SEASONAL-VARIATION OF PSYCHROTROPHIC BACTERIA IN SEDIMENT FROM LAKE-ONTARIO

Bacteria were isolated from sediment samples obtained from the Bay of Quinte, Lake Ontario, at four different seasons. Isolation of the bacteria was accomplished at 0°C and 20°C and the growth of randomly-selected isolates at each of these temperatures was assessed. The bacteria were identified using miniaturized identification methods and Pseudomonas and Flavobacterium were the most frequently isolated genera. Significant differences were found in the numbers of bacteria in the sediment samples taken at different sampling times and incubated at different temperatures. The numbers isolated with incubation at 20°C were always the same or higher than those isolated from the same sample at 0°C. Almost all bacteria isolated at 0°C were capable of growth at 20°C. The greatest population diversity occurred in the sediment samples collected when the in situ sediment temperatures were low. Distinct changes in population composition were noted at the different sampling times. The majority of the bacteria isolated were capable of growth at 0°C, so that a large psychrotrophic population was present throughout the year in the sediment. © 1979.