Microbial communities in streambed sediments recovering from desiccation

Abstract

Climate change affects running waters not only by increasing temperatures but also by increasing discharge variability as more frequent and severe floods and more frequent and longer droughts occur, especially in upper reaches. Mediterranean streams are known to experience droughts, but Central European headwaters are also beginning to be affected. The development of bacterial communities (abundance, composition) and the recovery of microbial functions (bacterial production, extracellular enzyme activity) were explored after rewetting desiccated streambed sediments via a sediment core perfusion technique. The bacterial community composition changed only slightly in the sediments from the Central European stream Breitenbach (Germany), but distinctly in the Mediterranean Mulargia River (Sardinia, Italy) during 4 days of experimental rewetting. Breitenbach sediments probably enabled survival of bacterial communities more similar to indigenous streambed communities, because they were less dry. High activity of enzymes involved in polymer degradation at the beginning of rewetting in both sediments indicated the persistence of extracellular enzymes during drought. After 4 days, nearly all microbial activities reached a level similar to unaffected sediments for the Breitenbach, but not for Mulargia. Here, much more intense drying resulted in a more distinct change and reduction of the microbial community, responsible for slower recovery of structure and functions.

Stream Biofilm Responses to Flow Intermittency: From Cells to Ecosystems

“…The rewetting phase may be associated with a new bacterial community composition, as has been observed in some systems (Marxsen et al, 2010), but not so clearly in others (Febria et al, 2015). These contradictory results indicate that community changes may be particular for each benthic compartment, according to their particular exposure and resilience, and highlight the prevalent environmental conditions at each site as a factor determining the fate of the microbial communities.…”

Contraction, fragmentation and expansion dynamics determine nutrient availability in a Mediterranean forest stream

“…Future research should focus on the effect of drying and rewetting on the underlying physical and microbial mechanisms driving the observed changes in nutrient availability Amalfitano et al 2008;Marxsen et al 2010) as well as on the biogeochemical processes occurring during the dry phase, when no surface water is present (Borken and Matzer 2009). At the catchment scale, a more thorough assessment of the temporal and spatial extent as well as of the physicochemical characteristics of temporary streams is needed (Larned et al 2010).…”

Importance of Extracellular Enzymes for Biogeochemical Processes in Temporary River Sediments during Fluctuating Dry–Wet Conditions

“…If the hydrolysis of organic matter continues in the dry sediment we can infer that the pool of organic compounds contained in the first water flush could be enriched with labile nutrients that accumulate in the sediments as bacteria are died or temporarily inactive. However, in the case of a complete stop of extracellular enzyme activity during extreme dryness, enzymes are able to become active immediately upon rewetting (Marxsen et al 2010), thus resulting in immediate delivery of these compounds. …”

“…The application of this approach enables the acquisition of new information on the time and mode of recovery of benthic microbial communities after flooding without major disturbances of the sediment core (Marxsen et al 2010). The response of two river sediments, originating from semi-arid (Mulargia, Italy) and temperate (Breitenbach, Germany) climatic regions, were analyzed.…”