|G. R. Bouck 



Supersaturation 



and Fishery Observations in 



Selected Alpine Oregon Streams 



ABSTRACT 



Several Alpine Oregon streams were sampled and found to con- 

 tain excess levels of dissolved gas tension. Effects of this natu- 

 rally supersaturated water on hatchery operations and results of 

 sampling of natural populations of aquatic organisms are 

 presented. 



Hyperbaric dissolved gas pressures may occur natu- 

 rally in streams for one or more of several reasons. 

 These reasons include geothermal heating of 

 groundwater (Egusa, 1959), solar or seasonal heat- 

 ing of lakes and reservoirs (Harvey, 1967), water 

 falls (Harvey and Cooper, 1962), photosynthesis 

 (Renfro, 1963) and high stream velocity (Lindroth, 

 1957). While these sources of supersaturation have 

 existed since time began and have been studied to 

 some extent by researchers, there has been rela- 

 tively little study of the biological impact of natu- 

 rally occurring supersaturation on wild aquatic 

 organisms. Conversely most of the supersaturation 

 bioassay research has been done in hatchery, live- 

 box, or laboratory circumstances. Therefore, it 

 seemed prudent to investigate the limnology and 

 fishery biology of naturally occurring supersatura- 

 tion, as is described in this report. 



Although supersaturation may be a new water 

 quality parameter to many people, it is not a new 

 phenomenon to fish or aquatic invertebrates in 

 general. During eutrophic periods of our geological 

 history, photosynthetically produced high oxygen 

 supersaturations must have occurred countless 

 times and impacted the evolving aquatic fauna. 

 In this regard, it is interesting to note that Rucker's 

 (1974) study provides strong evidence that fishes 

 tolerate oxygen supersaturation much better than 

 they tolerate nitrogen supersaturation (given iso- 

 baric total dissolved gas pressures in either case). 

 Likewise, many trout and salmon streams are 

 derived completely from springs that discharge 

 geothermally heated, hence usually supersaturated 

 groundwater. Such streams present a naturally 

 existing opportunity for studying the impact of 

 supersaturation on aquatic life, and as such, provide 

 an opportunity for a much needed field verification 

 of laboratory bioassay data. 



Several years experience with the lethality of 

 supersaturation has led the author to the conclusion 

 that the typical laboratory testing program is not 

 sufficiently robust to meet its ultimate purpose. For 

 example, the laboratory testing circumstance typi- 

 cally uses the "worst possible" conditions that a fish 

 might conceivably experience, such as crowded 

 conditions, shallow water, continuous exposure and 

 frequent disturbances. Moreover, the nutritional, 

 immunological, and acclimation state of the test 

 fish is typically unknown. All of these reasons 

 emphasize the need for evaluating the problem 

 in situ. 



Attempts to determine the impact of supersatu- 

 ration in the Columbia and Snake Rivers have been 

 frustrated, if not stymied, by the magnitude of the 

 required resources and efforts needed for its accom- 

 plishment. Detection limits for supersaturation 

 mortality therein are frightful, because ocean mor- 

 tality kills upwards of 98% of the salmon; hence a 

 slight change in marine survival can have major 

 effects on the adult salmon run. Mortality detection 

 limits are still bad in the Columbia River where a 

 flow of 250 x 10 3 cfs discharges about 1.35 trillion 

 lb of water per day; this would require a daily kill 

 of 13,500 lb of fish to achieve a 1 ppm detection 

 limit. Adult fish passage records at dams help reduce 

 the detection limit, but the accuracy of these records 

 has been disputed and in any event they fail to 

 indicate the cause of death. Thus, it would seem 

 that the circumstances in a small supersaturated 

 stream might present the required blend of natural 

 circumstances and appropriate size which might 

 overcome most of the previously listed objections. 



A fortuitous fish kill and subsequent investiga- 

 tion in the Klamath Basin revealed that several 

 Alpine Oregon streams were naturally supersatu- 

 rated. This in turn generated further studies which 

 are still in progress. Therefore, this is a preliminary 

 report. 



Bouck: U.S. Environmental Protection Agency, Western Fish 

 Toxicology Station, Corvallis, Oregon. 



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