Organic carbon and mineral nutrient limitation of oxygen consumption, bacterial growth and efficiency in the Norwegian Sea |
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Authors: | L Antonio Cuevas Jorun K Egge T Frede Thingstad Birte T?pper |
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Institution: | (1) Department of Biology, University of Bergen, P.O. Box 7803, 5020 Bergen, Norway |
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Abstract: | To evaluate the role of bacteria in the transformation of organic matter in subarctic waters, we investigated the effect of
mineral nutrients (ammonia and phosphate) and organic carbon (glucose) enrichment on heterotrophic bacterial processes and
community structure. Eight experiments were done in the Norwegian Sea during May and June 2008. The growth-limiting factor
(carbon or mineral nutrient) for heterotrophic bacteria was inferred from the combination of nutrient additions that stimulated
highest bacterial oxygen consumption, biomass, production, growth rate and bacterial efficiency. We conclude that heterotrophic
bacteria were limited by organic carbon and co-limited by mineral nutrients during the prevailing early nano-phytoplankton
(1–10 μm) bloom conditions. High nucleic acid (HNA) bacteria became dominant (>80%) only when labile carbon and mineral nutrient
sources were available. Changes in bacterial community structure were investigated using denaturing gradient gel electrophoresis
(DGGE) of polymerase chain reaction (PCR)-amplified 16S ribosomal RNA genes. The bacterial community structure changed during
incubation time, but neither carbon nor mineral nutrient amendment induced changes at the end of the experiments. The lack
of labile organic carbon and the availability of mineral nutrients are key factors controlling bacterial activity and the
role of the microbial food web in carbon sequestration. |
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