Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico-chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%-98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events.
- MeSH
- biofilmy růst a vývoj MeSH
- biologická dostupnost MeSH
- dusičnany analýza MeSH
- geologické sedimenty chemie MeSH
- klimatické změny MeSH
- listy rostlin chemie MeSH
- organické látky analýza MeSH
- podnebí MeSH
- řeky chemie MeSH
- živiny analýza MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND: Until recently, members of the Cronobacter genus (formerly known as Enterobacter sakazakii) were a relatively unknown cause of nosocomial infections. However, their association with infant infections, particularly through the consumption of contaminated reconstituted infant formula in neonatal intensive care units, has resulted in international efforts to improve neonatal health care. AIM: To investigate current understanding of this emergent group of bacterial pathogens and the steps taken to reduce neonatal infection. METHODS: A literature review was undertaken to determine current knowledge of the Cronobacter genus with respect to recent taxonomic revisions, sources and clinical relevance. FINDINGS: The majority of severe neonatal meningitis infections are associated with one of the 10 Cronobacter spp., the clonal complex known as C. sakazakii sequence type 4. International efforts by the Food and Agriculture Organization-World Health Organization (WHO) to reduce the risk of neonatal infection by this organism have resulted in improved microbiological safety of powdered infant formula (PIF), but revised guidelines for feeding practices have been problematic. In addition, the majority of infections occur in the adult population and the sources are unknown. CONCLUSION: International improvements in the microbiological safety of PIF and advice on feeding practices have focused on improving neonatal health care following the heightened awareness of Cronobacter infections in this particular age group. These measures are also likely to reduce neonatal exposure to other opportunistic bacterial pathogens, but a number of unresolved issues remain with respect to the practicalities of feeding premature neonates safely while following WHO advice.
- MeSH
- Cronobacter izolace a purifikace MeSH
- enterobakteriální infekce epidemiologie mikrobiologie MeSH
- infekce spojené se zdravotní péčí epidemiologie mikrobiologie MeSH
- kojenec MeSH
- lidé MeSH
- meningitida bakteriální epidemiologie mikrobiologie MeSH
- náhražky mateřského mléka MeSH
- nemoci přenášené potravou epidemiologie mikrobiologie MeSH
- novorozenec MeSH
- objevující se infekční nemoci epidemiologie mikrobiologie MeSH
- zdravotnická zařízení MeSH
- Check Tag
- kojenec MeSH
- lidé MeSH
- novorozenec MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
