1977). While the results of Gust's study are restricted to the specific flexible 

 chambers and conditions of his measurements, they show quite convincingly 

 that it is possible to obtain a small scale turbulent spectrum in a chamber that 

 is similar to that found in the surrounding coastal waters. Unfortunately, 

 almost all of these turbulence measurements were made in a metabolic 

 chamber used with benthic algae rather than in plankton studies, and no 

 biological data were included. 



This paper reports the results of a number of turbulence experiments carried 

 out at different times of the year using coupled benthic-pelagic microcosms 

 designed as analoges of Narragansett Bay, R.I. While some of the data from 

 experiments conducted during the spring have been reported previously (Perez 

 et al 1977), we have now carried out identical studies during winter and 

 summer months. In addition, we have explored in this paper a number of 

 techniques for characterizing the turbulent mixing levels in the microcosms and 

 compared them to the dissolution rate measurements used previously (Oviatt et 

 al 1977, Perez et al 1977). Finally, we have attempted to carry out 

 experiments to test our earher conclusion that phytoplankton and zooplankton 

 respond independently to different turbulence levels. The impression that the 

 phytoplankton and zooplankton were not coupled in their response to 

 turbulence was based on indirect evidence (Perez et al 1977) and we felt it 

 desirable to test this conclusion directly by adjusting the levels of zooplankton 

 in replicate tanks and observing whether concommitant but opposite changes 

 would occur in the phytoplankton. 



METHODS 



The Microcosms 



The microcosms used in these experiments have been described in detail in 

 earlier papers (Perez et al 1977; Oviatt et al 1977 and in press). Each 

 microcosm consisted of a 166 liter plastic tank containing 150 1 of water (0.7 

 m deep) collected by bucket from the lower West Passage of Narragansett Bay. 

 This area of the bay shows a well mixed water column about 8 m deep with 

 salinity between 28-31°^oo throughout the year. Characteristics of the bay have 

 been described in some detail by Kiemer and Nixon (1978). The microcosms 

 were maintained in a running sea water bath in the laboratory near field 

 temperatures and illuminated for the appropriate natural photoperiod by 

 Westinghouse Cool White fluorescent lights. The response of the microcosms to 

 hght input is complex and the choice of a value for any particular experiment 

 is difficult (Nixon et al, in press). The experiments described here were carried 

 out at 5-25 ly/day, values considerably below the average light energy found in 

 the water column of the bay. 



388 



