For this purpose we assumed that the photosynthetic rate in Section II of 

 Grays Harbor should be similar to that of Willapa Bay. This assumption is 

 based upon the similar size, and tidal range of the two bays. Their proximity 

 provides similar weather conditions and a great deal of similarity in the 

 composition of the ocean feed water. The available data suggest somewhat 

 similar rates of exchange with the ocean, but Grays Harbor does receive 

 more fresh water than Willapa Bay. 



We averaged the photosynthetic rate observed on the 5 trips in Section II 

 of Grays Harbor and compared this average with similar values derived for 

 Willapa Bay. The difference was 6.44 milligrams (mg) carbon per cubic meter 

 per hour. (These data are uncorrected for variation in light intensity). 

 Then using the formula suggested by Westlake (1963) (grams oxygen x 0.300 = 

 grams carbon) and using a P Q of 1.25, assuming 12 hours of effective light 

 per day and that the radioactive carbon method with a dark bottle correction 

 measures net photosynthesis; and applying a correction factor for nightlme 

 (dark) respiration from Westlake (1963) and Ryther (1959), we calculated 

 that due to reduced photosynthesis, the waters of Section II of Grays Harbor 

 have failed to receive the equivalent of .17 ppm dissolved oxygen each day 

 or 1.7 ppm dissolved oxygen for each 10-day period during the summer. While 

 several assumptions were made for this calculation, we have tried to be 

 conservative in these assumptions. Therefore, the actual value should be at 

 least as great as .17 ppm per day. The significance of this is that this 

 potential cumulative oxygen production per 10-day period (1.7 ppm) Is equal 

 to one-half of the amount of oxygen present in the waters of Upper Grays 

 Harbor during the seasonal oxygen minimum (3.0 ppm). 



SUMMARY 

 A limited study was carried out to learn the contribution of oxygen 

 from photosynthesis to the waters of Grays Harbor. It was demonstrated that 

 photosynthesis is nearly absent In the upper portion of Grays Harbor 

 (Section II), the area where the lowest dissolved oxygen values occur. 

 Turbidity of the water is a major season for the lack of photosynthesis. 

 By comparing the data with previous studies it Is indicated that SWL Interacts 

 with other factors to reduce photosynthesis both by increasing turbidity and 

 by converting inorganic phosphate to organic phosphate. 



