R. A. Marcello, Jr. 

 R. B. Fairbanks 



Gas Bubble I 



Disease Mortality 



of Atlantic 



Menhaden, Brevoortia Tyrannus, at 



a Coastal Nuclear Power Plant 



ABSTRACT 



A substantial mortality of Atlantic menhaden, 8revoort/a tyran- 

 nus, occurred in the discharge channel and discharge plume 

 area of the Boston Edison Company's Pilgrim Nuclear Power 

 Station Unit 1 during the period April 8 through April 24, 1973. 

 Gas bubble disease was implicated as the cause of their death. 

 Measurements of dissolved gas concentration of the station's 

 intake and discharge water during this fish mortality are pre- 

 sented. Observations on the behavior and results of the patho- 

 logical examination of menhaden afflicted with gas embolism 

 are discussed. 



Water supersaturated with dissolved gases can have 

 detrimental effects on fish and other aquatic organ- 

 isms. The manifestation of these effects in fish is 

 generally referred to as gas bubble disease. While 

 fish appear to tolerate mild cases of gas bubble 

 disease, extreme cases have resulted in mortalities 

 (Marsh and Gorham, 1905; Woodbury, 1942; Renfro, 

 1963; Ebel, 1969; Beiningen and Ebel, 1970; DeMont 

 and Miller, 1971; and others). 



Gaseous supersaturation of natural waters has 

 been attributed to increased photosynthetic activity 

 (Woodbury, 1942; Renfro, 1963), the falling of water 

 into plunge basins below dam spillways (Harvey and 

 Cooper, 1962; Ebel, 1969; Beiningen and Ebel, 1970), 

 and the drawing in of air at water pump intakes, 

 leaky pipelines, and similar situations (Marsh and 

 Gorham, 1905; Harvey and Smith, 1961). More 

 recently the passage of cooling water through the 

 circulating water systems of electric power gener- 

 ating stations has also been identified as having the 

 potential for creating gas-supersaturated conditions 

 in the cooling water discharge (DeMont and Miller, 

 1971). 



Dissolved gas supersaturation in the thermal 

 effluent of a power plant can occur due to the 

 inverse relationship between temperature and gas 

 solubility in water. When natural waters are at or 

 near saturation levels with dissolved gases and the 



water is subjected to a substantial temperature 

 increase upon passage through a power plant con- 

 denser system without allowing equilibration with 

 the atmosphere, the water will become gas super- 

 saturated. The return to normal saturation levels 

 under such conditions by gaseous diffusion across 

 the air-water interface appears to be a slow process 

 and usually does not take place before the discharge 

 water is again cooled to ambient by entrainment 

 mixing and heat loss to the atmosphere. Fishes 

 attracted to heated effluents supersaturated with 

 dissolved gases may develop gas bubble disease 

 and are subject to possible mortality. 



Mortality of fish due to gas bubble disease in 

 the heated effluent of power plants has been 

 observed (DeMont and Miller, 1971; Marcello and 

 Strawn, 1973). However, with only a few reported 

 cases of gas bubble disease mortality of fish in the 

 thermal effluents of power generating stations, 

 documentation of all such incidents is needed to 

 enhance our understanding of what environmental 

 conditions and power plant design features and 

 modes of operation may lead to gas bubble mortal- 

 ity of fish. This paper documents a substantial mor- 

 tality of Atlantic menhaden, Brevoortia tyrannus, 

 that occurred in the discharge channel and thermal 

 plume of Boston Edison Company's Pilgrim Nuclear 

 Power Station Unit 1 during April 8 through 24, 1973. 



PILGRIM NUCLEAR POWER STATION 



Pilgrim Nuclear Power Station is situated on the 

 western shore of Cape Cod Bay in the town of 



Marcello: Boston Edison Company, Nuclear Engineering 

 Department, Environmental Sciences Croup, Boston, Massa- 

 chusetts; Fairbanks: Massachusetts Department of Natural 

 Resources, Division of Marine Fisheries, Sandwich, Massa- 

 chusetts. 



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