Limited Heterotrophy of Some Photosynthetic Dinojlagcllates 107 



for by raising manyfold the concentrations of trace metals. Small 

 variations in pH resulted in deficiencies or toxicities of avail- 

 able trace metals. These difficulties were intensified when 

 the level of chelators and trace metals was high. When G. 

 californicwn, E. cassuhica and the cryptomonad Rhodomonas 

 lens (14) proved rather flexible in respect to salinities and vari- 

 ations in monovalent/divalent ratios. These obstacles were partly 

 circumvented by lowering the salinity and calcium concentra- 

 tions. 



During the search for a non-toxic pH buffer we found that 

 the three Gijrodinium are sensitive to triethanolamine ( inhibitory 

 at 30-100 mg%; toxic above). Tris ( hydromethyl ) amino-methane 

 (TRIS) is not inhibitory for the same species up to 600 mg%. 

 A concentration of 100 mg% is adequate for most marine algae, 

 although Droop (2) found that TRIS is inhibitory for Oxtjrrhis 

 marina. The use of diluted over-chelated trace metal mixtures and 

 of a pH buffer (TRIS) resulted finally in non-precipitating media 

 such as ASP2, ASP2NTA, ASPe ( 15 ) . These media were designed 

 to be — and indeed are — all-purpose media: they permit growth 

 of diatoms, ciyptomonads, chrysomonads, and dinoflagellates, 

 and have been recently employed for blue-green algae (19), 

 chlorophytes (8) and red algae (4, 5, 6). This versatility was 

 achieved by arbitrarily selecting levels of nutrients well within 

 the zone needed or tolerated by several species of marine algae 

 and flagellates. Although these media were derived from media 

 like DC, MGC, AC, (Table 1) which were arrived at experi- 

 mentally with a single organism (respectively Amphora perpusil- 

 la, G. splendens, Amphidinium carteri), they differ by being 

 more complete, e.g., containing silica (which is needed only by 

 diatoms and some cluysomonads ) and several additional B vita- 

 mins even though so far only B12, thiamine or biotin ha\ e been 

 shown to be needed by marine algae. None of these media is the 

 best for any one species, e.g., ASP,, ASP,, ASP.NTA, ASP,,NTA, 

 and DV (modified from DC) supported growth of tlie three 

 Gijrodinium, G. splendens, and of the two Amphidinium and 

 suitably diluted (to salinities of 0.6-1.0%), of P. balticum and P. 

 chattoni. 



