of any of the indicator organisnns at a concen- 

 tration of 0.1 p. p.m. All but 8 of the 32 com- 

 pounds were rejected. The supply of two of 

 the most toxic compounds was exhausted during 

 the tests. A supplier for one of them has not 

 been located, and a new supply of the second, 

 which we were able to obtain for $100 per 

 gram, was not toxic to G^. breve at any level 

 tested (mciximum 0.01 p. p.m.). This difference 

 suggests variation in toxicity of the chemical 

 in different lots or from different majiufac- 

 turers. 



Comparative tests of toxicants on G^. breve 

 cultured in an artificial medium and in sea 

 water from Florida suggested that the Florida 

 water medium contained an inhibitor which 

 reduced the effectiveness of the toxicants. 

 Further comparative tests with the two types 

 of medium are underway. 



OCEAN CURRENTS AND GYMNODINIUM 

 BREVE 



By Saul Broida 



Institute of Marine Science, University of 

 Miami, Miami, Fla. 



Streaks and ripples often occur in a fairly 

 calm sea, and these phenomena have a close 

 relationship with internal waves. Surface slicks 

 could be caused by oils associated with some 

 form of sea life--in the present instance, 

 possibly G. breve . Changes may occur in 

 the film of oil which floats on a shallow 

 surface layer over the trough of an internal 

 wave. The effect on surface tension can be 

 such that light wind will cause ripples and 

 slicks alternately. The high surface tension 

 of the water will allow the wind to generate 

 ripples, whereas the oil-covered surface with 

 its relatively low surface tension will remain 

 undisturbed. The progress of the associated 

 internal wave can be measured by the move- 

 ment of the alternating streaks. 



The question arises as to the ability of the 

 organisms to move. Is their inherent ability 

 to move sufficient to be effective in the ocean? 

 In my opinion, it is not. An analogy can be 

 made by considering molecular diffusion, which 

 is negligible in oceanic mixing or even in a 

 teacup. Eddy diffusion really mixes the water 

 masses. Probably, then, the ability of G. breve 

 to propel itself is far overshadowed by the 

 turbulent motion of the water itself. There- 

 fore, the understanding of red tide might be 

 advanced by the study of eddy diffusion in areas 

 where red tide occurs. 



It is my understanding that red-tide out- 

 breaks start in or near the passes between 

 offshore islands. Why not then induce turbu- 

 lence in one of these narrower passes and 

 observe the results? It could be done economi- 

 cally by laying a perforated plastic hose across 



the pass. An air pump attached to the hose 

 could bubble air through the holes, thus in- 

 ducing some vertical turbulence in the water. 

 I feel that the experiment is worth trying. 



It might be well also to survey the oceano- 

 graphic conditions in the area on a regular 

 monthly or semimonthly basis to identify sea- 

 sonal current patterns. Vessels of the U.S. 

 Coast and Geodetic Survey operating out of 

 ports on Florida's west coast might be asked 

 to cooperate in such a survey. 



GYMNODINIUM BREVE IN RELATION TO 

 PRIMARY PRODUCTION STUDIES 



By David V.-Aldrich 



Bureau of Commercial Fisheries Biological 

 Laboratory, Galveston, Tex. 



It seems appropriate to consider the study 

 of the red-tide organism in its broader con- 

 text--in relation to other research onprimary 

 producers. The Bureau of Comnnercial Fish- 

 eries is investigating several aspects of pro- 

 ductivity: field estimates of primary produc- 

 tivity; laboratory culturing of primary 

 producers for larval shrimp food; and studies 

 of G. breve , a toxic primary producer. As 

 George Rounsefell has pointed out, however, it 

 is very difficult to "distinguish the poison ivy 

 from the alfalfa," by the methods which are 

 available to us for studying primary produc- 

 tivity. It is suggested that this important prob- 

 lem (as well as the more specific ones posed 

 by toxic phytoplankton blooms) might be ap- 

 proached profitably by the inclusion of red-tide 

 studies in a broad research program on the 

 various aspects of productivity. 



LABORATORY CULTURE STUDIES AND 



THEIR RELATION TO GYMNODINIUM 



BREVE 



; By Theodore R. Rice 



Bureau of Commercial Fisheries 

 Radiobiological Laboratory, Beaufort, N.C. 



At present it cannot be predicted accurately 

 when and where outbreaks of red tide will 

 occur, what specific conditions are most favor- 

 able for their occurrence, cind how blooms of 

 red-tide organisnns can be most effectively 

 dispersed or destroyed. Three causes for 

 red-tide outbreaks may be hypothesized, how- 

 ever: (1) some change in water quality precip- 

 itates rapid cell division; (2) some reduction 

 in the normal rate of predation on the red-tide 

 organisms permits the normal rate of division 

 to produce a large population rapidly; and 

 (3) physical factors (or a combination of such 

 factors and the motility of the cells) bring 



