Contrasting effects of climate change on denitrification and nitrogen load reduction in the Po River (Northern Italy).

An increase in water temperature is one of the main factors that can potentially modify biogeochemical dynamics in lowland rivers, such as the removal and recycling of nitrogen (N). This effect of climate change on N processing deserves attention, as it may have unexpected impacts on eutrophication in the coastal zones. Intact sediment cores were collected seasonally at the closing section of the Po River, the largest Italian river and one of the main N inputs to the Mediterranean Sea. Benthic oxygen fluxes, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) rates were measured using laboratory dark incubations. Different temperature treatments were set up for each season based on historical data and future predictions. Higher water temperatures enhanced sediment oxygen demand and the extent of hypoxic conditions in the benthic compartment, favoring anaerobic metabolism. Indeed, warming water temperature stimulated nitrate (NO3-) reduction processes, although NO3- and organic matter availability were found to be the main controlling factors shaping the rates between seasons. Denitrification was the main process responsible for NO3- removal, mainly supported by NO3- diffusion from the water column into the sediments, and much more important than N recycling via DNRA. The predicted increase in the water temperature of the Po River due to climate change may exert an unexpected negative feedback on eutrophication by strongly controlling denitrification and contributing to partial buffering of N export in the lagoons and coastal areas, especially in spring.

Climate change triggered planktonic cyanobacterial blooms in a regulated temperate river.

Harmful algae blooms are a rare phenomenon in rivers but seem to increase with climate change and river regulation. To understand the controlling factors of cyanobacteria blooms that occurred between 2017 and 2020 over long stretches (> 250 km) of the regulated Moselle River in Western Europe, we measured physico-chemical and biological variables and compared those with a long-term dataset (1997-2016). Cyanobacteria (Microcystis) dominated the phytoplankton community in the late summers of 2017-2020 (cyano-period) with up to 110 µg Chlorophyll-a/L, but had not been observed in the river in the previous 20 years. From June to September, the average discharge in the Moselle was reduced to 69-76% and water temperature was 0.9-1.8 °C higher compared to the reference period. Nitrogen (N), phosphorus (P) and silica (Si) declined since 1997, albeit total nutrient concentrations remained above limiting conditions in the study period. Cyanobacterial blooms correlated best with low discharge, high water temperature and low nitrate. We conclude that the recent cyanobacteria blooms have been caused by dry and warm weather resulting in low flow conditions and warm water temperature in the regulated Moselle. Under current climate projections, the Moselle may serve as an example for the future of regulated temperate rivers.

Response and recovery of nitrifying moving bed biofilm reactor systems exposed to 1°C with varying levels of ammonia starvation.

This study investigated the impact of varying total ammonia nitrogen (TAN) feed levels along with water temperature decreases on the performance of nitrifying moving bed biofilm reactor (MBBR) at 1 °C and its recovery at 3 °C. Five MBBR reactors were operated with different TAN concentrations as water temperature decreased from 20 to 3 °C: reactor R1 at 30 mg N/L, reactor R2 at 20 mg N/L, reactor R3 at 15 mg N/L, reactor R4 at 10 mg N/L and reactor R5 at 0 mg N/L. The corresponding biofilm characteristics were also analyzed to understand further nitrifying MBBR under different TAN feeding scenarios. The findings revealed that the higher TAN levels were before reaching 1 °C, the better nitrification performance and the more biomass grew. However, the highest TAN concentration (30 mg N/L) might negatively affect the nitrification performance, the activity of nitrifiers, and the growth of biofilms at 1 °C because of the toxic effects of un-ionized or free ammonia (FA). It was observed that the activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were affected by FA concentrations ranging from 0.2 to 0.7 mg N/L at 1 °C, but they could gradually be adapted to such inhibitory environment, with NOB recovering more quickly and robustly than AOB. The study identified 20 mg N/L (67 % of maximum influent TAN at 1 °C in R2 as the optimal TAN feeding concentration, achieving over 90 % TAN removal and a surface area removal rate (SARR) of 0.78 ± 0.02 g N/m2·d at 1 °C. Meanwhile, R2 also exhibited the highest biofilm mass, with total solids at 13.3 mg/carrier and volatile solids at 11.3 mg/carrier. As TAN was removed, nitrite accumulation was observed at 1 °C, and higher influent TAN concentrations prior to 1 °C appeared to delay the accumulation. When water temperature increased from 1 °C to 3 °C, nitrification performance improved significantly in all reactors without nitrite accumulation, and the higher TAN feeding in the previous stage led to faster recovery. Compared with 20 °C, biofilm became thinner and denser at 1 °C and 3 °C. Furthermore, this study revealed significant shifts in microbial community composition and nitrifier abundances in response to changes in water temperature and influent TAN levels. The dominant nitrifiers were identified as Nitrosomonadaceae (AOB) and Nitrospiraceae (NOB). At 1 °C, the nitrifier abundances were significantly correlated with SARRs, FA, and biofilm density. R2, which exhibited the best nitrification performance, maintained higher nitrifier abundances at 1 °C.

Spatiotemporal variability of lake surface water temperature and water quality parameters and its interrelationship with water hyacinth biomass in Lake Tana, Ethiopia.

Urbanization, agriculture, and climate change affect water quality and water hyacinth growth in lakes. This study examines the spatiotemporal variability of lake surface water temperature, turbidity, and chlorophyll-a (Chl-a) and their association with water hyacinth biomass in Lake Tana. MODIS Land/ Lake surface water temperature (LSWT), Sentinel 2 MSI Imagery, and in-situ water quality data were used. Validation results revealed strong positive correlations between MODIS LSWT and on-site measured water temperature (R = 0.90), in-situ turbidity and normalized difference turbidity index (NDTI) (R = 0.92), and in-situ Chl-a and normalized difference chlorophyll index (NDCI) (R = 0.84). LSWT trends varied across the lake, with increasing trends in the northeastern, northwestern, and southwestern regions and decreasing trends in the western, southern, and central areas (2001-2022). The spatial average LSWT trend decreased significantly in pre-rainy (0.01 ℃/year), rainy (0.02 ℃/year), and post-rainy seasons (0.01℃/year) but increased non-significantly in the dry season (0.00 ℃/year) (2001-2022, P < 0.05). Spatial average turbidity decreased significantly in all seasons, except in the pre-rainy season (2016-2022). Likewise, spatial average Chl-a decreased significantly in pre-rainy and rainy seasons, whereas it showed a non-significant increasing trend in the dry and post-rainy seasons (2016-2022). Water hyacinth biomass was positively correlated with LSWT (R = 0.18) but negatively with turbidity (R = -0.33) and Chl-a (R = -0.35). High spatiotemporal variability was observed in LSWT, turbidity, and Chl-a, along with overall decreasing trends. The findings suggest integrated management strategies to balance water hyacinth eradication and its role in water purification. The results will be vital in decision support systems and preparing strategic plans for sustainable water resource management, environmental protection, and pollution prevention.

A trawl collected dataset of Johnius (Actinopterygii, Sciaenidae) species in central-western Taiwanese waters.

Background: Sciaenidae is one of the most important coastal fisheries in Taiwan, both in production and economic value. It is also significant as the main targetted diet of Chinese white dolphins, Sousachinensis, especially for the genus Johnius, such as J.taiwanensis, J.belangerii and J.distinctus, which is primarily found in central-western Taiwan coastal waters. Despite an abundance of Johnius species occurrences reported in the Global Biodiversity Information Facility (GBIF) and the Taiwan Biodiversity Information Facility (TaiBIF) data portals (Mozambique, Australia, Taiwan, Korea, India, Indonesia, South Africa, Pakistan, Vietnam and China), there are no specific datasets that properly document the regional distribution of this genus, especially in Taiwanese waters. Thus, this paper describes a dataset of genus Johnius occurrences in waters on the central-western coast of Taiwan. The data collection for the present study was conducted from 2009 until 2020 and comprised 62 sampling events and 133 occurrence records. All fish specimens were collected by trawling in Miaoli, Changhwa and Yunlin Counties, Taiwan and brought back to the lab for identification, individual number count and body weight measurement. These processing data have been integrated and established in the Taiwan Fish Database and published in GBIF. This dataset contains six Johnius species and 2,566 specimens, making it comprehensive Johnius fish fauna and spatial distributional data on the coastal habitat in central-western Taiwanese waters. New information: This dataset contains 133 occurrence records of Johnius species (Sciaenidae) with 2,566 specimens, making it the most extensive public dataset of Johnius distribution records in Taiwan. The publication of this dataset through the TaiBIF and GBIF dataset platforms demonstrated that the number of Johnius spatial and temporal records in Taiwan waters is influenced by the topographical structure of the Changyun Rise (CYR) in combination with the cold current of the China Coastal currents and bound with the warm currents of the Kuroshio and the South China Sea on the central-western coast of Taiwan. The data serve as the foundation for understanding the biogeography and Johnius species ecology in Taiwan's coastal waters, which present a 2°C water temperature difference split at the CYR.

Remarkable shifts in the megabenthic community structure over four decades in Tokyo Bay, Japan, in relation to environmental variations.

We investigated long-term changes in the megabenthic community in Tokyo Bay, Japan, using data from fisheries-independent trawl surveys conducted from 1977 to 2023. In addition, we examined the potential relationship between changes in biotic communities and environmental conditions. The total abundance and biomass exhibited an increasing trend until 1987, followed by a substantial decline from the late 1980s to the 1990s due to a decrease in small to medium-sized fish and crustacean species. Meanwhile, a marked increase in the number of large fish (including elasmobranchs), mollusks, and echinoids, was observed in the 2000s. These shifts in the megabenthic community structure were correlated with an increase in water temperature and a decrease in nutrient concentrations and copepod densities. Cumulative evidence suggests that a remarkable shift in the megabenthic community structure occurred between the 1970s and the 2020s, which was possibly associated with variations in the environmental conditions in Tokyo Bay.

Spatial Dynamics of Demersal Fish Assemblages off the Korean Coast in the East Sea.

This study assessed variations in demersal fish assemblages with respect to the study site and water depth. Seasonal samplings from May 2018 to March 2019 were conducted along the northern (Ayajin, Goseong) and southern (Hupo, Uljin) sites of the East Sea off the Korean coast, using commercial gill nets. Samples were collected at depths of ~50, ~80, ~150 m across the study sites, with concurrent monitoring of water column structures. A total of 73 species and 6250 specimens were collected. Distinctive fish species compositions were observed according to the study site and depth. Although Glyptocephalus stelleri was the most abundant fish species in both Ayajin and Hupo, Gadus macrocephalus, Icelus cataphractus, and Alcichthys elongatus were most predominant in Ayajin, whereas Cleisthenes pinetorum, Hippoglossoides dubius, and Gymnocanthus herzensteini were more prevalent in Hupo. In terms of depth layer, in Ayajin, G. stelleri dominated in both intermediate and deeper layers, with Hemilepidotus gilberti, A. elongatus, Enophrys diceraus common in shallower depths. Conversely, in Hupo, G. stelleri, C. pinetorum, and A. nadeshnyi dominated across all depth layers, whereas Dasycottus setiger and G. herzensteini dominated in deeper and shallower depths, respectively. Significant influences of the study site and water depth on fish assemblage structures were observed due to variations in water temperature at the seasonal thermocline boundary.

Investigating long-term changes in surface water temperature of Dongting Lake using Landsat imagery, China.

Lake surface water temperature (LSWT) plays a crucial role in assessing the health of aquatic ecosystems. Variations in LSWT can significantly impact the physical, chemical, and biological processes within lakes. This study investigates the long-term changes in surface water temperature of the Dongting Lake, China. The LSWT is retrieved using Landsat thermal infrared imageries from 1988 to 2022 and validated with in situ observations, and the change characteristics of LSWT and near-surface air temperature (NSAT) as well as the spatial distribution characteristics of LSWT are analyzed. Additionally, the contribution rates of different meteorological factors to LSWT are quantified. The results show that the accuracy assessment of satellite-derived temperatures indicates a Nash-Sutcliffe efficiency coefficient (NSE) of 0.961, suggesting an accurate retrieval of water temperature. From 1988 to 2022, both the annual average LSWT and NSAT of Dongting Lake exhibit an increasing trend, with similar rates of warming. They both undergo a mutation in 1997 and have the main periods on the 11-year and 4-year time scales. The changes in NSAT emerge as one of the important factors contributing to variations in LSWT. Among the multiple meteorological factors, NSAT exhibits a significant correlation with LSWT (R = 0.822, α < 0.01). Furthermore, NSAT accounts for the highest contribution rate to LSWT, amounting to 67.5%. The distribution of LSWT within Dongting Lake exhibits spatial variations, with higher LSWT observed on the west part compared to the east part during summer, while lower LSWT occurs on the west part during winter. The findings of this study can provide a scientific understanding for the long-term thermal regimes of lakes and help advance sustainable lake management.

Water temperature and energy balance of floating photovoltaic construction water area-field study and modelling.

Floating photovoltaics (FPV) are an emerging renewable energy technology. Although they have received extensive attention in recent years, understanding of their environmental impacts is limited. To address this knowledge gap, we measured water temperature and meteorological parameters for six months under FPV arrays and in the control open water site and constructed a numerical model reflecting the water energy balance. Our results showed that FPV arrays caused diurnal variation in water temperature and microclimate. Specifically, we found that FPV had a cooling effect on their host waterbody during the daytime and a heat preservation effect at night, reducing diurnal variation. The diel oscillation of water temperature below FPV panels lagged behind that of open waters by approximately two hours. The microclimate conditions below FPV panels also changed, with wind speed decreasing by 70%, air temperature increasing during the daytime (averaging +2.01°C) and decreasing at night (averaging -1.27°C). Notably, the trend in relative humidity was the opposite (-3.72%, +14.43%). Correlation analysis showed that the degree of water temperature affected by FPV was related to local climate conditions. The numerical model could capture the energy balance characteristics with a correlation coefficient of 0.80 between the simulated and actual data. The shortwave radiation and latent heat flux below FPV panels was significantly reduced, and the longwave radiation emitted by FPV panels became one of the heat sources during the daytime. The combined variations of these factors dominated the water energy balance below FPV panels. The measured data and simulation results serve as a foundation for evaluating the impact of FPV systems on water temperature, energy budget, and aquatic environment, which would also provide a more comprehensive understanding of FPV systems.

Isolation of Vibrio cholerae and Vibrio vulnificus from Estuarine Waters, and Genotyping of V. vulnificus Isolates Using Loop-Mediated Isothermal Amplification.

Bacteria in the genus Vibrio are ubiquitous in estuarine and coastal waters. Some species (including Vibrio cholerae and Vibrio vulnificus) are known human pathogens causing ailments like cholera, diarrhea, or septicemia. Notably, V. vulnificus can also cause a severe systemic infection (known as vibriosis) in eels raised in aquaculture facilities. Water samples were periodically collected from the estuary of the Asahi River, located in the southern part of Okayama City, Japan. These samples were directly plated onto CHROMagar Vibrio plates, and colonies displaying turquoise-blue coloration were selected. Thereafter, polymerase chain reaction was used to identify V. cholerae and V. vulnificus. A total of 30 V. cholerae strains and 194 V. vulnificus strains were isolated during the warm season when the water temperature (WT) was higher than 20 °C. Concurrently, an increase in coliforms was observed during this period. Notably, V. vulnificus has two genotypes, designated as genotype 1 and genotype 2. Genotype 1 is pathogenic to humans, while genotype 2 is pathogenic to both humans and eels. The loop-mediated isothermal amplification method was developed to rapidly determine genotypes at a low cost. Of the 194 strains isolated, 80 (41.2%) were identified as genotype 1 strains. Among the 41 strains isolated when the WTs were higher than 28 °C, 25 strains (61.0%) belonged to genotype 1. In contrast, of the 32 strains isolated when the WTs were lower than 24 °C, 27 strains (84.4%) belonged to genotype 2. These results suggest that the distribution of the two genotypes was influenced by WT.

Lake Surface Water Temperature in high altitude lakes in the Pyrenees: Combining satellite with monitoring data to assess recent trends.

Lake Surface Water Temperature (LSWT) influences critical bio-geological processes in lake ecosystems, and there is growing evidence of rising LSWT over recent decades worldwide and future shifts in thermal patterns are expected to be a major consequence of global warming. At a regional scale, assessing recent trends and anticipating impacts requires data from a number of lakes, but long term in situ monitoring programs are scarce, particularly in mountain areas. In this work, we propose the combined use of satellite-derived temperature with in situ data for a five-year period (2017-2022) from 5 small (<0.5km2) high altitude (1880-2680 masl) Pyrenean lakes. The comparison of in situ and satellite-derived data in a common period (2017-2022) during the summer season showed a notably high (r = 0.94, p < 0.01) correlation coefficient, indicative of a robust relationship between the two data sources. The root mean square errors ranged from 1.8 °C to 3.9 °C, while the mean absolute errors ranged from 1.6 °C to 3.6 °C. We applied the obtained in situ-satellite eq. (2017-2022) to Landsat 5, 7 and 8/9 data since 1985 to reconstruct the summer surface temperature of the five studied lakes with in situ data and to four additional lakes with no in situ monitoring data. Reconstructed LSWT for the 1985-2022 showed an upward trend in all lakes. Moreover, paleolimnological reconstructions based on sediment cores studies demonstrate large changes in the last decades in organic carbon accumulation, sediment fluxes and bioproductivity in the Pyrenean lakes. Our research represents the first comprehensive investigation conducted on high mountain lakes in the Pyrenees that compares field monitoring data with satellite-derived temperature records. The results demonstrate the reliability of satellite-derived LSWT for surface temperatures in small lakes, and provide a tool to improve the LSWT in lakes with no monitoring surveys.

Inland freshwater aquaculture in a warming world.

Climate change potentially threatens the sustainable production of highly valued cold-water fish species in flow-through systems, such as salmonids. By analysing the relationship of water temperature to hydrological characteristics, air temperature, solar exposure, and precipitation, this study predicted temperature dynamics of five temperate cold-water aquaculture facilities under four projected climate change scenarios. Air temperature was found to be directly associated with facility site water temperature, and based on rational assumptions, two of the five facilities were predicted to face critical warming by mid-century. Extreme precipitation events induced acute short-term increases in water temperature of up to 5 °C. Significantly lower warming, roughly equal to the projected climate change-induced increase, was seen with artificial shading lowering temperature by 1 °C. Complementary niche modelling revealed that 37-77 % of current cold-water facilities will likely incur suboptimal climate conditions by the end of the century. Shading of raceways, more efficient water use, and disease management are proposed as key actions to preserve cold-water aquaculture.

Climate change impacts on eutrophication in the Po River (Italy): Temperature-mediated reduction in nitrogen export but no effect on phosphorus.

Rivers worldwide are under stress from eutrophication and nitrate pollution, but the ecological consequences overlap with climate change, and the resulting interactions may be unexpected and still unexplored. The Po River basin (northern Italy) is one of the most agriculturally productive and densely populated areas in Europe. It remains unclear whether the climate change impacts on the thermal and hydrological regimes are already affecting nutrient dynamics and transport to coastal areas. The present work addresses the long-term trends (1992-2020) of nitrogen and phosphorus export by investigating both the annual magnitude and the seasonal patterns and their relationship with water temperature and discharge trajectories. Despite the constant diffuse and point sources in the basin, a marked decrease (-20%) in nitrogen export, mostly as nitrate, was recorded in the last decade compared to the 1990s, while no significant downward trend was observed for phosphorus. The water temperature of the Po River has warmed, with the most pronounced signals in summer (+0.13°C/year) and autumn (+0.16°C/year), together with the strongest increase in the number of warm days (+70%-80%). An extended seasonal window of warm temperatures and the persistence of low flow periods are likely to create favorable conditions for permanent nitrate removal via denitrification, resulting in a lower delivery of reactive nitrogen to the sea. The present results show that climate change-driven warming may enhance nitrogen processing by increasing respiratory river metabolism, thereby reducing export from spring to early autumn, when the risk of eutrophication in coastal zones is higher.

Effect of water temperature on the anesthetic effects of alfaxalone in carp (Cyprinus carpio).

Objective: To evaluate the effect of water temperature on intramuscular injected alfaxalone anesthesia in carp (Cyprinus carpio). Materials and Methods: Six healthy adult carp (C. carpio) were intramuscularly injected with alfaxalone (2.5, 5.0, or 7.5 mg/kg) at normal water temperature (25°C) and at low water temperature (2.5 mg/kg, 15°C). The respiratory rate, heart rate (HR), and anesthesia depth (AD) were evaluated every 5 min for 30 min after administration and every 1 h after 60 min after injection. Results: The respiratory and HRs did not change significantly upon alfaxalone injection, regardless of dose. However, a dose-dependent increase in AD scores was observed. Furthermore, 2.5 mg/kg alfaxalone injected in 15°C water showed an almost equal anesthetic effect to that of 5.0 mg/kg alfaxalone in 25°C water. Conclusion: Alfaxalone is readily available, and its anesthetic effect in carp was enhanced by lowering water temperature, illustrating the possibility of intramuscular injection of alfaxalone in fish.

Improving species distribution forecasts by measuring and communicating uncertainty: An invasive species case study.

Forecasting invasion risk under future climate conditions is critical for the effective management of invasive species, and species distribution models (SDMs) are key tools for doing so. However, SDM-based forecasts are uncertain, especially when correlative statistical models extrapolate to nonanalog environmental domains, such as future climate conditions. Different assumptions about the functional form of the temperature-suitability relationship can impact predicted habitat suitability under novel conditions. Hence, methods to understand the sources of uncertainty are critical when applying SDMs. Here, we use high-resolution predictions of lake water temperatures to project changes in habitat suitability under future climate conditions for an invasive macrophyte (Myriophyllym spicatum). Future suitability was predicted using five global circulation models and three statistical models that assumed different species-temperature functional responses. The suitability of lakes for M. spicatum was overall predicted to increase under future climate conditions, but the magnitude and direction of change in suitability varied greatly among lakes. Variability was most pronounced for lakes under nonanalog temperature conditions, indicating that predictions for these lakes remained highly uncertain. Integrating predictions from SDMs that differ in their species-environment response function, while explicitly quantifying uncertainty across analog and nonanalog domains, can provide a more robust and useful approach to forecasting invasive species distribution under climate change.

Infection dynamics of Shewanella spp. in Nile tilapia under varied water temperatures: A hematological, biochemical, antioxidant-immune analysis, and histopathological alterations.

In aquaculture, fluctuating water temperatures can act as a potent stressor, influencing the virulence and transmission dynamics of pathogenic bacteria, potentially triggering outbreaks and impacting fish health. The purpose of this work was to examine the impact of Shewanella spp. infection on hematological, biochemical, and antioxidant-immune parameters of Nile tilapia (Oreochromis niloticus) under different water temperatures. For this purpose, 180 fish were divided into 6 groups in triplicate (30 fish per group; 10 fish per replicate). Group 1 (G1), G2, and G3 were reared at varying water temperatures (22 °C, 28 °C, and 31 °C, respectively) without infection. While G4, G5, and G6 were IP-injected with 0.2 mL of Shewanella spp. (0.14 × 105) and reared at 22 °C, 28 °C, and 31 °C, respectively. Shewanella spp. infection induced significant lowering (p < 0.05) in hematological parameters (red and white blood cells, hemoglobin, and packed cell volume%) and immune-antioxidant responses (phagocytic activity%, phagocytic index, lysozyme, nitric oxide), total antioxidant capacity, catalase, and reduced glutathione, especially at 22 °C. Moreover, a significant increase (p < 0.05) in the hepato-renal function indicators (alanine aminotransferase, aspartate aminotransferase, urea, and creatinine), stress biomarkers (glucose and cortisol), malondialdehyde, and pro-inflammatory cytokines (interleukin-1ß and tumor necrosis factor-α) were the consequences of the Shewanella spp. infection, especially at 22 °C. The Shewanella spp. infection exhibited marked histopathological changes in the hepatic and renal tissues. Worthily, Shewanella spp. can cause detrimental alterations in Nile tilapia's hematological, biochemical, and antioxidant-immune parameters at various water temperatures, but the major detrimental changes were observed at a water temperature of 22 °C. Consequently, we can conclude that the infection dynamics of Shewanella spp. are exaggerated at 22 °C. These outcomes could help in understanding the nature of such an infection in Nile tilapia.

Impact of heat islands vs. city greening: Real-time monitoring and modeling of drinking water temperature in the city of Montreal in Canada.

Urbanization increases the land surface temperature through surface mineralization, adversely affecting vegetation and enhancing the urban heat island (UHI) effect. Global climate change has intensified this warming effect with more frequent and intense heatwaves during hot seasons. While these transformations influence soil temperature, their consequences on drinking water temperature within the drinking water distribution system (DWDS) remains poorly understood. Literature proposes to increase pipe burial depths to mitigate drinking water heating during summer. In this study, we monitored drinking water temperatures in a DWDS in Montreal, Canada with deeply buried pipes (average 1.8 m) during the summer of 2022, focusing on two contrasting zones in terms of UHI and green coverage. Monitoring revealed a 8°C heating effect compared to the water treatment plant, attributed to low green coverage and anthropogenic heat. Conversely, the greener zone exhibited cooler drinking water temperatures, reaching a maximum cooling effect of 8°C as compared to the temperature at the exit of the water treatment plant. Utilizing a soil and water temperature model, we predicted drinking water temperatures within the DWDS with acceptable accuracy. Soil temperature modeling results aligned well with measured water temperatures, highlighting DWDS water temperature approaching its surrounding soil temperature fairly quickly. Despite heatwaves, no immediate correlation emerged between air temperature records and measured water temperatures, emphasizing soil temperature as a superior indicator. An increase in water age displayed no correlation with an increase in measured water temperature, underscoring the dominant influence of UHI and green coverage on water temperature. These findings highlight the cooling advantages of green spaces during summer, providing valuable insights for sustainable urban planning.

Long-term patterns and changes of unglaciated High Arctic stream thermal regime.

Although water temperature is one of the most important factors influencing hydrochemistry and river ecology, long-term monitoring and modelling of stream thermal temporal variability are uncommon. There is sparse research regarding the thermal regimes of Arctic rivers, especially in Svalbard, a geographical hotspot affected by extreme climate change and Arctic amplification. There is a need for improvement and better understanding of the factors influencing the stream water temperature regime. To address this research gap, we present a study of the non-glaciated arctic catchment, Fuglebekken (Spitsbergen, Svalbard). We propose methods for reconstructing the thermal regime of the Arctic stream based on available in-situ data. This study evaluates different sets of input variables with hourly time steps required to explain the variability in water temperature. The study comprises two modelling approaches, a stochastic transfer function Multiple Input Single Output and a supervised machine learning technique, Gaussian Process Regression, to simulate the water temperature in the years 2005-2022. The ground temperature at a depth of 20 cm and total solar radiation were found to be the main forcings that explain most of the water temperature variability. The outputs of both models showed similar tendencies and patterns. A diurnal warming trend of 0.5-3.5 °C per decade has been detected in stream water temperature throughout the summer season. The highest increase of 6.0 °C in the water temperature in 2005-2022 was found to be present in the second part of June. The outcomes prove that the thermal regime of the Fuglebekken stream is sensitive to ongoing climatic changes. This variability is an important factor with many environmental implications.

Effect of subcritical water temperature on the chain conformation and immune activity of ginger polysaccharides.

In this study, the ginger polysaccharides extracted from hot water (HW-G) were modified with subcritical water (SW-G) to effectively regulate their immune activity, and the relationship between polysaccharide chain conformation and immune activity at different subcritical water temperatures was investigated. The results indicated that, compared with HW-G, the xylose and mannose were degraded at high temperatures. The molecular weight of ginger polysaccharide decreased from 1.083 × 106 g/mol to 3.113 × 105 g/mol after subcritical water modification (100-160 °C). The chain conformation transitioned from rigid rod chain to semi-rigid chain and eventually to random coil. The degree of relaxation of the polysaccharide chains showed a continuous increase trend. Additionally, ginger polysaccharide modified by subcritical water at 130 °C was found to promote the proliferation and phagocytosis of 264.7 cells more obviously and signally increase the secretion levels of NO, IL-6, TNF-α and IL-1ß. When the subcritical water temperature exceeds 130 °C, the activity of ginger polysaccharide begins to decline rapidly. These findings demonstrate a close correlation between polysaccharide chain conformation and immunomodulatory activity, confirming the feasibility of the subcritical water temperature effect as a means of immune activity regulation, which opens up a new approach to obtaining highly active polysaccharides.

Integration of deep learning and improved multi-objective algorithm to optimize reservoir operation for balancing human and downstream ecological needs.

Dam (reservoir)-induced alterations of flow and water temperature regimes can threaten downstream fish habitats and native aquatic ecosystems. Alleviating the negative environmental impacts of dam-reservoir and balancing the multiple purposes of reservoir operation have attracted wide attention. While previous studies have incorporated ecological flow requirements in reservoir operation strategies, a comprehensive analysis of trade-offs among hydropower benefits, ecological flow, and ecological water temperature demands is lacking. Hence, this study develops a multi-objective ecological scheduling model, considering total power generation, ecological flow guarantee index, and ecological water temperature guarantee index simultaneously. The model is based on an integrated multi-objective simulation-optimization (MOSO) framework which is applied to Three Gorges Reservoir. To that end, first, a hybrid long short-term memory and one-dimensional convolutional neural network (LSTM_1DCNN) model is utilized to simulate the dam discharge temperature. Then, an improved epsilon multi-objective ant colony optimization for continuous domain algorithm (ε-MOACOR) is proposed to investigate the trade-offs among the competing objectives. Results show that LSTM _1DCNN outperforms other competing models in predicting dam discharge temperature. The conflicts among economic and ecological objectives are often prominent. The proposed ε-MOACOR has potential in resolving such conflicts and has high efficiency in solving multi-objective benchmark tests as well as reservoir optimization problem. More realistic and pragmatic Pareto-optimal solutions for typical dry, normal and wet years can be generated by the MOSO framework. The ecological water temperature guarantee index objective, which should be considered in reservoir operation, can be improved as inflow discharge increases or the temporal distribution of dam discharge volume becomes more uneven.