Importance of Extracellular Enzymes for Biogeochemical Processes in Temporary River Sediments during Fluctuating Dry-Wet Conditions

The special hydrological circumstances that characterize temporary rivers (Fig. 6.1) make them particularly sensitive to environmental alterations. Temporary waters are found throughout the world and include intermittent streams and ponds, episodic rain puddles and seasonal limestone lakes. These natural bodies of water experience a recurrent dry phase of varying duration and spatial extent (Uys and O'Keeffe 1997). Temporary waters are widespread in semi-arid regions worldwide where they play an important role as water sources (e.g., water supply, irrigation and hydroelectric power generation). Climate change represents an emerging problem for these ecosystems by increasing the frequency and duration of drought periods, with potentially important effects on fluvial biogeochemical processes.