92
E. NAyMla
in the open sea but on the other hand there are experimental results
(see p. 78) and field observations (see p. 67) that fully marine and sublittoral species are less tolerant of high temperatures than intertidal
and estuarine forms. Effects are most striking in marine docks where not
only is there considerable retention of heat but many species there are
likely to be intolerant of high temperatures and the activity of shipping
would increase the chances of accidental introduction of heat tolerant
immigrant species. The effects in estuaries are perhaps least striking,
particularly if the lack of shipping reduces the chances of faunal replacement by immigrant species, though possible effects upon migratory
species such as crustacea and fish should not be ignored (see p. 72). A
significant problem in estuaries, too, is the extent to which mixing of
water and dissipation of heat is prevented by vertical salinity gradients
and the complexities of flushing (see p. 67).
The siting of heated effluents in marine and estuarine localities
should therefore be based on a sound ecological approach and future
studies would clearly benefit by investigation of faunal and hydrographical characteristics of a region before a heated effluent is discharged. Such investigations concerning a proposed heated discharge
from the Bradwell Nuclear Generating Station into the Blackwater
Estuary, Essex, have been described by Davis (1963), Key (1963),
Rippon (1963) and Parr (1963), others in the Chesapeake Bay area by
Whursky (1962) and Pritchard and Carter (1966), and others at the
Hunterston Generating Station are being carried out by Dr. P. R. 0.
Barnett (see Scottish Marine Biological Association, 1961, 1962, 1963).
Conditions in the Thames estuary am particularly well known, where
it is possible to predict the effect on temperature of any change which
would be made by the introduction of a new generating station
(Gameson et al., 1957, Department of Scientific and Indus$rial Research,
1964). The value of extended observations is also emphasized by the
results of Pannell et al. (1962) and Raymont and Carrie (1964), who
showed that temperatures in deep water adjacent to a power station
effluent were still rising slowly several years after the effluent was first
discharged.
Finally it is clear that most work so far has been carried out in
temperate regions where temperatures normally vary considerably and
organisms might correspondingly be expected to be fairly tolerant of
raised or lowered temperatures. Tropical and high latitude species, on
the other hand, often live in narrow limits of temperature (Kinne, 1963)
and of these, tropical species may live at temperatures very near to their
death temperatures (Mayer, 1914). Corals, for instance, die at temperatures only 2 or 3 Centigrade degrees above normal (Cahs, 1966). The
E. NAyMla
in the open sea but on the other hand there are experimental results
(see p. 78) and field observations (see p. 67) that fully marine and sublittoral species are less tolerant of high temperatures than intertidal
and estuarine forms. Effects are most striking in marine docks where not
only is there considerable retention of heat but many species there are
likely to be intolerant of high temperatures and the activity of shipping
would increase the chances of accidental introduction of heat tolerant
immigrant species. The effects in estuaries are perhaps least striking,
particularly if the lack of shipping reduces the chances of faunal replacement by immigrant species, though possible effects upon migratory
species such as crustacea and fish should not be ignored (see p. 72). A
significant problem in estuaries, too, is the extent to which mixing of
water and dissipation of heat is prevented by vertical salinity gradients
and the complexities of flushing (see p. 67).
The siting of heated effluents in marine and estuarine localities
should therefore be based on a sound ecological approach and future
studies would clearly benefit by investigation of faunal and hydrographical characteristics of a region before a heated effluent is discharged. Such investigations concerning a proposed heated discharge
from the Bradwell Nuclear Generating Station into the Blackwater
Estuary, Essex, have been described by Davis (1963), Key (1963),
Rippon (1963) and Parr (1963), others in the Chesapeake Bay area by
Whursky (1962) and Pritchard and Carter (1966), and others at the
Hunterston Generating Station are being carried out by Dr. P. R. 0.
Barnett (see Scottish Marine Biological Association, 1961, 1962, 1963).
Conditions in the Thames estuary am particularly well known, where
it is possible to predict the effect on temperature of any change which
would be made by the introduction of a new generating station
(Gameson et al., 1957, Department of Scientific and Indus$rial Research,
1964). The value of extended observations is also emphasized by the
results of Pannell et al. (1962) and Raymont and Carrie (1964), who
showed that temperatures in deep water adjacent to a power station
effluent were still rising slowly several years after the effluent was first
discharged.
Finally it is clear that most work so far has been carried out in
temperate regions where temperatures normally vary considerably and
organisms might correspondingly be expected to be fairly tolerant of
raised or lowered temperatures. Tropical and high latitude species, on
the other hand, often live in narrow limits of temperature (Kinne, 1963)
and of these, tropical species may live at temperatures very near to their
death temperatures (Mayer, 1914). Corals, for instance, die at temperatures only 2 or 3 Centigrade degrees above normal (Cahs, 1966). The