A peculiar H i cloud near the distant globular cluster Pal 4

We present 21-cm observations of four Galactic globular clusters, as part of the on-going Galactic Arecibo L-band Feed Array (GALFA) H  i survey at Arecibo. We discovered a peculiar H  i cloud in the vicinity of the distant (109 kpc) cluster Pal 4, and discuss its properties and likelihood of association with the cluster. We conclude that an association of the H  i cloud and Pal 4 is possible, but that a chance coincidence between Pal 4 and a nearby compact high-velocity cloud cannot be ruled out altogether. New, more stringent upper limits were derived for the other three clusters: M 3, NGC 5466, and Pal 13. We briefly discuss the fate of globular cluster gas and the interaction of compact clouds with the Galactic halo gas.     

Another Record: Ocean Warming Continues through 2021 despite La Ni?a Conditions

The increased concentration of greenhouse gases in the atmosphere from human activities traps heat within the climate system and increases ocean heat content (O...     

Vegetational response to human colonisation of the coastal and volcanic environments of Ketilsstaðir, southern Iceland

Tephra-dated, high-resolution pollen profiles from Ketilsstaðir, southern Iceland, indicate a largely unwooded pre-settlement environment, a probable consequence of the exposed coastal location. The degree of change associated with the Norse landnám is more limited than in many Icelandic pollen diagrams. There are three main periods of change in the post-settlement vegetational development of the area. Firstly, Norse settlement affected the hydrology of the bog, resulting in the near-disappearance of Sphagnum and agricultural activity led to a reduction of some species (e.g. Angelica spp. and, Salix). Secondly, the establishment of probable permanent settlement in the mid-11th century AD initiated expansion of such apophytic taxa as Plantago spp. Lactuceae, Ranunculus spp. and Pteridophytes. Thirdly, the ≥ 10 cm thick Katla tephra, deposited in AD 1357, enhanced drainage of the bog surface, favouring dryland taxa (e.g. Poaceae, Galium and Lactuceae). The tephra deposit and the associated drainage probably caused or contributed to the local extinction of the wetland beetle Hydraena britteni. The study has enabled a series of natural and humanly-related issues to be addressed including tephra-vegetation relationships, the anthropogenic reduction in plant diversity, and comparisons between historical and environmental settlement records.     

Organic matter heterogeneities in 2.72 Ga stromatolites: Alteration versus preservation by sulfur incorporation

The stromatolites of the weakly metamorphosed 2.72 Ga Tumbiana Formation present abundant organic globules that resemble in size, shape and distribution the microorganisms observed in modern stromatolites. In order to evaluate the significance of these cell-like organic materials, we characterized organic matter in-situ down to the nanoscale using a combination of Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Raman microspectroscopy, scanning transmission X-ray microscopy (STXM) and transmission electron microscopy (TEM).These analyses revealed the occurrence of two distinct types of organic matter forming μm-scale textural and chemical heterogeneities distributed in distinct mineralogical laminae of the stromatolites. Type A organic matter, which is by far the most abundant, consists of sulfur-poor organic matter that is located in mud-type laminae at grain boundaries, mostly in association with silicate minerals. In contrast, Type B organic matter is rare and preserved as inclusions in the core of calcite grains forming laminates. It occurs as micrometer-sized cell-like globules containing variable amounts of organic sulfur likely in the form of thiophenes.Different scenarios may account for these compositional heterogeneities in the kerogen. Based on textural and compositional analogies with modern stromatolites, it is argued that Type B sulfur-rich globules may represent microbial cells protected by mineral encapsulation and selectively preserved through polymerization by early diagenetic sulfurization. In modern sediments, this reaction is fuelled by bacterial sulfate reduction (BSR). This metabolism has been widely considered as a major driver in modern stromatolites calcification and could thus have played an important role in the formation of the Tumbiana Formation stromatolites. In contrast, Type A sulfur-poor organic matter corresponds to either fossil extracellular polymer substances (EPS) or recondensed kerogen. This pool was likely not sulfurized due to either local and/or timely variations in the concentrations of H₂S or adverse pyritization driven by the availability of iron. Our observations thus show the need to use spatially-resolved techniques to complement organic geochemistry analyses and provide a detailed analysis of the organic carbon pools composing Archean stromatolites.     

Rethinking the nature of urban environmental politics: Security, subjectivity, and the non-human

The growing field of urban political ecology (UPE) has greatly advanced understandings of the socio-ecological transformations through which urban economies and environments are produced. However, this field has thus far failed to fully consider subjective (and subject-forming) dimensions of urban environmental struggle. I argue that this can be overcome through bringing urban political ecology into conversation with both post-structural political ecology and critical geopolitics. Bridging these literatures focuses attention on practices of socio-ecological exclusion and attachment through which environmental subjectivities are formed. This argument is drawn out through a case study of the politics of local economic development and conservation within the watershed of the Big Darby Creek near Columbus, Ohio. This struggle was driven by a preservationist movement that coalesced around a shared understanding of socio-ecological hybridity as a source of metaphysical insecurity. Hybridity appears here as a site of political and ethical struggle over social and ecological exclusions produced in the pursuit of security. This case study demonstrates a paradox of environmental politics: the non-human is at once a site of constituent possibilities for identity and subjectivity as well as forces which seek to foreclose this radical openness. Recognizing the paradoxical nature of environmental struggle allows for a more complex and nuanced account of the multifarious forces that shape the formation of environmental subjectivities.     

Sand beach ridges record 6000 year history of extreme tropical cyclone activity in northeastern Australia

Sand beach ridges are considered to be derived either from aeolian processes and/or waves but their deposition by individual or multiple storms has not been investigated in any detail. We use numerical meteorological and oceanographic models to determine the origin of a sequence of 29 shore parallel sand beach ridges in northeastern Australia. The results suggest that the ridges were constructed by waves and that the final form or height of the ridges is a function of high-energy tropical cyclone generated waves plus storm tides. Hence these landforms archive a nearly 6000 year long history of intense tropical cyclones. The record implies that these extreme tempests occur considerably more frequently than that suggested by the short historical record for this region. The genesis of this sand beach ridge plain has implications for the interpretation of similar sequences elsewhere along the northeast coast of Australia and in comparable environments globally. If other similar sand beach ridge plains have also been deposited by like processes it stands to reason that these long-term records of high intensity tropical cyclones can be used to ascertain a regional scale risk assessment from this hazard.     

Movement,memory, landscape: an excursion in non-representational thought

This paper is an excursion in non-representational thought. The primacy of movement charges this creative geography. Movement as sensation, thought, matter and memory crystallizes in ongoing assemblages (effects) we term selves and landscapes. This movement ontology is animated by a stream of thought running through Bergson, Deleuze, and Massumi, and by Ingold’s temporality of landscape. Memory is vital, as past (virtual) and present (actual) coexist, pushing forward in duration, the dynamic continuation of movement and sensation. David Lynch’s film, The Straight Story, offers dramatic illustration of the entanglement of movement, memory, and landscape. Landscape is emergent as relational lines of movement, an ongoing meshwork of practices and movement signatures. Alvin Straight’s paced journey through Iowa on a John Deere lawn mower during autumn harvest is a road to reminiscence and reconciliation, an American sublime. Lynch’s movement-images and soundscapes are sensorial undulations that illumine landscape as movement of incorporation, ‘dwelling’ in the moment to moment, geographies of care. The take-home message is that we are nothing more and nothing less than agents, next selves, ‘passing’ through. The collective trace of our ‘passings’ constitutes the making and remaking of place.

Microbial carbon cycling in oligotrophic regional aquifers near the Tono Uranium Mine, Japan as inferred from δC and ΔC values of in situ phospholipid fatty acids and carbon sources

Microorganisms are ubiquitous in deep subsurface environments, but their role in the global carbon cycle is not well-understood. The natural abundance δ¹³C and Δ¹⁴C values of microbial membrane phospholipid fatty acids (PLFAs) were measured and used to assess the carbon sources of bacteria in sedimentary and granitic groundwaters sampled from three boreholes in the vicinity of the Tono Uranium Mine, Gifu, Japan. Sample storage experiments were performed and drill waters analyzed to characterize potential sources of microbial contamination. The most abundant PLFA structures in all waters sampled were 16:0, 16:1ω7c, cy17:0, and 18:1ω7c. A PLFA biomarker for type II methanotrophs, 18:1ω8c, comprised 3% and 18% of total PLFAs in anoxic sedimentary and granitic waters, respectively, sampled from the KNA-6 borehole. The presence of this biomarker was unexpected given that type II methanotrophs are considered obligate aerobes. However, a bacterium that grows aerobically with CH₄ as the sole energy source and which also produces 56% of its total PLFAs as 18:1ω8c was isolated from both waters, providing additional evidence for the presence of type II methanotrophs. The Δ¹⁴C values determined for type II methanotroph PLFAs in the sedimentary (−861‰) and granite (−867‰) waters were very similar to the Δ¹⁴C values of dissolved inorganic carbon (DIC) in each water (∼−850‰). This suggests that type II methanotrophs ultimately derive all their carbon from inorganic sources, whether directly from DIC and/or from CH₄ produced by the reduction of DIC. In contrast, δ¹³C values of type II PLFAs in the sedimentary (−93‰) and granite (−60‰) waters indicate that these organisms use different carbon assimilation schemes in each environment despite very similar δ¹³C_CH4 values (∼−95‰) for each water. The δ¹³C_PLFA values (−28‰ to −45‰) of non-methanotrophic bacteria in the KNA-6 LTL water do not clearly distinguish between heterotrophic and autotrophic metabolisms, but Δ¹⁴C_PLFA values indicate that >65% of total bacteria filtered from the KNA-6 LTL water are heterotrophs. Ancient Δ¹⁴C values (∼−1000‰) of some PLFAs suggest that many heterotrophs utilize ancient organic matter, perhaps from lignite seams within the sedimentary rocks. The more negative range of δ¹³C_PLFA values determined for the KNA-6 granitic water (−42‰ to −66‰) are likely the result of a microbial ecosystem dominated by chemolithoautotrophy, perhaps fuelled by abiogenic H₂. Results of sample storage experiments showed substantial shifts in microbial community composition and δ¹³C_PLFA values (as much as 5‰) during 2-4 days of dark, refrigerated, aseptic storage. However, water samples collected and immediately filtered back in the lab from freshly drilled MSB-2 borehole appeared to maintain the same relative relationships between δ¹³C_PLFA values for sedimentary and granitic host rocks as observed for samples directly filtered under artesian flow from the KNA-6 borehole of the Tono Uranium Mine.