Snowmelt in the Antarctic Peninsula region has increased significantly in recent decades, leading to greater liquid water availability across a more expansive area. As a consequence, changes in the ...biological activity within wet Antarctic snow require consideration if we are to better understand terrestrial carbon cycling on Earth's coldest continent. This paper therefore examines the relationship between microbial communities and the chemical and physical environment of wet snow habitats on Livingston Island of the maritime Antarctic. In so doing, we reveal a strong reduction in bacterial diversity and autotrophic biomass within a short (<1 km) distance from the coast. Coastal snowpacks, fertilized by greater amounts of nutrients from rock debris and marine fauna, develop obvious, pigmented snow algal communities that control the absorption of visible light to a far greater extent than with the inland glacial snowpacks. Absorption by carotenoid pigments is most influential at the surface, while chlorophyll is most influential beneath it. The coastal snowpacks also indicate higher concentrations of dissolved inorganic carbon and CO2 in interstitial air, as well as a close relationship between chlorophyll and dissolved organic carbon (DOC). As a consequence, the DOC resource available in coastal snow can support a more diverse bacterial community that includes microorganisms from a range of nearby terrestrial and marine habitats. Therefore, since further expansion of the melt zone will influence glacial snowpacks more than coastal ones, care must be taken when considering the types of communities that may be expected to evolve there.
Key Points
Microbial activity in wet Antarctic snow is detectable from its organic and inorganic carbon contents and the CO2 of interstitial air
Snow algae cause absorption of visible light and thus more melting due to carotenoid and chlorophyll pigment development
Inland Antarctic glacial snowpacks have far less diverse microbial communities than coastal snowpacks
Bone meal reduced metal release from a contaminated soil.
Metal-contaminated soil may be remediated in situ by the formation of highly insoluble metal phosphates if an appropriate phosphorus (P) ...source can be found. Leaching column experiments have been carried out to assess the suitability of bone meal as such a source. Bone meal additions reduced metal release from a contaminated soil, increased soil and leachate pH and decreased soil leachate toxicity. Minimal P leaching occurred from the soil. The data are consistent with a proton consuming bone meal (calcium phosphate) dissolution reaction followed by the formation of metal phosphates. Although, no metal phosphates were observed to form using X-ray diffraction or scanning electron microscopy this could be due to their low concentration. Relatively low (1:50 bone meal:soil) concentrations of fine (90–500 μm) bone meal would appear to be an effective treatment for metal-contaminated soils.
To investigate the influence of maturation on match running performance in elite male youth soccer players.
A total of 37 elite male youth soccer participants from an English professional soccer ...academy from the U14s, U15s, and U16s age groups were assessed over the course of 1 competitive playing season (2018-2019). Relative biological maturity was assessed using percentage of predicted adult height. A global positioning system device was used between 2 and 30 (mean = 8 5) times on each outfield player. The position of each player in each game was defined as defender, midfielder, or attacker and spine or lateral. A total of 5 match-running metrics were collected total distance covered, high-speed running distance, very high-speed running distance, maximum speed attained, and number of accelerations.
Relative biological maturity was positively associated with all global positioning system running metrics for U14s. The U15/16s showed variation in the associations among the global positioning system running metrics against maturity status. A multilevel model which allowed slopes to vary was the best model for all parameters for both age groups. In the U14 age group, advanced maturation was associated with greater high-speed running distance. However, maturation did not contribute toward variance in any of the indices of running performance in the U15/16s. In the U15/16 age group, significance was observed in the spine/lateral playing positions when undertaking actions that required covering distance at high speeds.
Maturation appeared to have an impact on match-running metrics within the U14s cohort. However, within the U15/16s, the influence of maturation on match-running metrics appeared to have less of an impact.
Summary
Biodiversity is responsible for the provision of many ecosystem services; human well‐being is based on these services, and consequently on biodiversity. In soil, earthworms represent the ...largest component of the animal biomass and are commonly termed ‘ecosystem engineers’. This review considers the contribution of earthworms to ecosystem services through pedogenesis, development of soil structure, water regulation, nutrient cycling, primary production, climate regulation, pollution remediation and cultural services. Although there has been much research into the role of earthworms in soil ecology, this review demonstrates substantial gaps in our knowledge related in particular to difficulties in identifying the effects of species, land use and climate. The review aims to assist people involved in all aspects of land management, including conservation, agriculture, mining or other industries, to obtain a broad knowledge of earthworms and ecosystem services.
Methane release from beneath lowland permafrost represents an
important uncertainty in the Arctic greenhouse gas budget. Our current
knowledge is arguably best developed in settings where permafrost ...is being
inundated by rising sea level, which means much of the methane is oxidised
in the water column before it reaches the atmosphere. Here we provide a
different process perspective that is appropriate for Arctic fjord valleys
where local deglaciation causes isostatic uplift to out pace rising sea
level. We describe how the uplift induces permafrost aggradation in former
marine sediments, whose pressurisation results in methane escape directly to
the atmosphere via groundwater springs. In Adventdalen, central
Spitsbergen, we show how the springs are historic features responsible for
the formation of open-system pingos and capable of discharging brackish
waters enriched with high concentrations of mostly biogenic methane (average
18 mg L−1). Thermodynamic calculations show that the methane
concentrations sometimes marginally exceed the solubility limit for methane
in water at 0 ∘C (41 mg L−1). Year-round emissions from the pingos
are described. During winter, rapid methane loss to the atmosphere occurs
following outburst events from beneath an ice blister. During summer, highly
variable emissions occur due to complex surface processes at the seepage
point and its inundation by surface runoff. In spite of this complexity, our
observations confirm that sub-permafrost methane migration deserves more
attention for the improved forecasting of Arctic greenhouse gas emissions.
Pingos are common features in permafrost regions that form by subsurface massive-ice aggradation and create hill-like landforms. Pingos on Spitsbergen have been previously studied to explore their ...structure, formation timing and connection to springs as well as their role in postglacial landform evolution. However, detailed hydrochemical and stable-isotope studies of massive-ice samples recovered by drilling have yet to be used to study the origin and freezing conditions in pingos. Our core record of 20.7 m thick massive pingo ice from Grøndalen is differentiated into four units: two characterised by decreasing δ18O and δD and increasing d (units I and III) and two others showing the opposite trend (units II and IV). These delineate changes between episodes of closed-system freezing with only slight recharge inversions of the water reservoir and more complicated episodes of groundwater freezing under semi-closed conditions when the reservoir was recharged. The water source for pingo formation shows similarity to spring water data from the valley with prevalent Na+ and HCO3- ions. The sub-permafrost groundwater originates from subglacial meltwater that most probably followed the fault structures of Grøndalen and Bøhmdalen. The presence of permafrost below the pingo ice body suggests that the talik is frozen, and the water supply and pingo growth are terminated. The maximum thaw depth of the active layer reaching the top of the massive ice leads to its successive melt with crater development and makes the pingo extremely sensitive to further warming.
Photosynthesis by microbes on the surfaces of glaciers and ice sheets has the potential to fix carbon, alter the albedo of ice surfaces via the production of organic matter and so enhance ice melt. ...It could also be important for supplying labile organic matter and nutrients to in situ and downstream ecosystems. This study compares in situ 24 hour incubation methods for measuring rates of gross photosynthesis, respiration and net community production (NCP) in cryoconite holes on three Svalbard valley glaciers. Rates of gross photosynthesis and respiration measured by the ΔCO2 method were closely balanced, resulting in rates of NCP close to the detection limit (mean of –1.3 μg C g−1 d–1) consistent with previous measurements in Arctic cryoconite holes. This suggests that organic matter within cryoconite holes may be derived largely from allochthonous sources. The molar ratio of ΔO2 to ΔCO2 in incubations gave mean respiratory and photosynthetic quotients of 0.80 ± 0.17 (1 × SD) and 1.24 ± 0.20 (1 × SD), respectively. The 14C method typically underestimated rates of gross photosynthesis (ΔCO2 method) by more than one order of magnitude and measured a rate closer to NCP.
We describe seasonal changes in the biogeochemistry, microbial community and ecosystem production of two glacial snowpacks in the maritime Antarctic during a cold summer. Frequent snowfall and low, ...intermittent melt on the glaciers suppressed surface photosynthesis and promoted net heterotrophy. Concentrations of autotrophic cells (algae and cyanobacteria) were therefore low (average: 150–500 cells mL−1), and short‐term estimates of primary production were almost negligible in early summer (<0.1 μg C L−1 d−1). However, order of magnitude increases in Chlorophyll a concentrations occurred later, especially within the mid‐snowpack and ice layers below. Short‐term primary production increased to ca. 1 μg C L−1 d−1 in mid‐summer, and reached 53.1 μg C L−1 d−1 in a mid‐snow layer close to an active penguin colony. However, there were significantly more bacteria than autotrophs in the snow (typically 103 cells mL−1, but >104 cells mL−1 in basal ice near the penguin colony). The ratio of bacteria to autotrophs also increased throughout the summer, and short‐term bacterial production rates (0.2–2000 μg C L−1 d−1) usually exceeded primary production, especially in basal ice (10–1400 μg C L−1 d−1). The basal ice represented the least diverse but most productive habitat, and a striking feature was its low pH (down to 3.3). Furthermore, all of the overlying snow cover became increasingly acidic as the summer season progressed, which is attributed to enhanced emissions from wet guano in the penguin colony. The study demonstrates that active microbial communities can be expected, even when snowmelt is intermittent in the Antarctic summer.
Plain Language Summary
We consider the importance of snow as one of Antarctica's most important land‐based ecosystems by describing snowpack ecosystem behavior at two sites upon a small maritime Antarctic ice cap. We show that a strong seasonal increase in the number of bacteria and snow algae occurs during the summer, despite the fact that our study coincided with a cold summer with frequent, wet snowfall events. These kept burying the snow algae, making photosynthesis difficult and allowing the bacterial community to dominate. An unexpected consequence was that the conditions also enhanced the decomposition of wet penguin guano, resulting in the release of organic acids whose subsequent deposition resulted in very acidic conditions within the snow matrix. Warmer summers with less snowfall will therefore experience completely different biological and chemical conditions in the snow habitat, emphasizing the climate sensitivity of this ice‐hosted ecosystem.
Key Points
Regional nutrient enrichment by marine fauna influences the microbial ecology of glacial snowpacks in the maritime Antarctic during summer
Cold summers with low melt and frequent snowfall reduce photosynthesis at the surface and allow bacterial production to dominate
Persistent moisture supply to penguin guano enhances the effects of ammonium and organic acid deposition onto the snow ecosystem
Interestingly, in three of the four families in which Goldschmidt's highly myopic probands had an affected sib, one or more of the parents was also affected. ...in the nine families that had at least ...one affected parent, 50% of sibs were affected. ...it was noted that the frequency distribution of myopia in Goldschmidt's unselected child population group conformed well to a biphasic distribution, consistent with the occurrence of two aetiologically distinct, major forms of myopia.
Summary Background The international standard radiotherapy schedule for early breast cancer delivers 50 Gy in 25 fractions of 2·0 Gy over 5 weeks, but there is a long history of non-standard regimens ...delivering a lower total dose using fewer, larger fractions (hypofractionation). We aimed to test the benefits of radiotherapy schedules using fraction sizes larger than 2·0 Gy in terms of local-regional tumour control, normal tissue responses, quality of life, and economic consequences in women prescribed post-operative radiotherapy. Methods Between 1999 and 2001, 2215 women with early breast cancer (pT1-3a pN0-1 M0) at 23 centres in the UK were randomly assigned after primary surgery to receive 50 Gy in 25 fractions of 2·0 Gy over 5 weeks or 40 Gy in 15 fractions of 2·67 Gy over 3 weeks. Women were eligible for the trial if they were aged over 18 years, did not have an immediate reconstruction, and were available for follow-up. Randomisation method was computer generated and was not blinded. The protocol-specified principal endpoints were local-regional tumour relapse, defined as reappearance of cancer at irradiated sites, late normal tissue effects, and quality of life. Analysis was by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN59368779. Findings 1105 women were assigned to the 50 Gy group and 1110 to the 40 Gy group. After a median follow up of 6·0 years (IQR 5·0–6·2) the rate of local-regional tumour relapse at 5 years was 2·2% (95% CI 1·3–3·1) in the 40 Gy group and 3·3% (95% CI 2·2 to 4·5) in the 50 Gy group, representing an absolute difference of −0·7% (95% CI −1·7% to 0·9%)—ie, the absolute difference in local-regional relapse could be up to 1·7% better and at most 1% worse after 40 Gy than after 50 Gy. Photographic and patient self-assessments indicated lower rates of late adverse effects after 40 Gy than after 50 Gy. Interpretation A radiation schedule delivering 40 Gy in 15 fractions seems to offer rates of local-regional tumour relapse and late adverse effects at least as favourable as the standard schedule of 50 Gy in 25 fractions.
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