Microbial biofilm structure and organic matter use in mediterranean streams |
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Authors: | Anna M Romaní Stefano Amalfitano Joan Artigas Stefano Fazi Sergi Sabater Xisca Timoner Irene Ylla Annamaria Zoppini |
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Institution: | 1. Institute of Aquatic Ecology, University of Girona, Campus de Montilivi, 17071, Girona, Spain 2. Water Research Institute (IRSA), National Research Council (CNR), Via Salaria km 29.3-CP10, 00015, Monterotondo, Italy 3. Irstea, 3 Quai Chauveau CP 220, 69336, Lyon, France 4. Catalan Institute for Water Research (ICRA), Emili Grahit 101, Edifici H2O Parc Científic i Tecnològic de la Universitat de Girona, 17003, Girona, Spain
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Abstract: | River and stream biofilms in mediterranean fluvial ecosystems face both extreme seasonality as well as arrhythmic fluctuations. The hydrological extremes (droughts and floods) impose direct changes in water availability but also in the quantity and quality of organic matter and nutrients that sustain the microbial growth. This review analyzes how these ecological pulses might determine unique properties of biofilms developing in mediterranean streams. The paper brings together data from heterotrophic and autotrophic community structure, and extracellular enzyme activities in biofilms in mediterranean streams. Mediterranean stream biofilms show higher use of peptides during the favorable period for epilithic algae development (spring), and preferential use of cellulose and hemicellulose in autumn as a response to allochthonous input. The drying process causes the reduction in bacterial production and chlorophyll biomass, but the rapid recovery of both autotrophs and heterotrophs with rewetting indicates their adaptability to fluctuations. Bacteria surviving the drought are mainly associated with sediment and leaf litter which serve as “humid refuges”. Some algae and cyanobacteria show resistant strategies to cope with the drought stress. The resistance to these fluctuations is strongly linked to the streambed characteristics (e.g., sediment grain size, organic matter accumulation, nutrient content). |
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