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

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