5,477 research outputs found
Marine biodiversity-ecosystem functions under uncertain environmental futures
No full textAnthropogenic activity is currently leading to dramatic transformations of ecosystems and losses of biodiversity. The recognition that these ecosystems provide services that are essential for human well-being has led to a major interest in the forms of the biodiversity-ecosystem functioning relationship. However, there is a lack of studies examining the impact of climate change on these relationships and it remains unclear how multiple climatic drivers may affect levels of ecosystem functioning. Here, we examine the roles of two important climate change variables, temperature and concentration of atmospheric carbon dioxide, on the relationship between invertebrate species richness and nutrient release in a model benthic estuarine system. We found a positive relationship between invertebrate species richness and the levels of release of NH(4)-N into the water column, but no effect of species richness on the release of PO(4)-P. Higher temperatures and greater concentrations of atmospheric carbon dioxide had a negative impact on nutrient release. Importantly, we found significant interactions between the climate variables, indicating that reliably predicting the effects of future climate change will not be straightforward as multiple drivers are unlikely to have purely additive effects, resulting in increased levels of uncertainty
Ecosystem Services and Policy: A Review of Coastal Wetland Ecosystem Services and an Efficiency-Based Framework for Implementing the Ecosystem Approach
No full textThe Ecosystem Approach (EA) to environmental management aims to enhance human well-being within a linked social and ecological system, through protecting the delivery of benefits and services to society from ecosystems in the face of external pressures such as climate change. However, our lack of understanding of the linkages between the human and natural components of ecosystems inhibits the implementation of the EA for policy decision-making. Coastal wetland systems provide many benefits and ecosystem services to humans, including nutrient recycling, climate and water quality regulation, timber, fuel and fibre, but they are under considerable threat from population pressure and climate change. In this chapter, we review the ecosystem services provided by coastal wetlands, and the threats to these services. We then present a new integrative conceptual framework to underpin the EA. The framework is divided into three sub-systems: one relating to ecosystem functions, one to ecosystem services, and one to social development and well-being. The pathways linking these sub-systems represent transfers of state, for example, ecosystem functions being transferred into ecosystem services, or ecosystem services being transferred into benefits. The focus of our approach is on enhancing the magnitude and efficiency of these transfers, by introducing or making use of any existing catalysts and overcoming any constraints in the system. The framework represents a dynamic system for implementing the EA in which interventions can be planned and managed in an adaptive way.</jats:p
The workshop as the work: white anti-racism organising in 1960s, 70s, and 80s US social movements
No full textThis thesis explores the rise of anti-racism workshops developed by white activists in various United States social movements from the late 1960s through the mid-1980s. The shifting ideology of the black freedom movement in the late 1960s, from integration to Black Power, transformed white activists‘ place within racial justice struggles. While recent scholarship has begun to turn its attention towards whites‘ ongoing racial justice activities, one of the most radical and widespread of these efforts is consistently overlooked: anti-racism workshops. Increasingly prevalent from the late 1960s through to the diversity-trainings explosion of the 1990s, this thesis demonstrates that these workshops had their roots in the black freedom, women‘s liberation and gay liberation movements. White activists from these movements led these workshops in order to examine white racial domination and privilege within both leftist social movements and larger US society.
Analysing case studies from the black freedom, women‘s liberation and gay liberation/rights movements, this thesis explores the foundational assumptions of anti-racism workshops. It seeks to explain how and why these efforts sought to frame race and racism as issues of knowledge and consciousness and why such efforts constituted radical praxis. It is argued that early anti-racism workshops were pedagogical projects that sought to confront the racial ignorance that structured the lives of whites in the US, including progressives and their liberation movements. This thesis draws attention to the efficacy and power of these workshops in terms of their epistemological effects, in the transformations they brought about in whites‘ understanding, or awareness, of racial realities
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Retelling racialized violence, remaking white innocence: the politics of interlocking oppressions in transgender day of remembrance
No full textTransgender Day of Remembrance has become a significant political event among those resisting violence against gender-variant persons. Commemorated in more than 250 locations worldwide, this day honors individuals who were killed due to anti-transgender hatred or prejudice. However, by focusing on transphobia as the definitive cause of violence, this ritual potentially obscures the ways in which hierarchies of race, class, and sexuality constitute such acts. Taking the Transgender Day of Remembrance/Remembering Our Dead project as a case study for considering the politics of memorialization, as well as tracing the narrative history of the Fred F. C. Martinez murder case in Colorado, the author argues that deracialized accounts of violence produce seemingly innocent White witnesses who can consume these spectacles of domination without confronting their own complicity in such acts. The author suggests that remembrance practices require critical rethinking if we are to confront violence in more effective ways. Description from publisher's site: http://caliber.ucpress.net/doi/abs/10.1525/srsp.2008.5.1.2
Hot DAVs: a probable new class of pulsating white dwarf stars
No full textWe have discovered a pulsating DA white dwarf at the lower end of the temperature range 45 000–30 000 K where a few helium atmosphere white dwarfs are known. There are now three such pulsators known, suggesting that a new class of theoretically predicted pulsating white dwarf stars exists. We name them the hot DAV stars. From high-speed photometric observations with the ULTRACAM photometer on the 4.2-m William Herschel Telescope, we show that the hydrogen atmosphere white dwarf star WD1017−138 pulsates in at least one mode with a frequency of 1.62 mHz (a period of 624 s). The amplitude of that mode was near 1 mmag at a 10σ confidence level on one night of observation and an 8.4σ confidence level on a second night. The combined data have a confidence level of 11.8σ. This supports the two other detections of hot DAV stars previously reported. From three Very Large Telescope Ultraviolet and Visual Echelle Spectrograph spectra we confirm also that WD1017−138 is a hydrogen atmosphere white dwarf with no trace of helium or metals with Teff = 32 600 K, log g = 7.8 (cgs) and M = 0.55 M⊙. The existence of pulsations in these DA white dwarfs at the cool edge of the 45 000–30 000 K temperature range supports the thin hydrogen layer model for the deficit of helium atmosphere white dwarfs in this range. DA white dwarfs with thick hydrogen layers do not have the superadiabatic, chemically inhomogeneous (μ-gradient) zone that drives pulsation in this temperature range. The potential for higher amplitude hot DAV stars exists; their discovery would open the possibility of a direct test of the explanation for the deficit of helium atmosphere white dwarfs at these temperatures by asteroseismic probing of the atmospheric layers of the hot DAV stars. A search for pulsation in a further 22 candidates with ULTRACAM on the European Southern Observatory New Technology Telescope gave null results for pulsation at precisions in the range 0.5–3 mmag, suggesting that the pulsation amplitudes in such stars are relatively low, hence near the detection limit with the ground-based telescopes used in the survey
Drawing the Line: How African, Caribbean and White British Women Live Out Psychologically Abusive Experiences
No full textThe final, definitive version of this paper has been published in Violence Against Women, 19 (9):1104-32, Sept 2013 by SAGE Publications Ltd, All rights reserved. © The Author(s) 2013.
The online version of this article can be found at: http://vaw.sagepub.com/content/19/9/110
A magnetic white dwarf in a detached eclipsing binary
No full textSDSS J030308.35+005444.1 is a close, detached, eclipsing white dwarf plus M dwarf binary which shows a large infrared excess which has been interpreted in terms of a circumbinary dust disc. In this paper, we present optical and near-infrared photometric and spectroscopic data for this system. At optical wavelengths, we observe heated pole caps from the white dwarf caused by accretion of wind material from the main-sequence star on to the white dwarf. At near-infrared wavelengths, we see the eclipse of two poles on the surface of the white dwarf by the main-sequence star indicating that the white dwarf is magnetic. Our spectroscopic observations reveal Zeeman-split emission lines in the hydrogen Balmer series, which we use to measure the magnetic field strength as 8 MG. This measurement indicates that the cyclotron lines are located in the infrared, naturally explaining the infrared excess without the need for a circumbinary dust disc. We also detect magnetically confined material located roughly midway between the two stars. Using measurements of the radial velocity amplitude and rotational broadening of the M star, we constrain the physical parameters of the system, a first for a magnetic white dwarf, and the location of the poles on the surface of the white dwarf. SDSS J030308.35+005444.1 is a pre-cataclysmic variable that will likely evolve into an intermediate polar in ∼1 Gyr
Influence of macrofaunal assemblages and environmental heterogeneity on microphytobenthic production in experimental systems
No full textDespite the complexity of natural systems, heterogeneity caused by the fragmentation of habitats has\ud
seldom been considered when investigating ecosystem processes. Empirical approaches that have included\ud
the influence of heterogeneity tend to be biased towards terrestrial habitats; yet marine systems offer\ud
opportunities by virtue of their relative ease of manipulation, rapid response times and the well-understood\ud
effects of macrofauna on sediment processes. Here, the influence of heterogeneity on microphytobenthic\ud
production in synthetic estuarine assemblages is examined. Heterogeneity was created by enriching\ud
patches of sediment with detrital algae (Enteromorpha intestinalis) to provide a source of allochthonous\ud
organic matter. A gradient of species density for four numerically dominant intertidal macrofauna (Hediste\ud
diversicolor, Hydrobia ulvae, Corophium volutator, Macoma balthica) was constructed, and microphyto-\ud
benthic biomass at the sediment surface was measured. Statistical analysis using generalized least squares\ud
regression indicated that heterogeneity within our system was a significant driving factor that interacted\ud
with macrofaunal density and species identity. Microphytobenthic biomass was highest in enriched\ud
patches, suggesting that nutrients were obtained locally from the sediment–water interface and not from\ud
the water column. Our findings demonstrate that organic enrichment can cause the development of\ud
heterogeneity which influences infaunal bioturbation and consequent nutrient generation, a driver of\ud
microphytobenthic production
Impact of biodiversity-climate futures on primary production and metabolism in a model benthic estuarine system
No full textAll work was supported by NERC grant NE/E006795/1Understanding the effects of anthropogenically-driven changes in global temperature, atmospheric carbon dioxide and biodiversity on the functionality of marine ecosystems is crucial for predicting and managing the associated impacts. Coastal ecosystems are important sources of carbon (primary production) to shelf waters and play a vital role in global nutrient cycling. These systems are especially vulnerable to the effects of human activities and will be the first areas impacted by rising sea levels. Within these coastal ecosystems, microalgal assemblages (microphytobenthos: MPB) are vital for autochthonous carbon fixation. The level of in situ production by MPB mediates the net carbon cycling of transitional ecosystems between net heterotrophic or autotrophic metabolism. In this study, we examine the interactive effects of elevated atmospheric CO2 concentrations (370, 600, and 1000 ppmv), temperature (6°C, 12°C, and 18°C) and invertebrate biodiversity on MPB biomass in experimental systems. We assembled communities of three common grazing invertebrates (Hydrobia ulvae, Corophium volutator and Hediste diversicolor) in monoculture and in all possible multispecies combinations. This experimental design specifically addresses interactions between the selected climate change variables and any ecological consequences caused by changes in species composition or richness.Peer reviewe
- …
