Spatial and temporal changes of outdoor thermal stress: influence of urban land cover types

Green infrastructure (GI) has emerged as a feasible strategy for promoting adaptive capacities of cities to climate change by alleviating urban heat island (UHI) and thus heat stress for humans. However, GI can also intensify the winter cold stress. To understand the extent of UHI within a city as well as the link between outdoor thermal stress both diurnally and seasonally, we carried out an empirical study in Würzburg, Germany from 2018 to 2020. At sub-urban sites, relative humidity and wind speed (WS) was considerably higher and air temperature (AT) lower compared to the inner city sites. Mean AT of inner city sites were higher by 1.3 °C during summer and 5 °C during winter compared to sub-urban sites. The magnitude followed the spatial land use patterns, in particular the amount of buildings. Consequently, out of 97 hot days (AT > 30 °C) in 3 years, 9 days above the extreme threshold of wet bulb globe temperature of 35 °C were recorded at a centre location compared to none at a sub-urban site. Extreme heat stress could be halved with 30–40% cover of greenspaces including grass lawns, green roofs, and green walls with little compromise in increasing winter cold stress.

Ice in caves and its effect on thermal inversion and permafrost in the case of the Velika ledena jama v Paradani, Smrekova draga and neighbouring dolines

In the Velika ledena jama v Paradani, in the karstic blowholes on the slopes of Smrekova draga and in the nearby dolines I measured and interpreted air temperatures and the effect of the summer outflow of cold air from them into the surrounding area. In winter, cold air enters the cave, radically cooling the entrance part of the cave, where for this reason there is permanent cave ice. The summertime circulation is reversed: emerging from the inner part of cave, which has an average temperature of around 4° C, is air which only when it transits through the sub-cooled entrance part is then cooled to around 1° C. This air comes to the surface and in the hollow at the cave entrance maintains a distinct thermal inversion during the warm part of the year. There is a similar air circulation and similar development of annual temperatures observed at the vents, where cave air emerges through rubble spread over cave entrances on slopes or at the bottom of dolines. The stable summer air temperatures of around 1° C in the vents where I conducted measurements indicate that underneath them there is also permafrost or sub-cooled rock and permanent ice. This is created and preserved, just like in the caves, due to the advection of cold air in winter. In Trnovski gozd, such karstic permafrost is found at an altitude of 1,100 m above sea level. The outflow of cold air from the vents in the summer, just like inside the cave, causes a distinct thermal inversion in dolines on the surface.

Impact of Environmental Stressors on the Metabolic Functioning of a Temperate Cnidarian-Dinoflagellate Symbiosis

<p>Cnidarian-dinoflagellate symbioses occur across a wide latitudinal range, from temperate to tropical locations in both hemispheres. In the tropics, this association provides the foundation for the development of highly diverse coral reef ecosystems. Tropical associations are particularly sensitive to thermal variability, however, leading to dysfunction of the relationship and eventual expulsion of the symbiont, known as ‘coral bleaching’. In contrast, temperate associations maintain stable symbiotic relationships in highly fluctuating thermal environments. The reason behind the relative thermal tolerance of temperate associations is still unclear, though the ability to maintain cellular homeostasis through adjustments to metabolic processes is likely a core feature of their resilience. Both a field study and laboratory experiment were conducted to determine the metabolic responses to thermal change of the symbiosis between the temperate anemone Anthopleura aureoradiata and the dinoflagellate Symbiodinium. For the field component, A. aureoradiata were collected from Point Halswell in Wellington Harbour in both summer and winter. For the laboratory experiment, specimens collected at Pautahanui inlet were thermally acclimated in the laboratory, after which temperatures were altered over the course of one week to either 8°C (cold) or 28°C (hot) and maintained at these temperatures for six weeks. Gas chromatography coupled to mass spectrometry was then employed to determine the identity and relative quantity of a wide range of metabolites involved in primary metabolism including organic acids, fatty acids, amino acids and sugars. Based on these data, pathway activity profiling was used to determine the activity of different metabolic pathways both between seasons and in response to cold and heat treatment. A wide range of changes to metabolic processes were observed in both host and symbiont. Photosynthetic capacity was reduced in the symbionts at low temperatures and increased at high temperatures. The only organic acid to be significantly impacted was propanedioic acid, which increased in the host in response to cold treatment, potentially related to increased translocation from the symbiont. Altered fatty acid content in both host and symbiont was related to the role of fatty acids as energy sources and storage compounds and in cell signalling processes. Changes in fatty acid-associated metabolic pathways were exemplified by arachidonic acid and linoleic acid metabolism. Alterations to free amino acids and amino acid related pathways in both host and symbiont were associated with their role as antioxidants and osmoprotectants and the catabolism of amino acids for the production of energy. In symbionts only, altered amino acid content was associated with the role of amino acids in the production of alkaloids. Changes in a number of sugar derivatives in both host and symbiont were associated with their role as antioxidants and osmoprotectants. Altered sugar metabolism in the symbiont clearly indicated an increase in the production of energy rich sugar molecules and production of cellular energy in summer/hot conditions and a decrease in winter/cold conditions. Notably impacted pathways included the Calvin cycle, glycolysis, the pentose phosphate pathway and oxidative phosphorylation. Patterns of sugar related pathway activity in the host were generally opposite to that observed in the symbiont. Overall, prominent but opposing changes in the host and symbiont were detected in the central carbohydrate and energy metabolic pathways. In general, the activity of these pathways increased in the host in winter/cold conditions and decreased in summer/hot conditions, while in the symbiont the pattern was the opposite. These findings highlight the role of metabolic processes in enabling the persistence of a temperate cnidarian-dinoflagellate symbiosis in the face of large temperature fluctuations. This work provides a foundation upon which a deeper understanding of metabolic functioning in the cnidarian-dinoflagellate symbiosis can be built and provides a comparative platform for studies of the more thermally sensitive tropical associations.</p>

Impact of Environmental Stressors on the Metabolic Functioning of a Temperate Cnidarian-Dinoflagellate Symbiosis

<p>Cnidarian-dinoflagellate symbioses occur across a wide latitudinal range, from temperate to tropical locations in both hemispheres. In the tropics, this association provides the foundation for the development of highly diverse coral reef ecosystems. Tropical associations are particularly sensitive to thermal variability, however, leading to dysfunction of the relationship and eventual expulsion of the symbiont, known as ‘coral bleaching’. In contrast, temperate associations maintain stable symbiotic relationships in highly fluctuating thermal environments. The reason behind the relative thermal tolerance of temperate associations is still unclear, though the ability to maintain cellular homeostasis through adjustments to metabolic processes is likely a core feature of their resilience. Both a field study and laboratory experiment were conducted to determine the metabolic responses to thermal change of the symbiosis between the temperate anemone Anthopleura aureoradiata and the dinoflagellate Symbiodinium. For the field component, A. aureoradiata were collected from Point Halswell in Wellington Harbour in both summer and winter. For the laboratory experiment, specimens collected at Pautahanui inlet were thermally acclimated in the laboratory, after which temperatures were altered over the course of one week to either 8°C (cold) or 28°C (hot) and maintained at these temperatures for six weeks. Gas chromatography coupled to mass spectrometry was then employed to determine the identity and relative quantity of a wide range of metabolites involved in primary metabolism including organic acids, fatty acids, amino acids and sugars. Based on these data, pathway activity profiling was used to determine the activity of different metabolic pathways both between seasons and in response to cold and heat treatment. A wide range of changes to metabolic processes were observed in both host and symbiont. Photosynthetic capacity was reduced in the symbionts at low temperatures and increased at high temperatures. The only organic acid to be significantly impacted was propanedioic acid, which increased in the host in response to cold treatment, potentially related to increased translocation from the symbiont. Altered fatty acid content in both host and symbiont was related to the role of fatty acids as energy sources and storage compounds and in cell signalling processes. Changes in fatty acid-associated metabolic pathways were exemplified by arachidonic acid and linoleic acid metabolism. Alterations to free amino acids and amino acid related pathways in both host and symbiont were associated with their role as antioxidants and osmoprotectants and the catabolism of amino acids for the production of energy. In symbionts only, altered amino acid content was associated with the role of amino acids in the production of alkaloids. Changes in a number of sugar derivatives in both host and symbiont were associated with their role as antioxidants and osmoprotectants. Altered sugar metabolism in the symbiont clearly indicated an increase in the production of energy rich sugar molecules and production of cellular energy in summer/hot conditions and a decrease in winter/cold conditions. Notably impacted pathways included the Calvin cycle, glycolysis, the pentose phosphate pathway and oxidative phosphorylation. Patterns of sugar related pathway activity in the host were generally opposite to that observed in the symbiont. Overall, prominent but opposing changes in the host and symbiont were detected in the central carbohydrate and energy metabolic pathways. In general, the activity of these pathways increased in the host in winter/cold conditions and decreased in summer/hot conditions, while in the symbiont the pattern was the opposite. These findings highlight the role of metabolic processes in enabling the persistence of a temperate cnidarian-dinoflagellate symbiosis in the face of large temperature fluctuations. This work provides a foundation upon which a deeper understanding of metabolic functioning in the cnidarian-dinoflagellate symbiosis can be built and provides a comparative platform for studies of the more thermally sensitive tropical associations.</p>

Association between winter cold spells and acute myocardial infarction in Lithuania 2000–2015

Acute myocardial infarction (AMI) is a major public health problem. Cold winter weather increases the risk of AMI, but factors influencing susceptibility are poorly known. We conducted an individual-level case-crossover study of the associations between winter cold spells and the risk of AMI, with special focus on survival at 28 days and effect modification by age and sex. All 16,071 adult cases of AMI among the residents of the city of Kaunas in Lithuania in 2000–2015 were included in the study. Cold weather was statistically defined using the 5th percentile of frequency distribution of daily mean temperatures over the winter months. According to conditional logistic regression controlling for time-varying and time-invariant confounders, each additional cold spell day during the week preceding AMI increased the risk of AMI by 5% (95% CI 1–9%). For nonfatal and fatal cases, the risk increase per each additional cold spell day was 5% (95% CI 1–9%) and 6% (95% CI − 2–13%), respectively. The effect estimate was greater for men (OR 1.07, 95% CI 1.02–1.12) than for women (OR 1.02, 95% CI 0.97–1.08), but there was no evidence of effect modification by age. Evidence on factors increasing susceptibility is critical for targeted cold weather planning.

Ecological effects on female bill colour explain plastic sexual dichromatism in a mutually-ornamented bird

Sex differences in ornamentation are common and, in species with conventional sex roles, are generally thought of as stable, due to stronger sexual selection on males. Yet, especially in gregarious species, ornaments can also have non-sexual social functions, raising the possibility that observed sex differences in ornamentation are plastic. For example, females may invest in costly ornamentation more plastically, to protect body and reproductive ability in more adverse ecological conditions. We tested this hypothesis with experimental work on the mutually-ornamented common waxbill (Estrilda astrild), supplementing their diets either with pigmentary (lutein, a carotenoid) or non-pigmentary (vitamin E) antioxidants, or alleviating winter cold temperature. We found that both lutein and vitamin E supplementation increased red bill colour saturation in females, reaching the same mean saturation as males, which supports the hypothesis that female bill colour is more sensitive to environmental or physiological conditions. The effect of vitamin E, a non-pigment antioxidant, suggests that carotenoids were released from their antioxidant functions. Alleviating winter cold did not increase bill colour saturation in either sex, but increased the stability of female bill colour over time, suggesting that female investment in bill colour is sensitive to cold-mediated stress. Together, results show that waxbill bill sexual dichromatism is not stable. Instead, sexual dichromatism can be modulated, and even disappear completely, due to ecology-mediated plastic adjustments in female bill colour.

Aerosol removal coefficients based on 7Be, 210Pb, and 210Po radionuclides in the urban atmosphere

In this study, the aerosol removal coefficients based on 7Be, 210Pb and 210Po radionuclides in the urban air, in Lodz, Poland, were investigated over 3 years, between May 2014 and December 2017. Results representing the summer/warm and winter/cold seasons were applied to quantity and quality estimates of aerosol removal processes. The values for the removal processes were closely dependent on the meteorological conditions; therefore, a set of nine meteorological parameters was employed in the analysis. The multiple regression method was applied to explain the relationship between the removal coefficients of aerosols and independent factors identified using Principal Component Analysis.

Links between atmospheric blocking and North American winter cold spells in two generations of Canadian Earth System Model large ensembles

Due to the significant negative consequences of winter cold extremes, there is need to better understand and simulate the mechanisms driving their occurrence. The impact of atmospheric blocking on winter cold spells over North America is investigated using ERA-Interim and NCEP-DOE-R2 reanalyses for 1981–2010. Initial-condition large-ensembles of two generations of Canadian Earth System Models (CanESM5 and its predecessor, CanESM2) are evaluated in terms of their ability to represent the blocking-cold spell linkage and the associated internal-variability. The reanalysis datasets show that 72 and 58% of cold spells in southern and northern North America coincide with blocking occurring in the high-latitude Pacific-North America. Compared to the two reanalyses, CanESM2 and CanESM5 ensembles underestimate by 19.9 and 14.3% cold spell events coincident with blocking, due to significant under-representation of blocking frequency over the North Pacific (− 47.1 and − 29.0%), whereas biases in cold spell frequency are relatively small (6.6 and − 4.7%). In the reanalyses, regions with statistically significant above-normal cold spell frequency relative to climatology lie on the east and/or south flanks of blocking events, whereas those with below-normal frequency lie along the core or surrounding the blocking. The two ensembles reproduce the observed blocking-cold spell linkage over North America, despite underestimating the magnitude of blocking frequency. The two ensembles also reproduce the physical drivers that underpin the blocking-cold spell linkage. Spatial agreement with the reanalyses is found in the simulated patterns of temperature advection and surface heat flux forcing anomalies during blocking events. While CanESM5 shows an improved representation of the blocking climatology relative to CanESM2, both yield similar results in terms of the blocking-cold spell linkage and associated internal-variability.