DAM REMOVAL EFFECTS ON GASEOUS CARBON FLUXES IN A MOUNTAINOUS MEDITERRANEAN STREAM

The global prevalence of obsolete or unsafe old dams necessitates the development of effective restoration approaches and expanded knowledge in this field. Here, we investigated the effects of dam removal on gaseous carbon fluxes in a mountainous Mediterranean stream. This ecosystem function was compared among three reaches: one where a dam was removed (restored), one with an intact dam (impacted), and one in natural conditions (reference). In total, four sampling campaigns were conducted, one in each season: autumn (October 2022), winter (February 2023), spring (April 2023), and summer (June 2023). Gaseous carbon fluxes were measured by using the headspace equilibration method. The fluxes of CO₂ (FCO₂) in the restored reach (mean ± standard deviation: 88.77 ± 62.80) was similar to those in the reference reach (88.78 ± 108.18) (ANOVA test; p = 1.000) and higher than those in the impacted reach (66.18 ± 59.42 mmol m^-2 d^-1) (p = 0.017), whereas the fluxes of CH₄ in the restored reach (0.47 ± 0.56) was higher than those in the reference (0.10 ± 0.06) (p < 0.001) and impacted (0.18 ± 0.12 mmol m^-2 d^-1) (p < 0.001) reaches. Lotic waters are expected to present greater FCO₂ than impounded waters as shallower streams with higher water velocities are often associated with higher interfacial turbulence. Since the dam removal occurred only six years before the sampling, residual organic material from the dam's operational period likely continues to affect CH₄ emissions. These findings are important for guiding future dam removal and restoration efforts.

Presentation Preference: Oral

Primary Presenter: João Miguel Merces Bega, University of São Paulo (joaobega@usp.br)

Authors:

João Miguel Merces Bega, Universidade de São Paulo  (joaobega@usp.br)

Davi Gasparini Fernandes Cunha, Universidade de São Paulo  (davig@sc.usp.br)

Alba Camacho-Santamans, Universitat de Barcelona  (a.camacho-santamans@ub.edu)

Daniel von Schiller, Universitat de Barcelona  (d.vonschiller@ub.edu)