332 Marine Microbiology 



counts of Metschnikowiella zobellii (18) that ranged from 500 

 to 39,000 cells per wet gram of algae. In contrast, the closely 

 related M. krissii has not been found in the algal heaps but was 

 frequent in the surrounding waters. Apparently the products of 

 microbial decomposition on the surface of the kelp are not 

 utilized by M. krissii. 



In open ocean areas, dense yeast populations have been as- 

 sociated with planktonic zones rich in organic matter (11). Other 

 regions suitable for yeast growth and reproduction are current 

 boundaries where contiguous water masses of opposing densities 

 result in the accumulation of organic matter. Kriss ( 8, 9 ) observed 

 that at such interfaces the rate of reproduction and total popu- 

 lation of microorganisms far exceeds that occurring within the 

 adjacent water masses. Similar data were obtained in our work 

 by means of a series of vertical casts taken to depths of 500 

 meters in the Gulf Stream near Cat Cay. Bahamas (Figure 1). 

 Oceanographic data obtained by our laboratory indicated that 

 the 340 meter peak with approximately 2300 cells per liter coin- 

 cides with an intrusion of Atlantic water into the Gulf Stream, 

 while the 500 meter peak with 2000 cells per liter indicates a 

 nutrient maximum at this depth. Although these studies are in 

 a preliminary phase, it would appear that quantitative differences 

 in yeast population could be of practical value in the location 

 of current boundaries. 



Terrestrial run-off is a major factor that influences the 

 character of the yeast population of coastal areas. A comparison 

 of yeast species collected from waters and sediment of Biscayne 

 Bay, an area subjected to terrestrial pollution, and the relatively 

 uncontaminated Gulf Stream ( Table 1 and Table 2 ) suggests two 

 points. First, the predominate species found in offshore regions 

 are highly oxidative. C parapsilosis, normally an actively fer- 

 menting species, customarily fails to ferment both glucose and 

 galactose upon initial isolation from the open ocean and attains 

 this capacity only after continued maintenance in culture. In 

 contrast, estuarian stiains of this species do not require a period 

 of adaptation to manifest fermentative abilities. This tendency 

 toward reliance on oxidative dissimilation may be due to the 

 low organic content of offshore waters. Second, it is to be noted 



