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- Sjöström, Jenny K., 1978-, et al.
(författare)
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Complex evolution of Holocene hydroclimate, fire and vegetation revealed by molecular, minerogenic and biogenic proxies, Marais Geluk wetland, eastern Free State, South Africa
- 2023
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Ingår i: Quaternary Science Reviews. - 0277-3791 .- 1873-457X. ; 314
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Tidskriftsartikel (refereegranskat)abstract
- The Holocene climate history of Southern Africa remains inconclusive despite the increasing number of proxy records from the region. This might be related to the diversity of proxy records, how the proxies are interpreted, or that proxies may respond to more than one forcing (e.g. hydroclimate, fire, temperature.). Here, a 175-cm peat sequence from Free State, South Africa (28°17′53″S, 29°25′10.9″E), was analyzed using a comprehensive set of novel and conventional proxies, including isotopic (δ13C), elemental (CS-XRF), mineral (pXRD), molecular (FTIR-ATR and pyrolysis-GC-MS), grain size (Malvern 3000) and GSSC phytolith composition. The chronology was constructed through AMS radiocarbon dating (n = 7). The early Holocene (10,380–7000 cal yr BP) was characterized by an initial wet phase, followed by relative dryness, at least seasonally, evidenced by slow accumulation rates, low organic content and dominance of terrestrial vegetation in the organic matter matrix. From 7000 cal yr BP, decreasing temperatures, as evidenced in regional climate reconstructions, were associated at Marias Geluk with higher biogenic silica and organic matter content and an increase of moisture-adapted grasses, indicating increasingly mesic conditions. This trend was amplified after 6000 cal yr BP, co-occurring with a southward displacement of the ITCZ. Complex proxy dynamics were observed between 4300 and 2180 cal yr BP, with bulk organic proxies indicating a drier environment (lower carbon content, slow accumulation rates, enriched δ13C values) but the phytolith record pointing towards relatively mesic conditions. The period was also associated with increased fire frequency, that also reached the local wetland. We suggest that the period was associated with seasonally mesic conditions together with increased fire incidence, which affected some of the organic proxies. Increased fire activity was also recorded in the region, while the hydroclimatic indications differed. The last 2000 years, during which human activity is known to have increased in the region, was characterized by lower fire incidence and variable, but relatively moist, conditions. The hydroclimatic inferences for the last 2000 years are in line with previous studies from the region, but additional studies are needed to decipher if the decline in fire incidence was associated to climate forcings, human activities, or a combination of both. The multiproxy approach applied here - in particular the inclusion of FTIR-ATR and pyrolysis GC-MS - revealed a complex interplay between vegetation dynamics, hydrology and paleofire variability. This study confirms that relatively small Holocene temperature variations (compared to northern higher latitudes) were associated with major hydrological variability at Marais Geluk, and reinforces concerns from earlier studies that the hydroclimate of the region is vulnerable to climate change. The result s also show that the southward displacement of the ITCZ, and associated tropical air masses, likely had significant effects on regional hydrology and fire incidence.
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- Ainsbury, Elizabeth A., et al.
(författare)
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Inter- and intra-laboratory comparison of a multibiodosimetric approach to triage in a simulated, large scale radiation emergency
- 2014
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Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 90:2, s. 193-202
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The European Union's Seventh Framework Programme-funded project 'Multi-disciplinary biodosimetric tools to manage high scale radiological casualties' (MULTIBIODOSE) has developed a multiparametric approach to radiation biodosimetry, with a particular emphasis on triage of large numbers of potentially exposed individuals following accidental exposures. In November 2012, an emergency exercise took place which tested the capabilities of the MULTIBIODOSE project partners. The exercise described here had a dual purpose: Intercomparison of (i) three biodosimetric assays, and (ii) the capabilities of the seven laboratories, with regards to provision of triage status for suspected radiation exposed individuals. Materials and methods: Three biological dosimetry tools - the dicentric, micronucleus and gamma-H2AX (the phosphorylated form of member X of histone H2A, in response to DNA double-strand breaks) foci assays - were tested, in addition to provision of the triage status results (low exposure: <1 Gy; medium exposure: 1-2 Gy; high exposure: >2 Gy) by the MULTIBIODOSE software. The exercise was run in two modes: An initial triage categorisation of samples (based on the first dose estimates for each assay received from each laboratory) followed by collation of the full set of estimated doses (all the results from all modes of each assay carried out by the participating laboratories) calculated using as many modes of operation as possible of the different assays developed during the project. Simulated acute whole body and partial body exposures were included. Results: The results of the initial triage categorisation and the full comparison of assays and methods within and between laboratories are presented here. Conclusions: The data demonstrate that the MULTIBIODOSE approach of applying multiparametric tools to radiation emergencies is valid and effective.
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- Barboza, F. R., et al.
(författare)
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Geographic variation in fitness-related traits of the bladderwrack Fucus vesiculosus along the Baltic Sea-North Sea salinity gradient
- 2019
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 9:16, s. 9225-9238
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Tidskriftsartikel (refereegranskat)abstract
- In the course of the ongoing global intensification and diversification of human pressures, the study of variation patterns of biological traits along environmental gradients can provide relevant information on the performance of species under shifting conditions. The pronounced salinity gradient, co-occurrence of multiple stressors, and accelerated rates of change make the Baltic Sea and its transition to North Sea a suitable region for this type of study. Focusing on the bladderwrack Fucus vesiculosus, one of the main foundation species on hard-bottoms of the Baltic Sea, we analyzed the phenotypic variation among populations occurring along 2,000km of coasts subjected to salinities from 4 to >30 and a variety of other stressors. Morphological and biochemical traits, including palatability for grazers, were recorded at 20 stations along the Baltic Sea and four stations in the North Sea. We evaluated in a common modeling framework the relative contribution of multiple environmental drivers to the observed trait patterns. Salinity was the main and, in some cases, the only environmental driver of the geographic trait variation in F.vesiculosus. The decrease in salinity from North Sea to Baltic Sea stations was accompanied by a decline in thallus size, photosynthetic pigments, and energy storage compounds, and affected the interaction of the alga with herbivores and epibiota. For some traits, drivers that vary locally such as wave exposure, light availability or nutrient enrichment were also important. The strong genetic population structure in this macroalgae might play a role in the generation and maintenance of phenotypic patterns across geographic scales. In light of our results, the desalination process projected for the Baltic Sea could have detrimental impacts on F.vesiculosus in areas close to its tolerance limit, affecting ecosystem functions such as habitat formation, primary production, and food supply.
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- Berdan, Emma L, 1983, et al.
(författare)
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Genetic divergence and phenotypic plasticity contribute to variation in cuticular hydrocarbons in the seaweed fly Coelopa frigida
- 2019
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 9:21, s. 12156-12170
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Tidskriftsartikel (refereegranskat)abstract
- Cuticular hydrocarbons (CHCs) form the boundary between insects and their environments and often act as essential cues for species, mate, and kin recognition. This complex polygenic trait can be highly variable both among and within species, but the causes of this variation, especially the genetic basis, are largely unknown. In this study, we investigated phenotypic and genetic variation of CHCs in the seaweed fly, Coelopa frigida, and found that composition was affected by both genetic (sex and population) and environmental (larval diet) factors. We subsequently conducted behavioral trials that show CHCs are likely used as a sexual signal. We identified general shifts in CHC chemistry as well as individual compounds and found that the methylated compounds, mean chain length, proportion of alkenes, and normalized total CHCs differed between sexes and populations. We combined these data with whole genome resequencing data to examine the genetic underpinnings of these differences. We identified 11 genes related to CHC synthesis and found population-level outlier SNPs in 5 that are concordant with phenotypic differences. Together these results reveal that the CHC composition of C. frigida is dynamic, strongly affected by the larval environment, and likely under natural and sexual selection.
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