Dam removal effects on carbon processing in a mountainous Mediterranean stream.

Area of Science:

• Environmental Science
• Ecology
• River Restoration

Background:

• Obsolete dams pose risks, necessitating effective restoration strategies.
• Dam removal is a key strategy for restoring riverine ecosystems.
• Understanding impacts on carbon processing is crucial for dam removal success.

Purpose of the Study:

• To evaluate the effects of dam removal on carbon processing in a Mediterranean stream.
• To compare ecosystem functions (organic matter decomposition, metabolism, gaseous carbon fluxes) between restored, impacted, and reference reaches.
• To assess the seasonal variability and timeframe for ecological recovery after dam removal.

Main Methods:

• Field study comparing three stream reaches: restored (dam removed), impacted (intact dam), and reference (natural).
• Year-long seasonal measurements of organic matter decomposition, whole-reach metabolism, and gaseous carbon fluxes (CO2, CH4).
• Analysis of hydromorphological and physicochemical characteristics to explain seasonal variations.

Main Results:

• Restored reach showed intermediate decomposition and metabolic rates between reference and impacted reaches.
• Carbon dioxide fluxes in the restored reach were similar to the reference reach.
• Methane fluxes were higher in the restored reach; seasonal variations in functions were inconsistent.

Conclusions:

• Dam removal positively impacts carbon processing but requires a longer timeframe for full ecological emulation.
• Seasonal hydromorphological and physicochemical changes influence restoration outcomes.
• Holistic approaches beyond dam removal are needed for complete stream ecosystem restoration; ecosystem function metrics are vital indicators.