Macht. Wissen. Teilhabe.: Sammlungsinstitutionen im 21. Jahrhundert

Macht, Wissen, Teilhabe – diese Begriffe sind für die Entwicklung von Sammlungsinstitutionen im 21. Jahrhundert zentral. Wie können Museen und Bibliotheken ihre Rolle als Vermittler, Bewahrer und Produzenten von kulturellem Wissen neu denken? Welche Rolle spielen ihre Besucherinnen und Besucher? Wer kann in einer globalisierten und digitalen Welt Deutungsmacht ausüben? Die Beiträge aus Wissenschaft und Praxis reflektieren aus unterschiedlichen Perspektiven, wie sich Museen und Bibliotheken in diesem Spannungsfeld positionieren. So befassen sich Karl-Siegbert Rehberg, Horst Bredekamp, Lambert Wiesing und Wolfgang Ullrich grundlegend mit Praktiken des Sammelns, Zeigens und Ausstellens. Ursula Rao, Stefanie Mauksch und Sarah Fründt gehen auf die besondere Rolle von Ethnologischen Museen ein, während Susanne Wernsing und Cindy Denner aus kuratorischer Perspektive neue Wege der Wissensproduktion in Ausstellungen beschreiben

Physiological control on carbon isotope fractionation in marine phytoplankton

One of the great challenges in biogeochemical research over the past half a century has been to quantify and understand the mechanisms underlying stable carbon isotope fractionation (ϵp) in phytoplankton in response to changing CO2 concentrations. This interest is partly grounded in the use of fossil photosynthetic organism remains as a proxy for past atmospheric CO2 levels. Phytoplankton organic carbon is depleted in 13C compared to its source because of kinetic fractionation by the enzyme RubisCO during photosynthetic carbon fixation, as well as through physiological pathways upstream of RubisCO. Moreover, other factors such as nutrient limitation, variations in light regime as well as phytoplankton culturing systems and inorganic carbon manipulation approaches may confound the influence of aquatic CO2 concentrations [CO2] on ϵp. Here, based on experimental data compiled from the literature, we assess which underlying physiological processes cause the observed differences in ϵp for various phytoplankton groups in response to C-demand/C-supply, i.e., particulate organic carbon (POC) production / [CO2]) and test potential confounding factors. Culturing approaches and methods of carbonate chemistry manipulation were found to best explain the differences in ϵp between studies, although day length was an important predictor for ϵp in haptophytes. Extrapolating results from culturing experiments to natural environments and for proxy applications therefore require caution, and it should be carefully considered whether culture methods and experimental conditions are representative of natural environments

Ocean Acidification Reduces Growth and Calcification in a Marine Dinoflagellate

Abstract Ocean acidification is considered a major threat to marine ecosystems and may particularly affect calcifying organisms such as corals, foraminifera and coccolithophores. Here we investigate the impact of elevated pCO 2 and lowered pH on growth and calcification in the common calcareous dinoflagellate Thoracosphaera heimii. We observe a substantial reduction in growth rate, calcification and cyst stability of T. heimii under elevated pCO 2 . Furthermore, transcriptomic analyses reveal CO 2 sensitive regulation of many genes, particularly those being associated to inorganic carbon acquisition and calcification. Stable carbon isotope fractionation for organic carbon production increased with increasing pCO 2 whereas it decreased for calcification, which suggests interdependence between both processes. We also found a strong effect of pCO 2 on the stable oxygen isotopic composition of calcite, in line with earlier observations concerning another T. heimii strain. The observed changes in stable oxygen and carbon isotope composition of T. heimii cysts may provide an ideal tool for reconstructing past seawater carbonate chemistry, and ultimately past pCO 2 . Although the function of calcification in T. heimii remains unresolved, this trait likely plays an important role in the ecological and evolutionary success of this species. Acting on calcification as well as growth, ocean acidification may therefore impose a great threat for T. heimii

Physiological control on carbon isotope fractionation in marine phytoplankton

One of the great challenges in biogeochemical research over the past half a century has been to quantify and understand the mechanisms underlying stable carbon isotope fractionation (ϵp) in phytoplankton in response to changing CO2 concentrations. This interest is partly grounded in the use of fossil photosynthetic organism remains as a proxy for past atmospheric CO2 levels. Phytoplankton organic carbon is depleted in 13C compared to its source because of kinetic fractionation by the enzyme RubisCO during photosynthetic carbon fixation, as well as through physiological pathways upstream of RubisCO. Moreover, other factors such as nutrient limitation, variations in light regime as well as phytoplankton culturing systems and inorganic carbon manipulation approaches may confound the influence of aquatic CO2 concentrations [CO2] on ϵp. Here, based on experimental data compiled from the literature, we assess which underlying physiological processes cause the observed differences in ϵp for various phytoplankton groups in response to C-demand/C-supply, i.e., particulate organic carbon (POC) production / [CO2]) and test potential confounding factors. Culturing approaches and methods of carbonate chemistry manipulation were found to best explain the differences in ϵp between studies, although day length was an important predictor for ϵp in haptophytes. Extrapolating results from culturing experiments to natural environments and for proxy applications therefore require caution, and it should be carefully considered whether culture methods and experimental conditions are representative of natural environments

Combined Effects of Ocean Acidification and Light or Nitrogen Availabilities on ¹³C Fractionation in Marine Dinoflagellates

Along with increasing oceanic CO2 concentrations, enhanced stratification constrains phytoplankton to shallower upper mixed layers with altered light regimes and nutrient concentrations. Here, we investigate the effects of elevated pCO2 in combination with light or nitrogen-limitation on 13C fractionation (ep) in four dinoflagellate species. We cultured Gonyaulax spinifera and Protoceratium reticulatum in dilute batches under low-light (‘LL’) and high-light (‘HL’) conditions, and grew Alexandrium fundyense and Scrippsiella trochoidea in nitrogen-limited continuous cultures (‘LN’) and nitrogen-replete batches (‘HN’). The observed CO2-dependency of ep remained unaffected by the availability of light for both G. spinifera and P. reticulatum, though at HL ep was consistently lower by about 2.7‰ over the tested CO2 range for P. reticulatum. This may reflect increased uptake of (13C-enriched) bicarbonate fueled by increased ATP production under HL conditions. The observed CO2-dependency of ep disappeared under LN conditions in both A. fundyense and S. trochoidea. The generally higher ep under LN may be associated with lower organic carbon production rates and/or higher ATP:NADPH ratios. CO2-dependent ep under non-limiting conditions has been observed in several dinoflagellate species, showing potential for a new CO2-proxy. Our results however demonstrate that light- and nitrogen-limitation also affect ep, thereby illustrating the need to carefully consider prevailing environmental conditions

Least Prompts Approach for Improving Reading Comprehension of Students with Intellectual Disabilities

In this study, the researcher employed a least prompts intervention to improve listening comprehension responses for three participants with intellectual disabilities (ID). All participants were required to (a) be diagnosed with a moderate ID or have a medical diagnosis of a disability typically co-occurring with ID (e.g., Downs Syndrome), (b) be in grades one to seven, (c) communicate orally, and (d) have normal hearing and vision. In addition, all participants expressed choices through orally responding yes/no or by pointing to a response board. The researcher used a multiple baseline design across three participants to determine if there was a functional relation between the intervention and the participants’ ability to correctly answer listening comprehension questions. The researcher provided opportunities for participants to apply these skills using a system of least prompts intervention over short chapters from a series of books read by the researcher. Results indicated that all participants increased the number of independent correct responses and decreased the number of prompts needed for each intervention session across the course of the intervention. In addition, all participants responded correctly when given the opportunity to generalize the system of least prompts to an unfamiliar book series. Advisor: Michael A. Heber

Isotopic fractionation during carbon acquisition in dinoflagellates : a new proxy for pCO2?

Atmospheric CO2 concentrations (pCO2) have markedly changed over geological timescales, thereby considerably influencing Earth’s climate and ecosystems. Reconstructing pCO2 is therefore one of the major challenges for the scientific community today. This thesis aims at investigating if past pCO2 can be reconstructed based on the carbon isotopic composition of dinoflagellates. In order to do so, experiments were carried out with four dinoflagellate species and correlations between the carbon isotopic composition in the dinoflagellates and the CO2 concentrations in the growth medium were determined. Next to CO2, nitrogen concentration and light availabilities were modified and thereby their influences on the carbon isotopic fractionation were tested. Furthermore, inorganic carbon fluxes were measured by means of membrane inlet mass spectrometry. Such in vivo assays allowed for estimating the preferred inorganic carbon source (i.e. bicarbonate or CO2) and the degree of CO2 efflux/leakage during photosynthesis, both key determinants for carbon isotope fractionation. My results show a general positive correlation of dinoflagellate carbon isotopic fractionation with CO2 availability. In addition to CO2, carbon isotopic fractionation was found to be affected by growth rates and particulate organic carbon quotas. Accounting for these growth parameters improved the correlations significantly in most species. However, these correlations were found for dinoflagellates grown under replete conditions. Reduced light levels showed comparable CO2 dependencies, but increased the overall carbon isotopic fractionation in one species, while under nitrogen limitation no CO2 dependency was observed. Results of in vivo assays showed that carbon isotopic composition in dinoflagellates was influenced by CO2 because increased CO2 availability decreased the relative uptake rates of bicarbonate, i.e. the inorganic carbon species containing more 13C compared to CO2, and increased leakage, i.e. the amount of CO22 diffusing out of the cell in relation to total inorganic carbon uptake, thereby preventing the accumulation of 13C. Results of this thesis are promising with respect to proxy development. However, measuring CO2 dependencies of the carbon isotopic composition in dinoflagellates under higher CO2 concentrations than tested here, and estimating the potential influence of other environmental factors than nitrogen and light, besides CO2, are important next steps. In addition, it remains to be tested whether there is an isotopic offset between the carbon isotopic composition of the dinoflagellate cells and the dinoflagellate cysts. Such experiments could not be performed within the frame of this thesis but should certainly be considered in future work to allow an eventual application of the proxy