ing to tide from about 3 to G m. The liarbor water 

 was sampled directly with a dissolved oxygen 

 sampling bottle ^ at a depth of 2 m. at the same 

 time the pumped water was sampled, except that 

 during tlie first winter only one sample was taken 

 each month. 



For the first 6 months, samples were analyzed 

 with a polarographic dissolved oxygen meter, but 

 this method proved somewhat unreliable at low 

 temperatures. After the first winter, all determi- 

 nations were made by the unmodified Winkler pro- 

 cedure. Because the Winkler metliod has several 

 sources of error, the routine technique was peri- 

 odically checked on standai'ds of water saturated 

 with air under controlled conditions. The errors 

 averaged about ±0.1 p.p.m.; I did not consider 

 them serious for the purpose of this study. Solu- 

 bility data for oxygen were obtained from the 

 tables of Green (1965). 



Measurements of dissolved nitrogen were not 

 made during the first year (1904). In 1965 a few 

 determinations were made with a manometric Van 

 Slyke apparatus, and in 1966 and 1967 periodic 

 nitrogen determinations were made according to 

 the micro-gasometric method of Scholander, Van 

 Dam, Claff, and Kanwisher (1955). Solubility 

 data for nitrogen were obtained from the tables of 

 Eakestraw and Emmel ( 1938) . 



The amount of dissolved oxygen sometimes 

 varied considerably during the day. This fluctua- 

 tion reflects in part the diurnal cycle of oxygen 

 sometimes called the "oxygen pulse." To obtain 

 comparable measurements from day to day, sam- 

 ples were taken in the afternoon, when concentra- 

 tions of dissolved oxygen were approaching their 

 maximum. Tides also caused some variation that 

 was reflected as irregularities in the seasonal 

 trends. 



OBSERVATIONS IN 1964 



The highest oxygen concentration in the labora- 

 tory water during 1964 was 12.7 p.p.m. on June 23 ; 

 the saturation was 153 percent. At the same time, 

 the oxygen in the surface water at Boothbay Har- 

 bor was 10.8 p.p.m. and the saturation was 131 

 percent. Daily maxima of 130 to 140 percent satura- 

 tion were frequent during June, but thereafter 

 during the summer the levels decreased and fluctu- 

 ated between 110 and 120 percent saturation. 



1 Type rpcommended by A. P. HA. Standard Methods of Water 

 Analysis. 



lis 



Samples taken elsewhere along the coast in July 

 ranged from 107 to 115 percent saturation in Casco 

 Bay, 100 to 104 percent saturation in Penobscot 

 Bay, and 102 to 112 percent saturation along the 

 eastern Maine coast. Unfortunately, these meas- 

 urements were not made until after the extremely 

 high values of dissolved oxygen at Boothbay Har- 

 bor had diminished; hence, they may be lower 

 than would have been observed earlier in the year. 



OBSERVATIONS IN 1965 



Oxygen measurements were discontinued toward 

 the end of 1964, but were resumed in January 1965. 

 The water remained close to 100 percent saturation 

 during the winter, but in mid-March the first of 

 a series of peaks in both concentration and satura- 

 tion appeared; concentration reached 13.5 p.p.m. 

 and saturation 120 percent. The second major peak 

 was in early May when the concentration was 13.5 

 p.p.m. and saturation over 130 percent. At that 

 time dissolved nitrogen was also high (in excess 

 of 120 percent saturation) for a few days. There- 

 after, the concentration of dissolved oxygen de- 

 creased slowly and irregularly until the end of 

 ,Tuly, but because of rising temperature the satura- 

 tion remained between 120 and 130 percent. Except 

 for a few days in May, dissolved nitrogen, when- 

 ever measured, was close to 100 percent saturation. 

 AVinds can sometimes produce dramatic changes 

 in the amounts of dissolved oxygen. A precipitous 

 decrease in dissolved oxygen took place after a 

 strong northwest wind on August 28 and 29 ; the 

 concentration dropped to 7.3 p.p.m. and saturation 

 to less than 90 percent, but rose shortly to levels as 

 liigh as before. A second northwest wind-storm on 

 September 26 again dropped the oxygen to below 

 100 percent saturation where, except for a slight 

 rise during October, it remained for the rest of the 

 year. 



For localities other than Boothbay Harbor, satu- 

 rations in June were 114 to 119 percent in Casco 

 Bay and 1 17 to 127 percent along the eastern Maine 

 coast. 



OBSERVATIONS IN 1966 



Saturation of oxygen began to rise above 100 

 percent late in January. Three major peaks oc- 

 curred during the spring. In the laboratory water 

 supply these reached 128 percent in late March, 

 128 percent again in mid-April and 137 percent in 



U.S. FISH AND WILDLIFE SERVICE 



