Dynamics of a benthic microbial community in a riverine environment subject to hydrological fluctuations (Mulargia River, Italy)

• Published in: Hydrobiologia Vol. 657; no. 1; pp. 37 - 51
• Main Authors: Zoppini, Annamaria, Amalfitano, Stefano, Fazi, Stefano, Puddu, Alberto
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01.12.2010; Springer Netherlands; Springer Nature B.V
• Subjects: alpha-Proteobacteria; bacteria; Bacterial Diversity; beta-Proteobacteria; Biochemistry; biodegradation; Biomedical and Life Sciences; carbon; Climate change; Community composition; community structure; Ecology; Enzymatic activity; enzyme activity; Extracellular enzymes; Firmicutes; Floods; Freshwater; Freshwater & Marine Ecology; gamma-Proteobacteria; Global Change and River Ecosystems; Global warming; Hydrology; Italy; Life Sciences; Microbial activity; microbial communities; Microbial degradation; Microbial metabolic rates; Microbiology; Nutrient concentrations; Nutrients; Organic carbon; Organic matter; Outlets; Planctomycetes; Riparian ecology; River beds; Rivers; Sardinia; sediments; spring; stream channels; Streambed Bacteria; Temporary rivers; Water flow; Zoology; Italy; Sardinia; Italy, Sardegna; Microbial metabolic rates; Temporary rivers; Water flow; Extracellular enzymes; Bacterial Diversity; Streambed Bacteria
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/s10750-010-0199-6

Temporary rivers are characterized by recurrent dry phases, and global warming will stress their hydrology by amplifying extreme events. Microbial degradation and transformation of organic matter (OM) in riverbed sediment are key processes with regard to carbon and nutrient fluxes. In this study, we describe structural and functional changes of benthic microbial communities in a riverine environment subject to hydrological fluctuation. Sampling was carried out in the outlet section of the Mulargia River (Sardinia, Italy) under various water regimes, including one flood event. Overall, sediments were characterized by low bacterial cell abundance (range 0.6-1.8 × 10⁹ cell g⁻¹) as a consequence of their low nutrient and OM concentrations. No major differences were found in the community composition. Alpha-Proteobacteria dominated during the whole year (range 21-30%) followed by Beta-Proteobacteria, Gamma-Proteobacteria, and Cytophaga-Flavobacteria which always contributed <18%. Planctomycetes and Firmicutes were found in smaller amounts (<7%). In spring, when the highest total organic carbon content was also detected (0.42% w/w), both bacterial abundance and C production (BCP, 170 nmol C h⁻¹ g⁻¹) reached relatively high values. During the flood event, an increase in BCP and the highest values of community respiration (CR, 74 nmol C h⁻¹ g⁻¹) were observed. Moreover, most of the extracellular enzyme activities (EEA) changed significantly during the flood. The variation of the water flow itself can explain part of these changes and other factors also come into play. The presence of different patterns of functional parameters could suggest that the quality of the OM could be the major driving force in nutrient flux.