Subproject 3 will investigate the effect of shifting from continuously flooded rice cropping to crop rotation (including non-flooded systems) and diversified crops on the soil fauna communities and associated ecosystem functions. In both flooded and non-flooded systems, functional groups with a major impact on soil functions will be identified and their response to changing management regimes as well as their re-colonization capability after crop rotation will be quantified. Soil functions corresponding to specific functional groups, i.e. biogenic structural damage of the puddle layer, water loss and nutrient leaching, will be determined by correlating soil fauna data with soil service data of SP4, SP5 and SP7 and with data collected within this subproject (SP3). In addition to the field data acquired directly at the IRRI, microcosm experiments covering the broader range of environmental conditions expected under future climate conditions will be set up to determine the compositional and functional robustness of major components of the local soil fauna. Food webs will be modeled based on the soil animal data available to gain a thorough understanding of i) the factors shaping biological communities in rice cropping systems, and ii) C- and N-flow mediated by soil communities in rice fields. Advanced statistical modeling for quantification of species - environment relationships integrating all data subsets will specify the impact of crop diversification in rice agro-ecosystems on soil biota and on the related ecosystem services.
Das Jena Experiment hat es sich zum Ziel gesetzt Zusammenhänge zwischen Pflanzendiversität und Ökosystemprozessen zu untersuchen. Unsere Arbeiten beschäftigen sich mit einer der Schlüsselgruppen in unterirdischen Ökosystemprozessen - den Pilzen. Das Wirtsspektrum arbuskulärer Mykorrhizapilze (AMF) wird innerhalb der Monokultur-Plots untersucht. In Polykulturen unterschiedlicher Diversität soll der Zusammenhang zwischen Artenreichtum von Pflanzen und AMF vertiefend studiert werden. Durch ein Experiment mit stabilen Isotopen soll der Beitrag der AMF für die Nährstoffverteilung zwischen einzelnen Pflanzenarten, aber auch zwischen funktionellen Gruppen näher beleuchtet werden. Weiterhin wird untersucht, ob Zusammenhänge zwischen Stickstoffmineralisierung, Anreicherung organischer Substanzen sowie der Diversität und dem Expressionsprofil pilzlicher Laccasegene bestehen.
Selenium is a double edged chemical element, since it is both essential yet highly toxic. Besides its high acute toxicity, selenium is characterized to be strongly bioconcentrated from dissolved selenium species (selenite, selenate, selenoaminoacids) in aquatic primary producers and further biomagnified during food chain transfer. In consequence, water borne selenium concentrations of as little as 2 myg / L have been documented to cause severely adverse effects on top predators such as water birds and fish. Although the ecotoxic impact was first noticed in the early 1980s, to date no definitive solution has been found to remediate selenium contaminated drainage and waste waters. Due to the water insolubility of elemental selenium, the dogma that 'elemental selenium is not bioavailable and not toxic' dominates current scientific literature and forms the basis for various remediation approaches using microorganisms to convert selenium oxyanions to elemental selenium. However, a number of considerations and recent studies suggest that the dogma might only be true for 'bulk' elemental selenium, yet not for microbially formed, so called biogenic selenium. Biogenic differs from bulk elemental selenium considerably regarding its physico-chemical properties. Biogenic elemental selenium consists of nanometer sized spheres, which do not crystallize to larger particles of trigonal elemental selenium, the thermodynamically stable allotrope. The latter is due to stabilization by proteins associated with the particles. As a consequence, biogenic elemental selenium does not settle yet remains in waters as a colloidal suspension, thus being subject to uptake by biota. Although the general bioavailability of biogenic elemental selenium has been proven, it has not been studied in detail, in particular not in aquatic environments. We aim at quantifying acute and chronic toxicity in the model organism Daphnia magna, elucidating the underlying mechanism of toxicity. Furthermore, we will quantify biogenic elemental selenium uptake, depuration and biotransformation to proteinous forms (the species most relevant for trophic transfer). Thus we will be able to deliver an improved model of selenium food chain transfer in aquatic environments, the basis for appropriate selenium risk assessment. During the course of the proposed research, such questions as the following will be answered: - Is biogenic elemental selenium bioavailable and / or toxic to Daphnia magna? Which are the mechanisms underlying toxicity? - To which extent is biogenic selenium biotransformed to proteinous (highly bioaccumulative) species? Does biogenic elemental selenium represent a significant entrance port for selenium at base of aquatic food chain?
The expansion and intensification of agricultural areas and the associated deforestation, eutrophication and modification of habitat heterogeneity remain the most important stressors to stream ecosystem functioning worldwide. The alteration of key environmental characteristics may cause the loss of functional attributes specific for streams in different climate zones and may ultimately lead to a homogenisation of stream ecosystem functioning. Previous studies were mostly restricted to a single function in a particular biome and a thorough understanding on the potential for an agriculturally driven functional homogenisation of stream ecosystems among climate zones is lacking. The project HECTARE analyses ecosystem functioning of pristine and agricultural streams situated in the German Harz and in the Brazilian Cerrado and Atlantic forest. By the novel combination of quantification of food webs and measurements of ecosystem productivity and respiration, HECTARE delivers a mechanistic understanding on energy- and matter fluxes in temperate and Neotropical streams including their trophic coupling to the catchments. Building on that, key pathways of whole-ecosystem matter and energy fluxes that are impacted by agricultural land use will be identified. The inter-biome approach proposed with HECTARE will allow for a synthesis of impact patterns associated with agricultural land use and an analysis of the degree of functional homogenisation of stream ecosystems.
Introduction: In aquatic systems, the bioavailability of a compound is dependent on numerous factors such as partitioning between water, different organisms and solids, biotransformation and food web transfer. This project dealt with the fate of an important environmental xeno-estrogen, 17-ethinylestradiol (EE2), in the aquatic environment. Therefore, the kinetics of EE2 in indicator species representing the different trophic levels of an ecosystem were assessed. As primary producers, green algae (Desmodesmus suspicatus) were selected. The water flea Daphnia magna and larvae of the midge Chironomus riparius were introduced as primary consumers of the water phase and the sediment, respectively. Finally, water as well as dietary uptake of EE2 were investigated in a target species and secondary consumer: zebrafish (Danio rerio). Methodology: In a first series of experiments, uptake of 14C-labelled EE2 (14C-EE2) from the water phase and elimination by the different organisms were investigated over time. In a second test series, both primary consumers were fed 14C-EE2 spiked algae in order to study bioaccumulation. Uptake of 14C-EE2 by chironomid larvae after water and sediment spiking was compared, including sediments of different composition. In a third series of experiments, male fish were short term (48 h) exposed to 14C-EE2 through different routes: by water exposure (WE) and by dietary exposure (DE) via both contaminated daphnids and chironomid larvae. Distribution of 14C-EE2 in the fish was studied by measuring the amount of radioactivity (RA) in the different fish tissues. Additionally, the effect of EE2 on the vitellogenin (Vtg) induction in male fish was compared after WE and DE in a long term (14 d) experiment. The RA in liquid samples was quantified by means of liquid scintillation counting (LSC). Solid samples were subjected to combustion in a biological oxidiser, trapping (14)CO2, measured with LSC. Water and organism extracts were analysed by means of HPLC with a radiodetector, except for algae extracts that were subjected to TLC. Metabolites were identified with GC-MS, high resolution LC-MS and enzymatic hydrolysis followed by HPLC with radiodetection. Metabolites, detected in the water phase, were tested for estrogenic activity by means of YES and ER-CALUX assays. Results: Accumulation and effects: Of the four organisms mentioned above, bioconcentration of 14C-EE2 was highest in the algae. Whereas the growth rate of D. subspicatus was significantly affected at high EE2 concentrations compared to unexposed algae, EE2 had no acute effects on D. magna and C. riparius. Daphnids showed a higher bioaccumulation potential after exposure via spiked algae. For chironomids, water exposure was the predominant uptake route. The presence of sediment lowered the bioavailability of 14C-EE2 to the larvae after both water and sediment spiking. Nevertheless, uptake was higher when the nutritional quality of the sediment was better. Etc.
The effects of invertebrate herbivory on ecosystem processes will be tested by excluding above-ground invertebrates from 5 m x 5 m subplots of all experimental plots using biocides. Net primary productivity and other ecosystem processes will be quantified in both treated and unmanipulated parts of the plot to study the relationships between plant diversity, invertebrate herbivory and ecosystem functioning. A second objective of this project is to test the interactions between plant diversity, plant productivity and the structure of the invertebrate community. Above-ground invertebrates will be sampled repeatedly from all grassland plots and allocated to a certain trophic role, i.e. herbivore, predator, parasitoid, or detritivore. Statistical modeling will reveal the influence of plant diversity manipulations on invertebrate density and invertebrate diversity at different trophic
Objective: NACLIM aims at investigating and quantifying the predictability of the climate in the North Atlantic/European sector related to North Atlantic/Arctic sea surface temperature (SST) and sea ice variability and change on seasonal to decadal time scales. SST and sea-ice forcing have a crucial impact on weather and climate in Europe. Rather than running climate forecasts ourselves, we will analyse the multi-model decadal prediction experiments currently performed as part of the fifth Coupled Model Intercomparison Project (CMIP5) and critically assess the quality of predictions of the near-future state of key oceanic and atmospheric quantities relevant to the SST and sea-ice distribution and the related climate. Long-term observations of relevant ocean parameters will be carried out, necessary to assess the forecast skill of the model-based prediction results. We will identify those observations that are key to the quality of the prediction and in turn optimize the present observing system. We will quantify the impact of North Atlantic/European climate change on high trophic levels of the oceanic ecosystem as well as on urban societies.
The main aim of the proposed research is a quantitative evaluation of the potential impact of global warming on the trophic balance of the upper ocean. Primary production, as well as autotrophic and heterotrophic respiration are all expected to increase with temperature, and a number of experimental culture studies suggest that the increase with temperature is more pronounced for respiration than for production. This notion has been further confirmed on the ecosystem level in recent short-term mesocosm studies. According to these results, an expected direct effect of global warming is a weakening of the biological carbon pump. In contrast to indirect effects arising from changes in circulation and stratification, such a direct temperature effect has not yet been investigated quantitatively on a global scale. Using an Earth System Model of intermediate complexity, the proposed study will investigate the sensitivity of the model's biological pump to different parameterisations of temperature effects on autotrophic and heterotrophic processes, each calibrated by available experimental data from culture and mesocosm studies. The ability of different parameterisations to closely reproduce regional patterns of biogeochemical tracer distributions will first be evaluated for pre-industrial steady-state solutions. In a second step, the model will be forced with IPCC-type CO2 emission scenarios over the 21st century in order to estimate the impact of direct temperature effects on the marine biota relative to indirect effects via changes in circulation and stratification.
Microbial food webs dominate the functioning of marine and freshwater ecosystems. Conclusions on the impact of climatic changes on aquatic ecosystems have generally been based on studies of constant increases in experimental temperatures. However, since the invention of deterministic chaos in the 60ies of the last century, it is known that organisms are confronted with non-linear dynamics of external temperatures. One important forecast for climate changes is the increase of weather (e.g. temperature) variability especially in the middle of Europe. Thus, we would like to contribute to the studies of the current consortia working in the frame of AQUASHIFT with a model study on the dynamic behaviour of experimental food webs. Organisms are not only faced with external irregularities but also with internal (intrinsic) fluctuations of population dynamic parameters. Here we would like to investigate the interaction between non-linear dynamic behaviours of extrinsic and intrinsic factors. We have developed an exceptional model systems consisting of a microbial two-preyone-predator-systems that allows for a detailed analysis of dynamic behaviour under defined chemostat conditions. We will analyze match/mismatches occurring due to the interference of non-linear dynamics of extrinsic (temperature) and intrinsic (population sizes) parameters on different trophic levels and would like to contribute to create a theoretical basis for the understanding of the impact of global changes on aquatic communities.
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