Control data on the ice algal bloom at Cape Hatt, northern Baffin Island, during 18 May-2 June 1982 were typical of those at other arctic locations. Ice algae were dominated by pennate diatoms (80% of total cells), particularly Nitzschia grunowii (55%) and N. frigida (15%). In various locations and sampling periods, cell densities ranged from 1.7-384.7 x 100,000,000 cells/sq m, and chlorophyll a concentrations ranged from 3.4-16.7 mg/sq m, both increased over the study period. Mean productivity rates based on particulate radiocarbon fixed were from near zero to 2.95 mg C/sq m/h. Dissolved organic radiocarbon concentrations were almost always higher than particulate radiocarbon concentrations, probably because of cell rupture. Total (dissolved + particulate) productivity rates were up to 12.7 mg C/sq m/h, with an overall mean of 4.4 mg C/sq m/h in control samples. Productivity and productivity per unit chlorophyll increased during May and decreased slightly by 1-2 June. Undisturbed, enclosed areas of the under-ice surface were treated with oil on 23-24 May. Dispersed oil (Venezuela Lagomedio crude + Corexit 9527, BP CTD, or BP 1100 WD) was in contact with the ice for 5 h, whereas untreated oil and solidified oil (BP treatment) remained in the enclosures for the duration of the study (12 days post-treatment). Sampling was carried out in areas where oil contacted the ice and moved away or in areas near oil that remained in contact with the under-ice surface. Five hours after treatment, oil concentrations in the water within the enclosures were similar (0.15-0.28 ppm) in untreated oil, solidified oil and control enclosures. ... No adverse effects of any oil treatment on ice algae were detected in analyses of group composition, cell densities, chlorophyll a concentrations, productivity, productivity /chlorophyll or ratios calculated to standardize for light effects. Untreated and solidified oil may have stimulated ice algal growth and productivity near ... the oiled areas.Key words: Arctic, ice algae, productivity, oil effects, dispersed oil effects, solidified oil effects, Baffïn IslandMots clés: arctique, algues glaciaires, productivité, effets dus au pétrole, effets dus au pétrole dispersé, effets dus au pbtrole solidifié, île Baffi