EFFECTS OF HEATED EFFLUENTS
85
abundant at 20”C, that green algae were most abundant at about 32°C
and blue green algae most prolific at 40°C. Blue green algae therefore
appear to be indicators of extreme thermal pollution as they also seem
to be of organic and chemical pollution (Cairns, 1956; Trembley, 1965).
Amongst brackish-water forms, too, Nitzschia Jiliformis (W. Sm.) grows
best under conditions of slight heating at 26°C. Indeed, in marine and
estuarine localities unicellular algae grow prolifically where there is
local warming in areas which are well supplied with nutrients, often
resulting in “ red tide ’’ and other forms of algal blooms (BrongersmaSanders, 1948 ; Hayes and Austen, 1951). Artificially heated regions
in temperate waters would therefore be more prone to occurrence of
such blooms. In Britain it has been shown that heated effluents do
result in increased total plankton production (Pannell et al., 1962;
Hockley, 1963) and that the spring outburst of phytoplankton may
occur earlier than in unheated areas (Pearce, 1965).
C. Replacement faunas
In general discussions of the effects of pollution Hynes (1959, 1960)
distinguishes two types of pollution, “ man-made ” and “ natural ”. The
first of these usually results in the elimination of some species, often
accompanied by a corresponding increase in those that remain. The
second type on the other hand may result in the substitution of “ replacement ’’ organisms which are pre-adapted to the peculiar conditions
of the polluted area. This effect is produced by types of pollution which
closely parallel naturally occurring conditions, such as pollution by
organic matter, mineral salts and reduced salts of iron. Thermal
pollution is also a “natural” type of pollution and might be expected to
be tolerated by a replacement warm water fauna, provided such forms
had a suitable means of dispersal. Indeed, efforts to find indicator
species for marine pollution both in the United States and in Japan
suggest that the polychaete Capitella capitata (Fabricius) is particularly
abundant in areas affected by mixed domestic pollution including heat
(Filice, 1954, 1959; Kitamori and Kobayashi, 1958; Kitamori et al.,
1959; Kitamori and Funae, 1959; Kitamori and Kobe, 1959; Reish,
1955, 1957). In addition, the crab Rhithropanopeus harrisi Gould also
occurs in greater abundance around mixed industrial outfalls than in
unpolluted areas nearby (Filice, 1954, 1959 ; Reish, 1955, 1957, 1960).
However, whereas replacement faunas for most types of natural pollution can occur in the same geographical areas as species which are
eliminated, heat-tolerant species would normally be expected to occur
only in low latitudes. An important prerequisite, therefore, if thermal
pollution is to resiilt in the substitution of replacement animals, is that
85
abundant at 20”C, that green algae were most abundant at about 32°C
and blue green algae most prolific at 40°C. Blue green algae therefore
appear to be indicators of extreme thermal pollution as they also seem
to be of organic and chemical pollution (Cairns, 1956; Trembley, 1965).
Amongst brackish-water forms, too, Nitzschia Jiliformis (W. Sm.) grows
best under conditions of slight heating at 26°C. Indeed, in marine and
estuarine localities unicellular algae grow prolifically where there is
local warming in areas which are well supplied with nutrients, often
resulting in “ red tide ’’ and other forms of algal blooms (BrongersmaSanders, 1948 ; Hayes and Austen, 1951). Artificially heated regions
in temperate waters would therefore be more prone to occurrence of
such blooms. In Britain it has been shown that heated effluents do
result in increased total plankton production (Pannell et al., 1962;
Hockley, 1963) and that the spring outburst of phytoplankton may
occur earlier than in unheated areas (Pearce, 1965).
C. Replacement faunas
In general discussions of the effects of pollution Hynes (1959, 1960)
distinguishes two types of pollution, “ man-made ” and “ natural ”. The
first of these usually results in the elimination of some species, often
accompanied by a corresponding increase in those that remain. The
second type on the other hand may result in the substitution of “ replacement ’’ organisms which are pre-adapted to the peculiar conditions
of the polluted area. This effect is produced by types of pollution which
closely parallel naturally occurring conditions, such as pollution by
organic matter, mineral salts and reduced salts of iron. Thermal
pollution is also a “natural” type of pollution and might be expected to
be tolerated by a replacement warm water fauna, provided such forms
had a suitable means of dispersal. Indeed, efforts to find indicator
species for marine pollution both in the United States and in Japan
suggest that the polychaete Capitella capitata (Fabricius) is particularly
abundant in areas affected by mixed domestic pollution including heat
(Filice, 1954, 1959; Kitamori and Kobayashi, 1958; Kitamori et al.,
1959; Kitamori and Funae, 1959; Kitamori and Kobe, 1959; Reish,
1955, 1957). In addition, the crab Rhithropanopeus harrisi Gould also
occurs in greater abundance around mixed industrial outfalls than in
unpolluted areas nearby (Filice, 1954, 1959 ; Reish, 1955, 1957, 1960).
However, whereas replacement faunas for most types of natural pollution can occur in the same geographical areas as species which are
eliminated, heat-tolerant species would normally be expected to occur
only in low latitudes. An important prerequisite, therefore, if thermal
pollution is to resiilt in the substitution of replacement animals, is that