| Summary: | Records of high latitude oceanic and climate dynamics obtained from high-resolution marine archives like the high arctic crustose coralline alga Clathromorphum compactum are invaluable for placing current environmental change in the context of historical variability. In addition to serving as an excellent marine archive, these algae also perform important ecosystem services by providing substrate and habitat for many benthic fauna, as well as contributing to regional primary productivity and carbon sequestration. This dissertation aims to advance our knowledge of the subannual-scale growth and calcification in the long-lived crustose coralline alga Clathromorphum compactum in the context of environmental change and historical reconstructions, and to explore novel proxies for building long-term high-resolution records of surface ocean temperature in the Canadian Arctic and northwest Atlantic Oceans. Chapter 1, "Experimental investigation of the effects of temperature, light, and salinity on rates of linear extension and calcification in the Arctic/Subarctic crustose coralline alga Clathromorphum compactum" examines the effects of environmental variability on algal calcification rates and growth. A 3-month controlled laboratory culturing experiment, isolating the effect of light level, salinity and temperature on net calcification and growth in algal specimens collected from Arctic Bay, Nunavut, Canada is presented. The experiment tests the specific hypotheses that (1) calcification is positively impacted by increased environmental temperature, (2) calcification is negatively impacted by reductions in salinity and (3) calcification rates are increased with increased light availability. The work elucidates C. compactum's potential response to expected warming, declining salinity, and lengthening of the growing season. Algal calcification rates were found to be best described by a combination of light exposure, salinity, and temperature, where temperature and salinity were positively correlated, and light level was ...
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