Decomposition of reed swamp detritus in the Danube Delta: a case study of four eutrophic systems

Abstract

1. Leaf litter decomposition rates in aquatic ecosystems are known to be related to many abiotic and biotic factors.
2. Here, field experiments were carried out during fall 2005 in four sites of the Danube Delta system, differing mainly in terms of type and characterised by euthrophycation.
3. The litter bag technique was used to study reed decomposition and evaluate the relevance of ecosystem characteristics to reed leaf decay rates.
4. Trophic conditions were very high in all sites (TRIX > 8.0), indicating poor water quality. Overall, the processing rate k of Phragmites australis in the Danube Delta was equal to 0.016 days-1.
5. The mass remaining in the leaf bags differed among ecosystems (ANOVA, P < 0.001) with higher decay rates in Isac lake (k = 0.024) than in the other systems. P. australis leaf processing varied considerably in the studied lakes and channel (cv = 30.7%).
6. A high percentage (>60%) of leaf breakdown variability was related to differences in phosphorus compound concentrations in the water.