Reduction In Water Temperature Research Articles

The Effects of a Fishery Complementary Photovoltaic Power Plant on the Near-Surface Meteorology and Water Quality of Coastal Aquaculture Ponds

To date, most studies focus on the ecological and environmental effects of land-based photovoltaic (PV) power plants, while there is a dearth of studies examining the impacts of water-based PV power plants. The effects of a fishery complementary PV power plant, a kind of water-based PV technology, on the near-surface meteorology and aquaculture water environment were investigated in coastal aquaculture ponds in southeast China. The results showed that PV prevented 89~93% of the solar radiation on the surface of the pond, resulting in an average reduction in water temperature of 1.5 °C and a substantial decrease in light intensity of 94%. Furthermore, it weakened the wind speed by 41~50% and elevated the surface air temperature by an average of 0.6 °C. In addition, PV power results in an impressive decrease in chlorophyll-α of 72~94% and a notable increase in dissolved oxygen (DO) concentrations of 8~24%. PV power also reduced the concentration of labile phosphate, active silicate, total nitrogen, total phosphorus, and total organic carbon. However, the PV power did not have a substantial influence on the concentrations of nitrate and ammonium. Our results highlight that fishery complementary PV power plants may be able to improve water quality and benefit shade-loving species.

Plane heating with a transparent heater film in a fish tank

The water temperature in a fish tank is important for fish health. A conventional aquarium heater produces localized heating that causes water temperature variation, resulting in thermal stress to fish. This study presents plane heating with a transparent heater film that is aesthetically attractive when applied to fish tanks. The transparent heater film comprises a metal mesh with an optical transparency of 81 %, sheet resistance of 0.6 Ω/□, and mean heating surface temperature of 57 °C at 20 W. In the test setup, 100 W is applied to compare an aquarium heater and a transparent heater film. Increasing the water temperature from 23 °C to 24 °C at the center of the fish tank needs 28 min with the transparent heater film operating at 33 °C, whereas the same temperature increase needs 50 min with an aquarium heater operating at 49 °C. The planar heater thus results in enhanced heat diffusion and reduced water temperature variation due to its extended heating surface area.

Shading Influenced Water Quality and Seed Production of Nile Tilapia (Oreochromis niloticus L.) in the Hapa-within-Pond System During Warm Months

This study evaluated the influence of shading designs on water quality and Nile tilapia seed production in hapa-within-pond system. Metal frames were installed in three 200 m2 ponds and covered with greenhouse nets. Treatments were: no shading (NoS); top portion of frame covered (TopS); half of top and side portions of frame covered (HalfS); and top and sides of frame covered (TotalS). Twenty-four conditioned breeders (6♂:18♀) were bred on each hapa (1 m x 2 m x 1 m) installed in the ponds. Seeds were collected after 14 days. In both trials, significant differences in water temperature at 1500 h were observed among all treatments, with the lowest recorded in the TopS. The spawning rates of NoS (18.1±10.5%; 2.8±5.6%) were significantly lower than those of TopS (72.2±12.0%; 65.3±10.5%), HalfS (56.9±22.4%; 58.3±13.2%) and TotalS (66.7±23.6%; 65.3±10.5%). TotalS (8,563+3769 fry) and TopS (7,305+2491 fry) had significantly higher total seed production (TSP) than that of NoS (1,219+1150 fry) during the first trial, while TSP of HalfS (5,200+3051 fry) was comparable to those of the other treatments. During the second trial, shaded treatments had comparable TSPs but were significantly higher than NoS. For economic reasons, maximum reduction of water temperature, and optimum seed production during summer, the TopS design is recommended.

Field demonstrated extended Graetzian viscous dissipative thermo-photonic energy conversion with a blended MgO/PVDF/PMMA coated glass-PDMS micro-pillar heat exchanger

Chilled water harvesting is a fundamental application of passive radiative cooling and promotes energy conservation for space cooling in buildings potentially, which relies on well-designed radiative cooling materials and heat transfer interface. This paper reports a scenario leading to viscous dissipative thermo-photonic energy conversion, which takes place in low Peclet number regime of an order of magnitude of 100, where heat transfer is non-Graetzian. Compared to benchmarked glass-polydimethylsiloxane radiative cooler and barium sulphate coating, a newly developed trinary micro-porous 32/4/4 magnesium-oxide/poly(vinylidene-fluoride)/poly(methyl-methacrylate) radiative cooling blend, featuring high atmospheric window emissivity and solar reflectivity, both exceeding 97%, demonstrated a superior cooling performance with additional temperature reduction of 1.6 °C at daytime. Meanwhile, it chilled water at a flow rate of 6.3 µL/s by 1.3 °C upon coating on a glass-polydimethylsiloxane micro-pillar heat exchanger. Quantitative evaluation on the chilled water capacity was carried out at nighttime when the system ran pseudo-steadily. Cooling power measurement on a radiative cooler of same materials recorded a cooling power of 134 W/m2 which is close to the ideal limit. And measured water temperature reduction and cooling efficiency were 2.5 °C and 6.3% respectively. They were significantly lower than the saturation limit. Degraded thermal and energy conversion performances, attributive to extended Graetzian viscous dissipation, were discussed theoretically.

The biological characteristics of the Nile tilapia (Oreochromis niloticus) in the Weija Reservoir, Ghana

Abstract. Kpelly DK, Blay Jr.J, Yankson K. 2022. The biological characteristics of the Nile tilapia (Oreochromis niloticus) in the Weija Reservoir, Ghana. Intl J Bonorowo Wetlands 12: 41-54. Studies on the biological characteristics of the Nile tilapia (Oreochromis niloticus L.) were undertaken in a manufactured lake, the Weija Reservoir, in Ghana from September 2007 to August 2008. From commercial landings, a sum of 657 specimens of O. niloticus was examined, of which 357 were males and 300 were females (sex ratio of 1: 0.84; P < 0.05). GSI was highest in March and May 2008 and low in December 2007 and August 2008, which suggested that O. niloticus spawned throughout the year, but major spawning occurred in March. The length at first sexual maturity (L50) was 16.33 cm for males and 13.49 cm for females. Observations on the frequency distribution of ovum size measured between 1.2 to 3.1 mm showed two distinct peaks that were not completely separated, which were probably shedding eggs in batches, indicating protracted spawning in the population. Fecundity ranged from 563 to 1542 ova for fish of total length 15.6-21.5 cm with a mean of 851 ± 13.2 eggs. The relationships between fecundity and body weight (BW) and fecundity (F) and total length (TL) were: F = 0.519 BW + 785.4 and F = 12.36 TL + 628.5. Furthermore, based on studies on monthly fluctuations in the GSI and the occurrence of the ripe gonad, the major reproductive activity of O. niloticus in the reservoir coincided with months with increasing total alkalinity, reduced water temperature, and dissolved oxygen. The regression coefficient of 3.1 for the length-weight relationship (for both females and males) was not significantly different from the expected value of (P > 0.05), indicating isometric growth of the population. Therefore, collection of the species as seed for stocking or brood stock or by fish farmers is recommended in March-April. Moreover, appropriate management policies with periodic studies of the fishery and the limnology of the reservoir are essential to sustain fishery production.

Patterns and predictors of condition indices in a critically endangered fish

Condition indices are key predictors of health and fitness in wild fish populations. Variation in body condition, therefore, can be used to identify stressful conditions that may impact endangered species, such as California’s endemic Delta Smelt (Hypomesus transpacificus McAllister, 1963). Here, we examined spatiotemporal variation in the condition indices of > 1600 Delta Smelt collected over nine years (2011–2019), a period characterized by tremendous variability in hydrodynamic and water quality conditions. The population exhibited low hepatosomatic index (HSI) and condition factor (CF) during September/October/November (fall), and both condition indices declined over the nine-year study during fall. HSI was positively correlated with indicators of pelagic productivity (e.g., Chlorophyll a, zooplankton biomass, and proximity to tidal wetlands), whereas CF was negatively correlated with temperature, peaking at a relatively cool 10–13 °C. In sum, seasonal and interannual variation in body condition corresponded most strongly with pelagic productivity and water temperature, with little correlation to freshwater outflow. Management actions that increase pelagic productivity, restore and freshen productive wetlands during late summer-fall, and reduce water temperatures overall are likely to benefit condition indices and, therefore, fitness of the Delta Smelt population.

Advanced treatment of low C/N ratio wastewater treatment plant effluent using a denitrification biological filter: Insight into the effect of medium particle size and hydraulic retention time

Three denitrification biological filters (DNBFs) with different ceramsite medium particle sizes (2–4 mm, 4–12 mm and 12–20 mm) were used to treat wastewater treatment plant effluent. The influence of ceramsite particle size and hydraulic retention time (HRT) on the denitrification efficiency was compared. The results show that with increasing particle size (2–4 mm, 4–12 mm, 12–20 mm), the average total nitrogen (TN) degradation efficiency reduced from 76.9% to 46.4% and 41.6%. The filter medium with smaller particle size can enrich more denitrifying bacteria, improve the activity of denitrifying enzymes and electron transport system, and is more conducive to the removal of nitrate (NO 3 − -N) in low C/N wastewater. When the HRT was 3 h and the medium particle size was 2–4 mm, the denitrification effect was the best, with degradation efficiencies of TN and NO 3 − -N of 78.6% and 97.2%, respectively. Extending the HRT was beneficial to enhancing the denitrification efficiency of the DNBF, which could compensate for the effect of water temperature reduction on the denitrification efficiency. The total quantity of denitrifying bacteria reached 58.68% at the bottom of the DNBF with particle size of 2–4 mm, 48.06% in the DNBF with particle size of 4–12 mm and 40.17% in the DNBF with particle size of 12–20 mm. NO 2 − -N and chemical oxygen demand significantly influenced the microbial community structure. This study provides a basis to select a filter media particle size for denitrification treatment of wastewater treatment plant effluent with a low C/N ratio. • Denitrification rate of the DNBF increased with decreasing medium particle size. • Extended HRT improved the DNBF denitrification efficiency at low water temperature. • Denitrifying bacteria were enriched at the bottom of the DNBF. • NO 2 - -N and COD Cr had significant effects on the phylum-level microbial community.

Riparian Land Cover, Water Temperature Variability, and Thermal Stress for Aquatic Species in Urban Streams

Thermal regime warming and increased variability can result in human developed watersheds due to runoff over impervious surfaces and influence of stormwater pipes. This study quantified relationships between tree canopy, impervious surface, and water temperature in stream sites with 4 to 62% impervious land cover in their “loggersheds” to predict water temperature metrics relevant to aquatic species thermal stress thresholds. This study identified significant (≥0.7, p < 0.05) negative correlations between water temperature and percent tree canopy in the 5 m riparian area and positive correlations between water temperature and total length of stormwater pipe in the loggershed. Mixed-effects models predicted that tree canopy cover in the 5 m riparian area would reduce water temperatures 0.01 to 6 °C and total length of stormwater pipes in the loggershed would increase water temperatures 0.01 to 2.6 °C. To our knowledge, this is the first time that the relationship between stormwater pipes and water temperature metrics has been explored to better understand thermal dynamics in urban watersheds. The results highlight important aspects of thermal habitat quality and water temperature variability for aquatic species living in urban streams based on thermal thresholds relevant to species metabolism, growth, and life history.

Development and experimental investigation of a novel solar-powered cooling system

The development of novel and improvement of existing technologies for utilising solar thermal energy for cooling purposes traditionally attracts increased attention in both industry and academia. This work presents the development of a novel cooling system with a simple design and direct utilisation of solar thermal energy. The cooling system combines a liquid piston engine and cooling machine and is driven by an evacuated tube solar collector. A prototype of such the system was designed, built and tested in laboratory conditions using a solar radiation simulator. Variations in pressures, temperatures, and the fluid piston oscillation amplitudes in the system during its operation were recorded, and the indicated power of the engine and cooling capacity of the system were determined for a range of operation and design parameters. For the heat input range of 700–900 W and the constant temperature of the cooling water equal to 26.0 °C, the engine indicated power and cooling capacity of the system varied in the range of 70.0–88.0 and 51.0–61.0 W. The corresponding indicated efficiency of the engine and cooling system were in the range of 10.0–9.7 and 7.2–6.7%. The temperature in the cooling chamber was registered in the range of 20.0–18.2 °C at an ambient temperature of 24.0 °C. The COP of the cooling machine decreased from 0.71 to 0.69. The system performance improved in tests with a constant heat input (700 W) and reducing cooling water temperature. For cooling water temperature reduction from 26.0 to 18.0 °C, the engine indicated power and cooling capacity of the system varied in the range of 70.0–111.9 and 51.0–72.0 W. The corresponding indicated efficiency of the engine and cooling system were in the range of 10.0–16.0 and 7.2–10.3%. The COP of the cooling machine decreased from 0.71 to 0.64. The temperature in the cooling chamber was registered in the range of 20.0–14.4 °C at an ambient temperature of 24.0 °C. Experimental results obtained using the system's initial design demonstrate that the engine has efficiency comparable to low-temperature steam and Organic Rankine Cycle turbines. The Coefficient of Performance of the system is similar to that of single-stage absorption chillers.

Evaluation of Rodent Cage Processing Using Reduced Water Temperatures

Studies published in 1994 and 2000 established a temperature range of 143-180 °F for effective cage sanitization in animal facilities. These 2 studies were, respectively, theoretical and based on experiments using hot water to sanitize bacteria-coated test tubes. However, such experimental methods may not capture the practical advantages of modern washing technology or account for the routine use of detergent in cage wash. Moreover, these methods may not translate to the challenges of removing adhered debris and animal waste from the surfaces being sanitized. A sample of highly soiled cage bottoms, half of which were autoclaved with bedding to create challenging cleaning conditions, were processed at 6 combinations of wash and rinse cycles with 125 °F, 140 °F, and 180 °F water with detergent. All cycles were equipped with a data logging device to independently verify temperatures. After washing, cages underwent visual inspection and microbial sampling consisting of organic material detection using ATP detection and Replicate Organism Detection and Counting (RODAC) plates. Cages with any amount of visible debris failed inspection, as did cages that exceeded institutional sanitization thresholds. Results indicate that wash and rinse temperatures of 140 °F for a programmed wash duration of 450 s and rinse of 50 s effectively clean and disinfect both highly soiled and autoclaved cages. Accounting for both steam and electrical energy, these parameters result in an annual savings of $21,867.08 per washer on an equivalent run basis using the current institutional standard of 180 °F.

Coupled influence of flow velocity and water temperature on grass carp swimming behaviour and gonad development

AbstractReproductive migration is an essential phase in the life of many fish. During this process, swimming behaviour and gonad development are key factors related to the migration quality, and both factors are strongly influenced by water temperature and flow velocity. Many studies have explored the separate effects of these variables on fish swimming ability or gonad development, but researchers have seldom investigated the simultaneous effects of low flow velocity and water temperature on the fish swimming behaviour and gonad development. To provide that knowledge, we conducted laboratory experiments that explored the coupled effects of low water temperature and flow on warm water fish swimming behaviour and gonad development. At five temperatures (16, 18, 20, 22, and 24°C), we observed the movement of migratory warmwater grass carp (Ctenopharyngodon idellus) at seven flow velocities (0.15, 0.2, 0.25, 0.3, 0.35, 0.40, and 0.45 m/s), then explored their gonad development by comparing the level of plasma 17β‐estradiol and testosterone in fish travelling through a simulated fish way (flow stimulation) and in a fish tank (no flow stimulation). We used Bayesian networks to explore the acceptable hydrological condition for fish migration. We found that the minimum flow velocity for acceptable migration quality is a function of the water temperature, and that increasing water temperature improves fish movement success and increases the movement distance, especially at a low flow velocity. In addition, increasing water temperature (between 16 and 24°C in this experiment design) can enhance the effect of flow stimulation on gonad development. Overall, our results can broaden the understanding of reducing water temperature and flow velocity in fish swimming behaviour and gonad development, provide basic data to support hydrological process controls and the development of measures to protect fish migration.

Characterization of simultaneous heat, oxygen, and carbon dioxide transfer across a nonporous polydimethylsiloxane (PDMS) hollow fiber membrane

The provision of atmospheric oxygen, removal of carbon dioxide and heat is essential to sustain crew health during human spaceflight missions. Microgravity and reduced gravity environments (such as a planetary surface) limit the use of bubble-forming technologies, since surface tension and inertial or viscous forces may dominate buoyancy, creating an adverse effect in the system. Gas-to-liquid contacting membranes would allow for non-bubbling mass transfer through solution-diffusion, with the potential for simultaneous heat transfer, as done in membrane distillation operations. Previously published work, with similar applications, have focused on characterizing microporous membranes. In this study, a commercially available, nonporous polydimethylsiloxane (PDMS) hollow fiber membrane separated carbon dioxide from an ambient gas stream (296 K) while deoxygenating a cooling-water feed (274 K). Control experiments were conducted with gas and water at ambient temperatures (296 K and 292 K, respectively). Results show that increasing water feed rate (0.5 to 1.5 LPM) reduced the percentage of oxygen transferred from the water to the gas stream (approximately 25% less). Also, a reduction in water temperature significantly reduced percent oxygen transferred (approximately 35% reduction). System heat transfer and carbon dioxide transfer rates were positively correlated to gas flow rates, showing gas-phase dependence. Coefficients derived from the experimental results were used to form semi-empirical mass transport models. Results of this study developed two findings, that a nonporous PDMS membrane could be used for simultaneous heat and mass transfer which could also be described from first-order principles.

IMPLEMENTATION OF FUZZY LOGIC CONTROLLERS TO MAINTAIN WATER TEMPERATURE IN HYDROPONICS NFT FOR LOLLO VERDE LETTUCE (LACTUCA SATIVA L.)

Objective: The purpose of this study was to maintain the nutritional water temperature in the range of 25-27 °C for Lollo Verde lettuce (Lactuca sativa L.).
 Methods: The method was the Fuzzy Logic Mamdani (FLM) with two inputs, i.e. real time clock and temperature. The output was crisp speed PWM with the center of area method.
 Results: The results showed that Fuzzy logic was succeeded in reducing water temperature in the NFT system from 28-32 °C to 26-27 °C, with an average delta of 3.5 °C. Fuzzy logic maintained the nutrient water temperature in the Lollo Verde lettuce with an average of 26.57±0.5 °C. Water temperature affected the yield of Lollo Verde lettuce.
 Conclusion: The yield of NFT FLM system was better compared to the conventional NFT system.

Criopreservación espermática de Ambystoma mexicanum (Shaw & Nodder, 1798)

Ambystoma mexicanum is in danger of extinction in free-living, due to anthropogenic actions; sperm cryopreservation for captive breeding can help in its ex-situ conservation. This research aimed to identify the viability of fresh and post-thawing sperm from different spermatophores. During the breeding season, spermatophores releasing was induced in nine specimens by reducing water temperature. The mean concentration per spermatophores was 2.6 ± 0.6 x104 sperm. A reduction of 30 % of living sperms and an increase of 15 % of abnormal morphology were determined in fresh and post-thawing sperm. With the WGA and PNA lectins bounded to FITC, two different fluorescence patterns were determined in each one, which showed the membrane presence and distribution of N-acetyl glucosamine, sialic acid, and mannose respectively. Sperm percentages in each fluorescence pattern showed differences associated with the number of spermatophores in each release. Differences in sperm viability from releases with different numbers of spermatophores were determined. The sperm collection and cryopreservation protocol of A mexicanum were efficient as tools for using cryopreserved semen for ex situ reproduction.

Climate change effects on the thermal stratification of Lake Diefenbaker, a large multi-purpose reservoir

Large multi-purpose reservoirs serve not only to generate hydropower but to supply water for agricultural irrigation, animal and human consumption and to provide flood control. One of the key factors affecting physical functioning and deteriorating aquatic ecosystems in reservoirs is climate change. For instance, increases in water temperature accelerate chemical reaction rates, decomposition rates and oxygen demand at the water-sediment interface. Earlier thermal stratification onset, and longer and more intense reservoir thermal stratification are all consequences of global warming. Such disruptions in thermal stratification have been associated with reductions in hypolimnion dissolved oxygen, increasing anoxia events and enhancing reservoir eutrophication. In this research paper, we implement the 2 D hydrodynamics and water quality model, CE-QUAL-W2, to investigate the effects of climate change and streamflow scenarios on the thermal structure of Lake Diefenbaker, a large, multipurpose reservoir, located in Saskatchewan, Canada. Model results indicate that meteorological variability will dictate a nonlinear increase in reservoir water temperature in the coming decades, where larger increases in water temperature will occur during summer and fall in the upper layers. Also, decreases in reservoir streamflows will reduce water temperature at intermediate layers during summer and fall. Our model can be used as a tool to mitigate and manage the effects of climate change on the reservoir water quality.

Calibration of physicochemical parameters in aquaculture. A case study of tilapia breeding in Mozambique

This paper discusses the adequacy of methods used in monitoring the aquatic environment in aquaculture. It is assumed that the strategy of controlling each of the environmental parameters by observing their compliance with the technical limits established in aquaculture is not sufficient to highlight all the aspects that may compromise the quality of the process. Therefore, the univariate methods that are usually used in water monitoring in aquaculture cannot show aspects of the process derived from the joint variability between the parameters. Thus, a multivariate method for monitoring the aquatic environment in aquaculture based on Hotelling’s T2 chart was proposed in this paper. Data on four physicochemical parameters (oxygen, temperature, pH and transparency) were collected from four aquatic species breeding ponds at the company Aquapesca in Mozambique, located in southeastern Africa. The correlation structure evidenced in the four physicochemical parameters analyzed showed a strong and positive relationship between temperature and pH, oxygen and transparency are inversely correlated. This correlation structure indicates that a possible reduction in water temperature also reduces the pH and vice versa, while a reduction in transparency implies an increase in dissolved oxygen. The multivariate method used shows the relationship between the parameters and the strategies to manage them, as well as the control strategy of the multivariate structure through Hotelling’s T2 chart, pointing out and correcting all the aspects that may compromise the quality of the breeding of the species in aquaculture.

Identification and characterization of p38MAPK in response to acute cold stress in the gill of Pacific white shrimp (Litopenaeus vannamei)

Acute cold snaps induce a sudden reduction in water temperature and lead to high mortality of cultured Pacific white shrimp (Litopenaeus vannamei); however, little is known about the regulatory mechanisms in this shrimp species when adapting to acute cold stress. Mitogen-activated protein kinase (MAPK) signaling pathways are highly conserved and well known for their important roles in transducing environmental stress signals into the cell nucleus. In this study, the potential roles of p38MAPK in the response to acute cold stress in L. vannamei were identified. The transcript levels of p38MAPK in the gills were found to be significantly upregulated after challenge with acute cold stress for the first 12 h, while no distinctly differential expression was detected in the other two types of MAPKs (JNK and ERK). The phosphorylation levels of p38MAPK under acute cold stress continued to increase and reached a peak 1 h after cold exposure. The phosphorylation signaling of p38MAPK in re-chilled shrimp (5 min) appeared more quickly than that in primary shrimp (15 min). The results suggest that p38MAPK might play an essential role in transducing acute cold stress signals from the environment to the cell nucleus in L. vannamei. Our study is the first to characterize p38MAPK during acute cold stress adaptation, and the results will contribute to further research.

Small temperature difference in the middle and later water cooling stages of RCC dam

Water cooling is the main measure to reduce temperature cracks in RCC dams. But later cooling usually means reducing water temperature rapidly after 120 days of the concrete age, which may cause larger self stress and tensile stress inside the concrete. The small temperature difference cooling can advance the starting time of middle and late cooling stages, and reduce the temperature stress effectively. However, the difference of temperature stress produced by different middle and late stages water cooling methods is large. It is necessary to analyse precisely how to use the small temperature difference methods in the middle and late cooling stages of dams properly. The cooling methods of RCC dam in the middle and late stages are studied by using the self-developed 3-D FEM floating mesh method temperature controlling simulation program. Result shows that when the small temperature difference is used to cool the dam in the middle and late stages, the temperature and temperature stress of the dam reduces obviously. When the age of the concrete is over, the dam should be cooled immediately, several levels of water temperature should be set in the middle and late cooling stages, the temperature of the water should be reduced slowly, which can reduce the temperature and temperature stress of the dam effectively. Study result will provide a favourable reference for practical projects.

Can the impacts of cold-water pollution on fish be mitigated by thermal plasticity?

Increasingly, cold-water pollution (CWP) is being recognised as a significant threat to aquatic communities downstream of large, bottom-release dams. Cold water releases typically occur during summer when storage dams release unseasonably cold and anoxic hypolimnetic waters, which can decrease the temperature of downstream waters by up to 16°C. Depending on the release duration, these hypothermic conditions can persist for many months. The capacity of ectothermic species to tolerate or rapidly adjust to acute temperature changes may determine the nature and magnitude of the impact of CWP on affected species. This study assessed the impacts of an acute reduction in water temperature on the physiological function and locomotor performance of juvenile silver perch (Bidyanus bidyanus) and examined their capacity to thermally compensate for the depressive effects of low temperatures via phenotypic plasticity. Locomotor performance (Ucrit and Usprint) and energetic costs (routine and maximum metabolic rate) were measured at multiple points over a 10-week period following an abrupt 10°C drop in water temperature. We also measured the thermal sensitivity of metabolic enzymes from muscle samples taken from fish following the exposure period. Cold exposure had significant depressive effects on physiological traits, resulting in decreases in performance between 10% and 55%. Although there was partial acclimation of Ucrit (~35% increase in performance) and complete compensation of metabolic rate, this occurred late in the exposure period, meaning silver perch were unable to rapidly compensate for the depressive effects of thermal pollution. The results of this study have substantial implications for the management of cold water releases from large-scale dams and the conservation of native freshwater fish species, as this form of thermal pollution can act as a barrier to fish movement, cause reduced recruitment, ecological community shifts and disruptions to timing and success of reproduction.

Presence of Vibrio mediterranei associated to major mortality in stabled individuals of Pinna nobilis L.

A major epizootic event attributed to Haplosporidium pinnae leading to 100% mortality of Pinna nobilis L. populations along Mediterranean coastlines started in the fall of 2016. As a result, a project to rescue 221 adult individuals of the endangered pen shell, Pinna nobilis was conducted in November 2017 in the two areas of the Spanish coast where the species was still abundant and apparently free from infection by H. pinnae: Port Lligat in the Costa Brava, and the Alfacs Bay in the Ebro Delta. For biosecurity reasons, the 106 individuals from the Ebro Delta were stabled at the IRTA facilities located next to Alfacs Bay, whereas the 115 individuals from Port Lligat were stabled in different institutions throughout the Spanish territory. Initial biopsies showed that individuals from the Ebro Delta were free of the parasite, whereas most individuals from Port Lligat were already parasitized and died in the following months. Individuals at IRTA were hold in five tanks and fed ca. 4% of their dry weight with a mix of three species of phytoplankton and fine riverine sediments (13% OM). Seawater was filtered through 10, 5 and 1 μm to ensure the absence of the parasite and disinfected with UV light. No individuals died during the 4 initial months of captivity, but two died in April–May at temperatures from 17 to 19 °C. A peak of mortalities occurred during the summer months and early fall (53%) with maximums coinciding with temperatures above 25 °C. Individuals were again analyzed by PCR and histology for the presence of H. pinnae, Mycobacteria sp., and other locally important pathogens of commercial bivalves (Vibrio splendidus, V. aestuarianus and Herpesvirus OsHV-1 microVar), and therefore considered as potential pathogens of pen shells. However, with the exception of 3 individuals that were positive for Mycobacteria sp., results were all negative for the studied pathogens. Microbiological culture and isolation of bacteria from three moribund individuals, sacrificed for study purposes, showed V. mediterranei as the dominant species, and further PCR analyses confirmed the presence of the bacterium in ten deceased individuals. Overall, our results suggest the V. mediterranei is an opportunistic pathogen of stabled individuals possibly subjected to stress from captivity, and that antibiotic treatment (Florfenicol) combined with vitamins and mineral supplementation and reduction of water temperature (15 to 18 °C), can be used to mitigate (not to eradicate) the disease. Further research is needed to determine diets and stabling conditions that minimize captivity stress and prevent the emergence of the disease.