outbreaks of red tide generally follow long 

 periods of no wind. 



When considering the detection of G. breve 

 through use of cameras, aircraft, and instru- 

 ments, it should be remembered that the red- 

 tide organism is not the only one that discolors 

 coastal waters. Numerous Trichodesmium are 

 often present, for instance, but can often be 

 recognized with the naked eye because many 

 of the organisnns float on the surface. When- 

 ever plankton (including zooplankton) is dense, 

 conditions are usually excellent for a red-tide 

 bloom. In other words, G. breve cannot be 

 studied without reference to other organisms. 

 This fact has been stated before but needs to 

 be re-emphasized. 



A DESIGN FOR FURTHER RED- TIDE 

 RESEARCH 



By Luigi Provasoli 

 Haskins Laboratories, New York, N.Y. 



The need for a continued program of re- 

 search is stressed. Red tides, though very 

 obnoxious, are simply sporadic algal blooms. 

 They cannot be understood if we do not con- 

 sider them in the larger context of the regular 

 succession of phytoplankton species of the 

 Florida Gulf. 



It is inadvisable to institute crash programs 

 when red tides appear and dismantle them 

 when the outbreaks subside. This very costly 

 and wasteful procedure cannot be justified, 

 even for political expediency. Since red tides 

 will continue to reappear, we should support 

 a modest, well-planned research program 

 which will end only when we know the reasons 

 for the outbreaks--the prerequisite for finding 

 a way to control them. 



Such a program should aim at the discovery 

 of the mechanisms governing the succession 

 of phytoplankton species. The red tides are 

 only one of the blooms in this succession. 

 The phenomena underlying the succession of 

 species are the key to our understanding of 

 phytoplankton production, which in turn gov- 

 erns the entire productivity of all the or- 

 ganisms feeding directly or indirectly on 

 algae, i.e., oysters, shrimp, and fish. The 

 program therefore should be of special in- 

 terest to the Fish and Wildlife Service. 



The research program could be modeled 

 after the ecological study of the Sargasso Sea 

 by a taxonomist, a chemist, and two plant 

 physiologists from Woods Hole Oceanographic 

 Institution. A hydrological study will also be 

 necessary, but this work could be done more 

 efficiently by an outside oceanographic insti- 

 tution. 



In the Woods Hole approach, the general 

 chemical and biological features of the eco- 

 logical situation were assessed by the taxon- 



omist and the chemist, who made a 2-year 

 study of the qualitative and quantitative com- 

 position of the phytoplankton and the fluctuations 

 in nutrients. The Sargasso Sea proved to be 

 very poor in nutrients: nitrogen and phos- 

 phorus vary little, and iron does not show any 

 seasonal peak. The flora is equally poor-- 

 essentially a yearly diatom bloom in the spring. 

 A coccolithophorid, Coccolithus huxleyi , is 

 present the year-round as an almost steady, 

 but sparse population. 



This picture posed a main question: since 

 nitrogen, phosphorus, and iron varied, but not 

 widely, other factors must have been respon- 

 sible for the endemicity of C. huxleyi, and for 

 the spring bloom of diatoms. This was espe- 

 cially true because temperature varies little 

 during the year. The main species of spring 

 diatoms and C. huxleyi were cultured bacteria - 

 free, and their nutrition was studied by the 

 plant physiologists. 



The main results were: all diatoms needed 

 vitamin Bj^ but C. huxleyi required only 

 thiamine. This finding seemed to offer a fitting 

 explanation, but necessitated field confirma- 

 tion. A vitamin B12 bioassay was perfected, 

 employing one of the Sargasso diatoms, Cyclo- 

 tella nana, that requires B12. and the yearly 

 cycle of B12 in the waters was determined. 

 Vitamin B12 varied from an undetectable to 

 scarce level from May to October. It rose 

 steadily and slowly during the winter and 

 reached a maximum before the spring diatom 

 bloom exhausted the vitamin. 



Vitamins in this situation govern species 

 composition; the quantity of Bl2 determines 

 diatom growth, and C. huxleyi is independent 

 of the vitannin. 



The importance of the other nutrients was 

 assessed by using depleted Sargasso water 

 (i.e., at the end of the diatom bloom) that con- 

 tained its natural algal populations. The water 

 was then enriched with various nutrients, 

 singly and in various connbinations. It was 

 found that iron is the most limiting factor- -no 

 diatom growth occurred without its addition. 

 Iron alone, however, induces only a short burst 

 of growth. Sustained growth is achieved only 

 by the addition of iron, nitrogen, and phos- 

 phorus, indicating that nitrogen and phosphorus 

 are also limiting. Laboratory data on C. huxleyi 

 show that it can be grownfor several transfers 

 without added iron. 



The validity of the findings seenns assured 

 since all the laboratory and field data are in 

 agreement. Further study will be needed to 

 find the causes that underlie the succession 

 of species during the diatom bloom. 



This highly successful research was done 

 by four talented scientists and their research 

 assistants. If a sinnilar group is formed for 

 the study of the blooms of the Gulf (including 

 red tides), it should be similarly small and 

 competent; nunnber does not substitute for 

 competence, and talent is rare and expensive. 



