together large concentrations of cells. 

 It is possible that a combination of 

 two or all the factors is required, or 

 that one set of factors is required to 

 initiate a red tide and another set to main- 

 tain it. 



The classical technique of growing cultures 

 in confined volumes of medium has been used, 

 but little confidence can be placed in relating 

 nutritional requirements observed underthese 

 confined conditions to those present in a bloom 

 in the ocean. A continuous culture system, 

 however, permits algae to be grown in the 

 laboratory under conditions more nearly sim- 

 ulating conditions in nature. This system makes 

 it possible to maintain an alnnost constant 

 population of cells and a desired level of 

 nutrients in the water, and to assay the capacity 

 of sea water collected simultaneously in dif- 

 ferent geographical locations and at different 

 times in the same location to support red-tide 

 organisms. Populations obtained in "natural 

 water" collected at different times and in 

 different locations can be compared to deter- 

 mine when and where water conditions are 

 most favorable for the growth of G. breve . 

 Also, the concentration of individual nu- 

 trients can be varied to determine optimum 

 concentrations, and river water or other 

 natural waters can be mixed in any desired 

 proportions. Organic compounds, vitamins, 

 and water conditioned by growing certain 

 organisms in it can be compared with un- 

 treated water. Finally, the effects of preda- 

 tors, competitors, and poisons (such as cop- 

 per) on population growth of G. breve can be 

 tested. 



Additional nutritional data can be obtained 

 by chemical analysis of G. breve grown in 

 different media. By relating concentrations in 

 the cells with concentrations of the same 

 nutrient in the water, a better understanding 

 can be obtained of conditions in natural water 

 prior to a bloom. These data could be obtained 

 in the field only by very frequent sampling, 

 or luck in the timing of sampling. 



Since grazing affects the abundance of phy- 

 toplankton, the specific organisms which feed 

 on G^. breve should be sought out amd identified 

 to determine if a reduction in grazers is the 

 mechanisnn which touches off a red tide. Here, 

 laboratory research should precede field work 

 since zooplankton shows some discrimination 

 in feeding, and there is no reason to suppose 

 that the total quantity of zooplankton is in any 

 way related to the abundance of G. breve . 



Physical factors apparently form one mech- 

 anism which initiates or maintains a red tide 

 by bringing together G. breve at convergences 

 between water masses. From laboratory re- 

 search it can be determined if the motility of 

 G. breve meets the requirements of the theory, 

 and from field work it can be determined if 

 the distribution of red-tide corresponds to the 

 distribution of areas of convergence in the sea. 



Red tides should be established to test the 

 various theories of red-tide formation. This 

 experimentation should be restricted to en- 

 closed bodies of water. 



CALIFORNIA RED TIDE 



By John G. Carlisle, Jr. 



California Department of Fish and Game 

 Terminal Island, Calif. 



The species mainly involved in California 

 red tide in recent years is Gonyaulaix polyedr a . 

 It is a larger dinoflagellate than G. breve , 

 is not toxic, aind does not cause paralytic 

 shellfish poisoning as does Gonyaulax cate- 

 nella . Many species discolor water, and when 

 they are concentrated (usually 1 to 1-1/2 

 million cells per liter) the result is called 

 red tide. Several species of Ceratium also 

 occur in California outbreaks. Gonyaulax 

 causes the chief problems and occurs over a 

 wide area--not always in streaks and patches -- 

 along the southern California coast. Fish kills 

 are not as often associated with blooms as 

 they are along the Florida coast of the Gulf 

 of Mexico. Principal fish kills are of the 

 northern anchovy (Engraulis mordax ), which 

 is susceptible at low dissolved-oxygen levels. 

 During outbreaks of California red tide kills 

 usually occur in confined harbors. Mussels 

 and barnacles also die along groins and harbor 

 rocks, and here again, death is usually attrib- 

 uted to oxygen depletion in association with 

 blooms. 



RED TIDES IN SOUTHERN CALIFORNIA 



By Rimmon C. Fay 



Pacific Bio-Marine Supply Compsuiy 

 Venice, Calif. 



Dense blooms of dinoflagellates appear peri- 

 odically as red tides along the coasts of 

 southern California and Baja California. These 

 blooms are governed by an annual cycle of 

 events, and therefore may be expected when 

 suitable natural conditions exist. Since 1950, 

 an unanticipated increase in the frequency and 

 intensity of these blooms appears to have 

 occurred. Coincident ally, certain other changes 

 have also occurred at specific locations along 

 the coast of southern California which may 

 have created conditions more favorable to 

 red tide. 



In sequence, the major physical factors in 

 the annual cycle of the inshore phytoplankton 

 in southern California'^' include a winter 



■"■ Superscript numbers 1 to 8 refer to literature cita- 

 tions which can be obtained from author. 



