STATION 7 



STATION 6 C0 *\WZ *• 



Willamette R. 



Figure 1. — Sampling stations in the lower Columbia River. 



Units. 1 Conductivity and salinity were meas- 

 ured at 3-m. intervals from the surface to 1 5 

 m. with a Beckman Model RS 5-3 Portable In- 

 Situ Salinometer. 



Chemical Data 



pH and dissolved oxygen were measured at 

 the sampling site; other chemical determina- 

 tions were made in the laboratory. A Beckman 

 Model N pH meter and Hach colorimetric 

 narrow-range pH test kits were used. Dissolved 

 oxygen concentration (determined by the 

 Alsterberg modification of the Standard 

 Winkler Method) and pH were measured only 

 at the surface. 



Samples (500- ml.) of surface water were 

 filtered through Millipore HA filters (0.45 ) 

 at the sampling site. The filtrate was returned 

 to the laboratory in polyethylene bottles for 

 measurements of phosphate, silicate, calcium, 

 magnesium, and sodium concentrations. Total 

 soluble phosphate concentration was deter- 

 mined by a modification of the Hach Meta 

 Phosphate Test and silicate concentration by a 

 modification of the Hach Silicomolybdate 

 Method (Hach Chemical Co., 1967). Calcium 

 and magnesium concentrations weremeasured 



Trade names referred to in this publication do not 

 imply endorsement of commercial products by the Bureau 

 of Commercial Fisheries. 



on an Atomic Absorption Spectrophotometer 

 Eel 140 by the methods recommended by Evans 

 Electroselenium Limited (no date). Sodium 

 concentration was determined with the Eel 

 Emission Unit. 



Biological Data 



Chlorophyll a concentration was determined 

 in the laboratory from samples prepared on 

 site by filtering 500- ml. samples of surface 

 water through Millipore HA filters (0.45 n ). 

 The acetone extraction method of Strickland 

 and Parsons (1965) was used with substitution 

 of the equation for chlorophyll a recommended 

 by UNESCO (United Nations Educational, 

 Scientific, and Cultural Ortanization) (1966). 



Zooplankton was collected by making 10-m. 

 vertical hauls with a l/2-m. Nansen-type net, 

 constructed of No. 10 monofilament nylon 

 bolting cloth. The samples were preserved in 

 5-percent Formalin; the zooplankters were 

 later identified and counted at the laboratory. 



LIMNOLOGICAL CHARACTERISTICS, 1967-68 



Limnological characteristics of the lower 

 Columbia River varied seasonally and between 

 sampling stations. 



The greatest differences between any two 

 adjoining stations were between stations 1 and 

 2 (tables 1-7). Station 2 was usually higher in 



