Volume 61 of Advances in Limnology contains 12 peer reviewed, original papers focusing on the hyporheic zone of running waters (the transient zone in fluvial sediments between ground water and surface water).
The papers of this special issue address new studies carried out in the River Lahn (Germany), a right-bank tributary in the middle reach of the River Rhine. The studies were conducted in order
(i) to perform interdisciplinary research as a basis for understanding the processes relevant to hyporheic zone ecology,
(ii) to identify relevant spatial and temporal scales of abiotic and biological processes and
(iii) to consider a river ecosystem located in a landscape with "average" human impact. 12 original papers deal with four major topics:
a) Hydrology and hydraulics, emphasizing near bottom and hyporheic flows including bed load transport and colmation (reduction of hydraulic conductivity) of the river bed.
b) Spatial and temporal dynamics of water constituents and coupling with hydraulic exchange processes.
c) Microbiology and conversion of water constituents and considering community respiration and nitrification/denitrification processes.
d) The taxonomic and functional structure of meio- and macrobenthic communities in the hyporheic zone was studied and related to abiotic factors (1-3 above). Special attention was given to biological colmation and decolmation processes of hyporheic interstices and the reproductive success of gravel spawning fish in relation to eutrophication patterns.
The results presented here emphasize the important role of the hyporheic zone as a critical factor of the ecological integrity of many streams and rivers. Therefore, in both river ecology and water resources management, the hyporheic zone must be considered in detail and very carefully in order to analyze its relevance for the ecological functioning of running waters.