Late Holocene records of fire and human presence in New Zealand

New Zealand, and the South Island in particular, can be considered an excellent test site for the study of the early impact of humans on the environment for two main reasons: the Polynesian settlement occurred only about 700-800 y BP and resulted in abrupt and huge landscape modifications. Burning forest for land clearance impacted dramatically on an ecosystem that was not adapted to fire, changing the composition of the vegetation as documented by sedimentary charcoal and pollen records. Although charcoal data give incontrovertible evidence of some unprecedented fire events right after the arrival of the Maori, its significance as a tracer for local and anthropogenic fire events has been questioned, stressing the need for new markers to confirm and complete the information about human presence and its effective impact. In the present work, faecal sterols and polycyclic aromatic hydrocarbons (PAHs) were individuated as suitable molecular markers and analyzed by GC-MS in a sediment core from Lake Kirkpatrick, located in the Lake Wakatipu catchment at 570 m a.s.l. in the South Island of New Zealand. Coprostanol accounts for about 60% of total sterol content in human faeces, being much less relevant in animal dejections. Together with its degradation product epi-coprostanol, it is well conserved in sedimentary archives and can be highly useful in paleoenvironmental reconstructions of human settlements. PAHs are produced in relevant amounts by combustion in conditions of oxygen depletion, and diagnostic ratios (DR) between specific molecules can be used for inferring fuel and sources. The charcoal record for Lake Kirkpatrick shows major fire episodes around AD 1350, confirmed by corresponding high levels of PAHs ascribable to biomass burning (as further evidenced by DR) at c. AD 1350. Moreover, the same trend is observed also in the fluxes of coprostanol and epi-coprostanol, whose sum results in two peaks at c. AD 1346 and 1351. This finding confirms not only the massive presence of humans in the area and the large use of fire at the time, but also complements and refines the reconstructions enabled by charcoal analysis

Mutations in Bcl9 and Pygo genes cause congenital heart defects by tissue-specific perturbation of Wnt/β-catenin signaling

Bcl9 and Pygopus (Pygo) are obligate Wnt/β-catenin cofactors in Drosophila, yet their contribution to Wnt signaling during vertebrate development remains unresolved. Combining zebrafish and mouse genetics, we document a conserved, β-catenin-associated function for BCL9 and Pygo proteins during vertebrate heart development. Disrupting the β-catenin–BCL9–Pygo complex results in a broadly maintained canonical Wnt response yet perturbs heart development and proper expression of key cardiac regulators. Our work highlights BCL9 and Pygo as selective β-catenin cofactors in a subset of canonical Wnt responses during vertebrate development. Moreover, our results implicate alterations in BCL9 and BCL9L in human congenital heart defects

Lake sediment fecal and biomass burning biomarkers provide direct evidence for prehistoric human-lit fires in New Zealand

Deforestation associated with the initial settlement of New Zealand is a dramatic example of how humans can alter landscapes through fire. However, evidence linking early human presence and land-cover change is inferential in most continental sites. We employed a multi-proxy approach to reconstruct anthropogenic land use in New Zealand’s South Island over the last millennium using fecal and plant sterols as indicators of human activity and monosaccharide anhydrides, polycyclic aromatic hydrocarbons, charcoal and pollen as tracers of fire and vegetation change in lake-sediment cores. Our data provide a direct record of local human presence in Lake Kirkpatrick and Lake Diamond watersheds at the time of deforestation and a new and stronger case of human agency linked with forest clearance. The first detection of human presence matches charcoal and biomarker evidence for initial burning at c. AD 1350. Sterols decreased shortly after to values suggesting the sporadic presence of people and then rose to unprecedented levels after the European settlement. Our results confirm that initial human arrival in New Zealand was associated with brief and intense burning activities. Testing our approach in a context of well-established fire history provides a new tool for understanding cause-effect relationships in more complex continental reconstructions

Use of organic biomarkers for the Late Holocene reconstruction of fire and human presence in New Zealand

The Polynesian colonization of New Zealand occurred quite recently in history (about 700-800 years BP) and resulted in abrupt and huge landscape modifications, as documented by sedimentary charcoal and pollen records. The native forest was not adapted to fire, thus burning for land clearance impacted dramatically on the ecosystem by modifying the composition of vegetation (McWethy et al., 2014). Therefore, this location can be considered an extraordinary test site for the study of the very first human impacts on the environment. Despite the incontrovertible evidence of some unprecedented fire events right after the arrival of the Māori, reconstructed through charcoal, its significance as a tracer for local and anthropogenic fire events has been questioned, stressing the need for new markers to confirm and complete the information about human presence and its effective impact (Butler, 2008). In the present work, novel organic molecular proxies are proposed for the reconstruction of fire events in association with anthropic activities. Namely, faecal sterols (FeSt), polycyclic aromatic hydrocarbons (PAHs) and monosaccharide anhydrides (MAs) were individuated as suitable molecular markers of human presence and fire activity, respectively. In particular, coprostanol accounts for about 60% of total sterol content in human faeces, being much less relevant in animal dejections (Bull et al., 2002). Together with its degradation product epi-coprostanol, it is well conserved in sedimentary archives and can be highly useful in paleoenvironmental reconstructions of human settlements. PAHs are produced in relevant amounts by combustion in conditions of oxygen depletion, and diagnostic ratios (DR) between specific molecules can be used for inferring fuel and sources (Ravindra et al., 2008). MAs are specific tracers of biomass burning, being generated only by the combustion of cellulose and hemicelluloses above 300° C (Simoneit et al., 1999). The three classes of tracers were analyzed in a sediment core from Lake Kirkpatrick (570 m asl), and FeSt were analyzed also in a core from Lake Diamond (380 m asl). Both lakes are located in the Otago region, in New Zealand South Island. The charcoal record for Lake Kirkpatrick (LK) and Lake Diamond (LD) shows major fire episodes around AD 1350, confirmed for LK by corresponding high levels of PAHs, ascribable to biomass burning (as further evidenced by DR), and MAs, both peaking at c. AD 1350. Moreover, the same trend is observed also in the fluxes of coprostanol and epi-coprostanol, whose sum results in two peaks at c. AD 1346 and 1351, respectively. For LD, a peak in FeSt is observed as well, slightly preceding the increase in fire activity starting around AD 1330. These findings confirm not only an important presence of humans in the area and the large use of fire at the time, but also the validity of selected tracers for complementing and refining the reconstructions enabled by charcoal analysis

Source, timing and dynamics of ionic species mobility in the Svalbard annual snowpack

Nearly all ice core archives from the Arctic and middle latitudes (such as the Alps), apart from some very high elevation sites in Greenland and the North Pacific, are strongly influenced by melting processes. The increases in the average Arctic temperature has enhanced surface snow melting even of higher elevation ice caps, especially on the Svalbard Archipelago. The increase of the frequency and altitude of winter “rain on snow” events as well as the increase of the length of the melting season have had a direct impact on the chemical composition of the seasonal and permanent snow layers due to different migration processes of water-soluble species, such as inorganic ions. This re-allocation along the snowpack of ionic species could significantly modify the original chemical signal present in the annual snow. This paper aims to give a picture of the evolution of the seasonal snow strata with a daily time resolution to better understand: a) the processes that can influence deposition b) the distribution of ions in annual snow c) the impact of the presence of liquid water on chemical re-distribution within the annual snow pack. Specifically, the chemical composition of the first 100 cm of seasonal snow on the Austre Brøggerbreen Glacier (Spitsbergen, Svalbard Islands, Norway) was monitored daily from the 27th of March to the 31st of May 2015. The experimental period covered almost the entire Arctic spring until the melting season. This unique dataset gives us a daily picture of the snow pack composition, and helps us to understand the behaviour of cations (K+, Ca2+, Na+, Mg2+) and anions (Br−, I−, SO42−, NO3−, Cl−, MSA) in the Svalbard snow pack. We demonstrate that biologically related depositions occur only at the end of the snow season and that rain and melting events have different impacts on the snowpack chemistry

OsiriX: An Open-Source Software for Navigating in Multidimensional DICOM Images

A multidimensional image navigation and display software was designed for display and interpretation of large sets of multidimensional and multimodality images such as combined PET-CT studies. The software is developed in Objective-C on a Macintosh platform under the MacOS X operating system using the GNUstep development environment. It also benefits from the extremely fast and optimized 3D graphic capabilities of the OpenGL graphic standard widely used for computer games optimized for taking advantage of any hardware graphic accelerator boards available. In the design of the software special attention was given to adapt the user interface to the specific and complex tasks of navigating through large sets of image data. An interactive jog-wheel device widely used in the video and movie industry was implemented to allow users to navigate in the different dimensions of an image set much faster than with a traditional mouse or on-screen cursors and sliders. The program can easily be adapted for very specific tasks that require a limited number of functions, by adding and removing tools from the program’s toolbar and avoiding an overwhelming number of unnecessary tools and functions. The processing and image rendering tools of the software are based on the open-source libraries ITK and VTK. This ensures that all new developments in image processing that could emerge from other academic institutions using these libraries can be directly ported to the OsiriX program. OsiriX is provided free of charge under the GNU open-source licensing agreement at http://homepage.mac.com/rossetantoine/osirix