Severity and frequency of meteorological and hydrological droughts have increased worldwide affecting river functioning. In the Mediterranean climate region, the occurrence of wet and dry phases favors the adaptation of microbial streambed communities to intermittency. However, the prolonged periods of drought may determine a strong effect on streambed community structure, composition and functions, compromising the whole ecosystem functioning. This study investigates whether and to what extent the hydrological history affect streambed microbial resistance responses (i.e. production of extracellular polymeric substances - EPS, and carotenoids) and/or their functional fingerprinting (i.e. heterotrophic functional diversity by carbon substrate utilization profiles). We analyzed streambed surface sediments from a network of 37 sites in the Mediterranean region (NE Spain), including a wide range of hydrological history (perennial and temporary streams) previously monitored over one year. We hypothesized that drought duration would cause a decrease in heterotrophic functional diversity and a greater investment of energy to resistance strategies such as EPS production. Results showed no differences in heterotrophic functional diversity among sites but distinct functional fingerprinting among hydrological categories. When analyzing samples from intermittent sites, the longest drought sites showed the largest amount of EPS, while EPS in perennial sites was highly variable. Results suggest that extreme drought imposes strict conditions constraining streambed structure and function.

Primary Presenter: Anna Romaní, University of Girona (anna.romani@udg.edu)

Authors:

Anna M. Romaní, GRECO, Institute of Aquatic Ecology, University of Girona  (anna.romani@udg.edu)

Núria Perujo Perujo, UFZ, Helmholtz Centre for Environmental Research  (nuria.perujo-buxeda@ufz.de)

Marta Pujol, GRECO, Institute of Aquatic Ecology, University of Girona  (mpujolcosculluela@gmail.com)

Giulia Gionchetta, Eawag, Swiss Federal Institute of Aquatic Science and Technology  (giulia.gionchetta@eawag.ch)