Cooler Periods Research Articles

Solar Power Generation in Smart Cities Using an Integrated Machine Learning and Statistical Analysis Methods

Presently, photovoltaic systems are an essential part of the development of renewable energy. Due to the inherent dependence of solar energy production on climate variations, forecasting power production using weather data has a number of financial advantages, including dependable proactive power trading and operation planning. Megacity electricity generation is regarded as a current research problem in the modern features of urban administration, particularly in developing nations such as Iran. Machine learning could be used to identify renewable resources like transformational participation (TP) and photovoltaic (PV) technology; based on resident motivational strategies, the smart city concept offers a revolutionary suggestion for supplying power in a metropolitan region. The sustainable development agenda is introduced at the same time as this approach. Therefore, the article’s goals are to estimate Mashhad, Iran’s electrical power needs using machine learning technologies and to make innovative suggestions for motivating people to generate renewable energy based on the expertise of experts. The potential of solar power over the course of a year is then assessed in our research study in Mashhad, Iran, using the solar photovoltaic modelling tool. The present idea in this research uses linear regression techniques to forecast utilising artificial neural networks (ANN). The most important factor in sizing the installation of solar power producing units is the daily mean sun irradiation. The amount of power that will be produced by solar panels can be estimated using the mean sun irradiance at a particular spot. A precise prediction can also be used to determine the complexity of the system, return on investment (ROI), and system load metrics. Several regression techniques and solar irradiance-related metrics have been combined to forecast the mean sun irradiation in terms of kilowatt hours per square metre. Azimuth and zenith factors considerably enhance the performance of the model, as demonstrated by the proposed method. The results of this study demonstrate 99.9% reliability rate for ANN model prediction of the electrical power usage during the summer and winter seasons. Thus, the maximum of power requirement during the hottest and coolest periods can be managed by using the photovoltaic system’s renewable power projections.

Phylogeography and colonization pattern of subendemic round-leaved oxeye daisy from the Dinarides to the Carpathians

The Carpathians are an important biodiversity hotspot and a link between mountain ranges on the European continent. This study investigated the phylogeography of one the Carpathian subendemics, Leucanthemum rotundifolium, which is distributed throughout the range and in one isolated population outside it. Range-wide sampling was used to examine phylogeographic patterns by sequencing uniparentally inherited chloroplast markers that exemplify seed dispersal. Reconstruct Ancestral State in Phylogenies (RASP) software, Bayesian binary Markov Chain Monte Carlo (BBM) analysis, and ecological niche modeling based on concatenated results of five algorithms were used to infer migration routes and examine links with other species through phylogeny. The round-leaved oxeye daisy is an example of organisms that reached the Carpathians through a southern “Dacian” migration route, most probably through long-distance dispersal. Dating placed the events in the Pleistocene and supported migrations during cooler periods and stasis/isolation followed by separation in the interglacials. Haplotype diversification indicated that after L. rotundifolium reached the area around the Fagaras Mountains, several migration events occurred leading to colonization of the Southern Carpathians followed by migration to the Apuseni Mountains, the Eastern Carpathians, and finally the Western Carpathians. The results are consistent with previous phylogeographic studies in this region and indicate several novel patterns.

Dynamics of di-2-ethylhexyl phthalate (DEHP) in the indoor air of an office

Largely limited by measurement technique, dynamics of semivolatile organic compounds (SVOCs) in the indoor air is not well understood. This study reports time-resolved measurements of airborne concentration of di-2-ethylhexyl phthalate (DEHP) in an office, using semivolatile thermal desorption aerosol gas chromatography (SV-TAG). The measurements were conducted in two separate periods during the summer-to-fall transition in 2020, each for more than 10 days. The indoor gas-plus-particle DEHP concentration varied by more than one order of magnitude in each observation period, and the temporal pattern exhibited possible influences of the indoor temperature, particle mass concentration, and outdoor DEHP concentrations. Further analysis focusing on window-closed conditions (i.e., with less outdoor contribution) reveals that the DEHP dynamics was primarily driven by variations in the indoor temperature ( R 2 = 0.85) during the first, warmer period (24–29 °C), and by variations in the particle mass concentration ( R 2 = 0.83) during the subsequent cooler period (20–23 °C). The unexpected transition of the key driving factor with change of the temperature was qualitatively justified by a simplified mechanistic model. Moreover, the particle fraction of DEHP was measured during the latter, cooler period, and it exhibited strong dependence on particle concentration, which can be fitted assuming gas-particle equilibrium partitioning, with a best-fit apparent partitioning coefficient of 0.053 ± 0.006 m 3 /μg at 20 ± 1 °C. Overall, these results improve our understanding of real-world SVOC dynamics. • In a warmer period variation in temperature drove DEHP dynamics in an office. • In a cooler period variation in particle concentration drove DEHP dynamics in the office. • Transition of the key driving factor with change in temperature was justified by mechanistic model. • Observed gas/particle partitioning of DEHP can be fitted assuming equilibrium state.

Duration of the Cooling Period and Efficiency of Sunlight Protection

Maintenance of comfortable microclimate in premises is important throughout the year. During the building cooling period, microclimate is maintained by means of air conditioning and sunlight protection systems. Overheating of premises requiring their cooling is caused by growing of average daily ambient temperature above 21 °C and by heating of premises by direct sunlight. Duration of application of microclimate control systems may be calculated using daily or hourly methods. This work proposes the method of determination of building cooling duration during the cooling period based on diurnal ambient air temperature range and the method of determination of sunlight protection efficiency during this period.

Influence of Large‐Scale Atmospheric Dynamics on Precipitation Seasonality of the Tibetan Plateau and Central Asia in Cold and Warm Climates During the Late Cenozoic

AbstractThe hydroclimate of the Tibetan Plateau (TP) and Central Asia (CA) plays a crucial role in sustaining surface water reservoirs and thus water resources in the respective regions. In this study, we investigate the changes in Asian hydroclimate and its driving forces during specific time intervals in the last 3 Ma. We conduct high‐resolution (∼0.75° per grid cell) general circulation model ECHAM‐5 experiments with boundary conditions for the mid‐Pliocene (∼3 Ma), the Last Glacial Maximum (LGM; ∼21 ka), the mid‐Holocene (∼6 ka), and the pre‐industrial. Results suggest that seasonally relatively high precipitation rates (>1 mm day−1) were longer in the mid‐Pliocene and shorter in the LGM, relative to the pre‐industrial. We calculate different monsoon indices to detect changes in the intensity, strength and duration of the East Asian summer monsoon (EASM), South Asian summer monsoon (SASM), and the Indian summer monsoon (ISM), and construct climatologies of mid‐latitude high‐level westerly jet (WJ) stream occurrences based on the ECHAM5 wind fields. Our results suggest that in warm periods (e.g., mid‐Pliocene or interglacial), the WJ migrates northward earlier in the year (April) and reaches higher latitudes than in the pre‐industrial, resulting in a wetter TP and CA. During cooler periods (e.g., LGM or glacial), the WJ migrates northward later in the year (June) and remains over lower latitudes, resulting in a drier TP and CA. Increased/decreased local precipitation in TP and CA for the mid‐Pliocene/LGM experiments correlates strongly with (a) intensity, strength and duration of the EASM, SASM, and the ISM and (b) WJ latitudinal position.

The Quality of Roe Deer (Capreolus Capreolus) Diet in the Winter and Spring Periods Based on Rumen Contents

Summary The purpose of this study is to compare the specifics of winter and spring diets of the roe deer using rumen content analysis. A chemical analysis was performed on a total of 13 samples of roe deer rumen contents: 7 samples of winter diet rumen contents and 6 samples of spring diet rumen contents. The following parameters were examined in this study: the level of crude protein and the content of fiber (NDF, ADF and ADL). The results obtained were processed by descriptive statistics and compared using F-tests. Consequently, certain deviations in the quality of roe deer nutrition were found in both winter and spring periods of the year. A lack of protein and energy can pose significant problems to roe deer, especially in the cooler periods of the year. Approximately a total of 17MJ/day is the maximum assumed energy required for animals kept in enclosure. The need for crude protein varies from 30.8% to 34.4% DM. This problem can be tackled if roe deer are adequately fed with quality bulky and concentrated feed, despite the fact that the animals adapt metabolically to seasonal variations.

Paleoenvironmental evolution during the Early Eocene Climate Optimum in the Chicxulub impact crater

The Early Eocene represents the warmest climate during the Cenozoic Era punctuated by transient warming events. Here, we apply for the first time biomarker and stable isotope data to describe the depositional and environmental changes at the actual Chicxulub impact crater [International Ocean Discovery Program (IODP) Site M0077A] during the Early Eocene (∼56–48 Ma) including the Early Eocene Climate Optimum (EECO; ∼53–49 Ma). TEX86-based reconstructions indicate elevated sea surface temperature around 37°C for the entire succession, punctuated by warmer and cooler periods (37.8°C, 35.7°C, respectively). Biomarker and δ13C-org data of the core sediments reveal a shift from an organic-lean lower to an organic-rich upper section of the Early Eocene interval. Embedded in the lower section is a prominent organic-rich black shale layer. The lower section, directly overlying strata deposited upon the Paleocene-Eocene Thermal Maximum (PETM), is organically lean with low biomarker concentrations indicating low primary productivity. In the upper section, higher concentrations of algal and bacterial biomarkers are ascribed to high primary productivity and nitrogen fixation in an epipelagic zone, potentially supported by upwelling. The organic-rich black shale layer exhibits a negative δ13C-org isotope excursion ascribed to recycling of 13C-depleted organic matter via upwelling attributed to a transient hyperthermal event.

Surface Urban Energy and Water Balance Scheme (v2020a) in vegetated areas: parameter derivation and performance evaluation using FLUXNET2015 dataset

Abstract. To compare the impact of surface–atmosphere exchanges from rural and urban areas, fully vegetated areas (e.g. deciduous trees, evergreen trees and grass) commonly found adjacent to cities need to be modelled. Here we provide a general workflow to derive parameters for SUEWS (Surface Urban Energy and Water Balance Scheme), including those associated with vegetation phenology (via leaf area index, LAI), heat storage and surface conductance. As expected, attribution analysis of bias in SUEWS-modelled QE finds that surface conductance (gs) plays the dominant role; hence there is a need for more estimates of surface conductance parameters. The workflow is applied at 38 FLUXNET sites. The derived parameters vary between sites with the same plant functional type (PFT), demonstrating the challenge of using a single set of parameters for a PFT. SUEWS skill at simulating monthly and hourly latent heat flux (QE) is examined using the site-specific derived parameters, with the default NOAH surface conductance parameters (Chen et al., 1996). Overall evaluation for 2 years has similar metrics for both configurations: median hit rate between 0.6 and 0.7, median mean absolute error less than 25 W m−2, and median mean bias error ∼ 5 W m−2. Performance differences are more evident at monthly and hourly scales, with larger mean bias error (monthly: ∼ 40 W m−2; hourly ∼ 30 W m−2) results using the NOAH-surface conductance parameters, suggesting that they should be used with caution. Assessment of sites with contrasting QE performance demonstrates how critical capturing the LAI dynamics is to the SUEWS prediction skills of gs and QE. Generally gs is poorest in cooler periods (more pronounced at night, when underestimated by ∼ 3 mm s−1). Given the global LAI data availability and the workflow provided in this study, any site to be simulated should benefit.

Simulation of Wheat Response to Future Climate Change Based on Coupled Model Inter-Comparison Project Phase 6 Multi-Model Ensemble Projections in the North China Plain.

Global climate change results in more extreme temperature events, which poses a serious threat to wheat production in the North China Plain (NCP). Assessing the potential impact of temperature extremes on crop growth and yield is an important prerequisite for exploring crop adaptation measures to deal with changing climate. In this study, we evaluated the effects of heat and frost stress during wheat sensitive period on grain yield at four representative sites over the NCP using Agricultural Production System Simulator (APSIM)-wheat model driven by the climate projections from 20 Global Climate Models (GCMs) in the Coupled Model Inter-comparison Project phase 6 (CMIP6) during two future periods of 2031–2060 (2040S) and 2071–2100 (2080S) under societal development pathway (SSP) 245 and SSP585 scenarios. We found that extreme temperature stress had significantly negative impacts on wheat yield. However, increased rainfall and the elevated atmospheric CO2 concentration could partly compensate for the yield loss caused by extreme temperature events. Under future climate scenarios, the risk of exposure to heat stress around flowering had no great change but frost risk in spring increased slightly mainly due to warming climate accelerating wheat development and advancing the flowering time to a cooler period of growing season. Wheat yield loss caused by heat and frost stress increased by −0.6 to 4.2 and 1.9–12.8% under SSP585_2080S, respectively. We also found that late sowing and selecting cultivars with a long vegetative growth phase (VGP) could significantly compensate for the negative impact of extreme temperature on wheat yields in the south of NCP. However, selecting heat resistant cultivars in the north NCP and both heat and frost resistant cultivars in the central NCP may be a more effective way to alleviate the negative effect of extreme temperature on wheat yields. Our findings showed that not only heat risk should be concerned under climate warming, but also frost risk should not be ignored.

Assessing the Uncertainties in Modeling Water Temperatures During River Cooling and Freeze-Up Periods

Assessing the Uncertainties in Modeling Water Temperatures During River Cooling and Freeze-Up Periods

Late Pliocene continental climate and vegetation variability in the Arctic-Atlantic gateway region prior to the intensification of Northern Hemisphere glaciations

We describe Pliocene palynological assemblages from ODP Hole 910C on the Yermak Plateau, Arctic Ocean. Analysis of high-resolution (~10 ± 3 ka) sampling allows us to detect changes in late Pliocene vegetation biomes corresponding to climatic variability between ~3.4 to 2.6 Ma. Findings show that a cool temperate and mixed boreal forest ( Pinus-Tsuga-Picea-Alnus-Ulmus community) initially dominated the Arctic-Atlantic gateway region. Following the onset of Marine Isotope Stage M2 cooling, ~3.3 Ma, there was a marked decline in vegetation coverage (low abundance of Pinus, Abies community). The mid Pliocene warm period that followed at ~3.2 to 3.0 Ma showed an increase in percentage of thermophilic and moist boreal taxa ( Tsuga-Thuja- Cupressaceae -Betula-Ilex community) suggesting influx of warm Atlantic Current. The dominance of Pinus-Ulmus persisted until ~3.0 Ma. Intermittent cooler and warmer periods occurred after 2.9 Ma, with an increase in herbaceous pollen and cryptogamic spores. This was followed by an abrupt change at ~2.73–2.64 Ma marked by a prominent shift from taiga to tundra-steppe vegetation, and coinciding with the intensification of Northern Hemisphere Glaciation ~2.65 Ma. Occurrences of Impatiens pollen indicates frost-free conditions in the region until ~2.7 Ma. Our high resolution analysis of palynological assemblages synchronizes closely with the Marine Isotope record, in general; however, we show that the mid Pliocene warm period was interrupted by short spells of intermittent cooler periods. • Palynological succession ~3.40 to 2.62 Ma indicate biome change in ODP Hole 910C, Yermak Plateau. • Mixed boreal forest dominated until Marine Isotope Stage (MIS) M2 (~3.30 Ma ago). • During 3.21 to 3.02 Ma pollen taxa indicate warmer period obstructed by two cooling phases. • A shift from Taiga to Tundra-steppe vegetation was recorded between ~2.73–2.64 Ma and Impatiens pollen shows frost-free climate. • The intensification before Northern Hemisphere Glaciation was characterised by intermittent short-term interstadials.

Taxonomic inflation due to inadequate sampling: are girdled lizards (Cordylus minor species complex) from the Great Karoo one and the same?

Abstract The Great Karoo and Namaqualand of South Africa are home to a species complex of morphologically conserved lizards that occur in allopatry (Karoo: Cordylus aridus, Cordylus cloetei, Cordylus minor; Namaqualand: Cordylus imkeae). However, there are negligible morphological differences and a lack of obvious physical or climatic barriers, particularly among the three Karoo species. We hypothesized that poor geographic coverage in previous studies and lack of an explicit species concept has caused taxonomic inflation. We therefore tested species boundaries by examining multiple criteria: multi-gene phylogenetics, niche distribution modelling and re-examination of diagnostic morphological features with a larger sample size. We found that C. aridus, C. cloetei and C. minor lack diagnosable differences for both genetics and morphology. Distribution modelling, ranging from present day to the last interglacial period, show connectivity has been maintained especially during cooler periods. Conversely, C. imkeae is morphologically diagnosable, genetically distinct and lacks connectivity with the other taxa. By evaluating multiple operational criteria, we conclude that the C. minor species complex comprises only two species, C. minor (with C. aridus and C. cloetei as junior synonyms) and C. imkeae, demonstrating that species defined from inadequate data and lack of an explicit species concept can lead to taxonomic inflation.

Glaciers and Paleorecords Tell Us How Atmospheric Circulation Changes and Successive Cooling Periods Occurred in the Fennoscandia during the Holocene

Two major climatic phenomena that occurred during the Holocene are interpreted from the resonance in subharmonic modes of long-period Rossby waves winding around the North Atlantic gyre, the so-called gyral Rossby waves (GRWs). These are, on the one hand, the change in atmospheric circulation that occurred in the North Atlantic in the middle Holocene, and, on the other hand, the occurrence of abrupt cooling events more frequently than what is generally accepted. The amplitude of GRWs is deduced by filtering, within bands characteristic of various subharmonic modes, climate records from the Greenland ice sheet, pollen, and tree rings in northern Fennoscandia, and from two Norwegian glaciers in northern Folgefonna and on the Lyngen peninsula. While the subharmonic modes reflect the acceleration/deceleration phases of the western boundary current, an anharmonic mode is evidenced in the 400–450 year band. Abrupt cooling events of the climate are paced by this anharmonic mode while the western boundary current is decelerating, and the northward heat advection of air favors the melting of the pack ice. Then, the current of the northernmost part of the North Atlantic gyre cools before branching off to the north, which alters its buoyancy. On the other hand, according to high subharmonic modes, high-pressure systems prevailed over the North Atlantic in the first half of the Holocene while low-pressure systems resulted from baroclinic instabilities of the atmosphere dominate during the second half, favoring the growth of glaciers in Scandinavia by a better snowfall in winter and cooler summers.

Local and Temporal Effects on Ant Richness, Recruitment and Resource Dominance in Two Cerrado Areas

Ecological interactions and environmental conditions are associated with community structuring, where the resource quality and availability, in addition to interspecific competition, determine potential local interactions. Using ground-dwelling ant species as a methodological tool model, we evaluated how three different daily periods affected species richness, recruitment, and resource dominance (baits) within two Cerrado (Brazilian savanna) phytophysiognomies. We found a total of 34 ant species and significant differences in species composition between the cerrado areas. Camponotus and Pheidole genera were the most abundant in both studied areas in which several species shared baits. Ant richness did not vary between the cerrado areas, but ant recruitment was affected by observation periods: in both areas, the hottest period (afternoon) reflected the lowest recruitment, while the coolest period (morning) had the highest recruitment. We observed that the ant species that first found baits had a 29% chance of being the only species observed using the resource, while those that arrived after other species had only 7%. Both areas promote the coexistence of ant species by shaping their interactions. We suggest that environmental structuring promotes niche partitioning in both spatial and temporal scales, providing possibilities of microhabitats that allow species to explore the environment and forage.

Re-using ammonium-rich wastewater as a moisture conditioning agent during composting thermophilic period improves composting performance

A weakly acidic ammonium-rich wastewater (STL) was intended to reuse as a moisture conditioning agent for composting to increase nitrogen content of compost. The influence of adding STL in the mesophilic period (MP), thermophilic period (TP), and cooling period (CP) on composting performance was investigated. Results revealed that organic degradation was strongly suppressed in MP, whereas no difference (p > 0.05) was observed between CP and control group (using tap water as moisture conditioning agent). The hydrolysis and mineralization of organic matter in TP were partly stimulated because reusing STL reduced free ammonia concentrations (<400 mg/L) of windrows. Additionally, the ammonium and nitrate nitrogen content of compost in TP increased by 71% and 425% without additional greenhouse gas emissions compared with control group. Therefore, ammonium-rich wastewater like STL could substitute tap water to condition compost moisture content and increase the nitrogen content of compost during the thermophilic composting period.

The application of environmental isotopes to conceptualize groundwater recharge in a coastal aquifer system: Case study of the West Coast Aquifer System, South Africa

Knowledge of natural recharge mechanisms of the West Coast Aquifer is vital for the implementation of water resource management strategies, which would secure groundwater resources for the region. The analysis of stable (2H and 18O) and radioactive (3H and 14C) environmental isotopes have been employed to identify the source of recharge and residence times of the shallow, confined and bedrock aquifers based on sampling conducted during 2017 and 2018. The δ18O values for groundwater ranged from −4.34 and 0.65‰ while δ2H values ranged from −18.8 and 6.8‰. Groundwater 3H activity ranged from 0.0 to 1.2 T.U, rainwater tritium was 1.4 T.U while 14C contents ranged from 0.0 to 1.2pMC. The stable isotope signatures revealed four water groups: non-evaporative shallow and deep groundwater with similar isotopic composition indicating same source of recharge; bedrock groundwater with enriched isotopic signature which show evaporation effect indicating recharge from precipitation where clay lenses are locally absent; non-evaporative shallow groundwater indicate recently infiltrated water; groundwater is not recharged by surface water when drought conditions persist. Deep groundwater in the low-plain discharge zone is recharged by seawater intrusion which is evidenced elevated chloride concentration (35700 mg/l) and enriched stable isotope composition. High tritium (>0.8 T.U) containing groundwater were found downgradient from recharge area, which confirms recent active recharge occurs a distance from postulated recharge area. Tritiated bedrock groundwater with older 14C ages had the same δ18O values as younger shallow groundwater which is consistent with it being derived from locally from low altitudes. The calculated carbon-14 residence times suggest aquifers were recharged under different climatic conditions during cooler periods of the late Pleistocene and Holocene (~2717–33000). The calculated radiocarbon age reflected in the tritium containing groundwater in the deep aquifer supports active localized recharge to deep groundwater system via focused mechanism. The application of environmental isotope methodology combined with an understanding of geology in the study area led to the development of a coherent conceptual flow model.

Hybridization alters growth and migratory life-history expression of native trout.

Human‐mediated hybridization threatens many native species, but the effects of introgressive hybridization on life‐history expression are rarely quantified, especially in vertebrates. We quantified the effects of non‐native rainbow trout admixture on important life‐history traits including growth and partial migration behavior in three populations of westslope cutthroat trout over five years. Rainbow trout admixture was associated with increased summer growth rates in all populations and decreased spring growth rates in two populations with cooler spring temperatures. These results indicate that non‐native admixture may increase growth under warmer conditions, but cutthroat trout have higher growth rates during cooler periods. Non‐native admixture consistently increased expression of migratory behavior, suggesting that there is a genomic basis for life‐history differences between these species. Our results show that effects of interspecific hybridization on fitness traits can be the product of genotype‐by‐environment interactions even when there are minor differences in environmental optima between hybridizing species. These results also indicate that while environmentally mediated traits like growth may play a role in population‐level consequences of admixture, strong genetic influences on migratory life‐history differences between these species likely explains the continued spread of non‐native hybridization at the landscape‐level, despite selection against hybrids at the population‐level.

Management options for improved survival of perennial ryegrass (

In northern Victoria, Australia, perennial pastures for the dairy industry have historically been based on perennial ryegrass. However, perennial ryegrass does not perform well under high summer temperatures and water stress. We investigated irrigation, renovation and grazing management strategies for improving the resilience and survival of perennial ryegrass over summer on two farms in northern Victoria over 2.5 years. At each farm, two irrigation bays were sown in March 2015. During summer (late December–mid-March), one bay was not irrigated and the other bay received a single mid-summer irrigation. Each bay was sown to 12 ryegrass cultures: five cultivars of perennial ryegrass either oversown or not oversown, and two oversown cultivars of short-lived ryegrass (SLRG). A mid-summer grazing treatment was applied to one-half of each of these plots. All plots at both sites received the same irrigation and grazing management at other times of the year. There were significant variations in dry matter (DM) production, nutritive characteristics and plant frequencies across sites and seasons, and across renovation, irrigation and grazing management strategies. Cumulative DM yields were higher in the perennial ryegrass than the SLRG cultivars. Summer DM removal was very low at both sites; the ungrazed plots recovered and produced more DM in the following cooler period than the grazed plots in the first year but not the second. Metabolisable energy concentration was higher for perennial ryegrass than SLRG cultivars and was also higher in plots that had been grazed over the summer. There were large differences in plant frequency between species, and there were some differences among perennial ryegrass cultivars. The effect of summer grazing on plant frequency varied at each site and was not significant within an irrigation treatment. This research confirms that perennial ryegrass is not well suited to the hot, dry summers of northern Victoria and suggests that, under conditions of limited summer irrigation, farmers should focus on plant survival rather than summer yield if they are to maximise annual DM production.

Genes Associated With Chromatin Modification Within the Swine Placenta Are Differentially Expressed Due to Factors Associated With Season.

Seasonal reproductive inefficiency is still observed in modern swine facilities. We previously reported global placental methylation activity was reduced from summer breedings and tended to be less from semen collected during cooler periods. The objective of the current study was to evaluate chromatin modification marks within swine placenta in relationship to breeding season, semen collection season, and semen storage. White composite gilts were artificially inseminated in August or January using single-sire semen that was collected during warm or cool periods and stored as either cryopreserved or cooled-extended. Gilts were harvested 45 days post-breeding, and placental samples from the smallest, average, and largest fetus in each litter were collected and stored at −80°C until RNA extraction. An RT2 Profiler assay featuring 84 known chromatin modification enzyme targets was performed using placental RNA pooled by litter. Real-time quantitative polymerase chain reaction results were analyzed using the MIXED procedure, and P-values were Hochberg corrected using the MULTTEST procedure in SAS. The complete model included the fixed effects of breeding season (winter or summer), semen collection season (cool or warm), semen storage (cooled-extended or cryopreserved), interactions; boar as repeated effect; and plate as random effect. If interactions were not significant, only the main effects were tested. The genes, ATF2, AURKA, and KDM5B, were different (P < 0.05) by interaction of breeding season, semen collection season, and semen storage. In general, the greatest (P < 0.05) expression was in placentas derived from summer breedings. Expression of AURKA was also influenced by semen collection and storage. Expression of placental KDM5B from winter breedings was also greater (P < 0.05) from semen collected during cool periods. Placental expressions of ASH2L, DNMT3B, ESCO1, HDAC2, ING3, KDM6B, MYSM1, and SMYD3 were greater (P < 0.05) from summer breedings. Increased expressions of known chromatin modification genes, from placentas derived from summer breedings, are likely responsible for differences in gene transcription between summer- or winter-derived placentas.

Reconstructing oxygen deficiency in the glacial Gulf of Alaska: Combining biomarkers and trace metals as paleo-redox proxies

Marine anaerobic oxidation of ammonium (anammox) plays a central role in the nitrogen cycle of modern Oxygen Deficient Zones (ODZs). The newly developed bacteriohopanetetrol stereoisomer (BHT-x) biomarker for anammox, which is largely unaffected by early diagenesis, allows for the reconstruction of the presence and dynamics of past ODZs from the sedimentary record of continental margins. In this study, we investigate the development and dynamics of the ODZ in the Gulf of Alaska (GOA) between 60 and 15 cal ka BP using records of redox sensitive trace metals (TM) and the BHT-x anammox biomarker from IODP Site U1419 (~700 m water depth). The biomarker record indicates that the ODZ in the GOA was in concert with global climate fluctuations in the late Pleistocene. Anammox was more pronounced during warmer periods and diminished during cooler periods, as indicated by correlation with the δ18O signal obtained by the North Greenland Ice core Project (NGRIP). Trace metal enrichments, however, do not match the trend in BHT-x. Systematic metal enrichments in intervals where biomarkers point to more intense water column deoxygenation are not observed. We suggest that this proxy discrepancy was caused by environmental factors, other than water column redox conditions, with opposing effects on the TM and biomarker records. Two of the most widely used redox indicators, Mo and U, are not significantly enriched throughout the sediment record at Site U1419. Site U1419 experienced some of the highest sedimentation rates (100–1000 cm ka−1) ever reported for late Pleistocene continental margin sediments, leading to a continuous and rapid upward migration of the sediment-water interface. We suggest that despite water column and seafloor oxygen depletion, significant sedimentary enrichments of these redox sensitive trace metals were prevented by a limited time for their diffusion across the sediment-water interface and subsequent enrichment as authigenic phases. Thus, depositional conditions were ideal for biomarker preservation but prevented significant authigenic trace metal accumulations. Similar discrepancies between organic and inorganic redox proxies could exist in other high sedimentation rate environments, potentially putting constraints on paleo-redox interpretations in such settings if they are based on trace metal enrichments alone.