Chapter XV — 179 — Microorganisms in Marine Air 



The comparative freedom of air from contaminating molds is most striking 

 on research vessels and in seaside laboratories favored by prevailing on- 

 shore winds. Additional information on air-borne fungus spores is given 

 by Durham (1942). 



Microbial content of precipitation: — There has been little additional 

 work done on the microbial content of different forms of precipitation 

 since Frankland and Frankland (1894) reported half a century ago 

 that, "Curiously but few determinations of the number of organisms in 

 rain have been made." According to the Franklands, Miquel found an 

 average of 4.3 bacteria per ml. of rain water collected at Montsouris Ob- 

 servatory outside of Paris, and 19 per ml. in the middle of the city. The 

 average number for three years was 4.3 bacteria and 4.0 molds per ml., 

 which, with an annual rainfall of 60 cm., signified that about 5,000,000 

 organisms fall annually per square meter in that locality. Other workers 

 have reported the presence of several thousand organisms per ml. of 

 freshly fallen rain water. The Franklands stated that Bujwm found as 

 many as 21,000 organisms per ml. of water from hailstones and that Fou- 

 TiN found 729 organisms per ml. of hailstone water. 



The number and kinds of microorganisms in rain water are influenced 

 by the direction and velocity of the wind, the origin, course, and duration 

 of the storm, and other meteorological conditions. Rain water collected 

 at the Scripps Institution contained from 10 to 150 microorganisms per 

 ml. Terrestrial forms, particularly mold spores, predominated in rain 

 water containing the most microorganisms. The largest counts were 

 usually obtained in the first rain. The rain water approached sterility as 

 storms progressed, especially in the absence of local atmospheric turbu- 

 lence. Rain water collected at considerable distances offshore contained 

 an average of from i to 10 bacteria per ml., with few or no mold fungi. 



McLean (1918) recovered cocci, sporogenous rods, and yeasts from 

 falling snow on Adelie Land, Antarctica. He believed that they were car- 

 ried there from distant continents by air currents. 



Significant numbers of bacteria w^re found by Salimovskaja-Rodina 

 (1936) in snow from mountains ranging in elevation from 2,050 to 2,800 

 meters and also in snow from polar regions. Predominating were colorless 

 rods, although under certain conditions the snow was tinted by the 

 presence of large numbers of pigmented microorganisms. Nineteen 

 different species of yeast fungi colored white, pink, red, or black were 

 isolated from the snow. Two species of red cocci and two yellow rods 

 were found in freshly fallen snow. 



Species of Bacillus, Achromobacter, Flavohacterium, and Micrococcus 

 were found by Darling and Siple (1941) in freshly fallen snow on Little 

 America and Marie Byrd Land. Only one or two bacteria were found per 

 pint of snow. The same general types of bacteria were found on plates of 

 nutrient media exposed to air. Although they admit the possibility of 

 migrating terns, gulls, or petrels carrying bacteria to this snow-covered 

 region. Darling and Siple were convinced that most of the bacteria were 

 air-borne from the continents. Unfortunately, suitable media were not 

 employed to ascertain if there were any marine bacteria in the air and 

 snow of the Antarctic region. 



Pollens in marine air: — Erdtman (1938) made a quantitative study 

 of pollens in the atmosphere while crossing the Atlantic Ocean from 



