Reduction In Water Temperature Research Articles

Quantifying the impacts of the Three Gorges Reservoir on water temperature in the middle reach of the Yangtze River

The flow, sediment and temperature regimes of the Yangtze River have changed greatly due to the construction of the Three Gorges Reservoir (TGR). Although past work has focused mainly on the influence of the TGR on water and sediment regimes, less attention has been given to temperature effects. Water temperature changes have important implications for the quality of aquatic habitat and the health of the river ecosystem. This study investigates the impact of the TGR on the water temperature regime along the middle reach of the Yangtze River. To accurately quantify the impact of TGR on water temperature, a regression-modeling framework is employed to reconstruct the temporal pattern of flow and temperature variation along the middle reach of the river in the absence of the TGR. Based on this modeling, reconstructed water temperatures are compared to observed water temperature for the post-impounded period (period 2003–2014) to estimate the influence of impoundment on water temperature. Results show that the influence of the TGR on water temperature alteration exceeds the influence of natural factors. The effect of TGR, relative to unimpounded conditions, is to reduce water temperatures in the spring, summer, and autumn, and to increase water temperatures in the winter. The results of this study illustrate the pronounced effect of the TGR on the temperature regime of the Yangtze River and provide information that can help guide operation of Three Gorges Reservoir to enhance biological conservation.

Physical mechanisms influencing localized patterns of temperature variability and coral bleaching within a system of reef atolls

Interactions between oceanic and atmospheric processes within coral reefs can significantly alter local-scale (< km) water temperatures, and consequently drive variations in heat stress and bleaching severity. The Scott Reef atoll system was one of many reefs affected by the 2015–2016 mass coral bleaching event across tropical Australia, and specifically experienced sea surface temperature anomalies of 2 °C that caused severe mass bleaching (> 60%) over most of this system; however, the bleaching patterns were not uniform. Little is known about the processes governing thermodynamic variability within atolls, particularly those that are dominated by large amplitude tides. Here, we identify three mechanisms at Scott Reef that alleviated heat stress during the marine heatwave in 2016: (1) the cool wake of a tropical cyclone that induced temperature drops of 1.3 °C over a period of 8 days; (2) air–sea heat fluxes that interacted with the reef morphology during neap tides at one of the atolls to reduce water temperatures by up to 2.9 °C; (3) internal tidal processes that forced deeper and cooler water (up to 2.7 °C) into some sections of the shallow reefs. The latter two processes created localized areas of reduced temperatures that led to lower incidences of coral bleaching for parts of the reef. We predict these processes are likely to occur in other similar tide-dominated reef environments worldwide. Identifying locations where physical processes reduce heat stress will likely be critical for coral reefs in the future, by maintaining communities that can help facilitate local recovery of reefs following bleaching events that are expected to increase in frequency and severity in the coming decades.

Boundary identification between LBLOCA and SBLOCA based on stratification and temperature gradient in two-phase PTS

Temperature gradient on the thick Reactor Pressure Vessel (RPV), caused by sudden overcooling events, especially in the downcomer, would intensify the propagation of structural defects. This situation known as Pressurized Thermal Shock (PTS) could be created in case of Emergency Core Cooling System (ECCS) actuation which leads to injection of cold water into the cold leg of the primary loop in some accidents, e.g. Loss Of Coolant Accident (LOCA). Prediction of Plant response to LOCA and water temperature gradient in the downcomer are performed in thermal-hydraulic section of PTS analysis. Employment of system codes is one of the proposed procedures in literature to obtain plant response and flow condition in the cold leg during LOCA. Also the results of these codes would be used to find the flow regime in the cold leg with some limitations. In this paper simulation of different break sizes in Bushehr Nuclear Power Plant as VVER-1000 reactor is performed by RELAP system code to find the temperature gradient and flow regime in the cold leg according to different criteria. Due to some limitations of system codes, CFX code is employed to evaluate turbulence characteristics at the interface for identification of flow regime. The comparison between results of different LOCA scenarios reveals a sharp reduction of water temperature in downcomer for large breaks which would be used for classification of LOCA. Also the flow regime in the cold leg during ECCS injection changes from stable stratified flow to wavy flow when the break size increases beyond a certain value. Therefore, the difference of temperature gradient in downcomer and flow regime in cold leg will be proposed as a new definition of Small Break LOCA (SBLOCA) and Large Break LOCA (LBLOCA) relevant to PTS analysis.

Can riparian vegetation shade mitigate the expected rise in stream temperatures due to climate change during heat waves in a human-impacted pre-alpine river?

Abstract. Global warming has already affected European rivers and their aquatic biota, and climate models predict an increase of temperature in central Europe over all seasons. We simulated the influence of expected changes in heat wave intensity during the 21st century on water temperatures of a heavily impacted pre-alpine Austrian river and analysed future mitigating effects of riparian vegetation shade on radiant and turbulent energy fluxes using the deterministic Heat Source model. Modelled stream water temperature increased less than 1.5 ∘C within the first half of the century. Until 2100, a more significant increase of around 3 ∘C in minimum, maximum and mean stream temperatures was predicted for a 20-year return period heat event. The result showed clearly that in a highly altered river system riparian vegetation was not able to fully mitigate the predicted temperature rise caused by climate change but would be able to reduce water temperature by 1 to 2 ∘C. The removal of riparian vegetation amplified stream temperature increases. Maximum stream temperatures could increase by more than 4 ∘C even in annual heat events. Such a dramatic water temperature shift of some degrees, especially in summer, would indicate a total shift of aquatic biodiversity. The results demonstrate that effective river restoration and mitigation require re-establishing riparian vegetation and emphasize the importance of land–water interfaces and their ecological functioning in aquatic environments.

Numerical simulation of single-nozzle large scale spray cooling on drum wall

In this work the single-nozzle spray cooling on a large scale industry-used drum wall has been simulated by a verified numerical model. For a certain spray nozzle, the effects of four parameters, i. e. different spray pressures, different spray heights, different water temperatures, and different wall temperatures, on heat transfer have been analyzed. It is found that the mean heat flux distributions show concentric elliptical circles. Increasing spray pressures will enhance the cooling performance. Decreasing spray heights will improve the heat flux in direct spray areas other than whole simulated drum wall. As expected, reducing water temperature or advancing wall temperature will raise the average wall flux. Both relationships are exponential. The influencing degrees of the four parameters have been compared through Taguchi orthogonal experimental method and the result is: wall temperature > spray pressure > water temperature > spray height. The wall temperature, spray pressure, and water temperature show dominant effects except for the spray height.

Core Temperature Responses to Cold-Water Immersion Recovery: A Pooled-Data Analysis.

To examine the effect of postexercise cold-water immersion (CWI) protocols, compared with control (CON), on the magnitude and time course of core temperature (Tc) responses. Pooled-data analyses were used to examine the Tc responses of 157 subjects from previous postexercise CWI trials in the authors' laboratories. CWI protocols varied with different combinations of temperature, duration, immersion depth, and mode (continuous vs intermittent). Tc was examined as a double difference (ΔΔTc), calculated as the change in Tc in CWI condition minus the corresponding change in CON. The effect of CWI on ΔΔTc was assessed using separate linear mixed models across 2 time components (component 1, immersion; component 2, postintervention). Intermittent CWI resulted in a mean decrease in ΔΔTc that was 0.25°C (0.10°C) (estimate [SE]) greater than continuous CWI during the immersion component (P = .02). There was a significant effect of CWI temperature during the immersion component (P = .05), where reductions in water temperature of 1°C resulted in decreases in ΔΔTc of 0.03°C (0.01°C). Similarly, the effect of CWI duration was significant during the immersion component (P = .01), where every 1min of immersion resulted in a decrease in ΔΔTc of 0.02°C (0.01°C). The peak difference in Tc between the CWI and CON interventions during the postimmersion component occurred at 60 min postintervention. Variations in CWI mode, duration, and temperature may have a significant effect on the extent of change in Tc. Careful consideration should be given to determine the optimal amount of core cooling before deciding which combination of protocol factors to prescribe.

Thermal hydraulic design and analysis of Thorium-based Advanced CANDU Reactor (TACR)

The application of thorium fuel in advanced CANDU (CANadian Deuterium Uranium) reactors is an economic solution to sustainable development of nuclear energy. In this paper, the thermal hydraulic design and transient analysis of Thorium-based Advanced CANDU Reactor (TACR) heat transport system are conducted using self-programmed code CANTHAC (CANDU Thermal Hydraulic Analysis Code). In the code CANTHAC, the single channel model and the point kinetics model are adopted to simulate the core thermal hydraulic and neutronic behaviors. A distributed parameter model is adopted in the simulation of integral economizer U-tube steam generator (IEUTSG). Multi-region non-equilibrium model is applied to simulate the pressurizer. The characteristics of heat transport pumps were simulated by four-quadrant analogy curves. The code is verified with ACR-700 steady-state analysis. The calculation results agreed well with ACR-700 design values and the relative errors are all within 2%. With CANTHAC steady-state module, the preliminary thermal hydraulic design of TACR is conducted. A 1000MW double loop reactor with 520 fuel channels is designed. Single loop mass flow rate was designed to be 3202kg/s. Under the design scheme, the maximum cladding temperature and the maximum temperature are 340.2°C and 1369.9°C, which satisfied the design requirements. The transient analysis of TACR heat transport system was performed with CANTHAC transient module. SG feed water temperature reduction accident, and complete loss of Class IV accident were conducted. In the SG feed water temperature reduction accident, a new balance of neutron and thermal hydraulic is reached and the core power increases by 5% at last. In the complete loss of Class IV accident, the maximum fuel temperature reaches peak value at 1172°C and still has some safety margin. The ROH (Reactor Outlet Header) pressure does not exceed 105% of the design value, which meet the safety criterion demand.

Seasonal aquatic macrophytes reduce water temperatures via a riverine canopy in a spring-fed stream

AbstractMaximum water temperatures in streams throughout the western USA typically occur in late summer and early autumn, coinciding with low stream flow. However, in the spring-fed Big Springs Creek in northern California, where constant-temperature groundwater springs provide relatively stable stream flow throughout the year, peak water temperatures and maximum diurnal variability occur in spring. We attribute this anomaly to the riverine canopy provided by emergent aquatic macrophytes (e.g., Polygonum hydropiperoides and Nasturtium officinale), which mimics the shade function of a riparian canopy. Macrophyte biomass increased 264% between January and August 2011. This increase coincided with a 111% reduction in flow velocity and a 53% increase in stream depth. Solar radiation was reduced by an average of 88% in patches of macrophytes that covered ~50% of the water surface during the summer. Decreased solar radiation reduced rates of stream heating, maximum temperatures, and temperature variability. We ...

The impacts of reduced water temperature on gizzard shad production in two Missouri River Reservoirs during a historic flood

The impacts of reduced water temperature on gizzard shad production in two Missouri River Reservoirs during a historic flood

Sanitary evaluation of domestic water supply facilities with storage tanks and detection of Aeromonas, enteric and related bacteria in domestic water facilities in Okinawa Prefecture of Japan

To provide for temporary restrictions of the public water supply system, storage tanks are commonly installed in the domestic water systems of houses and apartment buildings in Okinawa Prefecture of Japan. To learn more about the sanitary condition and management of these water supply facilities with storage tanks (hereafter called “storage tank water systems”) and the extent of bacterial contamination of water from these facilities, we investigated their usage and the existence of Aeromonas, enteric and related bacteria.Verbal interviews concerning the use and management of the storage tank water systems were carried out in each randomly sampled household. A total of 54 water samples were collected for bacteriological and physicochemical examinations. Conventional methods were used for total viable count, fecal coliforms, identification of bacteria such as Aeromonas, Enterobacteriaceae and non-fermentative Gram-negative rods (NF-GNR), and measurement of residual chlorine. On Aeromonas species, tests for putative virulence factor and an identification using 16S rRNA and rpoB genes were also performed.Water from the water storage systems was reported to be consumed directly without boiling in 22 of the 54 houses (40.7%). 31 of the sampled houses had installed water storage tanks of more than 1 cubic meter (m3) per inhabitant, and in 21 of the sampled houses, the tank had never been cleaned. In all samples, the total viable count and fecal coliforms did not exceed quality levels prescribed by Japanese waterworks law. Although the quantity of bacteria detected was not high, 23 NF-GNR, 14 Enterobacteriaceae and 5 Aeromonas were isolated in 42.6%, 7.4% and 3.7% of samples respectively. One isolated A. hydrophila and four A. caviae possessed various putative virulence factors, especially A. hydrophila which had diverse putative pathogenic genes such as aer, hlyA, act, alt, ast, ser, and dam. Many bacteria were isolated when the concentration of residual chlorine was below 0.1 mg/l and the water temperature was above 20 °C. These results suggest that elevated water temperature and mismatch between tank size and water demand lead to loss of residual chlorine in tap water. Therefore, to minimize growth of aquatic bacteria such as Aeromonas spp. and Pseudomonas spp., we recommend that an appropriate size tank and/or volume of stored water is always used, and also suggest installation of some means of reducing water temperature such as shading.

A behavioural sensor for fish stress

Due to water turbidity, fish stress might be difficult to observe. Evaluation of fish stress by blood sampling requires removing a fish from the water, which is in itself a stressful event. Therefore, we designed and built a sensor to detect fish behaviour that reflects stress. The electronic sensor detected early signs of fish stress by scoring the fish's inactivity. LEDs and detectors are embedded on a steel wand that is held underwater by an operator. In this preliminary (feasibility) study, the new sensor was validated for Tilapia (Cichlidae) and Hybrid Striped Bass (Morone). We induced stressful situations in the fish tanks by manipulating oxygen and temperature levels. ResultsLowering the temperature and oxygen levels both significantly increased the average number of signals identified by the sensor, which indicate stress. The effect of reducing water temperature from 24°C to 15°C was three times stronger than was the effect of lowering the oxygen saturation level from 85% to 50%. The difference in the number of signals between the good and stressful conditions was statistically significant, amounting to approximately eight sensor signals, 10.57 compared to 2.49 respectively. Lowering the temperature increased the mean number of signals by 5.85 and 6.06 at 85% and 50% oxygen saturation respectively, whereas lowering oxygen levels increased the mean number of signals by 2.02 and 2.23 at 24°C and 15°C, respectively. The results indicate that the stress status of cultured fish can be evaluated using the proposed behavioural sensor. The new sensor may provide an earlier indication of a problem in a fish tank or pond than was heretofore possible. This early warning can enable the fish farmer to take action before many fish are harmed.

Legacies of stream channel modification revealed using General Land Office surveys,with implications for water temperature and aquatic life

Land use legacies can have a discernible influence in present-day watersheds and should be accounted for when designing conservation strategies for riverine aquatic life. We describe the environmental history of three watersheds within the Grande Ronde subbasin of the Columbia River using General Land Office survey field notes from the 19th century. In the two watersheds severely impacted by Euro-American land use, stream channel widths—a metric representing habitat simplification—increased from an average historical width of 16.8 m to an average present width of 20.8 m in large streams; 4.3 m to 5.5 m in small, confined or partly confined streams; and 3.5 m to 6.5 m in small, laterally unconfined steams. Conversely, we did not detect significant change in stream widths in an adjacent, wilderness stream with minimal human impact. Using a mechanistic water temperature model and restoration scenarios based on the historical condition, we predicted that stream restoration in the impacted watersheds could notably decrease average water temperatures—especially when channel narrowing is coupled with riparian restoration—up to a 6.6°C reduction in the upper Grande Ronde River and 3.0°C in Catherine Creek. These reductions in water temperature translated to substantial changes in the percentage of stream network habitable to salmon and steelhead migration (from 29% in the present condition to 79% in the fully restored scenario) and to core juvenile rearing (from 13% in the present condition to 36% in the fully restored scenario). We conclude that land use legacies leave an important footprint on the present landscape and are critical for understanding historic habitat-forming processes as a necessary first step towards restoration.

Use of guide vanes for improvement of flow pattern and enhancement of thermal performance of dry cooling towers

Environmental factors, such as cross winds, adversely affect the performance of a dry cooling tower. In this field study, use of a guide vanes cascade for improvement of thermal performance of a dry cooling tower has been investigated. A four-vane cascade was installed at a delta in a critical sector of the cooling tower and effects on flow pattern through the delta and subsequent enhancement of thermal performance of the radiators in the delta were evaluated. Results show that the use of guide vanes cascade at the delta eliminates the vortex shape flow conditions at the delta inlet, improves flow rate through the deltas by about 35% and reduces the average temperature distribution on the radiators surfaces by about 1.9 °C, which is the equivalent to the amount of reduction in water temperature at the radiators outlet. The results further show that the use of guide vanes cascades in all the affected deltas in the critical sectors would result in a 7% increase in the overall thermal performance of the investigated cooling tower.

Long wash cycle duration as a potential for saving energy in laundry washing

Reducing water temperatures in the wash phase of a washing programme and increasing the overall cycle durations are the latest trends in decreasing energy consumption of washing programmes, particularly for the so-called Standard programmes. This paper discusses the importance of saving energy in laundry washing, reasonable cycle duration for consumers and the link between saving energy and the duration of the wash cycle from a consumer point of view. This enables manufacturers to design appliances which are appreciated by the users. Information on consumers’ washing behaviour, experiences, habits and opinions concerning wash cycle duration was collected through a semi-representative survey in 11 European countries in 2015, with more than 5000 participants. The primary outcome of the study is that European consumers are willing to save water and energy in a laundry washing but are reluctant to use long programme cycles since they do not believe that the long cycles could be energy-saving.

Typha invasion associated with reduced aquatic macroinvertebrate abundance in northern Lake Huron coastal wetlands

Abstract Aquatic macroinvertebrates are a critical component of wetland nutrient cycling and food webs, with many fish and wildlife species depending upon them as food resources; but little is known about how invasion by dominant macrophytes may alter community dynamics. We examined the impacts of Typha invasion on aquatic macroinvertebrate communities in three northern Great Lakes coastal wetlands by comparing community composition between stands of native emergent marsh and those dominated by invasive Typha . Typha invaded zones were associated with shallower and cooler water than native emergent zones, and we detected decreased aquatic macroinvertebrate density and biomass in invaded zones. After accounting for the positive effect of plant species richness on macroinvertebrate abundance, we observed Typha invaded coastal zones had less total macroinvertebrate and insect biomass than native zones across all levels of plant richness. Our results suggest that Typha invasion reduces habitat quality for aquatic macroinvertebrates by homogenizing structural diversity and reducing water temperatures, which in turn may negatively impact predatory organisms by decreasing food resources. We recommend experimental tests of Typha management treatments to identify techniques that may promote structurally diverse and biologically rich Great Lakes coastal wetlands.

Understanding the Thermal Regime of Rivers Influenced by Small and Medium Size Dams in Eastern Canada

Although small and medium-size dams are prevalent in North America, few studies have described their year-round impacts on the thermal regime of rivers. The objective of this study was to quantify the impacts of two types of dams (run-of-river, storage with shallow reservoirs) on the thermal regime of rivers in eastern Canada. Thermal impacts of dams were assessed (i) for the open water period by evaluating their influence on the annual cycle in daily mean water temperature and residual variability and (ii) for the ice-covered winter period by evaluating their influence on water temperature duration curves. Overall, results showed that the run-of-river dam (with limited storage capacity) did not have a significant effect on the thermal regime of the regulated river. At the two rivers regulated by storage dams with shallow reservoirs (mean depth < 6 m), the annual cycle in daily mean water temperature was significantly modified which led to warmer water temperatures in summer and autumn. From August to October, the monthly mean water temperature at rivers regulated by storage dams was 1.4 to 3.9°C warmer than at their respective reference sites. During the open water period, the two storage dams also reduced water temperature variability at a daily timescale while increased variability was observed in regulated rivers during the winter. Storage dams also had a warming effect during the winter and the winter median water temperature ranged between 1.0 and 2.1°C downstream of the two storage dams whereas water temperature remained stable and close to 0°C in unregulated rivers. The biological implications of the altered thermal regimes at rivers regulated by storage dams are discussed, in particular for salmonids. Copyright © 2016 John Wiley & Sons, Ltd.

Propagation of Hybrid Devils Hole Pupfish × Ash Meadows Amargosa Pupfish

AbstractRecent censuses of Devils Hole Pupfish Cyprinodon diabolis revealed that fewer than 100 individuals currently remain in the wild. Captive propagation is among actions being considered to prevent their extinction, but no pure‐strain Devils Hole Pupfish were available for broodstock. To help provide emergency information, we investigated techniques to propagate their most closely related relative, hybrid Devils Hole Pupfish C. diabolis × Ash Meadows Amargosa Pupfish C. nevadensis mionectes. We tested various temperatures and larval feeds with respect to egg production, larval survival, and growth. Larval survival and growth were similar from 24°C to 32°C and egg production peaked at static 28°C; however, reducing water temperatures to 23°C and then raising them to 28°C resulted in even higher production. Larvae fed infusoria, Rio Grande Silvery Minnow Chow (RGSM), or Zeigler larval diet (ZLD) had the highest survival (79.4, 71.6, and 73.4%, respectively), and those fed Otohime (OTO) had the lowest survival (60.8%), although OTO provided greatest (14 mm) 30‐d growth. Supplementation of RGSM or ZLD with Artemia nauplii increased growth but decreased survival. Larval production was maximized by placing six spawning mops, constructed of yarn and tile, in each of four 437‐L parental aquaria, stocked with 24 adult fish each (1:1 sex ratio) for 3 d, to attract adults and provide spawning substrate. A 30% water change conducted on the same day of mop placement lowered water temperature from 28°C to 23°C. Water temperature was raised back to 28°C over 48 h. After 3 d, mops were transferred to hatching aquaria that were held at 28°C and aerated until larval hatch. Although some differences likely exist in effective propagation techniques for hybrid and pure‐strain Devils Hole Pupfish, these data help provide initial recommendations to aid recovery.

Morphofunctional changes of phytoplankton community during pluvial anomaly in a tropical reservoir.

The present study focuses on the structure and function of phytoplankton community during periods of marked changes in hydrological traits, influenced by an atypical climatic event (La Niña) and its impact on Armando Ribeiro Gonçalves Reservoir of Rio Grande do Norte, situated in the Caatinga biome of northeastern Brazil. The main questions addressed were: What are the effects of environmental factors on the temporal variation of Morphologically Based Functional Group (MBFG) of phytoplankton community? How does the composition of cyanobacterial species shift in relation to high and low trends of phytoplankton diversity? The samples were collected monthly during 2008-2009 and analyzed for pH, temperature, electrical conductivity, dissolved oxygen content and the nutrients, such as, nitrate-nitrogen, ammoniacal nitrogen, total nitrogen and orthophosphate. Phytoplankton samples were collected for both qualitative and quantitative analyses to evaluate species richness index and species diversity index. The data was divided into two distinct hydrodynamic periods of instability and stability. The results demonstrate considerable changes in dissolved oxygen content, water transparency and nitrogen nutrients, which directly influenced the MBFG of phytoplankton community in space and time. The instability of reservoir water was caused by heavy rainfall, which exerts atypical external disturbances. The seasonal variation of MBFG demonstrates a change in cyanobacterial composition and their diversity during instability and stability periods. MBFG VII, composed by colonial cyanobacteria with mucilage, was associated with reduced values of electrical conductance and alterations in pH. The predominance of filamentous species with heterocyst (MBFG III) occurs only during the hydrodynamic stability period and did not show significant association with analyzed parameters. The co-dominance of MBGFs III, V and VII along with high species diversity of phytoplankton community occurred during the second hydrodynamic instability period which was associated with the reduction in water temperature. It is concluded that the decrease in cyanobacterial species dominance and the general increase in the diversity of phytoplankton community are influenced by pluvial anomaly. The higher water level during the period of pluvial anomaly resulted in nutrient pulse and the mixing of water column in the reservoir, which determined the MBPG phytoplankton community distribution.

Sedimentary cladoceran assemblages and their functional attributes record late Holocene climate variability in southern Finland

We examined long-term relationships between Cladocera and limnogeological and climate variables in a late Holocene lake sediment sequence to assess cladoceran responses to climate change and reconstruct past climate variations in southern Finland, near the Baltic Sea coast. Elemental composition, organic matter, and inferred water quality variables were used to constrain paleoenvironmental (until 4500 cal BP) conditions and human impact. Fossil Cladocera assemblages, ephippia, and body size trends were utilized to estimate mean July air temperature (TJul) variability, open-water season length, and water-temperature regimes. Results revealed stable cladoceran communities, dominated by Eubosmina, until 500 cal BP, followed by major assemblage changes including increases in Chydorus cf. sphaericus, Alonella spp., and Bosmina longirostris. Pb and Cu concentrations were associated temporally with increasing human impact and warming climate during the past few centuries, and were the most significant factors in explaining cladoceran community changes, based on redundancy analysis. A Cladocera-based TJul reconstruction estimated elevated temperatures for the end of the Holocene Thermal Maximum, a cooler period during ~3000–2000 cal BP, slightly increased temperatures during 1200–800 cal BP corresponding to the Medieval Climate Anomaly (MCA), and lower temperatures during the Little Ice Age (LIA), 800–200 cal BP. The reconstruction also suggests that significant climate warming took place during the twentieth century. Cladocerans mostly associated with warm periods included B. longirostris and Pleuroxus uncinatus, whereas Alona affinis, A. quadrangularis, and C. cf. sphaericus were associated with colder climate. Compared to a reference Chironomidae-inferred TJul reconstruction from the same region, discrepancies were apparent in amplitude of temperature change, as the temperature variability in the cladoceran-based record was muted until ~200 cal BP. During the LIA, increased ephippia and body size agreed with the temperature reconstruction, but suggested a severely shorter open-water season and reduced water temperatures compared to the preceding late Holocene episodes, even though the cladoceran TJul showed quite similar temperatures for these periods. Our results suggest that fossil cladoceran assemblages, ephippia, and morphological attributes respond sensitively to long-term climate fluctuations and this record reflects well the major climate events of the late Holocene and provides realistic paleoclimatic estimates for maritime southern Finland.

Cortisol and glucose responses in juvenile striped catfish subjected to a cold shock

Cold-shock stress happens when a fish had been adjusted to a specific water temperature or range of temperatures and is consequently exposed to a rapid drop in temperature, resulting in a cascade of physiological and behavioral responses and, in some cases, death. In the current study, the stress response of striped Catfish (Pangasianodon hypophthalmus) was studied by evaluating serum cortisol and glucose level following an abrupt reduction in water temperature (from 28°C to 15°C) at different time points (prior to, and after 1h, 12h and 24h cold treatment, respectively). Regardless of some mortality occurred in cold challenged fish, none of the physiological parameters changed during evaluation period. The results, suggesting that despite of necessity of cortisol and glucose evaluation in any of stress assessment, yet, due to their high variability in different fish species, additional complementary tests such as measurement of other stress hormones e.g. heat shock proteins as well as blood-cell counts (preferably in chronic experiments) should also be included.