Chapter I — 3 — General Introduction 



quantitative significance, because his samples were analyzed only after 

 prolonged storage, his work is instructive. 



Certes believed that he had surmounted the special difficulties attend- 

 ing the collection of a rigorous sample from any desired depth. The oc- 

 currence of viable bacteria in samples collected from great depths showed 

 that they could survive high hydrostatic pressures and that they were not 

 killed by the decrease in pressure as the samples were hauled to the surface. 

 Certes found some sporeformers in both water and bottom deposits. 

 The latter yielded a variety of microorganisms. A predominating species 

 which was tested for pathogenicity gave negative results. 



During a decade of service as ship's physician, Bernhard Fischer 

 made many important observations on the distribution and characteristics 

 of marine microorganisms. On the expedition of the S.M.S. MoUke from 

 the Baltic Sea to the West Indies and return, Fischer (1886) found that 

 under ordinary circumstances ocean air contains few or no germs carried 

 there from land, but that large numbers of terrigenous bacteria occur in the 

 air near land masses. From West Indies waters Fischer (1887) isolated 

 and described a photogenic bacterium, Photobaclerium indicum. Pfluger 

 (1875) was probably the first to recognize photogenic bacteria as such on 

 fish, but he described no species. Bancel and HussoN (1879) found 

 photogenic bacteria on lobsters. 



Later Fischer (1888a) found Photobaclerium indicum in the Baltic 

 Sea along with a closely related photogenic species, Pseudomonas phos- 

 phorescens. In Kiel Harbor, Fischer (1888&) isolated 14 different species 

 of marine bacteria which grew at 0° C. After experimenting with various 

 methods of aseptically collecting water samples from any desired depth, 

 Fischer (1893) described a bacteriological water sampler (see page 27). 



Some of Fischer's best work was done during the Plankton Expedi- 

 tion of the Humboldt Foundation, the first expedition of its kind to make 

 provisions for studying the role of bacteria in the biology of the sea.^ On 

 this cruise across the Atlantic Ocean from July to November 1889, living 

 bacteria were found in nearly all i-ml. samples of water. Fischer (1894a) 

 reports finding an average of 1,083 bacteria per ml. in 175 samples exam- 

 ined, the highest count being 29,400 bacteria per ml. While much higher 

 counts have been obtained with the use of more modern media (see page 

 41), interesting ecological relationships were noted. Fischer used nutri- 

 ent gelatin or fish gelatin prepared with sea water for the cultivation of 

 marine microorganisms. In tropical waters it was necessary to use agar 

 as a solidifying agent. 



In general, Fischer found the largest bacterial populations in coastal 

 waters. More than twice as many bacteria were found in inland seas, such 

 as the Baltic or North Sea, as in waters from similar depths in the open 

 ocean. More bacteria were found at 200 to 400 meters than in surface 

 waters, which Fischer (1894&) attributed (probably erroneously) to the 

 lethal or inhibitory effect of sunlight near the surface (see page 69). At 

 depths exceeding 200 to 400 meters the bacterial population decreased 

 with depth. Very few bacteria were found in the water at depths ex- 

 ceeding 1 100 meters. 



The great variation in the number of bacteria was attributed to the 

 belief that bacteria do not normally hve in the water itself but grow 

 primarily on the dead bodies or excretions of marine plants and animals. 

 However, Fischer did estabUsh that bacteria can multiply in pure sea 

 water incubated in flasks. Significantly he noted that the greatest abun- 



