Arctic cyanobacteria and limnological properties of their environment: Bylot Island, Northwest Territories, Canada (73 degrees N, 80 degrees W)

Cyanobacteria were a major constituent of phototrophic communities in the lakes, ponds and streams of Bylot Island, in the Canadian high Arctic. The waters spanned a range of temperatures (1.8-16.8 degrees C in late July), pH regimes (6.2-9.2) and conductivities (1.5-1700 mu S cm(-1)) but nutrient concentrations were consistently low (< 1 mu g dissolved reactive P l(-1) at all sites; < 10 mu g NO3-N l(-1) at most sites). Picoplanktonic species (Synechococcus spp.) were often the numerical dominants in the plankton, and periphytic filamentous species (Oscillatoriaceae) commonly formed thick (5-50 mm) benthic mats. Bloom-forming species of cyanobacteria were either absent or poorly represented even in Chla-rich ponds. The total community biomass ranged from 0.1 to 29.8 mu g Chla l(-1) in the plankton and from 1.1 to 34.8 mu g Chla cm(-2) in the benthos. The in vivo absorbance characteristics of isolates from these environments indicated a genetically diverse range of species in each group of Arctic cyanobacteria. Growth versus irradiance relationships were determined for each of the isolates and similarly revealed large genetic differences (maximum growth rates from 0.17 to 0.61 day(-1)), even between morphologically identical taxa. A comparison of nutrients, pigment concentrations and species composition underscores the strong similarities between freshwater ecosystems in the north and south polar zones.