Effects Of Thermal Effluents Research Articles

Temperature selections of Anguilla japonica (L.) elvers, and their implications for migration

This study investigated the temperature selections of elvers of the Japanese eel, Anguilla japonica (L.), that had been acclimatized to various temperatures and salinities. The results provide information needed to assess the possible effects of thermal effluents from power plants and of naturally occurring thermal gradients on the freshwater migration and fishery harvest of elvers. A 7.14-m-long plastic pipe (i.d. 11 cm) fitted with two stainless-steel heat-exchange tubes was used for the study. The countercurrent design of the system provided a thermal gradient ranging from 11� C at one end of the pipe to 31� C at the other. Elvers could swim free of obstacles inside the pipe. They were acclimatized to 13, 15, 17, 19 or 21� C before being subjected to the thermal gradient. The distribution of elvers in the pipe was studied during a 24-h period. The results indicate that the temperature to which the elvers gravitated was higher than their acclimatization temperature for acclimatizaion temperatures between 13 and 21�C. The thermal preference of elvers acclimatized to salinities of 10 or 32 did not differ. The temperature- selection pattern of the elvers suggests that thermal effluents from power plants may not adversely affect the immigration of elvers.

Seasonal responses of lentic midge assemblages to environmental gradients

We examined biotic and abiotic factors associated with density and diversity of larval midges (Diptera: Chironomidae) in the littoral zone of Par Pond, an 1100 ha cooling reservoir located near Aiken, South Carolina, USA. A total of 144 core samples were removed from 12 areas during each of 3 sample periods. Principal component analysis. Mantel analysis, and various univariate statistical tests were used to detect seasonal differences in (1) associations among areas and genera of Chironomidae, and (2) responses of midges to a multi‐faceted environmental gradient. Water temperature, which in this case was a function of both season and thermal effluents, was the factor most strongly associated with relative changes in density and diversity within the chironomid assemblages. Plant biomass and/or plant diversity were significant factors correlated with midge density and diversity. Both particle size and organic content of the substratum, which varied little across stations, were relatively unimportant factors. Despite the presence of a multifaceted environmental gradient, the composition and relationships within the midge assemblages were remarkably similar across areas although total abundance and diversity varied.On the basis of their similarity in structure and function, we classify the midge assemblages within the reservoir as members of the same community. However, in response to dissimilar or unequal selective forces (principally the area‐specific effects of thermal effluents), these assemblages appear to behave environmentally as multiple units rather than as a single component of the benthic community in Par Pond.

The effect of thermal effluent, before and after macrophyte harvesting, on standing crop and species composition of benthic macroinvertebrate communities in Lake Wabamun, Alberta

The heated area of Lake Wabamun prior to macrophyte harvesting had higher submerged macrophyte production, greater amounts of plant detritus in the sediment, and a higher standing crop of benthic macroinvertebrates than the unheated area. Species composition of the benthic macroinvertebrate community was also much different in the heated area with the warmest areas supporting a community dominated by tubificid oligochaetes (Limnodrilus hoffmeisteri and Tubifex tubifex), and the moderately heated areas supporting a community dominated by large Chironomus species (Chironomus plumosus and Chironomus atroviridis). Benthos of the unheated parts of the lake consisted mainly of smaller chironomid species such as Chironomus maturus, C. (cf.) staegeri, Polypedilum nubeculosum, Cladotanytarsus spp., and Tanytarsus spp. The heated area was subjected to mechanical macrophyte harvesting which removed the majority of the submerged macrophytes. This reduced the amount of plant detritus within the sediment and also the standing crop of benthic macroinvertebrates in the heated area. Species composition of the oligochaete-dominated community was not affected by harvesting. Species composition of the Chironomus-dominated area was greatly affected by harvesting and became more similar to that of the unheated area; densities of the large Chironomus species were reduced to low levels, while the densities of smaller chironomid species increased.

Field experiments on interactions between vertebrate predators and larval midges (Diptera: Chironomidae) in the littoral zone of a reservoir.

A field experiment was designed to test a frequent assumption in the literature that vertebrate predators (in this case, fish and turtles) are capable of regulating the seasonal abundance and diversity of benthic communities in the littoral zone of lentic environments. Effects of thermal effluents from a nuclear reactor on predator-prey relationships were also examined. Benthic samples were removed after each of three, 3-month test periods from 36 predator exclusion cages (4m2) and 36 control plots located along a thermal gradient in Par Pond, an 1,100 ha freshwater reservoir in the southeastern United States.Results of our field experiments provide little evidence to suggest that either a single "keystone" species or vertebrate predators as a group were capable of regulating the abundance, diversity or productivity of chironomids in Par Pond. The relationship between predator treatment and community response (changes in density and species richness) was generally unaffected by either plot location or temperature fluctuations. When data from caged and control plots were pooled, however, both location and water temperature individually had significant impacts on the chironomid community. Alternative hypotheses are proposed to explain the lack of regulatory control of the benthic community by individual species or guilds of predators.

Effects of thermal effluent on body condition of largemouth bass

PAR POND, an 1,100-hectare reservoir in South Carolina, has received heated effluent from a nuclear production reactor since 1957. A notable feature of the reservoir1 is the abundance and abnormally high catchability of largemouth bass (Micropterus salmoides2). Most reported responses of bass to the thermal situation in Par Pond are interpreted as inconsequential3–7; increases in the densities of certain intestinal parasites8 and the incidence of red-sore disease9 in thermal areas are considered detrimental. Fishery scientists use body condition10 as an index for estimating a fish's well-being or fitness11 as well as the relative suitability of the habitat12. Body condition (K) of an individual is established by the relationship K = 105 W × L−3, where W = body weight (g) and L = standard length (mm). However, caution must be exercised to ensure that ontogenetic changes in body shape, seasonal and sex differences, and small sample sizes do not preclude the effective use of the index for comparative purposes among individuals10. This report takes these reservations into account and compares body condition of largemouth bass collected from heated and unheated waters in Par Pond. The unique feature of this study is that data from 10 years are available on a large sample (n > 10,000) of largemouth bass, an important species of warm water sport fish. Lower body condition is associated with moderate thermal conditions comparable to many industrial settings and is correlated with lower levels of stored fat and with the incidence of red-sore disease.

Effects of Thermal Effluent on Standing Crop and Net Production of Elodea canadensis and Other Submerged Macrophytes in Lake Wabamun, Alberta

SUMMARY (1) The dry matter production of aquatic macrophytes was measured over 2 years, at three depths, in Lake Wabamun, Alberta, Canada. Production was measured in an area receiving thermal effluent and at a control site, unaffected by thermal effluent. (2) A greater standing crop existed in winter in the thermal mixing zone. Elodea canadensis, which had no marked dormancy mechanism, was dominant in this zone in winter. (3) Higher light levels, due to the absence of ice cover, resulted in earlier spring growth in the effluent zone, but early spring productivity was limited by low water temperatures, caused by strong thermal stratification. Elodea dominated early spring production because of the large standing crop overwinter. (4) After turnover, the growth of E. canadensis increased and vegetative and potential sexual reproduction increased compared to the control site. Elodea comprised only approximately one-third of the maximum standing crop at the control site in the first year, and was absent the second year. (5) Large standing crops of Elodea near the surface were thinned by wave action. The resulting stem fragments were spread throughout the lake, where they established during the growing season but later declined. Following this process of thinning, a second peak in the standing crop was observed. (6) Changes in the species composition of submerged macrophytes in heated areas of Lake Wabamun do not seem to have spread to unheated acres of the lake.

Effects of thermal effluents on parasites and commensals of Physa gyrina Say (Mollusca: Gastropoda) and their interactions at Lake Wabamun, Alberta

Effects of thermal effluents on the dynamics of larval helminth parasites and on populations of Chaetogaster limnaei limnaei and Chaetogaster limnaei vaghini (Annelida: Oligochaeta) harbored by Physa gyrina (Mollusca: Pulmonata) were studied at Lake Wabamun, Alberta. Thermal effluents provided the necessary conditions to maintain digenean parasite transmission throughout the year between definitive and intermediate hosts, and increased the prevalence of certain parasites, especially the metacercarial stages.At temperatures above 24 °C prevalences of C. l. limnaei and C. l. vaghini decreased in the lake, and at these temperatures in the laboratory C. l. limnaei abondoned the snails and perished. Under experimental conditions the number of Echinoparyphium recurvatum larvae penetrated Physa gyrina was inversely related to the number of C. l. limnaei present. It was also observed that these oligochaetes actively ingested digenean larvae. Elimination of C. l. limnaei caused by thermal effluents has augmented the metacercarial infections.An ecological model depicting the interactions of Physa gyrina – digeneans – Chaetogaster l. limnaei is presented. This is a complex system in which water temperature acts as a main regulating factor. The three main components of the system interact with each other and are influenced by various external factors, resulting in a dynamic ecological system.

Effects of thermal effluents on the population dynamics of Physa gyrina Say (Mollusca: Gastropoda) at Lake Wabamun, Alberta

Effects of thermal effluents on the population dynamics of Physa gyrina Say (Gastropoda: Pulmonata) were studied at Lake Wabamun, Alberta, from May 1971 to August 1973. Thermal effluent increased the rate of development of eggs and the growth of P. gyrina, and allowed continuous reproductive activity throughout the year. These changes, and the increased period of growth of aquatic macrophytes, resulted in increased population densities of P. gyrina in the heated area during summer. Temperatures below 10 °C or small amounts of vegetation appear to limit the population of P. gyrina in winter.

The effect of thermal effluent upon the standing crop of an epiphytic algal community

AbstractThe investigation of the epiphyton associated with Scirpus validus VAHL. in Lake Wabamun commenced in May 1971 and continued until the end of August 1972. Seven stations encompassing heated, partially and non‐heated areas of the lake were investigated. From July 1971 until the termination of the investigation water temperature, dissolved oxygen and water chemistry were monitored. There were no large variations in these parameters except for water temperature and dissolved oxygen levels among the stations. However, there were increases in the dissolved silica, nitratenitrogen and phosphate‐phosphorus levels during the autumn and winter months at the heated stations while at a partially heated station only dissolved silica and nitrate‐nitrogen increased. The epiphyton at all stations showed a spring maximum, a summer minimum, and a maximum in the late summer/early autumn. The spring dominants at all stations were Fragilaria capucina and Diatoma elongatum. During the late summer/early autumn maximum diatoms were dominant at the non‐heated stations while chlorophycean species were dominant at the heated stations. The heated water caused a decrease in the number of species and a corresponding increase in the importance of a few species at the heated stations. The major impact of the heated water, however, was an extension of the period of open water and the corresponding increase in mean yearly standing crop size in the heated areas.

Possible effects of thermal effluents on fish: A review

Thermal stress is known to have general and specific effects on the physiology of fish. In general, over a species-specific temperature range, increasing temperatures increase metabolic rates and other activity. Deviations from optimum temperature could cause a cessation of spawning behaviour or an increase of abnormal fry. The final level of temperature acclimation is a function of species, size, condition, and past environment. Most fish can acclimate faster to higher temperatures than to lower temperatures. Fluctuating temperatures increase thermal resistance in some species. Temperature preferences in fish are a function of acclimation temperature and of the species-specific optimum temperature. Slight increases in temperature can be lethal because of synergism.