Biomass and nutritional requirements of psychrotrophic bacterial communities in Fram Strait and western Greenland Sea

Abstract

During the "Polarstern" expedition ARK Iv/2 in June 1987, water samples from 8 stations were taken to study biomass and substrate utilization of cold adapted bacteria.Bacterial biomasses determined from acridine orange direct counts (AODC) were between 0.4 and 31.4Ilg CIl, and ATP concentrations amounted from <0.1 to 40 ngll.Colony counts on seawater agar reached only 0.1 % of AODC, but with the MPN-method 1 to 10 % of AODC were recorded.With 14C_ glutamic acid or 14C-glucose as tracer substrate in oligotrophic broth containing 0.5 mg trypticase and 0.05 mg yeast extract per liter of seawater, obligately oligotrophic bacteria could be detected in one water sample.Although incubation was at 2 DC, only psychrotrophic bacteria showing growth temperatures between 1 and 30 DC were obtained.Organic substrate utilizations by 106 isolates were tested at 4 and 20 DC.Most carbohydrates, organic acids, alcohols, and alanine were assimilated at both temperatures, but arginine, aspartate and ornithine were utilized only at 20 DC by almost all strains.