Thermal Effluent Research Articles

Temperature, plankton and conspecific density influence dynamics of age‐0 gizzard shad: implications for a gape‐limited piscivore

AbstractAge‐0 gizzard shad Dorosoma cepedianum are the main prey fish for white crappies Pomoxis annularis in many US reservoirs. However, these prey fish commonly outgrow their vulnerability to white crappie predation in some, but not all, northern Missouri reservoirs. Potential variables that could influence abundance, growth and mortality of age‐0 gizzard shad were examined in three reservoirs that differed with respect to age‐0 gizzard shad growth rates. Because of thermal effluent from a power plant, gizzard shad spawned earlier in Thomas Hill Lake and initial densities of larvae were greater than in the other reservoirs. Larval and juvenile gizzard shad grew slowest in Thomas Hill Lake, followed by Mark Twain Lake and Long Branch Lake. Growth rate of larvae increased with increasing water temperature and food abundance, but decreased with increasing conspecific density. Similar relationships were found for juvenile growth, except that growth declined with increasing temperature. The slower growth of larvae and juveniles in Thomas Hill Lake was probably a consequence of their greater densities relative to their food abundance and higher water temperatures during the juvenile stage. Conversely, both larvae and juvenile gizzard shad grew more rapidly and juveniles attained large sizes in Long Branch Lake owing to their lower densities relative to their available food. Mortality of larvae and juveniles was mostly similar among the reservoirs. Because of their greater abundance and slower growth, gizzard shad were available as prey for white crappies for a longer period in Thomas Hill Lake than in the other reservoirs.

Dynamic coupling of near field and far field models for simulating effluent discharges

In many cases, (processed) wastewater or thermal effluents are discharged into the marine environment, rivers or lakes. To accurately determine the dispersion, recirculation and environmental impacts of outfall plumes, it is important to be able to model the different characteristics of the outfall plume in detail - from the near field (metres around the outfall) to the far field (up to kilometres away). The solution for engineering practice is to combine different types of models (near and far field models) that each focus on specific scales, with corresponding optimised resolutions and processes. However, to adequately describe the hydrodynamic processes on these different scales, it is essential to couple these models in a dynamic and comprehensive way. To achieve this, a dynamic coupling between the open-source Delft3D-FLOW far field model and the CORMIX near field expert system is proposed. This coupled modelling system is able to use the computed far field ambient conditions in the near field computations and, conversely, to use the initial near field dilution and mixing behaviour in the far field model. Preliminary results are presented to provide a first indication of the potential of the method for modelling the complete trajectory of effluent outfall plumes, allowing an accurate assessment of the environmental effects and the design of possible mitigating measures.

Modeling impacts of highly regulated inflow on thermal regime and water age in a shallow reservoir

Thermal regime and transport of dissolved pollutants, strongly related to water quality and algae bloom in reservoirs, may be quantized by indicators of water temperature and water age, respectively, and these indicators are more spatially and temporally variant in shallow reservoirs. Here, a two-dimensional model was used for studying characteristics of the indicators in Douhe Reservoir, based on data of the year 2008. Douhe Reservoir is a typical shallow reservoir in Northern China, characterized by highly regulated inflow and thermal effluent. The impacts of the regulated inflow on reservoir thermal regime and water age were then analyzed through numerical experiments. The results show that the effects of inflow are associated with the flow circulations induced by inflow, thermal effluent, and wind. The most efficient inflows for alleviating thermal pollution and improving water exchange are 32.5 and 19.5 m3/s, respectively. A positive logarithmic correlation is found between water temperature and water age under the impact of inflow, while thermal effluent and wind have a slightly negative effect on the correlation. These findings provide useful information for better understanding the complex hydrodynamic and mass transport processes in a shallow reservoir.

Integrated modelling of single port, steady-state thermal discharges in unstratified coastal waters

An integrated model is presented for the calculation of the discharge of thermal effluents from power plants into coastal waters; the model consists of the near field model CorJet and the far field model FLOW-3DL that are interconnected via an active coupling algorithm. Firstly, the model is validated using experimental data; moreover, calculations are compared with passive coupling simulations to identify the dominant differences among these methods. Then, the model is applied to simulate the single-port thermal discharge originating from a thermal power plant to the non-stratified coastal waters in the region of Mantoudi in Evia, Greece. Model predictions are compared with CORMIX far field estimations and calculations employing passive coupling. Calculations verify the need for the application of an integrated active model. The detailed information for the coupling algorithm that is contained in this paper, including its difficulties and their resolution, permits its implementation to any active coupling between practically any near field with any far field model.

Use of Human‐Altered Habitats by Bull Sharks in a Florida Nursery Area

AbstractBull Sharks Carcharhinus leucas in the Indian River Lagoon, Florida, have been documented to frequently occur in human‐altered habitats, including dredged creeks and channels, boat marinas, and power plant outfalls. The purpose of this study was to examine the short‐term movements of age‐0 and juvenile Bull Sharks to quantify the extent to which those movements occur in altered habitats. A total of 16 short‐term active acoustic tracks (2–26 h) were carried out with 9 individuals, and a 10th individual was fitted with a long‐term coded transmitter for passive monitoring by fixed listening stations. Movement and activity space statistics indicated high levels of area reuse over the span of tracking (hours to days). All but one shark usedaltered habitat at some point during tracking, such that 51% of all tracking positions occurred in some type of altered habitat. Of the sharks that used altered habitat, the mean (±1 SD) percent of positions within altered habitat was 66 (±40)%. Furthermore, tracks for 3 individuals indicated selection for altered habitats. The single passively monitored Bull Shark was detected in power plant outfalls almost daily over a 5‐month period, providing the first indication of longer‐term fidelity to thermal effluents. Use of one dredged creek was influenced by local salinity, the tracked sharks dispersing from the altered habitat when salinity declined. The affinity of young Bull Sharks to altered habitats in this system could help explain their reported accumulation of a variety of harmful contaminants, which could negatively affect their health and survival.Received July 27, 2012; accepted November 28, 2012

Response of fish-based metrics to anthropogenic pressures in temperate rocky reefs

The increasing degradation of marine ecosystems as a result of increasing impact caused by anthropogenic pressures, urges for well-founded knowledge to develop efficient tools to appraise the quality status of fish assemblages, as required by the “Marine Strategy Framework Directive”. This study analyzed the structural and functional response of rocky fish assemblages to several pressures on the Portuguese coast, i.e. fishing, sewage discharges, port activities and thermal effluent, by selecting fish-based metrics that best distinguished disturbed from control areas. One of the novel aspects of this research is the integrated assessment made through the analysis of several metrics representing numerous attributes of fish assemblages (namely diversity, abundance, trophic structure, mobility, resilience, habitat association, nursery function), which contrasts with the most commonly used approaches that in general focus on fish species/families. PERMANOVA results showed significant differences on metrics composition for all pressures with the exception of the thermal effluent. Moreover, two major patterns of stress were identified: (1) selective pressure, which affects differentially the fish assemblages (fishing); (2) broad-range pressure, which affects the entire fish assemblage with metrics of several attributes (e.g. structure, resilience, trophic guilds, nursery function) responding to its presence (sewage discharges, port activities). Taking into account the sensitivity results (discriminant analysis and Mann–Whitney test), biological meaning and redundancy with other metrics (Spearman correlations), the following metrics were selected as the most suitable to detect changes on temperate reef fish assemblages: “density of generalist individuals”, “density of territorial individuals”, “density of large individuals with medium to high commercial value (>20cm)”, “density of juveniles” and metrics relative to trophic guild (except zooplanktivores). Since metrics grouped species that have some degree of functional overlap, the present approach was useful to understand human-induced changes at the assemblage level, contributing for the future use of marine fishes as biological indicators.

Artificial Islands versus Natural Reefs: The Environmental Cost of Development in Dubai

While coral communities world-wide are currently threatened by a wide variety of factors, Persian Gulf corals are especially fragile due to human-caused factor sranging from oil spills, industrial thermal and substance effluents and military actions, as well as harsh environmental factors such as high salinity, extreme water temperatures and tidal action. In the United Arab Emirates, Dubai’s renowned real-estate boom has especially compromised formerly protected coral communities with the construction and development of the largest artificial islands in the world.Environmental protests have helped call attention to the tragedy, but much more proactive protection is necessary to ensure the survival and health of these endangered coral reef habitats.

Water temperature modeling in the Lower Ebro River (Spain): Heat fluxes, equilibrium temperature, and magnitude of alteration caused by reservoirs and thermal effluent

The lower Ebro River (Spain) is subject to the thermal and hydrological alterations caused by the system of reservoirs of Mequinenza, Riba‐roja, and Flix and to the thermal effluent of the nuclear power plant of Ascó, located 5 km downstream from the three reservoirs. In this paper, a modeling approach is used to determine the equilibrium temperature and recuperation distance at the study reach for different seasons and hydrological years. The intensity of the alteration caused by the reservoirs and nuclear power plant effluent is studied in reference to the equilibrium temperature and discharge rate. Mean daily water temperature downstream from the reservoirs is higher than mean daily equilibrium temperature in the fall and is lower during the rest of the year. Changes in the heat fluxes induced by thermal alteration are also addressed, showing important variations in evaporation and conduction to the atmosphere.

울진 주변 해역 대형저서동물 군집의 시·공간 분포와 환경요인과의 관계

Although thermal effluent from coastal power plants affects marine ecosystems, few studies have examined the spatiotemporal distribution of macrobenthic communities in a coastal area of Korea with thermal discharge. This study analyzed the species composition and abundance of a macrobenthic community in relation to environmental variables for a period of 1 year. In total 334 macrobenthic faunal species were collected; the mean density was 3,221 ind/㎡. The number of species and the density of macrobenthic fauna increased with distance from the thermal discharge site. Cluster analysis indicated that the macrobenthic community could be divided into two groups: group I in shallow (＞ 30 m deep) and group II in the outer areas (＞ 30 m deep). Group I showed the lowest species density and diversity. Four polychaetes, including Magelona japonica, Spiophanes bombyx, Scolotoma longifolia and Chaetozone setosa, all of which have been dominant species since 1987, exhibited higher mean densities in the area distant from the thermal discharge (the outer and north areas). Conversely, the warm-adapted and opportunistic species, such as the amphipods Urothoe convexa and Mandibulophoxus mai, the bivalve Felaniella sowerbyi, and the polychaete Rhynchospio sp., were more abundant in the thermal discharge region. The results of this study indicate that thermal effluent influences macrobenthic communities in the shallow area, while other environmental variables, such as depth, sediment grain size, and TOC, are more important determinants of the macrobenthic communities in deeper regions (＞ 30 m deep).

Histopathological changes in the gill architecture of Labeo rohita from the pond adjacent to thermal power station, Koradi, Nagpur, India

The hazardous effect of water pollution on the histopathology of selected organs of the freshwater fish Labeo rohita was studied with respect to thermal power plant effluent. The purpose of this research paper is to study whether the thermal plume can affect fish assemblages in the waters around the outlet area of the thermal power plant located at Koradi near Nagpur city. Both experimental and control fishes were monitored for a year from March 2010 to Feb. 2011. Histopathology serve as a tool to assess the extent of damage caused to the organism.Gill tissue showed fusion of primary lamellae, congestion of blood vessels and hyperplasia of bronchial plates. The histopathological changes in the gill tissue include epithelial hyperplasia, curling of secondary lamellae and changes in chloride cells. Besides these changes pyknotic nuclei, vacuolization, degradation of epithelial and pillar cells, were noticed, which point out towards deleterious effect of thermal power plant effluent on the freshwater fish L. rohita.

Environmental research on brine discharge optimization: A case study approach

Desalination plants constitute a new way of solving the shortage and degradation of Mediterranean hydric resources by providing a new source of water supply according to local demand, and, at the same time, being climatically independent. Since all desalination plants are located on the shoreline, environmental constraints have to do with water intake and sea outfall discharges. As for brine discharging, a wide range of case-study research is being carried out in order to solve technical uncertainties and provide our projects with preventive measures. The first of these case studies regards the prediction of brine discharge behaviour by using a reduced scale model to simulate the way it is likely to perform in a harbour. The second case-study deals with mixing brine with a thermal effluent in a pipeline to obtain a better dilution that might then minimize its impact on the area. The third case-study is aimed at protecting marine biodiversity by studying into the effects of salinity increase on the growth and survival of the seagrass Cymodocea nodosa.

Diatom to dinoflagellate shift in the summer phytoplankton community in a bay impacted by nuclear power plant thermal effluent

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 424:75-85 (2011) - DOI: https://doi.org/10.3354/meps08974 Diatom to dinoflagellate shift in the summer phytoplankton community in a bay impacted by nuclear power plant thermal effluent Tao Li1,2, Sheng Liu1,*, Liangmin Huang1, Hui Huang1,2, Jiansheng Lian1,3, Yan Yan1,3, Senjie Lin1,4 1Key Laboratory of Marine Bio-Resources Sustainable Utilization, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China 2Tropical Marine Biological Research Station in Hainan, Chinese Academy of Sciences, Sanya 572000, China 3Marine Biology Research Station at Daya Bay, Chinese Academy of Sciences, Shenzhen 518121, China 4Department of Marine Sciences, University of Connecticut, Groton, Connecticut 06340, USA *Corresponding author. Email: shliu@scsio.ac.cn ABSTRACT: Understanding how nuclear power plant thermal effluents influence the phytoplankton community may provide insights into the potential ecological consequences of global warming. In the present study, long-term trends in the phytoplankton community structure under the influence of nuclear power plant thermal effluent in the subtropical Daya Bay (DYB) in China were investigated in the summer season from 1982 to 2005. Water temperature at the outfall station was significantly higher than in the surrounding water, by as much as 5.6°C, and increased by 6.8°C during the 23 yr study period. The contribution of diatoms and dinoflagellates to the total phytoplankton showed significant correlation with temperature (R2 > 0.65), negative for diatoms, while positive for dinoflagellates. Although dinoflagellate abundance increased over time at both the outfall and adjacent (control) stations, the increase at the outfall station was much more dramatic and accelerated over time. No clear relationship between the phytoplankton shift and stratification was evident. When water temperature reached 35°C or >3.7°C above that at the control station, dinoflagellates, such as Ceratium furca, C. fusus, C. trichoceros, Dinophysis caudate and Protoperidinium depressum, grew to prominence, accounting for about 50% of the total phytoplankton abundance. On the contrary, the diatom contribution decreased during the study period, from 82.0% in 1982 to 53.1% in 2005. These results suggest that the rise in temperature caused by power plant thermal discharge has imposed strong influences on the phytoplankton community, favoring dinoflagellates over diatoms, with a remarkable diatom to dinoflagellate shift when temperature increases to a threshold level of 35°C or reaches a threshold differential of 3.7°C relative to the normal ambient temperature in DYB. KEY WORDS: Daya Bay · Nuclear power plant · Thermal effluent · Phytoplankton · Ecological effects Full text in pdf format PreviousNextCite this article as: Li T, Liu S, Huang L, Huang H, Lian J, Yan Y, Lin S (2011) Diatom to dinoflagellate shift in the summer phytoplankton community in a bay impacted by nuclear power plant thermal effluent. Mar Ecol Prog Ser 424:75-85. https://doi.org/10.3354/meps08974 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 424. Online publication date: March 01, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Synthesis, characterization and analytical applications of a new composite cation exchange material poly-o-toluidine stannic molybdate for the separation of toxic metal ions

A new composite cation exchange material poly-o-toluidine stannic molybdate was synthesized by the incorporation of an organic polymer poly-o-toluidine into the matrices of inorganic precipitate of stannic molybdate. The experimental parameters such as concentration, mixing ratio and pH were established for the synthesis of the material. The material was found to be granular and can be conveniently used in column operations. The newly synthesized composite material exhibits improved thermal stability, ion exchange capacity and selectivity for toxic heavy metal ions. The material is characterized using various analytical techniques like FTIR, TGA, DTA, XRD, SEM, TEM and elemental analysis. The X-ray diffraction study showed semicrystalline nature of the material. The pH titration studies revealed monofunctional weak acid behavior of the exchanger. The elution behavior of the exchanger was also examined. The distribution coefficient studies of metal ions on the material were performed in different solvent systems and the material was found to be selective for Hg 2+ and Pb 2+ ions. On the basis of distribution coefficient values, some analytically important binary separations of metal ions viz. Al 3+–Hg 2+, Cu 2+–Hg 2+, Cu 2+–Th 4+, Zn 2+–Hg 2+, Bi 3+–Hg 2+, Cd 2+–Pb 2+ were achieved on poly-o-toluidine stannic molybdate columns. Hg 2+ and Pb 2+ ions were also selectively separated from synthetic mixtures of metal ions. In order to demonstrate the practical utility of the material, quantitative separations of Hg 2+ from thermal power plant effluents and of Pb 2+ from lead storage battery industry wastes have been achieved.

발전소 온배수를 이용한 1MW급 폐쇄형 해양온도차발전 성능해석

발전소 온배수 및 폐열을 이용한 1 ㎿급 폐쇄형 해양온도차발전 사이클에 대한 성능을 비교 분석하였다. 폐쇄형 해양온도차발전 사이클에 대한 열역학적 모델은 랭킨 사이클이고, 기화기 증발 열원으로 발전소 온배수를 이용하여 사이클 효율, 기화기 및 응축기 열량 등 사이클 성능을 비교·분석하였다. 발전소 온배수 온도가 증가함에 따라 기화기 내 증발 포화압력은 상승하게 되고 그로 인해 사이클 효율은 증가하였고, 총 출력 1 ㎿에 필요한 기화기 및 응축기 용량은 감소하였다. 따라서 발전소 온배수는 폐쇄형 해양온도차발전에서 주요한 열원으로 사용될 수 있음을 알 수 있었다. 또한, 주위 이용 가능한 폐열이 있을 때 기화기 출구 작동유체와 열교환시켜 터빈으로 유입되는 작동유체의 온도를 상승시킨다면 사이클 효율은 크게 증가할 것이다.

Temporal variability in the thermal regime of the lower Ebro River (Spain) and alteration due to anthropogenic factors

Summary The Ebro River is one of the longest rivers in Spain and it also has the greatest discharge. Its lower part is highly regulated and includes a system of three reservoirs (Mequinensa, Riba-roja and Flix). The water temperature is altered because of the release of hypolimnetic water and the use of water for cooling at the Asco nuclear power plant. The thermal regime of the lower Ebro River on different time scales and the changes caused by anthropogenic factors, especially the system of reservoirs and the thermal effluent of the nuclear power plant, have been studied by installing a net of water temperature measuring stations and by using historical water temperature data provided by the thermal power plant at Escatron. An increase of 2.3 °C in the mean annual water temperature could be demonstrated in the period 1955–2000 at this site. The effects of the system of reservoirs and of the nuclear power plant were the usual for this kind of structures and could be detected many kilometres downstream. In the summer, the cooling effect of the reservoirs and the warming effect of the nuclear power plant compensated each other. In winter, the warming effect of both summed up.

Effects of thermal power station effluent on the seagrass benthic communities of Lake Macquarie, a New South Wales coastal lagoon.

The structure of seagrass macrofauna communities in the path of the outfall of Vales Point Power Station, Lake Macquarie, NSW, was assessed between July 1977 and April 1980 and related to distance from the outfall. During the first part of the study (power station generating capacity of 875 mW) major differences were shown in the structure of the site adjacent to the outfall when compared with controls. These included fewer species (especially large filter feeding bivalves), more individuals (particularly grazing gastropods) and different seagrass types. There were also slight differences in other sited within the thermal plume. The expansion of the generating capacity of the power station to 2195 mW resulted in a greater reduction in species number and individuals and total loss of seagrass adjacent to the outfall. Other areas within the plume underwent a change in seagrass type, a reduction in species numbers (especially filter feeding bivalves) and an increase in the numbers of grazing gastropods. Control sites remained unchanged. The possible role of various factors in determining community structure is discussed.

Threats and human influence on coastal ecosystem of Southern India

Populations of the majority of fish species showed drastic reduction over the past five decades in west coast of India. We conducted an intensive study of Aghanashini estuary for water quality and fish diversity in west coast of India. Coastal ecosystems are impacted by many stressors and are continually subjected to threats from multiple stresses imposed mostly by human activities predominantly as a result of increased population growth in India. The most significant categories of threats derive from water pollution from numerous sources including thermal effluents, heavy metals, oil, sewage, pesticides, pulp mills, habitat loss and degradation, overexploitation, eutrophication and misguided human perceptions. Wide array of prohibited fishing methods are rampant by using of insecticides as poisons, destruction and modification of habitats, dynamiting, using chemical and herbal poisons. Due to deteriorated water, quality from anthropogenic activities fish diversity has drastically reduced. In complex coastal ecosystems, strategies for restoration can become equally complicated.

Determination of an Empirical Transfer Function of a Solid Oxide Fuel Cell Gas Turbine Hybrid System Via Frequency Response Analysis

This paper presents the study of the effect variations in the heat effluence from a solid oxide fuel cell (SOFC) has on a gas turbine hybrid configuration. The SOFC is simulated through hardware at the U.S. Department of Energy, National Energy Technology Laboratory (NETL). The gas turbine, compressor, recuperative heat exchanger, and other balance of plant components are represented by actual hardware in the Hybrid Performance Test Facility at NETL. Fuel cell heat exhaust is represented by a combustor that is activated by a fuel cell model that computes energy release for various sensed system states System structure is derived by means of frequency response data generated by the sinusoidal oscillation of the combustor fuel valve over a range of frequencies covering three orders of magnitude. System delay and order are obtained from Bode plots of the magnitude and phase relationships between input and output parameters. Transfer functions for mass flow, temperature, pressure, and other states of interest are derived as a function of fuel valve flow, representative of fuel cell thermal effluent. The Bode plots can validate existing analytical transfer functions, provide steady state error detection, give a stability margin criterion for the fuel valve input, estimate system bandwidth, identify any nonminimum phase system behavior, pinpoint unstable frequencies, and serve as an element of a piecewise transfer function in the development of an overall transfer function matrix covering all system inputs and outputs of interest. Further loop shaping techniques and state space representation can be applied to this matrix in a multivariate control algorithm.

Cold shock and fish

Rapid decreases in water temperature may result in a number of physiological, behavioural and fitness consequences for fishes termed ‘cold shock’. Cold‐shock stress occurs when a fish has been acclimated to a specific water temperature or range of temperatures and is subsequently exposed to a rapid decrease in temperature, resulting in a cascade of physiological and behavioural responses and, in some cases, death. Rapid temperature decreases may occur from either natural (e.g. thermocline temperature variation, seiches and storm events) or anthropogenic sources (e.g. varied thermal effluents from power generation and production industries). The magnitude, duration and frequency of the temperature change as well as the initial acclimation temperatures of individuals can influence the extent of the consequences of cold shock on fishes. Early research on cold shock focused on documenting mortality events associated with cold shock. However, in recent years, a shift in research has occurred where the focus of cold‐shock studies now involves characterizing the sublethal effects of cold shock in terms of the stress response in fishes. This shift has revealed that cold shock can actually be used as a tool for fisheries science (e.g. to induce polyploidy). The cold‐shock stress response offers opportunities to develop many exciting research questions, yet to date, cold‐shock research has been largely unfocused. Few studies attempt to link laboratory physiology experiments with ecologically relevant field data on behaviour, growth, bioenergetics and fitness. Additional research will allow for the development of more focused and robust management policies and conservation initiatives. This review synthesizes the sublethal physiological and behavioural consequences of cold‐shock stress on fishes, identifies natural and anthropogenic sources of cold shock, discusses the benefits of cold shock to fisheries science and describes mitigation and management efforts. Existing knowledge gaps and opportunities for future cold‐shock research are presented.

Sulfur hexafluoride as a complementary method for measuring the extent of point-source thermal effluents

The transport and dilution dynamics of power-plant thermal effluent were measured for 10 consecutive days, between 25 June and 4 July 2006, by concurrently mapping the daily distributions of seawater temperature and concentrations of deliberately released sulfur hexafluoride (SF6) within the tidal Kwangyang Bay on the southern coast of Korea. Estimates of the daily extent of the thermal plume based on temperature and SF6 data showed distinct differences. These differences were particularly pronounced on sunny days during which solar radiation significantly heated river or bay waters moving across the tidal flats; in these cases, the estimates based on seawater temperature data were consistently greater than those based on SF6 data, indicating considerable overestimates of the extent of the thermal plume when temperature data were used. The present results indicate that the concurrent use of seawater temperature and SF6 data is a powerful method in determining the extent of thermal plumes, particularly for shallow areas in which the effects of solar heating lead to large uncertainties in temperature-based estimates.