EFFECT OF ORGANIC SUBSTANCES ON OYSTERS 



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SALINITY- % 



Figure 2. — Relation between carbohydrate concentration and salinity. The limits of the mean, plus and minus one 



standard deviation, are shown. 



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HOUR OF DAY 

 Figtjbb 3. — Average diurnal variation in carbohydrate concentration for the period November 13, 1949, to May 30, 



1950, plotted on semilogarithmic scale. 

 DIURNAL VARIATION entire period are ghown ^ figure 3 . alg0 p i ot ted are 



A distinct diurnal variation became evident the standard dev i a tions computed at each hour. 



when the logarithms of the carbohydrate concen 

 trations were plotted against the hour of day for 

 the period from November 13, 1949, (when the 

 observations were increased from bihourly to 

 hourly) until May 30, 1950. This cycle was evi 



From the curve (fig. 3) it is apparent that the 

 concentration reaches a minimum at about 

 02 h 00 m where it remains until about 14"00 m ; it 

 then increases steadily to a maximum at ll h 00 m . 



dent whether the data were averaged monthly or This maximum is maintained until 18"00 m , when 

 for the entire period. The data of averages for the the concentration begins a nocturnal decline. 



