The data collected show that the rate of phytoplankton photosynthesis 

 was very low in Section II of Grays Harbor during the fall of 1964 and 1965. 

 Comparisons with Wlllapa Bay, and with laboratory studies provide some 

 understanding of why primary productivity was low. A major factor in the 

 reduced photosynthesis in Section II of Grays Harbor seems to be reduced 

 light penetration or turbidity. However, photosynthetic efficiency expressed 

 in terms of an assimilation number indicates that photosynthesis is also 

 inhibited by some other cause. The data do not clearly indicate the 

 reason for this additional inhibition. However, the highest levels of SWL 

 were observed in Section II. Thus, lack of light penetration and some 

 undetermined inhibiting condition are the immediate reasons for lack of 

 photosynthesis in Upper Grays Harbor. The data also indicate that if 

 these inhibiting conditions were corrected the problem created by the con- 

 version of inorganic phosphate to organic phosphate by SWL would then soon 

 block any major increase of photosynthesis in Section II of Grays Harbor. 



The reason for the turbidity seems to be a combination of factors. 

 The Secchi disc data and the SWL data indicate a general relationship, with 

 the higher SWL values corresponding to the low light penetration. The notable 

 exception to this is Trip 9 when both the SWL and Secchi disc values (light 

 penetration) were the lowest observed. At that time the water of the entire 

 bay was observed to be quite muddy. 



Primary productivity of water is a complex subject, and it is not the 

 writer's intent to imply that turbidity and SWL are the only factors in- 

 fluencing primary productivity in Section II of Grays Harbor. However, the 

 data seem to indicate fairly clearly that both turbidity and SWL are major 

 factors in reduced phytoplankton photosynthesis in Section II of Grays Harbor. 



Effect of reduced photosynthetic rate on dissolved oxygen content of the 

 water of Upper Grays Harbor . 



The process of photosynthesis is known to be an important source of 



oxygen to water and in studies earned out by various workers relatively 



high dissolved oxygen content of the water has been observed to result from 



major photosynthetic activity. To make an estimate of the oxygen deficit in 



Grays Harbor due to reduced phytoplankton photosynthesis it is necessary to 



first estimate the extent that photosynthesis is depressed in Grays Harbor. 



