Mosaic fungal individuals have the potential to evolve within a single generation

Although cells of mushroom-producing fungi typically contain paired haploid nuclei (n + n), most Armillaria gallica vegetative cells are uninucleate. As vegetative nuclei are produced by fusions of paired haploid nuclei, they are thought to be diploid (2n). Here we report finding haploid vegetative nuclei in A. gallica at multiple sites in southeastern Massachusetts, USA. Sequencing multiple clones of a single-copy gene isolated from single hyphal filaments revealed nuclear heterogeneity both among and within hyphae. Cytoplasmic bridges connected hyphae in field-collected and cultured samples, and we propose nuclear migration through bridges maintains this nuclear heterogeneity. Growth studies demonstrate among- and within-hypha phenotypic variation for growth in response to gallic acid, a plant-produced antifungal compound. The existence of both genetic and phenotypic variation within vegetative hyphae suggests that fungal individuals have the potential to evolve within a single generation in response to environmental variation over time and space

Paleoclimatic and Paleoenvrionmental Changes Since the Last Glacial Maximum Recorded in Maar Lake Sediments From the Central Highlands of Vietnam

The paucity of long-term climate records from mainland SE Asia is a persistent limitation that inhibits comprehensive understanding of regional climate variability in this monsoon-dominated region. Hence, the ~30 kyr sediment record from Ia M’He, a crater lake in the Central Highlands of Vietnam, provides invaluable evidence of past precipitation in its δ2Hwax (fatty acid methyl esters) and other proxy (biomarkers, C/N, etc.) data. Dry conditions prevailed during the last glaciation as indicated by exceptionally slow, and possibly episodic, sedimentation of clay with very limited organic matter preservation. Persistent sub-aerial exposure of the lake floor is substantiated by the prominence of biomarkers indicative of microbially degraded organic matter (OM) and lack of diatoms. During the early Holocene, the δ2Hwax values, high C/N ratios, and lack of diatoms suggest continued dry conditions, albeit wetter than during the glacial period. These data contrast with other regional climate interpretations that report heightened moisture availability associated with peak monsoon rains linked to maximum summer insolation. Around 6.5 ka BP, the initiation of weak diatom preservation, decreased C/N ratios and δ2Hwax values all indicate a deepening of the lake and year-round water from an increase in effective moisture. By the late Holocene (~3 ka BP) diatoms are common, which is consistent with C/N ratios that reflect algal sources of OM and the concurrent minimum in δ2Hwax values. Biomarker distributions reflect better preserved OM from terrestrial vegetation, algae, and aquatic macrophytes. This change coincides with the onset of modern El Niño/Southern Oscillation (ENSO) conditions but does not conform with interpretations of decreased monsoon rainfall in response to waning summer insolation

Increased effective moisture in northern Vietnam during the Little Ice Age

We present a 650-yr record of hydroclimate, inferred from δ18O values of lacustrine carbonate from Ao Tiên (Fairy Pond), in northern Vietnam. Ao Tiên occupies a collapsed karst basin that formed during the worst drought of the last millennium (i.e., the Angkor I drought), which marks a dry transitional period between the Medieval Climate Anomaly and the Little Ice Age. A multi-centennial trend of increasing effective moisture spans the Little Ice Age, ending with aridity in the late 18th century that accompanied great societal turmoil across Southeast Asia. After ~1850 CE, the Ao Tiên record exhibits a drying trend that continues to the present. Over the last 650 years, the δ18O-inferred hydroclimate is significantly correlated with the reconstructed Southern Oscillation Index of precipitation (SOIpr) suggesting that a prolonged La Niña-like state existed during the Little Ice Age generating overall wetter conditions in Vietnam. Decadal-scale droughts and pluvials from the Ao Tiên record agree with a robust tree-ring hydroclimate reconstruction from southern Vietnam that identified the Angkor I and II droughts of the late 13th/early 14th centuries, and significant droughts during the early and late 17th century and latter half of the 18th century. The decrease in effective moisture during the last 30 years is also evident in the tree-rings and is consistent with a documented weakening of the Pacific Walker circulation. Major pluvials are indicated for the period between the two Angkor Droughts, and the wettest period of the record is during the early 18th century. Comparison of the Ao Tiên data with records from Indonesia to China indicates regionally coherent climate during the Little Ice Age; however, the overall wet conditions in easterly sites are difficult to ascribe to shifts in the ITCZ. Rather, the pattern suggests that Pacific Walker circulation may have been the overriding control on precipitation

220Rn (Thoron) Geohazard in Room Air of Earthen Dwellings in Vietnam

Thoron’s (220Rn) contribution to α-radiation exposure is usually considered negligible compared to that of 222Rn (radon). Despite its short half-life of 55.6 seconds, thoron can be exhaled from porous surface layers of building materials into indoor air where people subsequently inhale radioisotopes, including metallic radioactive progeny. Bare surfaces of dry porous soil with relatively high 232Th content can pose a thoron radiation hazard in indoor air. On northern Vietnam’s Đồng Văn karst plateau, the spatial distribution of thoron was determined in indoor air of traditional earthen and other types of dwellings using portable RAD7 and SARAD® RTM 2200 detectors. “Mud houses” are constructed with local compacted soil and typically do not have any floor or wall coverings (i.e., no plaster, wallpaper, or paint). Detailed measurements in a mud house revealed levels of thoron in room air averaging >500 Bq m-3. The spatial distribution of α-radiation from thoron in indoor air at a distance of about 1 m from interior walls was fairly homogeneous and averaged ~200 Bq m-3. Most concerning, from a human health perspective, were the high thoron concentrations of up to 884 Bq m-3 in sleeping areas near mud walls. The average annual thoron radiation dose to inhabitants of mud houses was estimated based on 13 hours of daily occupancy, including daily activities and sleeping. The estimated average thoron inhalation dose of 27.1 mSv a-1 during sleeping hours near mud surfaces accounts for nearly 75% of the total estimated radon and thoron inhalation dose of 37.4 mSv a-1 from indoor mud house air. Our conservative annual radiation dose estimates do not include subsequent radiation from inhaled metallic progeny of thoron. Our data demonstrate a significant human health risk from radiation exposure and a critical need for remediation in traditional northern Vietnamese mud house dwellings

Preliminary assessment of biomarkers in sediments from the Transkei Basin (IODP Site U1581)

A series of organic-rich sedimentary sequences that span the Paleocene through the Campanian was recovered from the Transkei Basin during IODP Expedition 392. Preliminary analyses of their organic geochemistry reveals suites of biomarkers that reflect diverse contributions of organic matter from both marine and terrestrial sources. The characteristics of the organic matter (OM) for a range of samples have been determined by shipboard and shore-based analyses that include evaluation of OM type and maturity by Rock-Eval pyrolysis, isotopic compositions of OM and the distributions of biomarkers including GDGTs. Samples from both the Paleocene and Campanian contain series of C37 to C40 diunsaturated alkenones, including the earliest record of C38 alkadien-2-ones and C39 alkadien-3-ones [1]. A sequence of Campanian samples also reveal an abundance of C28 sterenes and steryl ethers potentially indicative of upwelling conditions [2]. Polyaromatic hydrocarbons, including coronene, are present throughout the sequence likely reflecting inputs of OM associated with paleofires [3]. Variations in the abundance of organosulfur compounds [4,5] may afford evidence for temporal changes in redox conditions within the Transkei Basin during the Campanian. These initial results provide evidence that biomarker profiling will facilitate determination of the sources of OM throughout Late Cretaceous and Paleocene and the paleoenvironmental conditions of its deposition. [1] Brassell, 2014; [2] Brassell, 2009; [3] Finkelstein et al., 2005; [4] Valisolalao et al., 1984; [5] Brassell et al., 198

Preliminary Assessment of Organic Geochemistry in Sediments from the Transkei Basin (IODP Site U1581)

A series of organic-rich sedimentary sequences that span the Paleocene through the Campanian was recovered from the Transkei Basin during IODP Expedition 392. Preliminary analyses of their organic geochemistry reveals suites of biomarkers that reflect diverse contributions of organic matter from both marine and terrestrial sources. The characteristics of the organic matter (OM) for a range of samples have been determined by shipboard and shore-based analyses that include evaluation of OM type and maturity by Rock-Eval pyrolysis, isotopic compositions of OM, and the distributions of aliphatic and aromatic biomarkers. Samples from both the Paleocene and Campanian contain series of C37 to C40 diunsaturated alkenones, including the earliest record of C38 alkadien-2-ones and C39 alkadien-3-ones [1]. Samples from a section of the Campanian (~72.5 Ma) reveal an abundance of C28 steradienes and steryl ethers potentially indicative of upwelling conditions [2]. Polyaromatic hydrocarbons within the sequence include compounds that reflect inputs of OM derived from angiosperms and paleofires [3,4]. Dominant hopanoids in the samples include -homohopane, hop-17(21)-ene, and 29-norhop-17(21)-ene, accompanied by fernenes [5], a C35 hopanoid thiophene [6] and also dammarenes [7] in Paleocene samples. These initial results provide evidence that biomarker profiling will facilitate determination of the sources of OM from the Late Cretaceous to the Paleocene in the Transkei Basin and paleoenvironmental conditions of deposition

Sedimentological and geochemical properties of the uppermost sediment record of Biển Hồ maar lake, Central Highlands of Vietnam

Biển Hồ lake (14°03'03.5″ N, 108°00'00.2″ E) is a volcanic crater (i.e. maar) in Vietnam's Central Highlands that has been accumulating sediment since the Pleistocene. Here we show data from our bathymetric surveys and physical, chemical and diatom analyses of the uppermost sediment (0-2 m) (NAFOSTED project 105.99-2018.316). The data document environmental history recorded over the last 70 years in Biển Hồ Maar sediment and provide an empirical basis for the interpretation of Biển Hồ's deeper Holocene and pre-Holocene sedimentary record