Sea ice characteristics, nutrient dynamics and community structure and composition of ice biota from Gulf of St. Lawrence, Magdalen Islands area

• Main Author: De Sève, Michèle
• Format: Thesis
• Language: English
• Published: McGill University 1989
• Subjects: Biology; Oceanography; Arctic; Magdalen; ice algae; Sea ice
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75939

Sea ice characteristics were studied in relation to nutrient dynamics, biomass and community structure and composition of ice biota from the Gulf of St. Lawrence at landfast and drifting ice stations in the Magdalen Islands area. The instability of the ice substrate was demonstrated with respect to short duration of cover (8 weeks), ice melt and rafting processes. The study of nutrient dynamics in ice and in seawater suggests silicates and nitrogen (NO$ sb2$+NO$ sb3$+NH$ sb4$) limitation at landfast ice stations, as well as in situ regeneration of phosphorus in the bottom ice sections. No correlation was found between microalgal biomass and nutrients, but specific growth rates were in the lower range of values reported for Arctic ice algae. The composition of the microalgal ice biota revealed two types of communities. The first type was composed of a majority of pennate diatoms (abundance $>$ 98%), with dominant species such as Nitzschia cylindrus, N. polaris and Navicula kariana, similar to Arctic landfast ice biota communities. The second type was composed of a high percentage of centric diatoms (abundance $>$ 46%) due to the abundance of the planktonic diatom Thalassiosira norderskioldii. Community structure and composition are discussed with respect to the instability of the ice substrate, and the comparison between landfast and drifting pack ice.