IMPACT OF THERMAL EFFLUENT FROM 



A STEAM-ELECTRIC STATION ON A MARSHLAND 



NURSERY AREA DURING THE HOT SEASON 



William E. S. Carri and James T. Giesel^ 



ABSTRACT 



Seine samples of fishes were collected during the hot season from three similar marshland creeks 

 situated at various distances from a steam-electric station near Jacksonville, Fla. Thermal effluent 

 from the electric station is discharged directly into one creek and enters a second creek on the initial 

 stage of each rising tide. The third creek remained at ambient temperature. Fishes collected in the 

 samples were analyzed for species composition and for density and biomass per unit area. A total of 

 48 species belonging to 23 families were identified. Thirty-seven species were collected at least once 

 in the ambient temperature creek whereas 30 species were collected in the creek receiving the maxi- 

 mum amount of thermal effluent. 



Twenty species appearing in the samples are categorized as utilizable species because they are used 

 by man either as food or for various fishery products. Specimens of all utilizable species were juveniles. 

 In the thermally affected creeks, both the numbers and the biomass per unit area of juveniles of 

 utilizable species were 3- to 10-fold smaller than those obtained in collections from the ambient 

 temperature creek. When data for the entire hot season are considered, the creek receiving the largest 

 input of thermal effluent supported a population of fishes having approximately 19% of its numbers and 

 32% of its biomass composed of juveniles of utilizable species. In contrast, the ambient temperature 

 creek supported a population having approximately 73% of its numbers and 83% of its biomass 

 composed of such species. Whereas juveniles of two species of mullet (Mugil curema and M. cephalus) 

 accounted for the majority of the utilizable fishes using the thermally affected creeks as a nursery area, 

 large numbers of juveniles of at least five additional utilizable species occupied the ambient tempera- 

 ture creek. These species were as follows (in order of decreasing abundance): tidewater silverside, 

 Menidia beryllina; spot, Leiostomus xanthurus; Atlantic menhaden, Brevoortia tyrannus; silver perch, 

 Bairdiella chrysura; and Atlantic thread herring, Opisthonema ogUnum. 



There is no longer any doubt that estuarine areas 

 play a vital role in the life cycles of the majority of 

 species of finfish and shellfish that are harvested 

 annually in coastal fisheries. The role of estuaries 

 as nursery areas for both sport and commercial 

 species is now well documented (Skud and Wilson 

 1960; Smith et al. 1966; Sykes and Finucane 1966; 

 Carr and Adams 1973; others). The majority of 

 sport and commercial species must inhabit es- 

 tuarine areas during at least part of their life 

 cycles. Most frequently it is the early juvenile 

 stages that exhibit the most pronounced estuarine 

 dependence. 



Thermal additions from power plants are con- 

 sidered to pose a potentially serious threat to valu- 

 able estuarine habitats. Krenkel and Parker 

 (1969) have estimated that the amount of water 

 required for condenser cooling by power plants in 



*C. V. Whitney Marine Laboratory of University of Florida at 

 Marineland, Route 1, Box 121, St. Augustine, FL 32084 



^Department of Zoology, University of Florida, Gainesville, 

 FL 32601 



this country will increase from 50 trillion gallons 

 per year in 1968 to 100 trillion gallons per year by 

 1980. This latter amount represents approxi- 

 mately one-fifth of the total land runoff in the 

 contiguous United States. The immense volumes 

 of water required for cooling by power plants are 

 most readily obtained by building these plants 

 adjacent to estuaries or in other coastal locations. 

 The fact that estuarine areas "are among the most 

 productive natural ecosystems in the world" 

 (Schelske and Odum 1962) raises the question as 

 to whether meeting the increasing needs for elec- 

 tricity by our growing population is best satisfied 

 by using estuarine areas as the receiving waters 

 for ever increasing discharges of thermal 

 effluents. 



Although a large literature exists concerning 

 various biological facets of "thermal pollution" 

 (reviews are provided by Naylor 1965; Wurtz and 

 Renn 1965; Krenkel and Parker 1969; Jensen et 

 al. 1969; Coutant 1970, 1971; Sylvester 1972; 

 others) we are aware of no published studies that 



Manuscript accepted May 1974. 



FISHERY BULLETIN: VOL. 73, NO. 1, 1975. 



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