76
E. N A m R
111. OBSERVED EFFECTS
In a general paper concerning the effects of power station cooling
water on aquatic communities Markowski (1959) showed that some
animals were alive even after being circulated through the cooling
condensers and he found no difference in faunal composition between
the intake and outfall areas. However, in the first place Markowski’s
main conclusions apply to organisms in brackish regions which might
be presupposed to be rather more tolerant of heating than fully marine
species (see p. 68). Also, though some small, hardy, brackish-water
species were shown to survive for a few days after being circulated
through power station condensers, longer term effects upon the individual animals were not considered, nor were the possible effects
upon breeding (see p. 70). Moreover, from a number of other papers
upon the effects of heated effluents in both marine and estuarine waters,
several types of change have been observed which agree closely with
the conclusions drawn from a priori considerations discussed above.
There are known to be examples of the elimination of some native
species and of considerable effects upon the breeding and general
biology of others, some of which are of commercial importance. Also,
there are many examples of the introduction of immigrant species to
artificially heated localities.
A. Elimination of native species
Effects are most striking in the immediate vicinity of outfalls,
particularly in summer. Thus in the Delaware River van Vliet (1957)
reported the absence of Tardigrades from heated regions and Trembley
and his collaborators have shown an almost complete elimination of most
species of fish from the maximum heated zone in summer (Trembley,
1960,1961,1965). In the same river Coutant (1962) has shown that in
summer there is a substantial reduction in the number, diversity and
biomass of macroinvertebrate riffle organisms in that portion of the
river lying in the path of water discharged from the power station.
In the Schuylkill River (Pennsylvania) Wurtz and Dolan (1960) report
the elimination of thermally intolerant species below a power station
effluent and a differential increase in the numbers of tolerant species
which remain. Fish are sometimes killed by heated effluents (Alabaster
and Swain, 1962) but such forms usually avoid death by swimming to
cooler water nearby. The general problem of heated effluents in relation
to freshwater fish is discussed by Erichsen Jones (1964) who doubts
whether significant numbers of such fish are killed by thermal
pollution,
E. N A m R
111. OBSERVED EFFECTS
In a general paper concerning the effects of power station cooling
water on aquatic communities Markowski (1959) showed that some
animals were alive even after being circulated through the cooling
condensers and he found no difference in faunal composition between
the intake and outfall areas. However, in the first place Markowski’s
main conclusions apply to organisms in brackish regions which might
be presupposed to be rather more tolerant of heating than fully marine
species (see p. 68). Also, though some small, hardy, brackish-water
species were shown to survive for a few days after being circulated
through power station condensers, longer term effects upon the individual animals were not considered, nor were the possible effects
upon breeding (see p. 70). Moreover, from a number of other papers
upon the effects of heated effluents in both marine and estuarine waters,
several types of change have been observed which agree closely with
the conclusions drawn from a priori considerations discussed above.
There are known to be examples of the elimination of some native
species and of considerable effects upon the breeding and general
biology of others, some of which are of commercial importance. Also,
there are many examples of the introduction of immigrant species to
artificially heated localities.
A. Elimination of native species
Effects are most striking in the immediate vicinity of outfalls,
particularly in summer. Thus in the Delaware River van Vliet (1957)
reported the absence of Tardigrades from heated regions and Trembley
and his collaborators have shown an almost complete elimination of most
species of fish from the maximum heated zone in summer (Trembley,
1960,1961,1965). In the same river Coutant (1962) has shown that in
summer there is a substantial reduction in the number, diversity and
biomass of macroinvertebrate riffle organisms in that portion of the
river lying in the path of water discharged from the power station.
In the Schuylkill River (Pennsylvania) Wurtz and Dolan (1960) report
the elimination of thermally intolerant species below a power station
effluent and a differential increase in the numbers of tolerant species
which remain. Fish are sometimes killed by heated effluents (Alabaster
and Swain, 1962) but such forms usually avoid death by swimming to
cooler water nearby. The general problem of heated effluents in relation
to freshwater fish is discussed by Erichsen Jones (1964) who doubts
whether significant numbers of such fish are killed by thermal
pollution,