Perkin-Elmer) . Samples were prepared by diluting 0.1 ml aliquots 

 in various proportions so that the sample ionic concentrations were 

 within the working range of the spectrophotometer. The diluted 

 samples were analyzed at different wavelengths. Potassium concen- 

 tration was estimated by emission at a wavelength of -3^ my (visible 

 range) . Magnesium and calcium ion concentrations were determined by 

 absorption at wavelengths of 285.9 my (ultraviolet) and 210.9 my 

 (visible) , respectively. The instrument was calibrated with chemical 

 standards supplied by Harleco and was set to read the concentrations 

 in ppm; the readings were converted to mEq/L. Both standards and 

 samples were diluted with 0.1% lanthanum oxide to reduce the chemical 

 interference. The interference was particularly high in the case of 

 calcium ion. 



Determination of Oxygen Consumption 



The oxygen consumption rates were determined in a flow-through 

 respirometry apparatus using the Winkler method for oxygen analysis 

 (Standard Methods, 12th Edition, 1965) and galvanic cell oxygen ana- 

 lyzer techniques. 



Flow-through respirometry 



The flow-through respirometry apparatus consisted of four water 

 reservoirs (R,, R2, Rt, and R^) , 12 respiratory chambers and an oxy- 

 gen analyzer (Fig. 2) . The salinity and temperature control con- 

 ditions were maintained in reservoir 4 and test conditions were main- 

 tained in reservoirs 1 and 3. Reservoir 2 served as a thermal water 

 bath to maintain test temperatures. The solution was filtered and 

 aerated in reservoirs 1 or 4 and siphoned into a constant level 

 chamber in reservoir 2. From the constant level chamber water 

 passed into two distribution chambers. Each distribution chamber 

 supplied water to six respiratory chambers. Water which entered the 

 constant level chamber in excess of the constant level mark 



42 



