102 Marine Microbiology 



The species isolated from estiiarine or neritic environments 

 generally used either urea or uric acid or both significantly, again 

 in general agreement with Har\'e\''s findings. However, of the 

 nine clones isolated from the Sargasso Sea, only one, Skeletonenia 

 (?) (clone Men 5) did so; this clone, it should be noted, was able 

 to glow at somewhat lower salinities than the others isolated 

 from the Sargasso Sea. The two Sargasso clones of Coccolithiis 

 huxleiji (BT-5 and BT-6) were unable to use urea or uric acid, 

 while clone 92-A (from the algal collection at Plymouth, Eng- 

 land) was able to use uric acid about as well as Skeletonema 

 (clone Men 5). C. huxleiji is in fact common in polluted Scandi- 

 navian waters (2). Inability to use urea and uric acid may be 

 widespread in oceanic populations. For such algae, the best nitro- 

 gen source of those studied is glutamine. 



The organisms able to use uric acid best came from polluted 

 estuarine waters. There is evidence suggesting that the extent 

 to wliich such organisms dominate the plankton can at times 

 be associated with their capacity to grow on uric acid. Cyclotella 

 nana (clone 3H) dominated the waters in Great South Bay from 

 which it was isolated (9) and grew rapidly on uric acid. 

 Cyclotella caspia also used this source well and was common in 

 Great South Bay. Two other organisms from Great South Bay 

 were studied— Thalassiosira fhiviatilis and a small green flagellate 

 (not otherwise mentioned in this paper, but similar to BT-2). 

 These algae were almost always present in the plankton, but 

 never in large numbers; both used uric acid more slowly than Cy- 

 clotella nana (3H). Great South Bay has a rich and varied flora 

 of diatoms and flagellates. Phosphorus is present in excess in its 

 waters, and nitrogen becomes available in water of low salinity 

 at the heads of small creeks and streams. It is interesting that 

 those planktonic organisms that have been observed to dominate 

 its waters have not only been euryhaline, but able to use nitrogen 

 in organic combination relatively rapidly. 



SUMMARY 



A survey of growth of marine planktonic algae with nitrate, 

 nitrite, ammonia, urea, uric acid, glycine, glutamate and gluta- 

 mine as nitrogen sources ( 100 pM ) included 15 clones of centric 



