SHORT-TERM THERMAL RESISTANCE OF ZOEAE OF 

 10 SPECIES OF CRABS FROM PUGET SOUND, WASHINGTON 



Benjamin G. Patten 1 



ABSTRACT 



Zoeae of 10 crab species were subjected to tests that simulated thermal stress associated with steam- 

 powered electric stations. Shortly after hatching, the unfed zoeae were subjected to conditions 

 simulating passage through heat exchangers (held at elevated test temperatures for 20 min with an 

 abrupt increase and decrease from ambient) or mixing with thermal plumes (held at test temperature 1 

 to 4 h with temperatures gradually rising and decreasing from ambient). All species used in tests were 

 hatched from February to November and were naturally acclimated to ambient conditions of the 

 littoral zone. Observations were made on the point in temperature that zoeae became torpid in heat 

 exchanger tests and on the TL 50 (maximum temperature-time that 50% or more of the subjects 

 survived 48 h after testing). 



In the heat exchanger tests, the most sensitive species, the Bering hermit crab, Pagurus beringanus, 

 and the porcelain crab, Petrolisthes eriomerus , did not become torpid at 24°C; their torpid point and 

 their TL 50 were at 26°C. The economically important Dungeness crab, Cancer magister, did not become 

 torpid at 28°C; its TL 50 was at 30°C. The TL 50 of other species ranged from 30° to 34°C. 



The TL 50 of zoeae given the thermal plume test ranged from 26° to 34°C for a 1-h exposure and 24° to 

 32°C for a 2- to 4-h exposure. 



Thermal conditions in heat exchangers are postulated to be more critical to the survival of zoea than 

 mixing with thermal plumes. The maximum temperature that should be permitted in heat exchangers 

 to protect the most sensitive species studied is 24°C for the Puget Sound area. 



Thermal resistance of marine organisms should 

 be understood before seawater in a specific area is 

 used for industrial cooling. In the State of 

 Washington, for example, nuclear power plants 

 are being planned for construction by municipali- 

 ties and industries. These plants require large 

 quantities of seawater to cool condensers of the 

 steam turbine system; their waste hot water 

 would be discharged back into the environment, 

 along with toxic chemicals (Becker and 

 Thatcher 2 ). Organisms entrained into steam 

 electric stations would be subjected to mechanical 

 injury (Marcy 1973) from passage through such a 

 system. Studies are needed to fully evaluate the 

 impact of entrainment and the discharge of 

 altered waste water on the associated life; 

 temperature effects are considered here. 



Some information is available on the thermal 

 maximums and optimums of two species of Puget 



Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, NOAA, 2725 Montlake Boulevard East, 

 Seattle, WA 98112. 



2 Becker, C. D., and T. O. Thatcher (compilers). 1973. 

 Toxicity of power plant chemicals to aquatic life. 

 Battelle Pac. Northwest Lab., Richland, Wash., WASH- 

 1249, U.S. AEC, misc. pagination. 



Sound crabs (Todd and Dehnel 1960; Reed 1969; 

 Prentice 1971; Mayer 34 ). These studies show the 

 effects of long-term temperature increases but do 

 not depict situations related to industrial use of 

 seawater for cooling. Experiments reported here 

 were designed to simulate the stress that zoeae 

 would be exposed to in passing through heat 

 exchangers of steam electric stations and in 

 mixing with thermal plumes of the waste water 

 released into the environment. 



This study is one of a series describing the 

 thermal resistance of selected species of plank- 

 tonic organisms. The time-temperature combina- 

 tions used are considered a measure of thermal 

 resistance (Fry 1971) because they are probably 

 beyond the environmental tolerance of the species 

 used. This paper describes the elevated tem- 

 peratures that cause immediate and imminent 



Manuscript accepted January 1977. 

 FISHERY BULLETIN: VOL. 75, NO. 3, 1977. 



3 Mayer, D. L. 1973. Thermal tolerance of Cancer ma- 

 gister eggs. In Q. J. Stober and E. O. Salo (editors), 

 Ecological studies of the proposed Kicket Island nuclear 

 power site, p. 412-419. Univ. Wash., Coll. Fish., FRI-UW- 

 7304. 



4 Mayer, D. L. 1973. Response of Dungeness crab in a 

 thermal gradient. In Q. J. Stober and E. O. Salo 

 (editors), Ecological studies of the proposed Kicket Island 

 nuclear power site, p. 420-429. Univ. Wash., Coll. Fish., 

 FRI-UW-7304. 



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