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Figure 12. — Observed concentrations of dissolved oxygen (ml/liter) 

 at selected depths in Auke Bay, Alaska, 1960-68; data are observed 

 concentrations. 



off at the surface, and supersaturation will occur. Ap- 

 preciable supersaturation occurs in Auke Bay during the 

 spring and summer, even down to 10 to 20 m (Fig. 13). 

 This coincides with spring and summer phytoplankton 

 blooms. Lowest concentrations of oxygen occur during 

 the fall and winter when photosynthetic activity is reduc- 

 ed and bacterial decomposition and chemical oxidation 

 of detritus lower the oxygen content. 







60 



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DISSOLVED OXYGEN (\) 



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Figure 13. — Typical vertical profiles of percent saturation of dissolved 

 oxygen in Auke Bay. Alaska, for January, April, July, and October: 

 data are averages for 1960-68. 



Inorganic Nutrients 



The circulation of biologically active materials such as 

 phosphate, silicate, and nitrate, as well as their dis- 

 tribution in the water column, depends on biological and 

 physical processes and differs in detail from the cir- 

 culation and distribution of water and its conservative 

 properties. Because these materials are dissolved com- 

 ponents of water, they are affected by advective and 

 eddy diffusion processes. In addition, they are ex- 

 changed between the water and the biomass in a cyclic 

 process. During periods of high biological activity, ! 

 changes in the distribution and abundance of biological- j 

 ly active components of the water column may occur 

 rapidly relative to changes due to physical processes 

 alone. Thus, their study may add significantly to the 

 physical description of an area. 



During our study in Auke Bay, there was a regular 

 seasonal cycle in concentrations of inorganic phosphate, 

 silicate, and nitrate (Figs. 14, 15, 16). Maximum con- 

 centrations of all three nutrients occurred in winter 

 (January-April), and all were uniformly distributed 

 throughout the water column in this period. A rapid 

 reduction of the three nutrients above 20 m in April was 

 associated with the outburst of phytoplankton growth. In 

 each year of our study, we noticed a marked rise in num- 

 bers of diatoms and chlorophyll concentrations and a 

 corresponding drop in concentrations of phosphate, 

 silicate, and nitrate (unpublished data on file North- 

 west and Alaska Fisheries Center Auke Bay Laboratory). 

 Once stability is established in spring, high levels of 

 photosynthetic activity rapidly deplete the available 

 nutrients because vertical advection of nutrients into the 

 surface is inhibited by the stability of the water column. 

 Raymont (1963) reviewed the distribution and amounts 

 of phosphate, silicate, and nitrogen throughout the world 

 oceans, including many of the important coastal and in- 

 shore areas. In comparison with other nutrient-rich 

 coastal and inshore environments, the amounts of these 

 materials in Auke Bay water were relatively high. Friday 

 Harbor in western Washington had some of the highest 

 observed concentrations of both phosphate and 

 nitrate — about 1.8 /jg-at. /liter of phosphate arid 21.0 /jg- 

 at./liter of nitrate (Raymont 1963). Riley and Conover 

 (1956) found maximum phosphate and nitrate concen- 

 trations in Long Island Sound of 1.9 and 17.0/jg-at./liter, 

 respectively. Maximum concentrations in Auke Bay were 

 3.5 jug-at./liter of phosphate and 26.0 Mg-at. /liter of 

 nitrate. Maximum silicate concentrations in Auke Bay 

 were also comparatively high — 70.0 yug-at./liter. This is 

 significantly greater than the maximum values reported 

 for the English Channel, 5.0 yug-at./liter, or for Friday 

 Harbor, 53 Mg-at./liter (Raymont 1963). The highest 

 silicate concentration reported anywhere was 160 jug- 

 at./liter in the deep water of the North Pacific Ocean 

 i Raymont 1963). 



In general, throughout the summer, phosphate values 

 in Auke Bay in the upper 5 m tended to remain low, al- 

 though there were some fluctuations. Minimum concen- 

 trations of phosphate observed in surface water were 



