Seasonal Temperature Changes Research Articles

Reduced physiological plasticity in a fish adapted to stable temperatures

Plasticity can allow organisms to maintain consistent performance across a wide range of environmental conditions. However, it remains largely unknown how costly plasticity is and whether a trade-off exists between plasticity and performance under optimal conditions. Biological rates generally increase with temperature, and to counter that effect, fish use physiological plasticity to adjust their biochemical and physiological functions. Zebrafish in the wild encounter large daily and seasonal temperature fluctuations, suggesting they should display high physiological plasticity. Conversely, laboratory zebrafish have been at optimal temperatures with low thermal fluctuations for over 150 generations. We treated this domestication as an evolution experiment and asked whether this has reduced the physiological plasticity of laboratory fish compared to their wild counterparts. We measured a diverse range of phenotypic traits, from gene expression through physiology to behavior, in wild and laboratory zebrafish acclimated to 15 temperatures from 10 °C to 38 °C. We show that adaptation to the laboratory environment has had major effects on all levels of biology. Laboratory fish show reduced plasticity and are thus less able to counter the direct effects of temperature on key traits like metabolic rates and thermal tolerance, and this difference is detectable down to gene expression level. Rapid selection for faster growth in stable laboratory environments appears to have carried with it a trade-off against physiological plasticity in captive zebrafish compared with their wild counterparts.

Climate change impact on the population dynamics of exotic pathogens: The case of the worldwide pathogen Phytophthora cinnamomi

Worldwide, Mediterranean-climate type forests are seriously threatened by climate change and Phytophthora cinnamomi, an extremely aggressive soilborne pathogen listed among the 100 worst invasive alien species. This study examines for first time the effects of annual and seasonal changes in temperature and rainfall under different climatic scenarios on P. cinnamomi dynamics in a Mediterranean forest naturally infested. We followed seasonally and during four years (2016–2020) P. cinnamomi abundance in the soil taking advantage of a climate change infrastructure that simulates a 30% rainfall reduction using rainout shelters and an increase in soil temperature using open top chambers. Seasonal abundance of P. cinnamomi was strongly linked to spring precipitation: the large inoculum density during this season suffered a strong decrease during the dry summer that was maintained until the next spring, despite of fall rains. Thus, inoculum density in spring may be considered the best indicator of the potential of P. cinnamomi infection in natural ecosystems. The two climatic treatments had significant effects on P. cinnamomi abundance, but only in some combinations of seasons and years. Rainfall exclusion had a negative effect on the spring abundance of P. cinnamomi mostly in wet years, causing a reduction as large as 30% in comparison with the control treatment. Meanwhile, warming effect varied from slightly negative in winter to positive in spring and early summer, causing increases as large as 31% in comparison with the control treatment. Overall, we provide novel experimental evidence suggesting that a drier climate might limit the abundance and activity of P. cinnamomi in water-limited forests, but that this negative effect might be at least partly counteracted by the positive effects of warming. These results also imply that P. cinnamomi represents an increasing threat under climate change for the conservation of forest ecosystems where water is not a limiting factor.

The impact of temperature changes on patients with acute coronary syndrome

Abstract Funding Acknowledgements Type of funding sources: None. Background There are few studies about changes in temperature as a risk factor instability of atheromatous plaque and Acute Coronary Syndrome (ACS). It is the first study in our country. Purpose To evaluate the impact of temperature on patients with Acute Coronary Syndrome. Methods This is a retrospective, observational, analytical study conducted in a single-center, in the period January-December 2018. We included patients with the diagnosis of ACS, hospitalized in CCU, who performed emergency coronary angiography. Data were collected retrospectively using patient records from archived files at the Statistics Center. Data on atmospheric parameters, measured at the weather monitoring station, were obtained from the National Meteorological Service database (average daily temperature in each district of the country). The number of inhabitants for the respective districts is taken from the National Institute of Statistics. Results The study included 1165 patients. A significant association was found between the number of ACS per day with temperature changes (r=-0.13, p<0.01). The highest number of ACS was in October 10.4%, whereas the lowest number was in January 10.6%, with a significant decreasing trend during May-June and the peak in October (p=0.04). Significant changes in the average monthly values of temperature were accompanied by a statistically significant increase in the number of cases as occurred in March-April and October-November. (p≤0.05) A statistically significant relationship was observed between seasonal changes in temperature with the number of cases with ACS. The autumn season prevails with 27.9% of the total cases, followed by the spring season with 25.6%, the summer season with 24.2%, and the winter season with 22.3%, (p = 0.04). Most cases in the cold period (November-March) occurred on days with statistically significant changes in Temperature. Conclusion The study notes an important relationship between seasonal, monthly, and daily changes of temperatures, in relation to the frequency of cases with Acute Coronary Syndrome.

Middle to Late Jurassic stable isotopes and element ratios of fossils from western India: Developing a reference temperature curve for northeastern Gondwana

The stable isotope (δ13C, δ18O) and element (Mg/Ca, Sr/Ca) composition of 374 well-preserved belemnites, bivalves, and brachiopods of the Kachchh and Jaisalmer basins in western India were used to reconstruct climatic changes in the Middle and Late Jurassic time interval. Absolute water temperatures reconstructed from δ18Oshell values depend on the used δ18Osea value and equation, but indicate a long-term temperature decrease of around 8–9 °C in the study area from the Bajocian to the Tithonian. Measured Mg/Ca ratios also point to decreasing temperatures, but additionally reflect species-specific factors and a lower Mg/Ca ratio of Jurassic seawater compared to today. The recorded cooling in western India agrees with previous results from neighbouring Madagascar and the Indian Himalayas and can be connected to a drift of Eastern Gondwana into higher latitudes. This palaeogeographic shift is accompanied by changes in sedimentation indicating an increasingly humid climate and in the composition of ecosystems reflecting increasingly cooler water temperatures. High-resolution stable oxygen isotope analyses of three oyster shells point to seasonal temperature changes of 4–5 °C in the Kimmeridgian. The recorded δ13C values reflect sea-level changes with a positive excursion in the Oxfordian connected to a major transgressive event. Sr/Ca ratios are observed to follow changes in global ocean chemistry.

The influence of seasonal calcification depth change on the planktonic foraminiferal stable oxygen isotope signal

Seasonal changes in temperature and habitat migration both leave large imprints on the stable oxygen isotope composition (δ18O) of planktonic foraminiferal tests, but little is known about how much the depth habitat change affects the calcite δ18O on seasonal timescales, potentially introducing numerous errors to the study of seasonality applied individual foraminifera. In this study, two time series sediment trap moorings deployed in the northern South China Sea (SCS) from July 2012 to April 2013 and southern SCS (upwelling area) from April to October 2014 were used to infer seasonal calcification depth variations for four commonly used planktonic foraminiferal species, Globigerinoides ruber, Trilobatus sacculifer, without a sac-like final chamber, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei by analyzing their test δ18O values. The findings demonstrate that planktonic foraminifera deposit their tests shallower in the winter and during cold water upwelling activity, and deeper in the summer, with a changing seasonal depth habitat for all species that tends to follow the isothermals. More importantly, we devised a new approach for quantifying the effect of seasonal calcification depth changes on the δ18O signature of planktonic foraminiferal tests. After applying this method to our trap site and nine other published global sediment trap sites, the results show that foraminiferal seasonal δ18O signal is strongly distorted (amplified or damped) by seasonal variations in their habitat depth, particularly for the species living in low latitude, attributed to the strong vertical temperature gradient relative to the seasonal temperature change at a given water depth. Surface water species that live in the homogeneous mixed layer may be able to provide the most comprehensive seasonality information.

Seasonal changes in the parasite prevalence of a small Malagasy lemur species (Lepilemur edwardsi).

Parasitic infections can impact the fitness of individuals and can have influence on animals' population dynamics. An individuals' parasite prevalence often changes depending on external or seasonal changes, for example, rainfall and ambient temperatures, but also on internal changes, for example, changes in body condition. In this study we aimed to identify the environmental factors that may influence the intestinal parasite and ectoparasite prevalence of the folivorous Malagasy primate species, Lepilemur edwardsi, living in a seasonal dry deciduous forest. Species living in this habitat have to adapt to seasonal changes of ambient temperature, with almost no precipitation during the dry season and hence strong fluctuations of resource availability throughout the year. We sampled the feces and ectoparasites of L. edwardsi throughout the year. Intestinal parasite prevalence increased from the wet to the dry season and was highest in the late dry season, which might be due to the accompanying decrease in diet quality. Conversely, ectoparasite prevalence decreased in the dry season, presumably due to the prevailing unfavorable environmental conditions for the development of ectoparasites (i.e., mites and ticks). Paired with the higher resting metabolism and stress level of L. edwardsi during the late dry season, it seems that this species may struggle when dry seasons intensify in its habitat.

A periodic Chikungunya model with virus mutation and transovarial transmission

In this paper, a Chikungunya dynamical model with virus mutation and transovarial transmission is developed, which incorporates the effect of seasonal temperature changes on disease transmission through time-dependent parameters. Firstly, the threshold parameter R0m that determines the persistence and extinction of mosquito populations is given, and then the disease reproduction number R0 is defined. Secondly, it is proved that if R0m > 1 and R0 < 1, the disease disappears; if R0m > 1 and R0 > 1, then Chikungunya with mutants and non-mutants will persist simultaneously. Finally, a case study is carried out with the data in Kerala, India, where the virus mutation causes the outbreak of Chikungunya. Data on newly confirmed human cases in the state between 2007 and 2010 is fitted and the theoretical results obtained in the previous section are validated. In addition, the effects of seasonal temperature change, virus mutation and transovarial transmission on the prevalence of the disease are studied by numerical simulations from different aspects.2020 MSC: 34K13; 37N25; 92D30.

A field study of desalination of high-salinity surface brackish water via an RO-NF hybrid system

In this work, a pilot-scale membrane desalination demonstration system for producing drinking water from surface brackish water with a total dissolved solids (TDS) of ≤ 10 g/L was designed and constructed. The production capacity and water recovery were at least 1 m3/h and 50%, respectively. Brackish water was pretreated with microflocculation – precision filtration – ultrafiltration, and the quality of the produced water met the feed water requirements of nanofiltration (NF)/reverse osmosis (RO). The performances of various design configurations, including single NF, single RO, and NF-RO hybrid systems, were evaluated and compared in terms of water recovery and product water TDS. The hybrid RO-NF systems were found to be more effective than either NF or RO alone, and the 4RO-4NF design configuration was most favorable. At a TDS of 10 g/L in the feed, the processing capacity and product water TDS of the 4RO-4NF hybrid system was able to meet the design specs at a feed flow rate of 2 m3/h and an operating pressure of 1.5 MPa. Its long-term stability was examined as well, and it was demonstrated that the desalination performance of the system was mainly affected by seasonal temperature changes and rainfall. The total process cost was estimated to be $1.56/m3, which is considered economically suitable for remote areas where safe drinking water cannot be provided centrally.

Monitoring of Seasonal Variations in Ground Temperature

The paper considers the problem of monitoring seasonal changes in soil temperature in northern and mountainous areas in the light of ongoing climate changes. To study seasonal changes in soil temperature, a model site of the Moscow State University Meteorological Observatory was used with the ability to monitor air temperature, snow cover thickness, and ground freezing temperature and depth, which was a prototype of a system for monitoring the state of permafrost soils used in the Arctic and mountain territories. The paper presents the results of monitoring seasonal changes in soil temperature based on the results of numerical modeling of the penetration of seasonal fluctuations in soil temperature in 2014-2017 in MATLAB environment at the model site of the MSU Meteorological Observatory. The results of numerical simulation of the penetration of seasonal temperature fluctuations in the ground at the MSU meteorological site in 2014-2017 in the MATLAB environment are in good agreement with the thermometry data and, therefore, the developed calculation scheme shows fairly good simulation results. This makes it possible to use the calculation scheme to assess the thermal state of frozen soils and assess the stability of foundations and buildings and linear structures located on them in the conditions of the North and mountainous territories. Therefore, the presented methodology can serve as a good help for monitoring and preventing the destruction of the studied structures in the conditions of climate warming.

A case study of paleoenvironmental interactions during the Miocene Climate Optimum in southwestern Paratethys

The marine system of the Mediterranean-Paratethys region in the Middle Miocene was influenced by the global climatic changes corresponding to the Miocene Climate Optimum. The latter was characterized by global warming of deep oceanic waters succeeded by a decrease of wind activity and ocean water circulation together with a decline in oceanic productivity. This study provides a detailed paleoenvironmental and depositional history of the Middle Miocene deposits from Mt. Požeška Gora (the east part of Croatia). Stable carbon and oxygen isotope data with foraminiferal fauna coupled together with palynological data indicate both seasonal and long-term changes in surface water temperatures, nutrient contents, and salinity. Furthermore, it was possible to determine two phases of Middle Miocene flooding in the studied marine system: (a) a shallow, high nutrient marginal sea strongly affected by freshwater inputs corresponding to the thermal maximum and periods with enhanced precipitation during the Miocene Climate Optimum, and (b) a younger deeper marginal sea with a developed seasonal stratification, rather intermediate nutrient availability and reduced fresh-water inputs. Based on the microbiostratigraphy and strontium isotope stratigraphy (87Sr/86Sr) coupled with previously published high-precision geochronology, the timing of the first and second flooding can be correlated with the Langhian age - ≤15.4 Ma and 14.6 Ma, respectively Possibly, the properties of the surficial waters that were described as a part of the flooding phases in individual time intervals can indicate changes in circulation patterns as a result of potential influence of the open-sea water masses.

Nitrogen removal performance of anammox immobilized fillers in response to seasonal temperature variations and different operating modes: Substrate utilization and microbial community analysis

Four anaerobic ammonium oxidation (anammox) immobilized filler reactors (R1: 33 °C-normal, R2: seasonal temperature-normal, R3: seasonal temperature-feast, R4: seasonal temperature-starvation) were established to study the response of anammox immobilized fillers to seasonal temperature changes and different operating modes. The results showed that the anammox immobilized filler could better adapt to the seasonal temperature drop and maintain the activity potential by adjusting the hydraulic retention time (HRT). During the temperature rise phase, R2 activity increased rapidly with the highest nitrogen removal rate reaching 1.26 kgN·(m3·d)−1, which was equivalent to control sample R1 (1.33 kgN·(m3·d)−1). However, feasting and famine conditions severely impaired anammox performance and changed stoichiometric ratios; feasting, in particular, significantly lowered the nitrogen removal potential of R3. The specific anammox activity of R2, R3 and R4 was 92.2%, 52.6% and 67.9%, respectively, that of R1, respectively, where the accumulation of functional bacteria was the reason for the higher activity of R2. Degradation kinetics and NO2−-N inhibition curves showed that R3 was less sensitive to high concentrations of NH4+–N, while R4 responded earlier to low concentrations of NH4+–N, and the reduction of IC50 at low temperature was the reason for the inhibition of R3 activity. Furthermore, seasonal temperature fluctuations had little effect on the microbial community structure but had a considerable impact on bacteria abundance. The anammox functional bacteria Candidatus Kuenenia was found to be the dominant genus in R1-R4; however, the relative abundance of most bacteria, including anammox bacteria, decreased in R3, while the proportion of fermentation bacteria and denitrifying bacteria increased in R4. These findings highlight the necessity of rational regulation of HRT for the adaptation of anammox immobilized fillers to seasonal temperature changes, which could enhance our understanding of the synergistic effect of seasonal temperature changes and different operating modes on nitrogen removal.

Metabolic plasticity improves lobster\u2019s resilience to ocean warming but not to climate-driven novel species interactions

Marine species not only suffer from direct effects of warming oceans but also indirectly via the emergence of novel species interactions. While metabolic adjustments can be crucial to improve resilience to warming, it is largely unknown if this improves performance relative to novel competitors. We aimed to identify if spiny lobsters—inhabiting a global warming and species re-distribution hotspot—align their metabolic performance to improve resilience to both warming and novel species interactions. We measured metabolic and escape capacity of two Australian spiny lobsters, resident Jasus edwardsii and the range-shifting Sagmariasus verreauxi, acclimated to current average—(14.0 °C), current summer—(17.5 °C) and projected future summer—(21.5 °C) habitat temperatures. We found that both species decreased their standard metabolic rate with increased acclimation temperature, while sustaining their scope for aerobic metabolism. However, the resident lobster showed reduced anaerobic escape performance at warmer temperatures and failed to match the metabolic capacity of the range-shifting lobster. We conclude that although resident spiny lobsters optimise metabolism in response to seasonal and future temperature changes, they may be unable to physiologically outperform their range-shifting competitors. This highlights the critical importance of exploring direct as well as indirect effects of temperature changes to understand climate change impacts.

Global seasonal dynamics of inland open water and ice

Seasonal changes of temperature and precipitation cause inland open surface water and ice cover extents to vary dramatically through the year from local to global scales. These dynamics of land, water, and ice have a significant impact on climate and often are critical to natural ecosystem functioning. However, global seasonal dynamics of both water and ice extent have not been well quantified. Here, we present the quantification of monthly surface water and ice areas for 2019 with associated uncertainties. Time-series reference data were created for a probability sample of 10 m grid cells by interpreting the entire 2019 time-series of 10 m Sentinel-2 data and a subset of 3 m PlanetScope data in selected places with a mix of land and water. From the probability sample reference data, we estimate that 4.86 ± 0.16 million km2 had inland water presence at some point during the year. Globally, only 23% of the total area with water was permanent water that remained open year-round (1.13 ± 0.19 million km2). Permanent water with seasonal ice cover extended 1.97 ± 0.21 million km2, comprising 41% of the total area with water. Seasonal water-land transitions (both with and without ice/snow cover) covered the remaining 36% of the total area with water (1.76 ± 0.19 million km2). February had the maximum extent of ice over areas of inland permanent and seasonal water, totaling 2.49 ± 0.25 million km2, and January – March had a larger global extent of ice cover than of open water. To investigate the spatiotemporal distribution of ice cover and the suitability of Landsat, prototype maps of surface water ice cover phenology were created by integrating the ice/snow and no data labels from the quality assurance layer of the GLAD ARD of Potapov et al. (2020) with the monthly surface water layers of Pickens et al. (2020), both of which are Landsat-based. While limited by data availability, these maps reveal the high spatiotemporal variability of ice phenology. The near-daily observations near the poles and the 10 m resolution bands of Sentinel-2 provide unprecedented potential to examine surface water and ice dynamics for 2016 forward and to investigate the drivers and impacts of this variability.

Response to Cold: A Comparative Transcriptomic Analysis in Eight Cold-Adapted Yeasts

Microorganisms have evolved to colonize all biospheres, including extremely cold environments, facing several stressor conditions, mainly low/freezing temperatures. In general, terms, the strategies developed by cold-adapted microorganisms include the synthesis of cryoprotectant and stress-protectant molecules, cold-active proteins, especially enzymes, and membrane fluidity regulation. The strategy could differ among microorganisms and concerns the characteristics of the cold environment of the microorganism, such as seasonal temperature changes. Microorganisms can develop strategies to grow efficiently at low temperatures or tolerate them and grow under favorable conditions. These differences can be found among the same kind of microorganisms and from the same cold habitat. In this work, eight cold-adapted yeasts isolated from King George Island, subAntarctic region, which differ in their growth properties, were studied about their response to low temperatures at the transcriptomic level. Sixteen ORFeomes were assembled and used for gene prediction and functional annotation, determination of gene expression changes, protein flexibilities of translated genes, and codon usage bias. Putative genes related to the response to all main kinds of stress were found. The total number of differentially expressed genes was related to the temperature variation that each yeast faced. The findings from multiple comparative analyses among yeasts based on gene expression changes and protein flexibility by cellular functions and codon usage bias raise significant differences in response to cold among the studied Antarctic yeasts. The way a yeast responds to temperature change appears to be more related to its optimal temperature for growth (OTG) than growth velocity. Yeasts with higher OTG prepare to downregulate their metabolism to enter the dormancy stage. In comparison, yeasts with lower OTG perform minor adjustments to make their metabolism adequate and maintain their growth at lower temperatures.

Strong heatwaves with widespread urban-related hotspots over Africa in 2019

2019 was one of the hottest years in recent decades, with widespread heatwaves over many parts of the world, including Africa. However, as a developing and vulnerable region, the understanding of recent heatwave events in Africa is limited. Here, the authors incorporated different climate datasets, satellite observations, and population estimates to investigate patterns and hotspots of major heatwave events over Africa in 2019. Overall, 2019 was one of the years that experienced the strongest heatwaves in terms of intensity and duration since 1981 in Africa. Heatwave hotspots were clearly identified across western-coastal, northeastern, southern, and equatorial Africa, where major cities and human populations are located. The proportion of urban agglomerations (population) exposed to extreme (99th percentile) heatwaves in the Northern Hemisphere and Southern Hemisphere rose from 4% (5 million people) and 15% (17 million people), respectively, in the baseline period of 1981–2010 to 36% (43 million people) and 57% (53 million people), respectively, in 2019. Heatwave patterns and hotspots in 2019 were related to anomalous seasonal change in atmospheric circulation and above-normal sea surface temperature. Without adaptation to minimize susceptibility to the effects of heatwave events, the risks they pose in populated areas may increase rapidly in Africa.摘要2019 年是近几十年来最热的年份之一, 包括非洲在内的全球许多地区都受到大范围的热浪侵袭. 然而, 非洲作为脆弱的发展中地区, 我们对其近年热浪事件的了解非常有限. 本研究中, 我们结合了不同的气候数据集, 卫星观测资料和人口数据, 研究了 2019 年非洲地区主要热浪事件发生的时空特征和热点分布区. 总体而言, 2019 年是非洲地区自 1981 年以来热浪强度最强, 持续时间最久的年份之一. 在主要城市和人口所在的非洲西海岸, 东北部, 南部和赤道地区是热浪发生的热点区. 位于赤道以北的非洲地区, 暴露于极端 (第 99 个百分位) 热浪的城市人口比例从 1981–2010 年基准期的 4% (500 万人) 上升至2019 年的 36% (4300 万人). 位于赤道以南地区, 暴露于极端热浪的城市人口则从基准期的15% (1700 万人) 上升至57% (5300 万人). 2019 年的热浪时空特征和热点分布与大气环流的季节变化异常和海温的暖异常有关. 如果不及时采取适应措施以尽量减少人口对热浪事件影响的敏感性, 热浪对非洲人口稠密地区构成的风险可能会迅速增加.

Parental and Environmental Control of Seed Dormancy in Arabidopsis thaliana.

Seed dormancy-the absence of seed germination under favorable germination conditions-is a plant trait that evolved to enhance seedling survival by avoiding germination under unsuitable environmental conditions. In Arabidopsis, dormancy levels are influenced by the seed coat composition, while the endosperm is essential to repress seed germination of dormant seeds upon their imbibition. Recent research has shown that the mother plant modulates its progeny seed dormancy in response to seasonal temperature changes by changing specific aspects of seed coat and endosperm development. This process involves genomic imprinting by means of epigenetic marks deposited in the seed progeny and regulators previously known to regulate flowering time. This review discusses and summarizes these discoveries and provides an update on our present understanding of the role of DOG1 and abscisic acid, two key contributors to dormancy.

Mapping intrashell variation in Mg/Ca of brachiopods to external growth lines: Mg enrichment corresponds to seasonal growth slowdown

Determining secular changes in seawater temperature and Mg/Ca ratio is of high importance in paleooceanographic, paleoenvironmental and paleoecological studies. On the one hand, intra-shell variation in Mg/Ca in brachiopod shells is used to reconstruct historical changes in temperature and in seasonality. On the other hand, intra-shell analyses show a weak relationship between Mg/Ca and δ18O, but a positive correlation between Mg/Ca and Sr/Ca, and an increase of Mg/Ca at growth lines, indicating that Mg/Ca does not simply track seawater temperature alone. Internal growth lines are rarely visible in brachiopod shells, and the relation between growth lines that mark growth slowdown or cessation and Mg/Ca fluctuation is thus not properly understood. Here, using four species of extant brachiopods from the NE Pacific and the SW Pacific, from environments with low seasonality in seawater temperature (<5 °C), and two species of Late Triassic brachiopods (Western Carpathians), we measure intra-shell ontogenetic variation in Mg/Ca, S/Ca and Sr/Ca with laser ablation ICP-MS and electron microprobe. In contrast to previous studies, we map variation in Mg, S, and Sr to external growth lines. We find that, first, zones of Mg/Ca enrichment in the secondary layer form 10–50 μm-thick discrete bands or clusters of micrometric bands that consistently terminate at major external, predominantly annual growth lines that are associated with distinct notches that correspond to mantle retractions in most species. These bands generate distinct peaks in Mg/Ca that stand above low, more uniformly distributed background Mg/Ca values along laser-ablation and microprobe transects. The magnitude of Mg/Ca in these bands is comparable to Mg/Ca in the primary layer, exceeding background values of Mg/Ca in the secondary layer by 5–20 mmol/mol (by a factor of two to five). Second, Mg enrichment in discrete bands is closely associated with an increase in S concentrations in the secondary layer. Therefore, even when Mg and S uptake is expected to be highest under fast precipitation rate, these empirical observations show that Mg and S enrichment occur in the zones that were precipitated at times of a significant growth reduction (e.g., in cold-temperate brachiopods studied here during winters when primary productivity is low). The mechanisms for this paradox are unclear but can be related to uptake of Mg by amorphous calcium carbonate (ACC) to delay the transformation of ACC to calcite during the formation of growth lines. Therefore, intra-shell variation in Mg/Ca in brachiopods with major growth lines is primarily determined by seasonal decline or cessation in shell growth and not by seasonal changes in seawater temperature.

Water-pumping and purifying hydrogels driven by diurnal temperature variation

Diurnal temperature variation is an untapped energy source, although it has seldom been exploited as such. In this study, a novel system of thermo-responsive hydrogels uses diurnal temperature variation as the only power source to pump and purify water. Water is pumped at night and released during the day using an anisotropic xylem-mimetic structure whose composite phase functions as a water channel valve. The water-pumping efficiency ranges from 78% to 92%, and the weights of the pumped water per cycle are 2–3 times larger than those of the pumping materials. The anisotropic structure and the hydrophobic silicone phase are critical in determining pumping efficiency, which allow irreversible water flow upon temperature variation. Seasonal and regional temperature changes can be matched using thermo-responsive hydrogels with different volume transition temperatures. Purification of dye-contaminated water and separation of oil–water mixtures are also successfully achieved based on the hydrophilic and the pollutant-adsorbing nature of hydrogels. Since temperature changes even faster than the diurnal temperature cycle can also power this water pumping and purification system, this novel mechanism could provide a new operational solution for future water management.

Thylakoid fatty acid composition and response to short-term cold and heat stress in high-latitude Symbiodiniaceae

AbstractCoral reefs are restricted to warm waters, but are increasingly threatened by coral bleaching induced by sustained high sea surface temperatures. Coral endosymbiont thermal resilience has been proposed to depend, at least in part, on the lipid composition of their thylakoid membranes, which influences photosynthetic performance under sub- and super-optimal thermal conditions in photosynthetic organisms. Dinoflagellate symbionts of high-latitude coral reefs experience large seasonal changes in temperature, requiring a wide range of thermal tolerance, and so the thermal responses of their membrane lipids are of particular interest. Using gas chromatography–mass spectrometry, we investigated the composition and response to high- and low-temperature stress of thylakoid fatty acids of dinoflagellate symbionts isolated from corals of Lord Howe Island, the world’s southernmost coral reef. We detected genotype-specific differences in the quality of thylakoid fatty acids of two Cladocopium ITS2 consortia/genotypes, C100/118 and C111*, common local symbionts of the corals Pocillopora damicornis and Porites heronensis. The capability to adjust thylakoid fatty acid composition in response to temperature differed between distinct Cladocopium genotypes, and between the same Cladocopium consortium (C100/118) in the same coral species from different locations. Fatty acid adjustments were highly similar in response to short-term cold and heat stresses, with substantial increases in long-chain polyunsaturated fatty acids and a corresponding increase in the ratio of unsaturated to saturated fatty acids, but these changes did not correlate with the quantum yield of photosystem II. The response of thylakoid fatty acid composition to changes in temperature was a function of symbiont genotype, coral host species and, potentially, environmental history. Our data suggest the existence of common responses to high- and low-temperature stresses and that thylakoid fatty acid saturation is an unreliable predictor of photosystem efficiency under thermal stress in dinoflagellate symbionts.

Epicotyl morphophysiological dormancy in seeds of Paeonia ostii (Paeoniaceae): Seasonal temperature regulation of germination phenology

Paeonia is one of the most popular ornamental plants in temperate regions, and its seeds have epicotyl dormancy. Our primary aim was to determine the sequence of temperatures required for radicle and shoot emergence in seeds of P. ostii and how these two distinct stages of dormancy-break are correlated with natural seasonal temperature changes. We tested the effects of various temperature regimes and sequences of regimes on growth of the underdeveloped embryo inside the seed, radicle emergence and shoot growth in the laboratory and germination responses to temperature under natural temperatures in an experimental garden and analyzed ABA and GA concentrations during the dormancy-breaking process. Prior to radical emergence, embryo length increased c. 330%. Embryo elongation and radicle emergence occurred in early October following seed dispersal in summer. The epicotyl-plumule did not differentiate until after embryo growth was completed and the radicle had emerged. Cold stratification was required to break epicotyl dormancy; consequently, shoot emergence did not occur until February when the temperature began to increase. Thus, seed dormancy break in P. ostii is phenologically well adapted to the seasonal cycle of the temperate zone. ABA and GA analyses suggest that root dormancy might be due to high ABA content and shoot dormancy to low GA content. • Seeds of Paeonia ostii have deep simple epicotyl morphophysiological dormancy. • The plumule does not differentiate until embryo growth is competed. • Radicle emergence occurs only at warm temperatures in autumn. • Shoots emerge only in spring in root-emerged seeds that have been cold stratified. • The timing of dormancy-break is regulated by changes in seasonal temperatures.