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Estuaries are among the most valuable aquatic systems by their services to human welfare. However, increasing human activities at the watershed along with the pressure of climate change are fostering the co-occurrence of multiple environmental drivers, and warn of potential negative impacts on estuaries resources. At present, no clear understanding of how coastal ecosystems will respond to the non-stationary effect of multiple drivers. Here we analysed the temporal interaction among multiple environmental drivers and their changing priority on shaping phytoplankton response in the Bahía Blanca Estuary, SW Atlantic Ocean. The interaction among environmental drivers and the number of significant direct and indirect effects on chlorophyll concentration increased over time in concurrence with enhanced anthropogenic stress, changing winter climate and wind patterns. Over the period 1978-1993, proximal variables such as nutrients, water temperature and salinity, showed a dominant effect on chlorophyll, whereas in more recent years (1993-2009) climate signals (SAM and ENSO) boosted indirect effects through its influence on precipitation, wind, water temperature and turbidity. Turbidity emerged as the dominant driver of chlorophyll while in recent years acted synergistically with the concentration of dissolved nitrogen. As a result, chlorophyll concentration showed a significant negative trend and a loss of seasonal peaks reflecting a pronounced reorganisation of the phytoplankton community. We stress the need to account for the changing priority of drivers to understand, and eventually forecast, biological responses under projected scenarios of global anthropogenic change.

The economy of the semiarid region of the Argentine Pampas is based mainly on agriculture, so climate change is a fact that may have great influence on this type of activity. Therefore, it is necessary to evaluate future climate scenarios and the responses of hydrological variables such as precipitation, actual (ETreal) and potential evapotranspiration (ETc), and recharge rate. Climate change scenarios were based on temperature and precipitation variations predicted by CMIP5. Four representative concentrations pathways (RCP) were considered according to different greenhouse emissions to the atmosphere for the nearby future until the end of the twenty-first century (RCP2.6, RCP4.5, RCP6.0 and RCP8.5). Furthermore, one more scenario called RCP0.0 was considered, which is related to the actual climate conditions and represents the base line. In the study area, nitrogen (N) fertilization is a widely used practice to increase crop yields. This work assesses the impact of future climate on soil water fluxes and N compounds fate based on numerical simulations carried out with HYDRUS 1D. Actual evapotranspiration is going to increase between 1 and 6% from low to high climate-change scenarios. Although an increase in precipitation is also expected during all months of the year, there are periods when water availability will not be enough to supply the new potential evapotranspiration demand. The worst case is RCP8.5, where the ETreal/ETc ratio is expected to decline by 4%. Annual recharge is expected to decrease by 2.5% in the RCP2.6 scenario, while the rest of the scenarios shown positive trends. N leachate in the form of nitrates showed an increase of 2.8% in the RCP4.5 scenario which was also the one with the highest recharge rate raise. The use of a mathematical model as a predictive tool in soil water fluxes and fertilizers use is essential for planning the sustainable management of agroecology adapted to climate changes. This research is financially supported by the Universidad Nacional del Sur (UNS) and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).

In this paper, a land-use modelling framework is presented combining empirical and theory-based modelling approaches to determine economic potential of biofuel production avoiding indirect land-use changes (iLUC) resulting from land competition with other functions. The empirical approach explores future developments in food and feed production to determine land availability and technical potential of biofuel production. The theory-based approach assesses the economic performance of biofuel crops on the surplus land in comparison with other production systems and determines the economic potential of biofuel production. The framework is demonstrated for a case study in Argentina to determine the development of biofuel potential from soy and switchgrass up to 2030. Two scenarios were considered regarding future developments of productivity in agriculture and livestock production. It was found that under a scenario reflecting a continuation of current trends, no surplus land is expected to become available. Nevertheless, the potential for soybean biodiesel is expected to keep increasing up to 103 PJ in 2030, due to the existence of a developed agro-industrial sector jointly producing feed and biodiesel. In case large technological developments occur, 32 Mha could become available in 2030, which would allow for a technical potential of 472 PJ soybean biodiesel and 1445 PJ switchgrass bioethanol. According to the economic assessment, an economic potential of 368 PJ of soy biodiesel and 1.1 EJ switchgrass bioethanol could be attained, at a feedstock production cost of 100-155 US$/ton and 20-45 US$/ton, respectively. The region of southwest Buenos Aires and La Pampa provinces appeared to be particularly promising for switchgrass. The ability of jointly assessing future developments in land availability, technical and economic potential of biofuel production avoiding iLUC and spatial distribution of viable locations for growing biofuel crops means that the proposed framework is a step forward in assessing the potential for biofuel production that is both economically viable and sustainably produced. © 2014 Elsevier Ltd.

The sorption from water to wood (KWood) of 10 organic chemicals (log KOW, 1.48-6.20) was experimentally determined for oak (Quercus robur) and basket willow (Salix viminalis). Linear regression yielded log KWood = -0.27 (+/- 0.25) + 0.632 (+/- 0.063) log KOW for oak (r = 0.90, n = 27) and log KWood = -0.28 (+/- 0.40) + 0.668 (+/- 0.103) log KOW for willow (r = 0.79, n = 27). According to an equilibrium-partitioning model, wood should be an important storage compartment for lipophilic environmental chemicals, but this is contrary to analytical results. Diffusive uptake from air into wood was estimated to be a relevant transport process only for chemicals with a high KAW. Uptake of chemicals from soil via xylem into stem was simulated with a dynamic one-compartment model. This pathway seems to be important for chemicals with low and intermediate lipophilicity. In large trees, the chemicals are retained for a long time. If metabolism inside the stem occurs, wood can serve as a "safe sink" for environmental chemicals. This might be of use in phytoremediation.

Quantifying biotic feedbacks in response to environmental signals is fundamental to assess ecosystem perturbation. We analyzed the joint effects of eutrophication, derived from sewage pollution, and climate at the base of the pelagic food web in the Bahía Blanca Estuary (SW Atlantic Ocean). A two-year survey of environmental conditions and microplankton communities was conducted in two sites affected by contrasting anthropogenic eutrophication conditions. Under severe eutrophication, we found higher phytoplankton abundance consistently dominated by smaller sized, non siliceous species, while microzooplankton abundance remained lower and nutrient stoichiometry showed conspicuous deviations from the Redfield ratio. Phytoplankton growth in such conditions appeared controlled by phosphorous. In turn, microplankton biomass and phytoplankton size ratio (20μm) displayed a saturation relationship with nutrients in the highly eutrophic area, although mean phytoplankton growth was similar in both eutrophic systems. The strength of links within the estuarine network, quantified through path analysis, showed enhanced relationships under larger anthropogenic eutrophication, which fostered the climate influence on microplankton communities. Our results show conspicuous effects of severe sewage pollution on the ecological stoichiometry, i.e., N and P excess with respect to Si, altering nutrient ratios for microplankton communities. This warns on wide consequences on food web dynamics and ultimately in ecosystem assets of coastal pelagic environments.