Chapter XV 



— 181 — Microorganisms in Marine Air 



of any lifting force whatever, a water particle 0.5 mm. in diameter could 

 be carried about a mile by a steady wind having a velocity of 10 miles 

 per hour before it fell 100 meters. Larger droplets would not fall much 

 faster because they break into small ones when they attain a velocity ex- 

 ceeding 800 meters per second, unless frozen solid as in hailstones. The 

 rate of fall of water droplets of different sizes through air as calculated 

 from Store's law of falling bodies is given in Table XXXVII on page 180. 

 The calculations are based upon a steady state in which there is no turbu- 

 lence. Since there is nearly always some degree of turbulence which may 

 tend to retard the descent of falling bodies or actually carry them to higher 

 elevations, and since the wind velocity often exceeds 10 miles per hour, 

 the physical possibilities for the world-wide aerial transport of bacteria 

 become apparent. 



Fig. 1 2. — Principal ways in which bacteria in sea water are carried into the atmosphere: 

 (A) orographic uplift, (B) spray from crests of waves some of which are 20 to 30 feet high, 

 (C) convection, and (D) convergence of light warm air mass and heavy cold air front {taken 

 from ZoBell, 1942c). 



The horizontal distance over which microorganisms can be transported 

 is almost limitless and is largely determined by their ability to survive the 

 atmospheric environment. The presence of microorganism in the atmos- 

 phere at great elevations, far removed from their native habitats, shows 

 that certain forms may survive the adversities of the atmospheric environ- 

 ment for long periods of time. , -ri: j^-^-^s. 



