JOHN H. RYTHER 



391 



TABLE I 



Optimum and Maximum Range of Salinity for Growth of Some 

 Neritic Dinoflagellates 



Reference 



Nordli (1953) 



Braarud (1951) 



Braarud and Rossavik (1951) Prorocentrum micans 15-20 10-45 



Braarud and Pappas (1951) Peridinium triquetrum 15-20 10-40 



salinity for the growth of several species of common neritic dino- 

 flagellates as determined by Braarud and his co-workers. 



While all the species have salinity optima well below that of full 

 sea water, it is perhaps of even greater significance that they are also 

 able to grow within an extremely wide range of salinities. This high 

 degree of adaptability is a definite advantage to life in the variable 

 environment of coastal and estuarine waters, and it is perhaps one 

 of the means by which the neritic dinoflagellates are able to compete 

 successfully with other organisms, such as diatoms, which in general 

 have a more narrow range of salinity tolerance. 



Nutrient Requirements 



The autotrophic dinoflagellates, as other members of the phyto- 

 plankton, are dependent upon dissolved mineral salts for their nutri- 

 tion. According to Vinogradov (1935) the peridinians contain ap- 

 proximately the same relative concentrations of nitrogen, phosphorus, 

 calcium, and iron as does sea water. 



The dinoflagellates have often been credited with the ability to 

 utilize and flourish in extremely low concentrations of nitrogen and 

 phosphorus (Gran, 1926-27; Gilson, 1937). This concept has stemmed 

 largely from observations that dinoflagellate maxima, in temperate 



