500 



THE COMMUNITY 



This store of dissolved organic materials, 

 according to Putter's hypothesis, should be 

 available to zooplankton if other conditions 

 of temperature and pressure are favorable. 

 In the ocean depths where these dissolved 

 materials are maximal in amount, Krogh 

 (1931) reported a zoological desert. If 

 Piitter's original hypothesis is extended to 

 include the utilization of colloidal solutions 

 (GelUs and Clarke, 1935), this problem 

 of recombination of organic materials in the 

 sea water is still further obscured by a 

 dearth of exact information. At present 

 (Bond, 1933; Krogh, 1934, 1934a; Sver- 

 drup, Johnson, and Fleming, 1942) the 

 evidence for such utilization is restricted to 

 bacteria.* 



On the basis of an earher view that 

 there is a steady increase of dissolved or- 

 ganic material becoming unavailable to the 

 organic cycle in oceanic depths, the even- 

 tual prospect is indeed gloomy. This view 

 may be a consequence of lack of informa- 

 tion concerning the place of bacteria in the 

 metabolism of the marine community. In- 

 vestigations by Waksman (1934), Waks- 

 man and Carey (1935, 1935a), Waksman 

 and Renn (1936) and others reported by 

 Sverdrup, Johnson, and Fleming (1942), 

 and ZoBell (1946), suggest that the activity 

 of bacteria in the sea is on a large scale 

 and involves the decomposition of organic 

 material by heterotrophs. 



A second body of information tends to 

 clarify the results of bacterial activity in 

 the oceanic abyssal strata. These data are 

 applied inferentially, since they appertain 

 to the profundal strata of lake communities. 

 In the sediments on the bottoms of lakes, 

 under anaerobic conditions, organic mate- 

 rials are reorganized by heterotrophs into 

 marsh gas, or methane, and hydrogen 

 (Henrici, 1939). As these gases diffuse up- 

 ward into the aerated water, they are oxi- 

 dized by autotrophs. Another example in 

 lake metabolism applicable to marine prob- 

 lems is the reduction of sulfates to sulfides 

 by heterotrophs under anaerobic conditions. 

 As these salts diffuse or are carried upward 



• If the original Piitter hypothesis is ex- 

 tended to include the utilization of dissolved 

 mineral nutrients, an entirely new approach is 

 available. Such an extension is a logical sug- 

 gestion, and is an application of Bayliss ( 1924 ) 

 that food is any substance taken into any 

 organism and used for any purpose. 



by convection, they are oxidized to sulfates 

 again by autotrophs. It is reasonable to 

 assume, therefore, that there are broadly 

 similar bacterial activities on the sea floor 

 and in the abyssal region. The permanent 

 accumulations of hydrogen sulfide in the 

 depths of the Black Sea and in certain 

 Norwegian fjords appear to represent ex- 

 ceptional situations; the situation may be 

 more general (ZoBell, 1946, p. 109). 



Information gleaned from studies of 

 marine littoral strata present a well- 

 rounded picture of characteristic bacterial 

 activities in the marine community. Large 

 amounts of organic material are washed 

 into shallow waters. These materials have 

 been studied on the Beaufort beaches of 

 the North Carolina littoral by Humm 

 (Pearse, Humm, and Wharton, 1942). It 

 was shown that such organic matter is de- 

 composed, mineralized by bacterial action, 

 and returned to the sea. Bacterial activity 

 apparently goes on at the greatest rate in 

 the intertidal zone when tides are out. The 

 conclusion was reached that ammonifica- 

 tion, nitrification, denitrification, and nitro- 

 gen-fixation are carried out in littoral 

 waters along sand beaches at or near the 

 sand-water interface. 



Humm found an average of 200.000 

 bacteria per gram of seashore sand. This 

 stratal population figure was an average of 

 256 plate counts of sand samples taken in 

 the intertidal zone. The numbers of bac- 

 teria ranged from 5000 to 1,250,000 per 

 gram of intertidal sand, and the average 

 population figure was considered from 70 

 to 90 per cent of the total number of aero- 

 bic bacteria that would form macroscopic 

 colonies on the plate medium used. 



In these intertidal sand samples exam- 

 ined, several pure cultures were obtained 

 of Sarcina sribflava, Micrococcus holo- 

 philus, and Micrococcus varians. In addi- 

 tion, occasional plates were poured of or- 

 dinary fresh-water nutrient agar to discover 

 what bacteria from marine sand would 

 develop in fresh-water media. On such 

 fresh-water plates an average of 2000 bac- 

 teria per gram were sjrown from intertidal 

 sand habitats. This shows that some bac- 

 teria, or bacterial strains, may be identical 

 for fresh-water and marine communities, 

 while manv are certainly ecologically equiv- 

 alent. Findings of Humm, and of Stanier 

 (1941) suggest that there are specific 



