turbulent energy levels in the laboratory or in the field, it may also reflect the 

 feeling of many ecologists that the small size of plankton generally places them 

 below the size scale at which turbulence is "felt". Both of these considerations, 

 along with technical difficulties, have caused almost all marine microcosm 

 studies to neglect turbulence as a factor in their experimental design. In the 

 simplest terms, the justification appears to have been that since turbulence is 

 difficult to measure, hard to mimic, and of unknown importance, it was 

 reasonable to avoid the problem of deciding on how to include it in 

 microcosms. There is a certain amount of appeal to this argument, especially 

 since there are so many other problems to be resolved in developing a 

 microcosm. However, the evidence in the papers cited above, as well as the 

 experience of anyone who has tried to culture or maintain phytoplankton and 

 zooplankton in the laboratory, suggest that turbulence is an important 

 consideration in pelagic systems. Our earlier experiments with turbulence in 

 marine microcosms also indicated that the scaling of mixing energy in 

 laboratory tanks can dramatically influence the results of phytoplankton and 

 zooplankton growth studies in the microcosms (Perez et al 1977). The 

 argument about plankton being too small to "feel" turbulence is also 

 questionable. 



Turbulence 



Following Richardson (1926), Richardson and Stommel (1948), Stommel 

 (1949), Batchelor (1950) and others, the flow of turbulent energy from large 

 scale motion is passed down through successively smaller eddies until it is 

 dissipated in viscosity. Above a certain size, the energy content of eddies is 

 solely a function of their size (k) and the rate of energy flux (e) through the 

 system. Below this critical size, defined by 



(t1 



where v = the kinematic viscosity 



e = the energy flux per unit mass 



k = upper Umit of the Kolmogoroff viscous zone 



viscous forces become important and the energy content decays more rapidly 

 with decreasing size as energy is dissipated. In order to give some feeling for the 

 scale involved, it is possible to estimate k for the West Passage of Narragansett 

 Bay using a value for the energy dissipation of 4.3 x 10 ergs sec (Levine 

 and Kenyon 1975) and an approximate volume of 7.2 x 10 m . The result 

 suggests that k is on the order of 0.06 cm. While this is larger than individual 

 phytoplankton cells found in these waters (<0.01 cm), it is about the size of 



386 



