EFFEUTS OF HEATED EFFLUENTS
67
flow temperatures below a power station outfall were only 14 Centigrade
degrees above those which would be expected without warming
(Swain and Newman, 1962). However, heated water and other types of
pollution may be patchily distributed in estuaries owing to the complexities of flushing and layering which may be encountered (Ketchum,
1951a,b; Newell, 1959; Croft, 1960), so heating might be locally
severe. For instance, Pannell et al. (1962), Hockley (1963) and Raymont and Carrie (1964) have reported that in Southampton Water a
salinity gradient due to the River Test produced layering in the water
so that a generating station effluent of warm saline water was held
between a surface layer of cold fresh water and a bottom layer of cold
saline water. I n such conditions, Pannell et al. (1962) point out that
dispersion of heat will be by mixing and not by cooling to the
atmosphere. As a result of this the effects of the heated effluent are
felt a t a greater distance from the outfall than if the heated water
spread out and was cooled at the surface (Raymont and Carrie, 1964;
Ansell et al., 1964a).
11. A PRIORI CONSIDERATIONS
Before considering the direct effects of heated effluents it is useful
first to consider very briefly what is known of experimental and ecological effects of temperature upon marine and brackish-water animals.
There are innumerable papers on this subject which has been extensively reviewed in recent years, notably by Bullock (1955), Prosser
(1955), Precht et al. (1955), Gunter (1957), Crisp (1959, 1964a),
Brett (1960), Pennsylvania Dept. of Health (1962) and Kinne (1963).
From a study of this literature it is possible to consider 8 variety of
effects which heated effluents might be expected to bring about.
A. Heat death
Perhaps the first of many effects which should be considered is that
of heat death, for it is clear that many organisms are killed at temperatures not far in excess of those to which they ire accustomed (Gunter,
1957; Kinne, 1963). This is particularly true for tropical animals,
which often live at temperatures very near to their thermal death
points, whereas some arctic forms may live in water as much as 13 to
16 Centigrade degrees below their death temperatures (Mayer, 1914).
I n addition, despite the fact that acclimatization may take place (see
p. 72), another relevant factor is that within any limited geographical
area temperature tolerance may vary according to the habitat of
particular species. Thus intertidal molluscs show correspondingly
greater tolerance of high temperatures the higher up the shore they are
D 2
67
flow temperatures below a power station outfall were only 14 Centigrade
degrees above those which would be expected without warming
(Swain and Newman, 1962). However, heated water and other types of
pollution may be patchily distributed in estuaries owing to the complexities of flushing and layering which may be encountered (Ketchum,
1951a,b; Newell, 1959; Croft, 1960), so heating might be locally
severe. For instance, Pannell et al. (1962), Hockley (1963) and Raymont and Carrie (1964) have reported that in Southampton Water a
salinity gradient due to the River Test produced layering in the water
so that a generating station effluent of warm saline water was held
between a surface layer of cold fresh water and a bottom layer of cold
saline water. I n such conditions, Pannell et al. (1962) point out that
dispersion of heat will be by mixing and not by cooling to the
atmosphere. As a result of this the effects of the heated effluent are
felt a t a greater distance from the outfall than if the heated water
spread out and was cooled at the surface (Raymont and Carrie, 1964;
Ansell et al., 1964a).
11. A PRIORI CONSIDERATIONS
Before considering the direct effects of heated effluents it is useful
first to consider very briefly what is known of experimental and ecological effects of temperature upon marine and brackish-water animals.
There are innumerable papers on this subject which has been extensively reviewed in recent years, notably by Bullock (1955), Prosser
(1955), Precht et al. (1955), Gunter (1957), Crisp (1959, 1964a),
Brett (1960), Pennsylvania Dept. of Health (1962) and Kinne (1963).
From a study of this literature it is possible to consider 8 variety of
effects which heated effluents might be expected to bring about.
A. Heat death
Perhaps the first of many effects which should be considered is that
of heat death, for it is clear that many organisms are killed at temperatures not far in excess of those to which they ire accustomed (Gunter,
1957; Kinne, 1963). This is particularly true for tropical animals,
which often live at temperatures very near to their thermal death
points, whereas some arctic forms may live in water as much as 13 to
16 Centigrade degrees below their death temperatures (Mayer, 1914).
I n addition, despite the fact that acclimatization may take place (see
p. 72), another relevant factor is that within any limited geographical
area temperature tolerance may vary according to the habitat of
particular species. Thus intertidal molluscs show correspondingly
greater tolerance of high temperatures the higher up the shore they are
D 2