through the water cooling pipes of power plants without harm and settle, 

 forming normal populations in thermal discharge regions (Adams, 1969; 

 Barnett, 1972). 



It has been thought that the juveniles of various fish can pass 

 through the water cooling pipes of power plants without harm (Kerr, 

 1953; Markowski, 1959). New studies (Marcy, 1971), however, have shown 

 that the mortality of fry is very high in such situations. 



Thus, water cooling systems of power plants and industrial 

 enterprises located along sea coasts and estuaries have a significant 

 influence on the population and reproduction of plankton, benthos and 

 nekton. 



3.5 Change in the Specific Composition on Communities in Regions 

 of Thermal Discharge 



The change in the specific composition in regions of thermal 

 discharge has been most thoroughly studied for coastal benthic 

 communities. The barnacle Balanus amphi trite , entering western European 

 waters from the subtropics and tropics, has formed stable populations in 

 regions of thermal discharge along the coasts of southern England, Wales 

 and Holland (Stubbings, Houghton, 1964; Nlaylor, 1965a; Borghouts- 

 Biersteker, 1969). Near Southhampton, in the area of thermal discharge 

 from the Marchwood electric power plant, a stable, self-reproducing 

 population of the bivalve mollusk Mercenaria mercenaria has formed--an 

 intruder from the northwest Atlantic (Ansell, 1969). Tn Swansea Harbor 

 (Wales), due to the heating of the water by the thermal discharge of a 

 power plant, new warm-water species of corals, polychaetes, bryozoans, 

 camptozoans, cirripedians, isopods and fish have appeared, some from 

 subtropical and tropical waters, some from the warm- temperate regions 

 located to the south; at the same time, a number of local species have 

 disappeared from the benthos at the point where the warm waters are 

 discharged (Naylor, 1965a). 



A similar picture has been observed for the coastal benthos and 

 nekton in many other regions damaged by thermal pollution. 



3.6 Influence of Thermal Discharge of the Biology of Organisms 



The influence of heating of waters on the biology of organisms may 

 be either negative or positive. Thermal pollution may influence the 

 intensity of photosynthesis of phy topi ank ton, accelerate the occurrence 

 of biochemical processes in organisms and increase their susceptibility 

 to disease. Heating of water influences the intensity of respiration, 

 the stability and integrity of leaves and stolons of littoral and 

 sublittoral blooming plants and macrophytes. In the estuaries of 

 Florida, the turtle grass Thalassia testudinum has lost some of its 

 leaves under the influence of thermal discharge, but retained healthy 

 stolons; however, in cases of severe and permanent heating, the 

 accumulation of heat by sediment has resulted in loss of strength by the 

 stolons, which are then broken (Wood, Zieman, 1969). 



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