A Numerical Taxonomic Study of Pelagic and Benthic Surface-layer Bacteria in Seasonally-cold Coastal Waters

Abstract

Summary Heterotrophic bacteria from the pelagic zone and the benthic surface-layer of the continental shelf, near Newfoundland, were isolated. Using numerical taxonomy, clusters of related strains were identified and the characteristics of the clusters determined. The majority of the pelagic strains were facultatively anaerobic and were identified as Vibrio, although a few strains were not identified and others were assigned to the family Vibrionaceae. The few strictly aerobic strains from the pelagic zone were Alteromonas. The benthic bacterial population was more diverse and bacteria with strictly respiratory metabolism predominated. Among these were strains of Pseudomonas, Flavobacterium, and Alteromonas. The remaining strains were Vibrio, and some Vibrionaceae. Although some pelagic and benthic strains were fastidious, most utilized a broad range of substrates. This was most evident among, although not restricted to, the marine pseudomonads and the flavobacteria of the benthos. In seasonally-cold oceans the benthic surface-layer is an important zone for detrital breakdown and nutrient recycling. The nutritional versatility of Pseudomonas and Flavobacterium may, in part, account for their abundance in the substrate enriched benthic surface-layer.