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 Arc tic. 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 diss olved reactive P l(-1) at all sites; < 10 mu g NO3-N l(-1) at most sit es). Picoplanktonic species (Synechococcus spp.) were often the numeri cal dominants in the plankton, and periphytic filamentous species (Osc illatoriaceae) commonly formed thick (5-50 mm) benthic mats. Bloom-for ming 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 isol ates from these environments indicated a genetically diverse range of species in each group of Arctic cyanobacteria. Growth versus irradianc e 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 compari son of nutrients, pigment concentrations and species composition under scores the strong similarities between freshwater ecosystems in the no rth and south polar zones.