Arsenic-contaminated ground- and drinking water is a global environmental problem with about 1-2Prozent of the world's population being affected. The upper drinking water limit for arsenic (10 Micro g/l) recommended by the WHO is often exceeded, even in industrial nations in Europe and the USA. Chronic intake of arsenic causes severe health problems like skin diseases (e.g. blackfoot disease) and cancer. In addition to drinking water, seafood and rice are the main reservoirs for arsenic uptake. Arsenic is oftentimes of geogenic origin and in the environment it is mainly bound to iron(III) minerals. Iron(III)-reducing bacteria are able to dissolve these iron minerals and therefore release the arsenic to the environment. In turn, iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II)- oxidation at neutral pH followed by iron(III) mineral precipitation. This process may reduce arsenic concentrations in the environment drastically, lowering the potential risk for humans dramatically.The main goal of this study therefore is to quantify, identify and isolate anaerobic and aerobic Fe(II)-oxidizing microorganisms in arsenic-containing paddy soil. The co-precipitation and thus removal of arsenic by iron mineral producing bacteria will be determined in batch and microcosm experiments. Finally the influence of rhizosphere redox status on microbial Fe oxidation and arsenic uptake into rice plants will be evaluated in microcosm experiments. The long-term goal of this research is to better understand arsenic-co-precipitation and thus arsenic-immobilization by iron(II)-oxidizing bacteria in rice paddy soil. Potentially these results can lead to an improvement of living conditions in affected countries, e.g. in China or Bangladesh.
Water is an intrinsic component of ecosystems acting as a key agent of lateral transport for particulate and dissolved nutrients, forcing energy transfers, triggering erosion, and driving biodiversity patterns. Given the drastic impact of land use and climate change on any of these components and the vulnerability of Ecuadorian ecosystems with regard to this global change, indicators are required that not merely describe the structural condition of ecosystems, but rather capture the functional relations and processes. This project aims at investigating a set of such functional indicators from the fields of hydrology and biogeochemistry. In particular we will investigate (1) flow regime and timing, (2) nutrient cycling and flux rates, and (3) sediment fluxes as likely indicators. For assessing flow regime and timing we will concentrate on studying stable water isotopes to estimate mean transit time distributions that are likely to be impacted by changes in rainfall patterns and land use. Hysteresis loops of nitrate concentrations and calculated flux rates will be used as functional indicators for nutrient fluxes, most likely to be altered by changes in temperature as well as by land use and management. Finally, sediment fluxes will be measured to indicate surface runoff contribution to total discharge, mainly influenced by intensity of rainfall as well as land use. Monitoring of (1) will be based on intensive sampling campaigns of stable water isotopes in stream water and precipitation, while for (2) and (3) we plan to install automatic, high temporal-resolution field analytical instruments. Based on the data obtained by this intensive, bust cost effective monitoring, we will develop the functional indicators. This also provides a solid database for process-based model development. Models that are able to simulate these indicators are needed to enable projections into the future and to investigate the resilience of Ecuadorian landscape to global change. For the intended model set up we will couple the Catchment Modeling Framework, the biogeochemical LandscapeDNDC model and semi-empirical models for aquatic diversity. Global change scenarios will then be analyzed to capture the likely reaction of functional indicators. Finally, we will contribute to the written guidelines for developing a comprehensive monitoring program for biodiversity and ecosystem functions. Right from the beginning we will cooperate with four SENESCYT companion projects and three local non-university partners to ensure that the developed monitoring program will be appreciated by locals and stakeholders. Monitoring and modelling will focus on all three research areas in the Páramo (Cajas National Park), the dry forest (Reserva Laipuna) and the tropical montane cloud forest (Reserva Biologica San Francisco).
This project will provide quantitative estimates of the flow of low-salinity warm water through the Indonesian Gateway on suborbital timescales during MIS 2 and 3 (focusing on Dansgaard Oeschger (D-O) oscillations) and will assess the Indonesian Throughflow (ITF) s impact on the hydrography of the eastern Indian Ocean and global thermohaline circulation during this critical interval of high climate variability. ITF fluctuations, associated with sea level change, temperature and salinity variations in the West Pacific Warm Pool (WPWP) strongly influence precipitation over Australia, the strength of the southeast-Asian summer monsoon, and the intensity of warm meridional currents in the Indian Ocean. We will test the hypothesis that increased ITF is associated with warm interstadials of MIS 3, whereas a strong reduction in ITF occurred during stadials. We will use as main proxies planktonic and benthic foraminiferal isotopes in conjunction with Mg/Ca temperature estimates and radiogenic isotopes (mainly Nd) as tracers of Pacific water masses along depth transects in the Timor Passage and the eastern Indian Ocean. This project will provide the paleoceanographic framework that will be crucial to validate and refine circulation models of D-O events and high-frequency climate variability on a global scale.
In rivers and streams, biofilms are major sites of carbon cycling. They retain large amounts of dissolved organic carbon (DOC) and consequently are most important for the development of aquatic organisms on higher trophic levels. Besides autochthonous primary production, which supports heterotrophic production in biofilms, large amounts of organic carbon (OC) are derived from the surrounding catchment areas. More precipitation and more frequent and severe floods due to climate change will increase the transport of material into streams. Moreover, catchment characteristics including vegetation affect the transport and nature of DOC into aquatic ecosystems. Thus, carbon dynamics depend on how a stream is embedded within and interacts with its surrounding terrestrial environment. Despite its importance for carbon cycling it is not understood to which extent autochthonous or allochthonous carbon is used in biofilms and how increased addition of allochthonous carbon determines the relative use of both carbon sources. The combined application of 13C and 14C analysis on differently labeled DOC sources intend to answer to which extent DOC from different sources is used by bacteria in biofilms and finally transported to higher trophic levels. The use of 13C and 14C signals on carbon compounds and biomarkers is an excellent method to determine carbon sources for microorganisms and the transport of labeled material within the food web.
The world is currently experiencing a major biodiversity crisis due to human activities. A primary concern is the on-going and rapid biological consequences of global climate change. Climate change is impacting alpine landscapes at unprecedented rates, with severe impacts on landscape structure and catchment hydrodynamics, as well as temperature regimes of glacial-fed rivers. Most glaciers are expected to be dramatically reduced and many even gone by the year 2100, concomitantly with changes (timing and magnitude) in temperature and precipitation. These environmental changes are predicted to have strong impacts on the persistence and distribution of alpine organisms, their population structure and community assembly, and, ultimately, ecosystem functioning. However, how alpine biodiversity (aquatic macroinvertebrates in our case) will respond to these changes is poorly understood. Most previous studies predict the presence of species based on the distribution of putatively suitable habitats but ignore biotic traits, such as dispersal, and potential eco-evolutionary responses to such changes. Clearly, accurate predictions on species responses require integrative studies incorporating landscape dynamics with eco-evolutionary processes. The primary goal of the proposed research is to empirically test determinants of alpine macroinvertebrate responses to rapid environmental change mediated by glacial recession. Climate-induced glacial retreat is occurring rapidly and in a replicated fashion (i.e. over multiple catchments and continents), which provides a natural experiment for testing determinants of organismal and species diversity responses to climate change in alpine waters. The responses of alpine aquatic macroinvertebrates are highly important because of their known sensitivity (i.e. response rates) to environmental change and their fundamental role in ecosystem functioning. Using an integrative comparative and experimental approach, we will target the following main question: What are the roles of ecological and evolutionary processes in population level responses of macroinvertebrates to environmental change? The study will take advantage of rapid glacial recession (environmental change) to empirically examine spatio-temporal patterns in species distribution in nature, combined with experimental and population genetics approaches. The data generated will be used to explicitly address the role of eco-evolutionary processes (determinants) on population level responses for selected key species. Spatial and temporal variation in species distribution, phenotypic and genetic variation will be quantified for two stream macroinvertebrates (hemimetabolous mayfly Baetis alpinus, holometabolous caddisfly Allogamus uncatus), and measuring landscape features and physico-chemical parameters along longitudinal transects downstream of glaciers and selected side-slope tributaries (as potential stepping stones for dispersal and colonization).
Forecasted change in precipitation may lead to an increase of biomass in area covered by savannah and to a consequent increase in biomass burning, affecting the carbon emissions at global scale. Understanding how tropical ecosystems will react to those changes is relevant particularly for East Africa, where population density is the highest of the continent. We generated high-resolution sediment charcoal data spanning the last 2000 years across a climatic gradient (wet to dry savannah) to assess the long-term impact of fire, climate and land use on tropical savannah ecosystems. Records of biomass burnings show contrasting fire pattern among the two regions. In wet savannah ecosystems, fire was limited by wetter periods until the colonial period (AD 1800), when biomass removal led to a decrease in burning. In contrast, in the dry setting of Kenya, fire conditions during the last 2k years peaked at intermediate rainfall, and increased in recent times following land use intensification. On the basis of our data we hypothesize that under a future scenario with increased rainfall fire will increase in the wet savannah and decrease in the (eastern) dry savannah, unless fuel will be limited by agriculture practices. Yet, it is not understood how important vegetation properties and ecosystem services such as plant biomass and diversity will respond to inter-annual to seasonal variation in the moisture balance, and how tropical species will cope with extreme events, such as droughts. The following proposal addresses highly relevant questions for todays key issues of biodiversity and the adaptation of vulnerable communities to global change. Additionally, it will contribute to ongoing multi-proxy research concerning the magnitude, frequency, and rates of past climate change in equatorial East Africa. Finally, the project will improve our understanding of tropical ecosystem functioning and its interaction with cultural and economic systems at local to regional scales.
Sulfur isotope fractionation (34S/32S) has been used since the late 1940s to study the chemical and biological sulfur cycle. While large isotope fractionations during bacterial sulfate reduction were used successfully to interpret, e.g., accumulation of sulfate in ancient oceans or the evolution of early life, much less is known about fractionation during sulfide oxidation. The fractionation between the two end-members sulfide and sulfate is commonly much smaller and inconsistencies exist whether substrate or product are enriched. These inconsistencies are explained by a lack of knowledge on oxidation pathways and rates as well as intermediate sulfur species, such as elemental sulfur, polysulfides, thiosulfate, sulfite, or metalloid-sulfide complexes (e.g. thioarsenates), potentially acting as 34S sinks.In the proposed project, we will develop a method for sulfur species-selective isotope analysis based on separation by preparative chromatography. Separation of Sn2- and S0 will be achieved after derivatization with methyl triflate on a C18 column, separation of the other sulfur species in an alkaline eluent on an AS16 column. Sulfur in the collected fractions will be extracted directly with activated copper chips (Sn2-, S0), or precipitated as ZnS (S2-) or BaSO4 and analyzed by routine methods as SO2. Results of this species-selective approach will be compared to those from previous techniques of end-member pool determinations and sequential precipitations.The method will be applied to sulfide oxidation profiles at neutral to alkaline hot springs at Yellowstone National Park, USA, where we detected intermediate sulfur species as important species. Determining 34S/32S only in sulfide and sulfate, our previous study has shown different fractionation patterns for two hot spring drainages with sulfide oxidation profiles that seemed similar from a geochemical perspective. The reasons for the different isotopic trends are unclear. In the present project, we will differentiate species-selective abiotic versus biotic fractionation using on-site incubation experiments with the chemolithotrophic sulfur-oxidizing bacteria Thermocrinis ruber as model organism. For selected samples, we will test whether 33S and 36S further elucidate species-selective sulfide oxidation patterns. We expect that lower source sulfide concentrations increase elemental sulfur disproportionation, thus increase redox cycling and isotope fractionation. We also expect that the larger the concentration of intermediate sulfur species, including thioarsenates, the larger the isotope fractionation. Following fractionation in species-selective pools, we will be able to clarify previously reported inconsistencies of 34S enrichment in substrate or product, elucidate sulfide oxidation pathways and rates, and reveal details about sulfur metabolism. Our new methodology and field-based data will be a basis for more consistent studies on sulfide oxidation in the future.
In the South-Indian city of Chennai (formerly called Madras), disastrous tropical monsoon linked with excessive precipitation frequently lead to wide-flat floods in the coastal plains. Caused by rapid urbanisation, the population in urban and periurban areas is more and more affected by these events. Besides the marginalised population living in disfavoured areas, increasingly also the more wealthy population that settles in flood prone areas is affected. Interdisciplinary assessments are needed to explain the complex causes of floods. The project analysed environmental aspects of risk exposure as well as socioeconomic aspects of risk perceptions and response strategies. By combining natural-scientific with socio-scientific approaches, a holistic perspective of the complex reasons and impacts of flooding could be covered. The project consisted of the following steps: 1. Analysis of flood risk exposure: Physio-geographic, hydrological and meteorological realities in risk areas were assessed using remote sensing (RS) data and geographical information systems (GIS). 2. Analysis of risk perception and management: Affected marginalised poor segments of the population, affected middle class groups as well as local planning authorities were interviewed to analyse local perceptions of floods and dominant management strategies. 3. Development of a flood risk map: The results of the risk assessment were integrated in an interactive flood risk map. The map - using several different layers - functions as a flood risk management tool including often neglected socioeconomic and socio-cultural parameters which reflect local vulnerability. 4. Holding of two workshops: A policy workshop with different stakeholders involved in flood management and affected by floods was held in Chennai in August 2007. This workshop was to foster communication and dialogue between different stakeholders and to create awareness on the current situation and problems in the area. A roundtable with the partners from India and organisations dealing with flood management and flood relief measures took place in October 2007 in Freiburg in order to present and discuss the findings and to strengthen future co-operation, communication and networks.
Degradation of the soil productivity due to salt accumulation (salinization) is a major concern in arid, semi-arid and coastal regions. Soil salinization is an old issue but encouraged irrigation practices have been rapidly increasing its intensity and magnitude in the past few decades. Studies have shown that excess of the irrigated water contributes significantly to evaporation from the bare soil surface and therefore to the salinization. In some parts of the world soil salinity has grown so acute that the agricultural lands have been abandoned. Evaporation salinization is mainly influenced by interaction between the flow and transport processes in the atmosphere and the porous-medium. On the atmosphere side, wind velocity, air temperature and radiation have a strong impact on evaporation. Furthermore, turbulence causes air mixing, influences the vapor transport and creates a boundary layer at the soil-atmosphere interface which indeed influences evaporation. On the porous-medium side, dissolved salt is transported under the influence of viscous forces, capillary forces, gravitational forces and advective and diffusive fluxes. The water either directly evaporates from the water-filled pores or it is transported to air due to diffusive processes. Continuous evaporation promotes salt accumulation and precipitation resulting in soil salinization. In the scope of this work we attempt to develop a model concept capable of handling flow, transport and precipitation processes related to evaporative salinization of an unsaturated porous-medium.
As an isolated marginal sea, the Black Sea reacted particularly sensitive to paleoclimatic and paleoenvironmental changes and on both global and regional scales. In spite of its unique potential for high resolution paleoclimate reconstructions, late Quaternary sediment sequences of the Black Sea have only subordinately been studied with respect to paleoclimatic questions. This is somewhat surprising considering the key-geographic location of the Black Sea, where climate is strongly affected by two major climate systems; the North Atlantic/Siberian pressure system in winter and the Indian monsoon in summer. Highly-resolved and precisely dated paleoclimate records are crucial for reconstructing past regional climate variability, which can then be compared to paleoclimate records from the North Atlantic, Europe and the Indian monsoon domain. Several core sites in the Black Sea along the North-Anatolian rim can provide records of vegetation dynamics and changing precipitation regimes in the Anatolian hinterland as well as paleoceanographic/ paleolimnologic data of environmental changes in the marine/limnic Black Sea system itself. Uranium-series dated stalagmites from Sofular Cave located at the Black Sea coast in north-western Turkey will provide, as terrestrial counterpart, long complementary paleorecords of changes in vegetation and precipitation. When combined, such records will allow us to better quantify the far-field effects of North Atlantic climate and Indian monsoon during the Holocene, Eemian and the last two glacial/interglacial transitions (T1 and T2).
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