Konzeption und Durchführung der Evaluation einer virtuellen Lernumgebung: Das Projekt Methodenlehre-Baukasten

Die Universität Hamburg implementiert zusammen mit anderen Partneruniversitäten ein E-Learning-Programm, das in der Methodenlehre und Statistikausbildung eingesetzt werden soll. Dieses Programm, der Methodenlehre-Baukasten (MLBK), verfolgt ein didaktisches Konzept, das sich an der kognitivkonstruktivistischen Lerntheorie von Jean Piaget orientiert und sich an Jerome Bruners Konzept des entdeckenden Lernens anlehnt. Dieses didaktische Modell ist für die Zielgruppe des MLBK, Studierende der Sozialwissenschaften in den Anfangssemestern mit Ängsten und Desinteresse gegenüber Statistik (Statistik-Angst, s.u.), unserer Annahme nach besonders gut geeignet. Eingesetzt wird der MLBK an den vier beteiligten Universitäten Hamburg, Bremen, Rostock und Greifswald in den grundständigen Studiengängen Psychologie, Erziehungswissenschaften und Soziologie. Im Laufe der Evaluation gilt es zunächst, aus der Stichprobe aller teilnehmenden Studierenden diejenigen zu identifizieren, die unsere Zielgruppe ausmachen. Das geschieht mit Hilfe eines Fragebogens, der die Statistik-Angst misst. Als weiteres Merkmal zur Bestimmung der Zielgruppe erfolgt eine Gruppierung der untersuchten Personen vorab gemäß ihrer kognitiven Lernstile. Die Evaluation des MLBK untersucht systematisch, welche Lernchancen die Zielgruppe durch das Lernsystem erhält. Deshalb wird der Mehrwert des MLBK nicht global und kontextfrei ermittelt, sondern in Relation zu den Bedürfnissen der angestrebten Zielgruppen

An alternative fish feed based on earthworm and fruit meals for tilapia and carp postlarvae

(Uma ração alternativa baseada em farinha de minhoca e frutas para alevinos de tilápia e carpa). A busca por fontes proteicas e lipídicas alternativas na nutrição de organismos aquáticos em cativeiro é de extrema importância à luz da sustentabilidade e conservação de ecossistemas. Nós investigamos o potencial de uma nova ração alternativa, baseada em frutas, farinha de minhoca e soja, na nutrição de alevinos de duas espécies de grande interesse comercial mundial – Oreochromis niloticus (L.) e Cyprinus carpio (L.), i.e. tilápia e carpa. Os alevinos alimentados com a ração alternativa exibiram crescimento e ganho de peso similares àqueles alimentados com uma ração comercial baseada em farinha de peixe.  Embora as concentrações de minerais e de proteínas totais tenham sido maiores na ração comercial do que na ração alternativa, a concentração de lípides foi maior nesta última. As concentrações de minerais, proteínas e lípides nos tecidos dos alevinos, por outro lado, não diferiram significativamente entre os animais alimentados com a ração comercial e a ração alternativa. Este resultado sugere uma elevada eficiência de assimilação da ração alternativa comparada à ração comercial. A ração alternativa testada em nosso estudo provou ser eficiente em promover crescimento e ganho de peso de alevinos de tilápia e carpa. Devido à sua formulação simples, baseada em ingredientes comumente encontrados em países tropicais, a ração alternativa aqui proposta oferece uma alternativa economicamente viável e ecologicamente sustentável para pequenos proprietários e fornecedores de alevinos nestes países

A global synthesis of human impacts on the multifunctionality of streams and rivers

Human impacts, particularly nutrient pollution and land-use change, have caused significant declines in the quality and quantity of freshwater resources. Most global assessments have concentrated on species diversity and composition, but effects on the multifunctionality of streams and rivers remain unclear. Here, we analyse the most comprehensive compilation of stream ecosystem functions to date to provide an overview of the responses of nutrient uptake, leaf litter decomposition, ecosystem productivity, and food web complexity to six globally pervasive human stressors. We show that human stressors inhibited ecosystem functioning for most stressor-function pairs. Nitrate uptake efficiency was most affected and was inhibited by 347% due to agriculture. However, concomitant negative and positive effects were common even within a given stressor-function pair. Some part of this variability in effect direction could be explained by the structural heterogeneity of the landscape and latitudinal position of the streams. Ranking human stressors by their absolute effects on ecosystem multifunctionality revealed significant effects for all studied stressors, with wastewater effluents (194%), agriculture (148%), and urban land use (137%) having the strongest effects. Our results demonstrate that we are at risk of losing the functional backbone of streams and rivers if human stressors persist in contemporary intensity, and that freshwaters are losing critical ecosystem services that humans rely on. We advocate for more studies on the effects of multiple stressors on ecosystem multifunctionality to improve the functional understanding of human impacts. Finally, freshwater management must shift its focus toward an ecological function-based approach and needs to develop strategies for maintaining or restoring ecosystem functioning of streams and rivers

Simulating rewetting events in intermittent rivers and ephemeral streams: A global analysis of leached nutrients and organic matter

Climate change and human pressures are changing the global distribution and the ex‐ tent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (precon‐ ditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experi‐ mentally simulated, under standard laboratory conditions, rewetting of leaves, river‐ bed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative character‐ istics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dis‐ solved substances during rewetting events (56%–98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contrib‐ uted most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental vari‐ ables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached sub‐ stances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying event

Sediment respiration pulses in intermittent rivers and ephemeral streams

Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO2. We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32–66‐fold upon sediment rewetting. Structural equation modelling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2–0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting‐drying cycles on respiration and CO2 emissions in stream networks

A global analysis of terrestrial plant litter dynamics in non-perennial waterways

Perennial rivers and streams make a disproportionate contribution to global carbon (C) cycling. However, the contribution of intermittent rivers and ephemeral streams (IRES), which sometimes cease to flow and can dry completely, is largely ignored although they represent over half the global river network. Substantial amounts of terrestrial plant litter (TPL) accumulate in dry riverbeds and, upon rewetting, this material can undergo rapid microbial processing. We present the results of a global research collaboration that collected and analysed TPL from 212 dry riverbeds across major environmental gradients and climate zones. We assessed litter decomposability by quantifying the litter carbon-to-nitrogen ratio and oxygen (O2) consumption in standardized assays and estimated the potential short-term CO2 emissions during rewetting events. Aridity, cover of riparian vegetation, channel width and dry-phase duration explained most variability in the quantity and decomposability of plant litter in IRES. Our estimates indicate that a single pulse of CO2 emission upon litter rewetting contributes up to 10% of the daily CO2 emission from perennial rivers and stream, particularly in temperate climates. This indicates that the contributions of IRES should be included in global C-cycling assessments

Wer, wenn nicht wir? Projektmitarbeiter und Nachhaltigkeit von eLearning

Momentan ist allenthalben die Rede von Nachhaltigkeit des eLearning. Wie wird die Zukunft des eLearning aussehen? Wird es sich an den Hochschulen etablieren oder ist nach dem Auslaufen der verschiedenen Förderungen ein „Ende des Spuks“ abzusehen? Als allgemeiner Rettungsanker wird der Begriff Nachhaltigkeit hoch gehandelt. Wie kann ein eLearning-Projekt dauerhaft und breitenwirksam wirklich in der Lehre genutzt werden? Viele Faktoren, die die Nachhaltigkeit eines Projektes bestimmen, liegen leider nicht in den Händen des Projektteams. Einer der Wege, der direkt von den Projektmitarbeiterinnen und -mitarbeitern beschritten werden kann, ist das Herstellen einer didaktisch hohen Qualität. Denn eines ist sicher: Schlechte und einfallslose eLearning-Module werden in keinem Fall nachhaltig sein. (DIPF/Orig.

Der lange Weg vom Text zum Bildschirm. Didaktische Transformation im E-Learning am Beispiel des Themas Statistik

Dieser Beitrag möchte das Konzept der didaktischen Transformation, das aus der Lehrerforschung kommt, im Zusammenhang mit der Produktion von multimedialen Lernprogrammen fokussieren. Zunächst wird das Problemfeld der didaktischen Transformation im E-Learning dargestellt, bevor an einem Beispiel aus der Praxis des Projekts Methoden-Lehre-Baukasten [...] konkrete Ablaufschritte beschrieben werden. Der Beitrag schließt mit einem verallgemeinerbaren Vorgehensmodell bei der Realisierung virtueller Lernumgebungen. (DIPF/Orig.