ausblenden:
Schlagwörter:
stream; wood degration; extracellular enzyme activity; β-glucosidase; phenoloxidase
Zusammenfassung:
The degradation of beech wood (Fagus sylvatica L.) was followed over 16 months in a central European upland stream, the Breitenbach (near Schlitz, Germany). 1 cm³ cubes of beech wood were placed on the stream bed and sampled at monthly intervals. Besides mass loss, fungal biomass (ergosterol content) and lignin content, the activity of two extracellular enzymes was measured: β-D-glucosidase, an enzyme involved in the degradation of cellulose, and phenoloxidase, a ligninolytic enzyme. The suitability of the fluorigenic model substrate methylumbelliferyl-β-D-glucoside for measuring β-D-glucosidase activity in wood from aquatic environments was tested. This technique is much more sensitive than the conventional photometric method. The beech wood was degraded at a constant rate of k = 0.00272 d⁻¹ across the entire 16-month incubation period. There was a rapid onset of microbial colonisation as witnessed by the initial detection of enzyme activity, after only 7 days of exposure. Lignin and ergosterol content as well as β-glucosidase activity reached their highest values at the end of the 16-month incubation period. Phenoloxidase activity increased rapidly to a maximum after 6 weeks, and then decreased to almost zero by the end of the experiment. The combination of biochemical techniques for measuring extracellular enzyme activities with measurements of mass loss, chemical composition and microbial colonisation, provided valuable insights into the decomposition of wood in aquatic environments.
