Climate change effects on Antarctic benthos: a spatially explicit model approach

The Antarctic Peninsula is one of the regions on the Earth with the clearest evidence of recent and fast air warming. This air temperature rise has caused massive glacier retreat leading to an increased influx of glacier meltwater which entails hydrological changes in coastal waters, increasing sediment input and ice-scouring impact regime. It has been hypothesized that an increase of sediment load due to glacier retreat resulted in a remarkable benthic community shift in Potter Cove, a small inlet of the South Shetland Islands. In order to test this hypothesis, we developed an explicit spatial model to explore the link between sedimentation and ice-scouring increase upon four of the most conspicuous benthic species. This is a valuable novel approach since disturbances are strongly dependent of the space. The model takes into account sediment and population dynamics with Lotka-Volterra competition, a sediment-dependent mortality term and a randomized ice-scouring biomass removal. With the developed algorithm, and using a MATLAB environment, numerical simulations for scenarios with different sedimentation and ice-impact rates were undertaken in order to evaluate the effect of this phenomenon on biological dynamics. Comparing simulation results with biological data, the model not only recreates the spatial community distribution pattern but also seems to be able to recreate the shifts in abundance under sedimentation enhancement, pointing out its importance as a structuring factor of polar benthic communities. Considering the challenges of Antarctic field work, this model represents a powerful tool for assessing, understanding, and predicting the effects of climate change on threatened Antarctic coastal ecosystems.Fil: Torre, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Carmona Tabares, Paulo. Universidad del Quindio; ColombiaFil: Momo, Fernando Roberto. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Meyer, Joã F. C. A.. Universidade Estadual de Campinas; BrasilFil: Sahade, Ricardo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentin

Mediated modeling for integrating science and stakeholders: Impacts of enhanced ultraviolet-B radiation on ecosystem services

Mathematical modeling has historically been the province of experts (van den Belt 2004). When applied to policy questions, which span several disciplines and involve nontechnical stakeholders, the expert modeling approach is severely limited. Models for policy purposes usually become quite complex, and it is difficult to communicate results (or the underlying logic of the models) to decision makers in ways that are “credible” (Costanza and Ruth 1998). Models derive their credibility from two distinct sources: 1) the technical ability of the model to reproduce measured observations, and 2) the degree of “buy-in” to the assumptions of the model by stakeholders involved. Within a scientific discipline, the second source is often taken for granted. But in policy-relevant modeling, it often requires special attention. To achieve the necessary buy-in among the diverse stakeholders affected by a policy problem requires that the stakeholders participate in the modeling process. This chapter focuses on this participatory approach to model building in the context of the impacts of enhanced ultraviolet- B radiation (UVBR) on ecosystem services (Table 20.1). Enhanced UVBR is known from small-scale experiments to have several effects on organisms and ecosystems (Smith et al. 1992). But how those effects scale up and affect ecosystem services is not known. This chapter reports on both a mediated model-building process and the resulting model built jointly by scientists and stakeholders.Fil: Van den Belt, Marjan. Mediated Modeling Partners; Estados UnidosFil: Costanza, Robert. University Of Vermont.; Estados UnidosFil: Demers, Serge. Institut des sciences de la mer de Rimouski; CanadáFil: Diaz, Susana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Ferreyra, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gianesella, Sonia M. F.. Universidade de Sao Paulo; BrasilFil: Koch, Evamaria W.. University of Maryland; Estados UnidosFil: Momo, Fernando Roberto. Universidad Nacional de General Sarmiento; ArgentinaFil: Vernet, María. University of California; Estados Unido

Respiratory responses of three Antarctic ascidians and a sea pen to increased sediment concentrations

Glacial retreat and subglacial bedrock erosion are consequences of rapid regional warming on the West Antarctic peninsula. Sedimentation of fine grained eroded particles can impact the physiology of filter feeding benthic organisms. We investigated the effect of increasing concentrations of sediment on the oxygen consumption of suspension feeding species, the ascidians Molgula pedunculata, Cnemidocarpa verrucosa, Ascidia challengeri, and the pennatulid Malacobelemnon daytoni in Potter Cove (South Shetland Islands, Antarctica). In A. challengeri and C. verrucosa oxygen consumption increased gradually up to a critical sediment concentration (Ccrit) where species oxygen consumption was maximal (Omax in mg O2 g-1 dm d-1) and further addition of sediments decreased respiration. Ccrit was 200 mg L-1 for A. challengeri (Omax of 0.651 ± 0.238) and between 100 and 200 mg L-1 for C. verrucosa (Omax of 0.898 ± 0.582). Oxygen consumption of M. pedunculata increased significantly even at low sediment concentrations (15-50 mg sediment L-1). Contrary to the ascidians, sediment exposure did not affect oxygen consumption of the sea pen. The tiered response to sedimentation in the four species corroborates recent field observations that detected a reduction in abundance of the sensitive ascidian Molgula pedunculata from areas strongly affected by glacial sediment discharge, whereas sea pens are increasing in abundance. Our investigation relates consequences (population shifts in filter feeder communities) to causes (glacial retreat) and is of importance for modelling of climate change effects in Antarctic shallow coastal areas

Overview of recent TJ-II stellarator results

The main results obtained in the TJ-II stellarator in the last two years are reported. The most important topics investigated have been modelling and validation of impurity transport, validation of gyrokinetic simulations, turbulence characterisation, effect of magnetic configuration on transport, fuelling with pellet injection, fast particles and liquid metal plasma facing components. As regards impurity transport research, a number of working lines exploring several recently discovered effects have been developed: the effect of tangential drifts on stellarator neoclassical transport, the impurity flux driven by electric fields tangent to magnetic surfaces and attempts of experimental validation with Doppler reflectometry of the variation of the radial electric field on the flux surface. Concerning gyrokinetic simulations, two validation activities have been performed, the comparison with measurements of zonal flow relaxation in pellet-induced fast transients and the comparison with experimental poloidal variation of fluctuations amplitude. The impact of radial electric fields on turbulence spreading in the edge and scrape-off layer has been also experimentally characterized using a 2D Langmuir probe array. Another remarkable piece of work has been the investigation of the radial propagation of small temperature perturbations using transfer entropy. Research on the physics and modelling of plasma core fuelling with pellet and tracer-encapsulated solid-pellet injection has produced also relevant results. Neutral beam injection driven Alfvénic activity and its possible control by electron cyclotron current drive has been examined as well in TJ-II. Finally, recent results on alternative plasma facing components based on liquid metals are also presented.ISSN:0029-5515ISSN:1741-432