Nitrogen metabolism by heterotrophic bacterial assemblages in Antarctic coastal waters

• Published in: Polar biology Vol. 14; no. 3; pp. 195 - 204
• Main Authors: TUPAS, L. M, KOIKE, I, KARL, D. M, HOLM-HANSEN, O
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01-04-1994; Berlin
• Subjects: Animal, plant and microbial ecology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Marine; Microbial ecology; Various environments (extraatmospheric space, air, water); Antarctica; PSW, Antarctica, Antarctic Peninsula, Gerlache Strait; Marine environment; Bacteria; Nitrogen; Metabolism; Heterotrophy; Coastal zone
• ISSN: 0722-4060; 1432-2056
• DOI: 10.1007/BF00240524

Field studies to examine the in situ assimilation and production of ammonium (NH super(+) sub(4)) by bacterial assemblages were conducted in the northern Gerlache Strait region of the Antarctic Peninsula. Short term incubations of surface waters containing super(15)N-NH super(+) sub(4) as a tracer showed the bacterial population taking up 0.041-0.128 mu g-atoms N/ld, which was 8-25% of total NH super(+) sub(4) uptake rates. The large bacterial uptake of NH super(+) sub(4) occurred even at low bacterial abundance during a rich phytoplankton bloom. Estimates of bacterial production using super(3)H-leucine and -adenine were 1.0 mu g C/ld before the bloom and 16.2 mu g C/ld at the bloom peak. After converting bacterial carbon production to an estimate of nitrogen demand, NH super(+) sub(4) was found to supply 35-60% of bacterial nitrogen requirements. Bacterial nitrogen demand was also supported by dissolved organic nitrogen, generally in the form of amino acids. It was estimated, however, that 20-50% of the total amino acids taken up were mineralized to NH super(+) sub(4). Bacterial production of NH super(+) sub(4) was occurring simultaneously to its uptake and contributed, 27-55% of total regenerated NH super(+) sub(4) in surface waters. Using a variety of super(15)N-labelled amino acids it was found that the bacteria metabolized each amino acid differently. With their large mineralization of amino acids and their relatively low sinking rates, bacteria appear to be responsible for a large portion of organic matter recycling in the upper surface waters of the coastal Antarctic ecosystem.