An annual cycle of abundance and activity of heterotrophic bacteria and abundance of hydrocarbonoclastic bacteria in Newfoundland coastal water

Abstract

An annual cycle of abundance and activity was determined for bacteria in Newfoundland coastal water that is dominated by the Labrador Current. Both in abundance and activity, the population showed characteristics similar to those reported for bacteria in cold ocean environments. The number of bacteria per litre determined by the acridine orange direct count method ranged from an average low of 0.25 × 108 in winter to an average high of 2.8 × 108 in summer. Activity, determined by the kinetic method, was correlated with temperature. The average heterotrophic potential (Vmax) was 3 ng glutamate. L−1∙h−1 in winter and 54.7 ng glutamate. L−1∙h−1 in summer. The average turnover times were 2632 and 256 h, respectively, during the same periods. The population of hydrocarbonoclastic bacteria, estimated by a most probable number method, constituted 4.4% of the viable bacterial population estimated by the standard plate count method, although the former were most abundant near the water's surface. The number of hydrocarbonoclastic bacteria was correlated with temperature and with Vmax of the heterotrophic bacterial population.