396 PECK AND WARREN 



assured flushing of the effluent pond so that only the chlorine 

 concentration to be tested for a particular treatment was present. 



Nitrate Reductase 



Nitrate reductase was measured by a biochemical assay modified 

 from that of Eppley, Coats worth, and Solorzano (1969). Ten liters 

 of seawater from each station were placed in a 5-gal green Nalgene 

 (Nalge Co.) bottle and kept at ambient temperature in a seawater 

 bath until the enzyme assay could be run, usually within 3 hr of 

 sample collection. Nitrate reductase activity is expressed as micro- 

 gram atoms of NO2 formed per hter per hour and per cell per 

 hour. Nitrite produced was determined on a colorimeter by the 

 absorption at 550 nm after addition of sulfanilamide and 

 Ar-(l-naphthyl)ethylenediamine dihydrochloride solutions (Strickland 



and Parsons, 1968). Nitrite standards ranging from 1 to 8 )Ug 

 atoms /liter were determined in the same way. 



Total Protein 



Protein was determined by the method of Lowry et al. (1951). 



Primary Productivity 



Primary productivity was measured with the light— dark bottle 

 '"^C method of Steeman-Nielson (1952). For each sample station 

 500 ml of the 12 liters of water collected was used to fill four (three 

 light and one dark) 125-ml Pyrex bottles. To each bottle was added 

 0.7 juCi of NaH' '^C03. At each station the four bottles were shaken, 

 separately attached to curtain hooks, and lowered into the water to a 

 depth of 1 m for 4 hr of incubation in situ. After incubation the 

 contents of each bottle were filtered with suction onto glass-fiber 

 filters, which were then suspended in 20-ml vials containing Bray's 

 fluor and counted for 20 min on a liquid scintillation counter (Bray, 

 1960). Total carbon per cubic meter was determined from tempera- 

 ture—salinity data and the tables of Strickland and Parsons (1968). 

 Percent productivity for discharge and cut, relative to intake 

 productivity, was calculated from milligrams of carbon fixed per 

 cubic meter per hour. 



Phytoplankton Cell Concentration 



Subsamples of phytoplankton (100 ml) from the pooled 12 liters 

 of water collected at each station were preserved in Lugol's solution 

 in 100-ml bottles (Lund, Kipling, and Lecren, 1958). After concen- 



