Bacterial Growth on Photochemically Transformed Leachates from Aquatic and Terrestrial Primary Producers

• Published in: Microbial ecology Vol. 40; no. 3; pp. 200 - 208
• Main Authors: ANESIO, A. M, THEIL-NIELSEN, J, GRANELI, W
• Format: Journal Article
• Language: English
• Published: New York, NY Springer-Verlag New York Inc 01-08-2000; Springer
• Subjects: Animal, plant and microbial ecology; Bacteria; Bacterial biomass; Biologi; Biological and medical sciences; Biological Sciences; Biomass production; Brackish; Carbon; Ecology; Ekologi; Freshwater; Fundamental and applied biological sciences. Psychology; Irradiation; Isotopes; Macrophytes; Marine; Microbial ecology; Natural Sciences; Naturvetenskap; Nitrogen; Phytoplankton; Respiration; Various environments (extraatmospheric space, air, water); Aquatic environment; Microbial activity; Organic matter; Dissolved organic matter; Ultraviolet irradiation; Organic matter cycle; Bacteria; Nutrient; Bioavailability; Microbial biomass; Microbial community; Photochemical degradation
• ISSN: 0095-3628; 1432-184X; 1432-184X
• DOI: 10.1007/s002480000045

We measured bacterial growth on phototransformed dissolved organic matter (DOM) leached from eight different primary producers. Leachates (10 mg C liter-1) were exposed to artificial UVA + UVB radiation, or kept in darkness, for 20 h. DOM solutions were subsequently inoculated with lake water bacteria. Photoproduction of dissolved inorganic carbon (DIC), ranging from 3 to 16 μg C$\text{liter}^{-1}\ {\rm h}^{-1}$, and changes in the absorptive characteristics of the DOM were observed for all leachates upon UV irradiation. The effects of irradiation exposure on DOM bioavailability varied greatly, depending on leachate and type of bacterial growth criterion. Bacterial carbon utilization (biomass production plus respiration) over the entire incubation period (120 h) was enhanced by UV radiation of leachate from the terrestrial leaves, relative to carbon utilization in non-irradiated leachates. Conversely, carbon utilization was reduced by radiation of the leachates from aquatic macrophytes. In a separate experiment, the stable C and N isotope composition of bacteria grown on irradiated and non-irradiated DOM was estimated. Bacterial growth on UV-irradiated DOM was enriched in13C relative to the bacteria in the non-irradiated treatments; this result may be explained by selective assimilation of photochemically produced, isotopically enriched labile compounds.