Degradation of softwood [14C lignin] lignocelluloses and its relation to the formation of humic substances in river and pond environments

• Published in: Hydrobiologia 1988-03, Vol.159 (2), p.169-176
• Main Authors: FUSTEC, E, CHAUVET, E, GAS, G, LACAZE, D, ESCAUTIER, M
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; Synecology
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/BF00014725

Radioisotopic methods were used to determine the fate of lignin in water and sediment of the Garonne river and of a pond in its floodplain. Carbon-14 lignin lignocelluloses were directly incorporated into water and sediments. The extent of mineralization and of humic substances formation was estimated. In running water samples, willow, alder and poplar lignocelluloses showed no significant degradative differences: conversion of total radioactivity to carbon-14 carbon dioxide ranged from 18.7 to 24.45 per cent after 120 days' incubation. The extent of mineralization in standing water and sediments was lower and correlated with oxygen supply. Between 3.3 and 7.9 per cent of carbon-14 labelled lignin was recovered in water samples as microbially-derived DOC after 60 days' incubation. Only 0.4-1.3 per cent of the applied activity was recovered in water extracts from the sediment. The amount of activity recovered in total humic substances (including fulvic acids) ranged from 3.35 to 4.36 per cent, 10 times lower than in soils. No differences were observed between river and pond conditions for humic substances formation.