Ice algae living within the bottom interstices of sea ice significantly contribute to the amount of the primary production in the Arctic Ocean in the late-winter/spring. This thesis examines the influence of physical gradients, namely sub-ice currents and riverine input, on ice algal concentration and composition during the spring bloom. Through two separate case studies, it was found that (i) increased sub-ice currents in tidal straits enhance nutrient supply to bottom ice, supporting greater ice algal biomass, (ii) improved mechanisms of nutrient supply were proposed that explain the increased biomass as a result of strong sub-ice currents, and (iii) freshwater inflow to the marine system also has a negative influence on biomass, reducing biomass associated with decreasing salinity. These findings will help identify new biological hotpots of ice algal production in the Arctic, while highlighting a negative, yet limited, influence surrounding hydroelectric controlled river output during winter.