is photoautotrophic, requiring both light and 

 CO2 for growth and survival. 



3. Would a copper ore dike maintain a 

 high enough level of copper in the water to 

 inhibit growth of G. breve ? The answer is 

 no (Marvin, Lansford, and Wheeler, 196l). 



The Advisory Connmittee urged the Bureau 

 of Commercial Fisheries to attempt to pub- 

 lish both the data and the results of its red- 

 tide investigations. Since 1958 the Bureau has 

 published all its raw field data and a number of 

 reports on both field and laboratory projects. 



Laboratory Studies of the Organism 



Laboratory studies of both unialgal amd 

 bacteria-free cultures have yielded consider- 

 able information on the physiology of G . breve . 



More work is needed, however, especially 

 on the role of other plankton organisms in 

 promoting or inhibiting growth. This type of 

 work may involve the use of radioisotopes 

 to trace the flow of nutrients. 



There has been much discussion of the 

 possible role of chelators in stream water 

 or surface runoff in promoting growth. 



In both of the above cases it is possible 

 that experiments have been hampered by the 

 very high surface:volunne ratio of the test 

 tubes in which most experiments have been 

 carried out. In 1958 several advisers sug- 

 gested that cultures be grown in large tanks 

 to answer better such questions as killing 

 concentrations of G. breve and the effect of 

 dead fish, either in perpetuating a bloom, 

 or possibly in creating lethal concentrations 

 of bacteria. 



Some have advocated attempting to cause a 

 bloom of red tide by such measures as 

 dumping a barge of dead fish, dumping large 

 amounts of pollutants from selected localities, 

 or by fertilizing an area containing organisms 

 with specific nutrients. Most agreed that to 

 gain sufficient control over the experiments, 

 the studies might better be performed in 

 large tanks. Discovering how to create a 

 bloom is the opposite approach from ob- 

 serving blooms in the field and then trying 

 to decide the cause. We believe the prob- 

 lem should be approached from both direc- 

 tions. In any such tank experiments, we 

 believe that an attempt should be made to 

 imitate natural conditions insofar as prac- 

 ticable. Thus, a very large tank might offer 

 a fine opportunity to test the role of con- 

 vergences in concentrating the organisms, 

 and perhaps to solve their ability to grow 

 in water of low nutrient content. 



The life forms of G. breve have been ob- 

 served, but work is needed to determine the 

 factors causing encystment, the conditions 

 under which cysts can survive, the length 

 of tinne they can survive, cuid the conditions 



favoring resumption of the normal form. The 

 winter survival of G. breve in the deeper 

 (and warmer) offshore waters (as deep as 

 123 feet) has been stressed (Dragovich, 1960b; 

 Dragovich and May, 1961; Finucane, 1960), 

 but overwinter survival of encysted forms 

 in the shallower inshore waters is a dis- 

 tinct possibility that requires investigation. 

 Should this inshore survival occur it nnight 

 be remotely possible, following heavy red- 

 tide outbreaks in the fall, to modify the sudden 

 recurrences in the spring (as happened in 

 1947, 1954, and I960) by destruction of the 

 cysts on the bottom. 



Binary fission was the only method of repro- 

 duction observed by Lackey and Hynes (1955). 

 Conjugation was also observed by Wilson 

 (USFWS, 1958). Because it is apparently not 

 often observed, the discovery of what favors 

 conjugation and its role in maintaining popula- 

 tion abundance might be important. 



Although the red-tide organism normally 

 measures about 20 to 35 (i , large forms, per- 

 haps up to 80(1, have been observed. Wilson 

 (USFWS, 1958) mentioned that occasionally 

 in the field one observes "... a fairly large 

 form which appears to have no chromatin 

 material at all, . . ," He did not observe 

 these in the laboratory. It would be of in- 

 te rest- -perhaps of some importance --to dis- 

 cover whether this large fornn is a special 

 life form of G. breve or perhaps a distinct 

 species. 



Opinions seem to differ as to whether 

 G. breve csin form chains. Wilson (USFWS, 

 1958) said that cysts form chains, and that 

 when the culture is stirred these tend to 

 remain together, but he had never seen a 

 chain formation of normal free-swimming 

 cells. Collier (USFWS, 1958), however, men- 

 tioned watching the organisms form long 

 chains. His observation was apparently made 

 while he was watching a very high natural 

 concentration--probably much higher than any 

 encountered in the laboratory. It is possible 

 that dense concentrations may cause the 

 organisms to act in a different manner. The 

 possibility that a difference in life forms 

 or manner of reproduction may be triggered 

 by excessively high concentrations deserves 

 investigation. 



There appears to be some question whether 

 changes in color of red-tide water are caused 

 by density of the orgcinisms, by the angle of 

 the light, or by the age of the population, 

 Wilson (USFWS, 1958) said that each culture 

 seems to have a tendency to accumulate oil 

 droplets with age, which will give a different 

 color comprehension. If either color or oil 

 accumulation could be used as a gross meas- 

 ure of population age, it might be useful in 

 determining whether a population is increasing 

 or declining. 



15 



