Effects of the interaction between tubificid worms on the functioning of hyporheic sediments: an experimental study in sediment columns

Abstract

The main objective of this study was to quantify the importance of interactions between two genera of tubificid worms (Limnodrilus and Tubifex) on processes occurring in hyporheic sediments. The importance of interaction between tubificid worms was estimated by comparing, at a same density of 100 worms, the influence of individual genera with the combination of the two genera. We measured the effect of worms on sediment redistribution, dissolved oxygen consumption and microbial distribution within low filtration gravel-sand columns. The results showed that 100 Limnodrilus, 100 Tubifex, and the combination of the two genera (50 Limnodrilus and 50 Tubifex) all stimulated the O 2 consumption and bacterial numbers in the upper layer of sediment (from 5 cm above to 5 cm below the sediment surface). However, the combination of the two genera produced higher sediment redistribution and a higher stimulation of the number of bacteria in the top 5 cm of the sediment than Limnodrilus and Tubifex tested separately at the same density. Furthermore, the combination of the two genera produced lower oxygen consumption than the two genera tested separately in the deep layers of the sediment. Thus, the interactions within the group of tubificids played a significant role in the functioning of the first cm of the sediments and should not be neglected when assessing their roles in subsurface ecosystems.