range since the acclimation Q 10 is lower than the 

 acute Q 10 (Table 1). 



levels can affect migration patterns (Kamykowski 

 1981). 



Discussion 



Blooms of G. splendens occur off the coast of Peru 

 in temperatures ranging from 17° to 23 °C with op- 

 timum being 18°-21°C (Rojas de Mendiola 1979). 

 The lower temperature agrees with laboratory 

 measurements of vertical migration, as Kamykowski 

 (1981) found migration in the laboratory occurred 

 at temperatures above 16°C. In the laboratory, this 

 dinoflagellate can survive and divide at temperatures 

 from 12° to 29°C. The most rapid growth rates (0.4 

 divisions/d), however, occur at 20°-27°C (Thomas et 

 al. 1973). Within the optimum temperature range 

 suggested from these studies (18°-26°C), swimming 

 speed of G. splendens approximately doubles (Fig. 

 1). These speeds and their change with temperature 

 are similar to those reported for other dinoflagellate 

 species (Hand et al. 1965). 



The speeds of movement calculated from field 

 studies of vertical migration of G. splendens agree 

 with the speeds found in the present study. Blasco 

 (1979) calculated that a speed of 1 m/h was sufficient 

 to account for the migration off Peru during the 1976 

 El Nino. In the Gulf of California, G. splendens 

 migrated over a depth of about 9 m and had a 

 calculated descent velocity at sunset of 1.7 m/h 

 (Kiefer and Lasker 1975). The present study pre- 

 dicted this speed would occur at temperatures above 

 25°C. Unfortunately Kiefer and Lasker (1975) did 

 not state the water temperature at the time of 

 migration. 



An objective of the present study was to use the 

 measured swimming speeds to determine the 

 distance over which G. splendens should be capable 

 of migrating. A conservative estimate of distance can 

 be calculated from the speeds upon acclimation to 

 optimum temperatures (19°-25°C) and assuming the 

 dinoflagellate 1) swims continuously in either the up- 

 ward or downward direction for half of the migra- 

 tion cycle (12 h) and 2) does not have a diel rhythm 

 in swimming speed. At 19°, 22°, and 25°C the cal- 

 culated distances are 6.6, 11.3, and 13.9 m respec- 

 tively. These distances would increase slightly if a 

 temperature gradient existed because speed is ap- 

 proximately constant at 19°C and lower tempera- 

 tures, and acute exposure to higher temperatures, 

 which would occur high in the water column, would 

 elevate speeds above those upon acclimation (Fig. 1). 

 In addition, these values would probably vary if G. 

 splendens is exposed to different environmental con- 

 ditions, since salinity, light intensity, and nutrient 



Acknowledgments 



This work was supported by an International 

 Oceanographic Commission travel grant to BRM and 

 a National Science Foundation Grant No. OCE- 

 8110702. 



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