Chapter 27 



Succession of Phytoplankton, and the Ocean 

 as an Holocoenotic Environment* 



Theodore J. Smayda 



N, 



iimerous investigations of the annual phytoplankton cycle in 

 marine waters have revealed 1) a conspicuous recurrent suc- 

 cession of species, and 2) a marked cyclic abundance distin- 

 guished by one or more well defined maxima. Although tradi- 

 tionally treated as separate phenomena, there is little doubt that 

 succession and the attendant seasonal population dynamics are 

 inextricably related, even though the nature of this interdepend- 

 ence has yet to be adequately defined. 



Dating from Brandt's (5) application of Liebig's Law of 

 the Minimum to the sea, marine ecologists have sought to attrib- 

 ute the annual quantitative fluctuations of phytoplankton to 

 some environmental "limiting factors." Consistent with Liebig's 

 Law, nutrient limitation is frequently ascribed ( 19 ) , although 

 the limiting factor hypothesis has been extended to include those 

 conditions which control the initiation of growth as well: inade- 

 quate light (7) or water mass stability (4). 



Such specific environmental regulation has not satisfactorily 

 accounted for succession, however. While the magnitude of the 

 light, nutrient and temperature levels appears to determine how 

 much a community will produce, community re-organization 

 frequently begins before the productive limit is reached for that 

 stage. Accordingly, it does not necessarily follow that the fac- 

 tor(s) limiting production, such as nutrients, also regulate the 

 observed succession. Succession is accompanied by gradual sea- 

 sonal changes in the temperature, light and nutrient cycles, a 



* Contribution No. 33 from the Narragansett Marine Laboratory. This study was 

 aided by contract G- 14295 between the National Science Foundation and the 

 University of Rhode Island. 



260 



