Transport of microorganisms to Israel during Saharan dust events

Abstract

Dust storms are serious meteorological events that affect the East Mediterranean region, primarily during the spring season. The physical and chemical nature of dust storms, their origin, and the meteorological conditions leading to the generation of storms have been fully documented, but knowledge on their biological content is almost nonexistent. Four dust events that occurred in the period 2004-2005 were sampled in Haifa, Israel, an urban area on the East Mediterranean coast, for biological characterization. Samples were taken before or after (depending on the meteorological conditions) as well as during the dust events. Dust particles were collected as two size fractions using a dichotomous sampler, and their elemental content was determined using X-ray fluorescence analyses. Airborne bacteria and fungi were collected with the Six Stage Andersen Viable Impactor. Fungi were identified by optical microscopy. Compared to adjacent clear days, there was an increase in the concentration of both atmospheric particles and elements of geological and marine origin during the dust events. The concentration of airborne microorganisms during the dust events was also higher, and the fungal population content was affected. On a winter clear day the abundant airborne fungi were Paecilomyces variotii, Penicillium glabrum, and Alternaria alternata. On a spring clear day, the persisting airborne fungi were Alternaria alternata, Geotrichum candidum, Penicillium chrysogenum, and P. glabrum. However, during two dust events the fungal population was dominated by Alternaria alternata, Aspergillus fumigatus, A. niger, A. thomii, Cladosporium cladosporioides, Penicillium chrysogenum, and P. griseoroseum. This study suggests that Saharan and other desert dust events in the East Mediterranean have a significant effect on the airborne microbial populations, which might impact on health, agriculture, and ecology.

Measurements and modeling of surface–atmosphere exchange of microorganisms in Mediterranean grassland

“…Data from literature indicate a sampling efficiency ranging from 80 to 100 % for mildew spores (Schwarzbach, 1979). Given the Burkard sampler's high flow rate, sampling happens at a super-isomean-velocity compared with external wind speed.…”

“…where g is the gravitational acceleration (9.81 m s −2 ), ρ p is the particle density (1100 kg m −3 , Cox and Wathes, 1995), d is the particle diameter (3.3 × 10 −6 m, Raisi et al (2013) and Schlesinger et al, 2006), C c is the Cunningham slip correction factor, and η is the air viscosity (1.83 × 10 −5 Pa s, Kulkarni et al, 2011). The term V i represents the effect of interceptionimpaction on particle deposition and it has been computed following Slinn (1982):…”

ANaganishiain high places: functioning populations or dormant cells from the atmosphere?

“…Many microbes can be transported over global distances (Kellogg and Griffin 2006; Schlesinger et al 2006), and biogeographic patterns of microbial community structure suggest widespread long-distance dispersal at global scales (Barberán et al 2007, Darcy et al 2011; Itani and Smith 2016). Mathematical models of long-range transport also show that smaller particles – like spores – are likely to easily attain global distribution (Norros et al 2014, Wilkinson et al 2012).…”

Ocean–Atmosphere Interactions of Particles

“…However, dust events have been shown to introduce a significant pulse of microorganisms (Griffin 2007;Schlesinger et al 2006;Polymenakou et al 2008) and other microbiological materials (e.g. cellular fragments, fungal spores) into the atmosphere (Jaenicke 2005).…”