Ecology of Algae, Protozoa, Fungi and Viruses 37 



been identified from polluted areas in sea water, but cannot be 

 regarded as specifically marine, as they do not occur in oceanic 

 environments. However, more recently, phages active against 

 marine bacteria have been demonstrated from estuarine and 

 neritic waters and muds, and as recently reported by Spencer, 

 from the open sea. Spencer (Chapter 34) describes the methods 

 successfully used by him to isolate marine phages, and has also 

 very usefully characterized these phages. He points out tliat 

 phages from marine sources are usually inactivated at 55 C in one 

 hour while non-marine phages may resist temperatines up to 60 C 

 for that period. Also, while marine phages were not inactivated 

 in sea water, they were inactivated by NaCl isotonic with sea 

 water, i.e., inactivation is chemical rather than osmotic, a very 

 different reaction from that reported by Ritchie for the fungus 

 Zolerion. Marine phages were also active at lower temperatures 

 than terrestrial phages appear to be, they remain active far longer 

 in sea water than their terrestrial counterparts, and the monova- 

 lent-divalent cation ratios which they require are also different. 



It would appear, that not only do phages, active against 

 marine bacteria, occur in sea water but that they have character- 

 istics which distinguish them from terrestrial phages. 



It is interesting to consider that, while phages, bacteria and 

 Ascomycetes can with some certainty be classified as terrestrial 

 (including aquatic) or marine, other fungi ( Deuteromycetes ) 

 and yeasts cannot. These differences may be due to different 

 methods of adaptation e.g. osmosis, tolerance to Na+, to cation 

 ratios etc. 



Lewdn recorded the presence of a virus active against color- 

 less algae related to the Oscillatoriaceae and derived from ma- 

 rine muds. Moewus (Chapter 35) demonstrated the possil)ilit\' 

 of the existence of viruses in the sea by showing that such a virus 

 could exist in a ciliate Uronema associated with tumors of the sea 

 liorse. This would provide a vector whereby marine viruses, if 

 they exist, could be transferred from one host to another, and 

 also be a means of searching for such viruses. 



GENERAL CONSIDERATIONS 



It was difficult in my section to do justice to the several 

 disciplines involved, Phytoplankton, Mycology and Virology, but 



