Water Temperature Gradient Research Articles

Water temperature control on CO2 flux and evaporation over a subtropical seagrass meadow revealed by atmospheric eddy covariance

AbstractSubtropical seagrass meadows play a major role in the coastal carbon cycle, but the nature of air–water CO2 exchanges over these ecosystems is still poorly understood. The complex physical forcing of air–water exchange in coastal waters challenges our ability to quantify bulk exchanges of CO2 and water (evaporation), emphasizing the need for direct measurements. We describe the first direct measurements of evaporation and CO2 flux over a calcifying seagrass meadow near Bob Allen Keys, Florida. Over the 78‐d study, CO2 emissions were 36% greater during the day than at night, and the site was a net CO2 source to the atmosphere of 0.27 ± 0.17 μmol m−2 s−1 (x̅ ± standard deviation). A quarter (23%) of the diurnal variability in CO2 flux was caused by the effect of changing water temperature on gas solubility. Furthermore, evaporation rates were ~ 10 times greater than precipitation, causing a 14% increase in salinity, a potential precursor of seagrass die‐offs. Evaporation rates were not correlated with solar radiation, but instead with air–water temperature gradient and wind shear. We also confirm the role of convective forcing on night‐time enhancement and day‐time suppression of gas transfer. At this site, temperature trends are regulated by solar heating, combined with shallow water depth and relatively consistent air temperature. Our findings indicate that evaporation and air–water CO2 exchange over shallow, tropical, and subtropical seagrass ecosystems may be fundamentally different than in submerged vegetated environments elsewhere, in part due to the complex physical forcing of coastal air–sea gas transfer.

The influence of reinjection and hydrogeological parameters on thermal energy storage in brine aquifer

When brine aquifer is used as thermal energy storage medium, pore structure and permeability of brine aquifer may change owing to the difference of salinity and temperature between the reinjected water and underground. Consequently, heat transfer characteristics and thermal energy storage performance in brine aquifer may vary correspondingly. In present work, heat transfer in brine aquifer is investigated, which considers the effect of reinjected water salinity, temperature, effective porosity and hydraulic gradient. Based on the temperature variation of pumping water, thermal energy storage efficiencies are analyzed under different conditions. The results indicate that the heat transferred from reinjection well to pumping well decreases with the reduction of reinjected water salinity, temperature difference and effective porosity of brine aquifer. The occurrence of thermal breakthrough delays when reinjected water salinity and effective porosity reduce, while thermal breakthrough is almost unaffected by reinjected water temperature and hydraulic gradient. The effective porosity of brine aquifer has the greatest influence on performance of thermal energy storage. When effective porosity of brine aquifer increases from 0.33 to 0.43, cold storage efficiency and heat storage efficiency decreases about 56.56% and 40%, respectively. Reducing reinjected water salinity and hydraulic gradient result in the increase of thermal energy storage efficiency. Reinjected water temperature has opposite effect on heat and cold energy storage efficiency. Sensitivity analysis indicates that the sensitivity of heat energy storage efficiency to considered parameters is greater than that of cold energy storage efficiency does.

Effects of Different Water Stratification on the Vertical Distribution of Nitrogen in Sediment Interstitial Waters: A Case Study of the Three Gorges Reservoir and Xiaowan Reservoir

To determine the reasons for the variation in the vertical distribution of nitrogen in sediment interstitial waters between different stratified reservoirs, the characteristics of overlying water-interstitial water in Xiangxi Bay, Yangtze River mainstream, and Xiaowan Reservoir were monitored. The vertical distribution of nitrogen in sediment interstitial waters in these different stratified waters were then analyzed, and the reasons for the variation in this distribution were assessed. The results showed:① the ρ(TN) in the sediment interstitial waters of the Yangtze River mainstream and Xiangxi Bay gradually increased with depth, while that of Xiaowan Reservoir reached its maximum at 12 cm and the bottom layer presented a "C" distribution. The ρ(NH4+) in the sediment interstitial waters of the Yangtze River mainstream and Xiangxi Bay exhibited an increasing trend with depth, while that of Xiaowan Reservoir was slightly higher in the bottom layer than in the surface layer, although the change with depth was not significant. Overall, the ρ(NH4+) in the sediment interstitial waters of the Yangtze River mainstream and Xiangxi Bay was higher than that of Xiaowan Reservoir, and the concentration ranges were as follows:0.512-8.289 mg·L-1, 0.968-9.307 mg·L-1, and 0.950-1.450 mg·L-1. The vertical distribution of the ρ(NO3-) in the sediment interstitial waters of all three waterbodies were opposite to that of ρ(NH4+). Moreover, the ρ(NO3-) in the sediment interstitial waters of Xiangxi Bay and the Yangtze River mainstream was higher than that of Xiaowan Reservoir. The concentration ranges were as follows:0.143-0.674 mg·L-1, 0.107-0.647 mg·L-1, and 0.050-0.051 mg·L-1. ② There were also significant differences in the vertical distribution of physical and chemical indices in the three water bodies. There was no significant change in the vertical distribution of the water temperature in the Yangtze River mainstream and the N2 value was <5×10-5 s-2; hence, the water was well mixed, and the vertical range of the dissolved oxygen content was 6.180-6.318 mg·L-1. The water temperature in the upper and middle reaches of Xiangxi Bay decreased vertically, while the water temperature in the lower reach presented a ladder-like distribution and the N2 values were all>5×10-5 s-2; thus, the water was in a stable stratified state and the dissolved oxygen content presented a "C" distribution. There was obvious stratification at the depths of 5-15 m and 54-70 m in Xiaowan Reservoir. The dissolved oxygen content decreased significantly at higher water temperature gradients, and there was no significant change along the water depth below 80 m. ③ The main reasons for the variation in the vertical distribution of nitrogen in the sediment interstitial waters of the three waterbodies were the differences in the overlying water hydrodynamics, dissolved oxygen distribution, and sediment environment. The ρ(NH4+) and ρ(NO3-) were higher in Xiangxi Bay, which may have increased the denitrification rate and subsequently have helped to remove nitrogen and reduce the nitrogen load in these waters.

Latitudinal consistency of biomass size spectra - benthic resilience despite environmental, taxonomic and functional trait variability

Global warming is expected to cause reductions in organism body size, a fundamental biological unit important in determining biological processes. Possible effects of increasing temperature on biomass size spectra in coastal benthic communities were investigated. We hypothesized higher proportions of smaller size classes in warmer conditions. Soft bottom infauna samples were collected in six Norwegian and Svalbard fjords, spanning wide latitudinal (60–81°N) and bottom water temperature gradients (from −2 to 8 °C). Investigated fjords differed in terms of environmental settings (e.g., pigments or organic carbon in sediments). The slopes of normalised biomass size spectra (NBSS) did not differ among the fjords, while the benthic biomass and NBSS intercepts varied and were related to chlorophyll a and δ13C in sediments. The size spectra based on both abundance and biomass remained consistent, regardless of the strong variability in macrofauna taxonomic and functional trait composition. Variable relationships between temperature and body size were noted for particular taxa. Our results indicate that while benthic biomass depends on the nutritional quality of organic matter, its partitioning among size classes is consistent and independent of environmental and biological variability. The observed size structure remains a persistent feature of studied communities and may be resilient to major climatic changes.

Oversummer growth and survival of juvenile coho salmon (Oncorhynchus kisutch) across a natural gradient of stream water temperature and prey availability: an in situ enclosure experiment

Conservation efforts for Pacific salmon (Oncorhynchus spp.) increasingly prioritize maintenance of cool water temperatures that protect all freshwater life stages. However, development of appropriate temperature standards requires a robust understanding of the interactions among water temperature, ecosystem productivity, and fish performance. We used a series of in situ enclosures to examine how natural spatiotemporal gradients in thermal conditions and prey availability affected the summer growth and survival of age-0+ coho salmon (Oncorhynchus kisutch). Coho salmon absolute growth rates peaked at a mean daily average water temperature (mean T) of 16.6 °C and an associated maximum weekly maximum temperature (MWMT) of 21.1 °C. Juvenile growth under these thermal conditions was sixfold greater than the growth rates observed for conspecifics rearing in the coolest study reach (mean T = 13.0 °C; MWMT = 16.0 °C). Even at the highest rearing temperature (mean T = 18.1 °C; MWMT = 24.0 °C), growth rates remained positive and above the study-wide average, although overall survival was reduced. Among the predictor variables examined, invertebrate prey abundance was the predominant factor influencing age-0+ coho salmon growth. These results suggest that abundant prey resources may mitigate the negative effects of elevated water temperature on fish growth in riverine environments. Given the likelihood of increasing stream temperatures with climate change, productive ecosystems may provide critical refuges for juvenile salmonids.

Dissecting the factors shaping fish skin microbiomes in a heterogeneous inland water system

BackgroundFish skin microbiomes are rarely studied in inland water systems, in spite of their importance for fish health and ecology. This is mainly because fish species distribution often covaries with other biotic and abiotic factors, complicating the study design. We tackled this issue in the northern part of the Jordan River system, in which a few fish species geographically overlap, across steep gradients of water temperature and salinity.ResultsUsing 16S rRNA metabarcoding, we studied the water properties that shape the skin bacterial communities, and their interaction with fish taxonomy. To better characterise the indigenous skin community, we excluded bacteria that were equally abundant in the skin samples and in the water samples, from our analysis of the skin samples. With this in mind, we found alpha diversity of the skin communities to be stable across sites, but higher in benthic loaches, compared to other fish. Beta diversity was found to be different among sites and to weakly covary with the dissolved oxygen, when treated skin communities were considered. In contrast, water temperature and conductivity were strong factors explaining beta diversity in the untreated skin communities. Beta diversity differences between co-occurring fish species emerged only for the treated skin communities. Metagenomics predictions highlighted the microbiome functional implications of excluding the water community contamination from the fish skin communities. Finally, we found that human-induced eutrophication promotes dysbiosis of the fish skin community, with signatures relating to fish health.ConclusionsConsideration of the background water microbiome when studying fish skin microbiomes, across varying fish species and water properties, exposes patterns otherwise undetected and highlight among-fish-species differences. We suggest that sporadic nutrient pollution events, otherwise undetected, drive fish skin communities to dysbiosis. This finding is in line with a recent study, showing that biofilms capture sporadic pollution events, undetectable by interspersed water monitoring.8DMM-yJDvkFzwjiP7KfL4NVideo abstract.

Regional environmental variation and local species interactions influence biogeographic structure on oyster reefs.

Although species interactions are often assumed to be strongest at small spatial scales, they can interact with regional environmental factors to modify food web dynamics across biogeographic scales. The eastern oyster (Crassostrea virginica) is a widespread foundational species of both ecological and economic importance. The oyster and its associated assemblage of fish and macroinvertebrates is an ideal system to investigate how regional differences in environmental variables influence trophic interactions and food web structure. We quantified multiple environmental factors, oyster reef properties, associated species, and trophic guilds on intertidal oyster reefs within 10 estuaries along 900km of the southeastern United States. Geographical gradients in fall water temperature and mean water depth likely influenced regional (i.e., thenorthern, central and southern sections of the SAB)variation in oyster reef food web structure. Variation in the biomass of mud crabs, an intermediate predator, was mostly (84.1%) explained by reefs within each site, and did not differ substantially among regions; however, regional variation in the biomass of top predators and of juvenile oysters also contributed to biogeographic variation in food web structure. In particular, region explained almost half (40.2%) of the variation in biomass of predators of blue crab, a top predator that was prevalent only in the central region where water depth was greater. Field experiments revealed that oyster mortality due to predation was greatest in the central region, suggesting spatial variation in the importance of trophic cascades. However, high oyster recruitment in the middle region probably compensates for this enhanced predation, potentially explaining why relatively less variation (17.9%) in oyster cluster biomass was explained by region. Region also explained over half of the variation in biomass of mud crab predators (55.2%), with the southern region containing almost an order of magnitude more biomass than the other two regions. In this region, higher water temperatures in the fall corresponded with higher biomass of fish that consume mud crabs and of fish that consumejuvenile and forage fish, whereas biomas oftheir prey (mud crabs and juvenile and forage fish, respectively)was generally low in the southern region. Collectively, these results show how environmental gradients interact with trophic cascades to structure food webs associated with foundation species across biogeographic regions.

Water temperature gradient shapes the structure and composition of nearshore marine fish communities in southern Europe

The nearshore ecosystem is an important nursery ground for many fish species. Considering that these areas have a considerable economic value because they support a wide variety of highly valuable species, it is essential to study the structure of their fish communities and the factors that may inlfuence them. The nearshore fish assemblages were studied from March to November of 2015 at 15 sandy beaches, arranged in 6 seaports, along 700 Km in the coast of Portugal. This Atlantic coastline is an important geographical transition area between cold-temperate and warm-temperate regions. Sampling was performed by the beach seine fishery, an artisenal fishery that operates in these areas. The fish assemblage was studied according to its species richness, biogeographical origin, habitat use and resource exploitation, in both biomass and number of individuals. The nearshore fish assemblage was diverse with 70 species belonging to 32 families, though a few species dominated the community: Engraulis encrasicolus, Trachurus trachurus, Sardina pilchardus and Scomber colias. Results indicated that the structure and composition of the fish assemblage from northern and southern seaports are different. Overall, species richness was higher in the southern seaports. Planktivorous species dominated the community in the northernmost seaport, and piscivorous species dominated the community in the remaining seaports. As expected, cold-temperate species presented higher abundance in the northern seaports, and both warm-temperate and sub-tropical species increased in number towards the southern limits. Tropical species were only present in the southernmost area. The main driver for variations in the fish community structure and composition was the water temperature gradient imposed by latitude, highlighting the environmental control in shaping marine biological communities.

Development of a simulation-optimization model for sustainable operation of groundwater heat pump system

Groundwater heat pump (GWHP) system directly uses a stable temperature of groundwater for cooling and heating of buildings or districts. In this study, a simulation-optimization model for the sustainable operation of GWHP system was developed. The simulation model computed the coupled groundwater flow and heat transport with considering thermal recycling. As an optimization technique, genetic algorithm was linked with the simulation model. The developed model can determine the optimal extraction and injection rates of GWHP system to maximize system performance and efficiency, to maintain stable operation, and to minimize costs and environmental impacts. Assuming a 2D hypothetical aquifer, it was demonstrated how the optimal operation of GWHP system obtained from the model can be changed according to several operational and hydrogeological conditions, including well distance, regulation on injection water temperature, hydraulic conductivity, and regional hydraulic gradient. The results highlighted a necessity to determine an operational strategy of GWHP system through the optimization able to consider site-specific condition. In addition, the performance and capability of the developed model were demonstrated by obtaining the optimal strategy for the cooling operation of a research-oriented GWHP facility installed in Korea.

The relationship between geographic range extent, sea surface temperature and adult traits in coastal temperate fishes

AbstractAimWe use publicly available data to assess the influence of ocean basin, various biological traits and sea surface temperature on biogeographic range extent for temperate, continental shelf fish species spanning 141 families.LocationCoastal waters of the temperate Northern Hemisphere.TaxonTeleost Fishes (Infraclass Teleostei).MethodsWe assess the relationship between species range extent and depth range, maximum body length, schooling behaviour and use of multiple habitats for 1,251 species of northern, temperate, continental shelf fishes in different basins (Atlantic vs. Pacific) and margins (east vs. west) using linear mixed‐effect models with family and genus as nested random effects. We further assess the relationship between species range endpoint distribution and latitudinal temperature gradient using generalized linear models.ResultsWe found strong positive relationships between the number of species northern range endpoints and the steepness of the latitudinal sea surface temperature gradient on the western margins of the Atlantic and Pacific Oceans, but no relationship on the eastern margins of these ocean basins. The strongest predictors of range extent in our global model are ocean basin/margin and depth range. Maximum body length, schooling behaviour and use of multiple habitats are also significant predictors of range extent in the global model. The factors influencing range extent differ by basin and margin.Main conclusionsThere are broad differences in patterns of species range extent and distribution of species ranges among basins/margins. These differences appear to be driven in part by variation in latitudinal water temperature gradient between basin margins. Our data suggest that sharp latitudinal temperature gradients may pose a barrier to dispersal and range expansion along the western margins of the Atlantic and Pacific Oceans, but not necessarily on the eastern margins. Our work also suggests that several post‐settlement traits may be associated with range extent either globally or in some temperate basins.

Numerical study on the summertime patches of red tide in the adjacent sea of the Changjiang (Yangtze) River Estuary, China

High incident rates of red tide have occurred off the coast of the Changjiang (Yangtze) River Estuary in summer, resulting from a magnified population growth discharging substantial nutrient loads into this vicinity. The presence of elevated Chlorophyll-a concentrations (≥36.3 μg/l), low suspended sediment concentrations in surface and mid-layers (<10 mg/l), a strong saline front and surface water temperature gradient, veering surface winds, and a bimodal shape to the Changjiang Diluted Water (CDW) revealed two red tide patches appearing between August 6–13, 2010. Two distinguishable hydrodynamic driving mechanisms, connected to these incidents, are diagnosed. Field observations and numerical simulations determined a red tide patch in the northeastern offshore area is caused by a northeast transport of the CDW truncated by a northwest intrusion of the Taiwan Warm Current (TWC) as winds deviated. Red tide occurrence in the southern nearshore area originated from a plume front where CDW interfaces with the TWC.

Effective depth controls the nitrate removal rates in a water supply reservoir with a high nitrate load

The Occoquan Reservoir is part of an indirect potable reuse system where a water reclamation plant (WRP) discharges a nitrified product water to prevent the onset of anaerobic conditions in the bottom sediments during the summer months. The elongated narrow shape of the reservoir combined with water temperature gradients in the inlet results in density currents that enhance the transport of nitrate from the surface to the bottom waters. The morphology of the reservoir also causes a longitudinal change in the ratio of water volume to sediment area, herein defined as the effective depth (ZED). Field observations revealed that first-order nitrate removal rate coefficients (k) varied inversely with ZED, suggesting that the upper reaches of the reservoir have a higher potential for nitrate removal compared to the areas closer to the dam. A similar relationship between k (d−1) and ZED was confirmed during laboratory experiments. Differences in k values were attributed mainly to the change in the nitrate supply rate as a result of the increase in water volume flowing over a specific sediment area, which limited nitrate transport to the sediments. The low variability found between the mass transfer coefficients for nitrate (Coefficient of Variation = 0.25) suggested a nearly constant biotic nitrogen removal and confirmed that k values were mainly affected by changes in ZED. Finally, similarities in k values between field and laboratory samples with similar ZED values suggested that different segments of natural systems may be properly downscaled to laboratory-sized configurations for analytical purposes by means of the ZED concept.

Life history strategies drive size‐dependent biomass allocation patterns of dryland ephemerals and shrubs

AbstractPlant biomass allocation patterns are important to understanding and predicting ecosystem carbon cycles and other important ecological processes. Consequently, many attempts have been made to study these patterns. However, most studies focus on data from species in temperate forests to the neglect of data from desert species adapted to arid conditions. We hypothesize that different life history strategies drive or at least participate in different plant biomass allocation patterns, as, for example, the life history differences between desert ephemeral and shrub species. We tested this hypothesis using field data gathered directly from the entire desert vegetation in Northwestern China. When the data from each of the two species groups are pooled, ephemeral and shrub species manifest different scaling relationships between above‐ and belowground biomass, unlike the isometric scaling relationships typically reported for forest tree species. The observed scaling relationships are sensitive to water stress and temperature gradients. The scaling exponents numerically decrease with increasing drought stress, and relatively more biomass is allocated to shoot growth in ephemeral species (presumably to rapidly complete their life history). In the case of shrubs, the numerical value of the scaling exponent is insensitive to rainfall, presumably because these species allocate more biomass to root growth to access belowground water. However, the scaling exponent is significantly sensitive to temperature, which also regulates root growth. Moreover, for the two species groups, root–shoot ratios are jointly regulated by precipitation and temperature. The different biomass allocation patterns appear to result from different life histories that maximize either competition among neighboring plants, or escaping damage from drought and low temperatures. These findings show how overall body size and life histories jointly regulate biomass allocation patterns under different extreme conditions and provide insights into estimating the dry carbon content in dryland ecosystems.

Baseline geochemical study of the Aberpergwm mining site in the South Wales Coalfield

This paper presents the baseline geochemistry and hydrogeology of a site in the South Wales Coalfield. Three deep exploration boreholes were drilled up to 650 m for that purpose and investigated together with the surrounding surface environment. The present study reports (i) General geological description, mineralogy and chemical composition (ii) Geochemistry of the coal seam water, surface waters and water from a shallow water table (iii) Periodic monitoring of temperature, water level and (iv) Adsorbed methane on rock samples and free gas concentrations acquired from three exploration boreholes. Rock specimens from the deep (425 m to 656 m) contained a minor amount of clay minerals such as clinochlore and kaolinite. Along with the major sandstone constitutions such as quartz and feldspar, rutile was also found in minor quantities. The trace elements such as arsenic, barium and thorium were found in various depths. The water temperature was stable around 13.5 °C (at 240 m) in Borehole 1, 15.6 °C (at 255 m) in Borehole 2 and 18.1 °C (at 453 m) in Borehole 3 throughout the monitoring period. The thermal profiling indicated the temperature gradient of 1.5 °C/100 m with maximum water temperatures at 22 to 24 °C which shows the thermal energy potential of the site. The low water temperature gradient in deep strata below 580 m, where the coal seams were encountered, indicated fluid movement in the deep coal seam aquifers. The gas analysis results showed the availability of the methane in the coal seams, and the water chemistry from the boreholes also exhibited the similar characteristics of the methane-producing wells around the world. The water chemistry of the shallow aquifers at the site was different from the water chemistry of the aquifers near the coal seam. The water quality measurements demonstrated the surface water quality was not affected by the drilling operations. Overall, this paper provides insights into the geochemistry and hydrogeology of the South Wales Coalfield that represents the environmental baseline data for any future industrial exploration or development activities.

Water temperature gradients drive early life-history patterns of the common sole (Solea solea L.) in the Northeast Atlantic and Mediterranean

The existence of a temperature gradient across latitudes is crucial to explain the patterns presented in the early life-history characteristics of marine fish species over large geographical areas. Hence, the aim of the present work was to analyse the temperature-related pattern in the early life-history events and characteristics of the common sole, Solea solea, along most of its geographical distribution area, focusing on key nursery areas for this species: Venice lagoon (Italy), Mondego estuary (Portugal), Vilaine estuary (France) and Balgzand (Netherlands). Otolith microstructure from metamorphosed age 0 juveniles was used to estimate age, the pelagic larval and metamorphosis stages duration, and the spawning period. A latitudinal cline was found for the main processes of the early life cycle: spawning started in December in the southernmost areas (Mondego estuary and Venice Lagoon) and in February in the Balgzand population. Hatching started earlier in the Venice lagoon, where warmer water temperatures in the winter led to an earlier development. The longest pelagic stage was observed in the French coast populations, which differed significantly from those of the Mediterranean, while metamorphosis lasted longer in the North Sea (Balgzand), when compared with the Portuguese Atlantic coast (Mondego). Populations further north were characterized by higher growth rates, suggesting an adaptation to local conditions. Despite that several abiotic factors play an important role in flatfish early life history, the observed temperature gradient seems to be one of the most important drivers.

Numerical investigation of the effect of moisture on buoyancy-driven low turbulence flow in an enclosed cavity

This paper reports a numerical investigation of low turbulence buoyancy-driven flow of moist air and heat transfer inside a rectangular cavity with differentially heated vertical walls. The variations of the flow, temperature and moisture inside the cavity has been analysed together with heat transfer coefficients for a range of mass fraction of water vapour and temperature gradients between the vertical walls of the cavity. The accuracy of the numerical methodology was also scrutinised by conducting a rigorous validation study of benchmark experimental data for the average Nusselt number for similar buoyancy driven cavity flow.The results of this investigation showed that during the natural convection process, the change in moisture content in the moist air has a significant influence on the flow and temperature fields inside the enclosure and the variation of the vertical wall temperature gradients have also shown to affect the moisture concentration inside the cavity. The percentage change in the average heat transfer varied significantly depending on the mass fraction of moisture in the air and the temperature gradient between the vertical walls. The results also showed a 3.5% increase in the average heat transfer for every 0.02 kg/kg increment in the mass fraction of water vapour. The findings from the study are significance to scientists and practitioners who are responsible for moisture management in enclosed space at the design threshold and for optimisation of energy used in buildings.

Agro-climatic zoning of Spanish forests naturally producing black truffle

Black truffle is a highly appreciated edible fungus that grows wild in southwestern Europe, although its cultivation has recently spread to other continents. In Spain the widespread exploitation of wild truffles began only after 1950, whereas plantations play a relevant role in truffle production from the late 1990s. However, most plantations continue to apply empiric practices not taking into account local environmental conditions. The identification of environmental factors driving black truffle distribution and yield could help to optimise cultivation practices, but no agro-climatic zoning is currently available for this fungus in Spain. This study characterises the climate of Spanish forests naturally producing black truffle, defines an agro-climatic zoning for the fungus and examines the climatic patterns across its spatial distribution. The examined forests presented climatic ranges coherent with the available experts' surveys, except for an extended low end in annual precipitation. The clustering identified three agro-climatic zones, with dry environments tending to be dominant. The principal components analysis indicated that the examined forests tended to cluster along water availability and temperature gradients. Only in one of the zones mean precipitations during the vegetative period were similar to those characterising optimum years for black truffle fruiting, thus suggesting that plantations could benefit from practices increasing soil water content. Similarly, the results suggested that in two of the zones plantations could benefit from practices increasing soil temperature in winter and early spring. The study provides a basis for large-scale planning of truffle cultivation and identification of research priorities in Spain.

Warmer and browner waters decrease fish biomass production.

Climate change studies have long focused on effects of increasing temperatures, often without considering other simultaneously occurring environmental changes, such as browning of waters. Resolving how the combination of warming and browning of aquatic ecosystems affects fish biomass production is essential for future ecosystem functioning, fisheries, and food security. In this study, we analyzed individual‐ and population‐level fish data from 52 temperate and boreal lakes in Northern Europe, covering large gradients in water temperature and color (absorbance, 420 nm). We show that fish (Eurasian perch, Perca fluviatilis) biomass production decreased with both high water temperatures and brown water color, being lowest in warm and brown lakes. However, while both high temperature and brown water decreased fish biomass production, the mechanisms behind the decrease differed: temperature affected the fish biomass production mainly through a decrease in population standing stock biomass, and through shifts in size‐ and age‐distributions toward a higher proportion of young and small individuals in warm lakes; brown water color, on the other hand, mainly influenced fish biomass production through negative effects on individual body growth and length‐at‐age. In addition to these findings, we observed that the effects of temperature and brown water color on individual‐level processes varied over ontogeny. Body growth only responded positively to higher temperatures among young perch, and brown water color had a stronger negative effect on body growth of old than on young individuals. Thus, to better understand and predict future fish biomass production, it is necessary to integrate both individual‐ and population‐level responses and to acknowledge within‐species variation. Our results suggest that global climate change, leading to browner and warmer waters, may negatively affect fish biomass production, and this effect may be stronger than caused by increased temperature or water color alone.

Temperature-mediated feeding between spring-associated and riverine-associated congeners, with implications for community segregation.

Freshwater fish communities segregate along water temperature gradients attributed in part to temperature-mediated physiological processes that affect species fitness. In spring complexes of southwest USA, spring complexes with narrow range of water temperatures are dominated by a community of fishes (i.e., spring-associated fishes), whereas riverine habitats with wide-range of water temperatures are dominated by a different community of fishes (i.e., riverine-associated fishes). The purpose of this study was to test a prediction of the concept that temperature-mediated species performance is a mechanism in maintaining community segregation. We predicted that a spring-associated fish (Largespring Gambusia Gambusia geiseri) would feed first and more often in a pairing with a riverine-associated fish (Western Mosquitofish G. affinis) at an average spring temperature (23 °C) and that the riverine-associated fish would feed first and more often in a pairing with the spring-associated fish at a warm riverine temperature (30 °C). Among four trails consisting of 30 pairings, at the spring complex temperature (23 °C), Largespring Gambusia had a greater number of first feeds (mean ± 1 SD, 5.0 ± 0.82) than Western Mosquitofish (2.5 ± 1.73) and had greater mean number of total feeds (1.9 ± 0.31) than Western Mosquitofish (0.81 ± 0.70). At the riverine environment temperature (30 °C), Western Mosquitofish had a greater number of first feeds (5.25 ± 1.71) than Largespring Gambusia (2.5 ± 1.73) and had greater mean number of total feeds (2.78 ± 1.05) than Largespring Gambusia (0.94 ± 0.68). Our findings suggest that temperature-mediated species performance could be maintaining segregation between the two fish communities. This study benefits our understanding of distributional patterns and improves threat assessments of stenothermal aquatic organisms.

The effect of heat exchanger geometry on adsorption chiller performance

The adsorption technology applied to cooling production is one of the possible means of waste heat utilization and it therefore contributes to a reduction of power consumption in air-conditioning and desalination facilities. Increasing the performance of the adsorption chiller can be achieved by the intensification of heat transfer in the sorption bed which in turn is directly influenced by heat exchanger geometry. The carried out research utilized numerical methods to define the correlation between the fin-tube heat exchanger design and the main factors influencing adsorption chiller performance such as gradient of heating water temperature, logarithmic mean temperature difference, effective mass factor of silica gel, silica gel average temperature and spatial temperature distribution in the sorption bed. The obtained correlations can be used by sorption bed designers to balance the thermal effectiveness of the device and its overall dimensions and mass.