorophyll a concentrations in the experimental lakes after repeated lime treatments. 3. After the second lime application to Halfmoon Lake, mean winter total phosphorus release rates (TPRR) decreased to < 1 mg m–2 day–1 compared with 3.6 mg m–2 day–1 during the winter after initial treatment. In the final year of lime application, mean summer TPRR decreased to 4.5 mg m–2 day–1 compared with 7.6 mg m–2 day–1 in the pre‐treatment year. 4. Mean macrophyte biomass declined and species composition was altered at 1 and 2 m depths in Figure Eight Lake during lime application. Over the first 6 years of treatment, macrophyte biomass at 2 m declined by 95% compared with concentrations recorded during the initial treatment year. In the last year of the study, macrophyte biomass at 2 m reached initial treatment concentrations, which coincided with the greatest water transparency. Over the treatment period, macrophyte species shifted from floating to rooted plants. 5. Multiple lime applications can improve water quality in eutrophic hardwater lakes for periods of up to 7 years.

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