Impacts of warming and increasing pCO2 on natural phytoplankton communities = Einflüsse von Erwärmung und steigenden CO2 Konzentrationen auf natürliche Phytoplanktongemeinschaften

Following the predictions of the IPCC (2014), the water surface temperature in the oceans is proposed to increase by 3-5°C, while at the same time CO2 concentrations in the water are expected to double until the year 2100. A large number of experiments observed effects of warming or rising CO2 concentrations in the water on phytoplankton’s biomass, growth and chemical composition. The combined effects of both climate change factors are to a large extent still unclear. To address the combined effects of warming and rising pCO2 on natural plankton communities, I conducted three mesocosm experiments. Furthermore, I wanted to find out, if seasonal bloom events with their characteristic differences in phytoplankton species composition and growth conditions vary in their responses to climate change. Overall my studies evidence that warming enhances grazing pressure and can alter trophic relations between phytoplankton and their grazers in the pelagic food web. The results showed that warming effects can be translated to the next higher trophic level by switching a summer plankton community from a bottom-up to a mainly top-down controlled system. Further my results point out that warming has the potential to influence phytoplankton’s chemical composition. Observed changes in the content of essential polyunsaturated fatty acids (PUFAs) suggest a possible impact on the food quality for higher trophic levels. Increasing pCO2 concentrations, instead, seem to affect biomass and chemical composition of natural phytoplankton communities only to a lesser extent

Einflüsse von Erwärmung und steigenden CO2 Konzentrationen auf natürliche Phytoplanktongemeinschaften

Following the predictions of the IPCC (2014), the water surface temperature in the oceans is proposed to increase by 3-5°C, while at the same time CO2 concentrations in the water are expected to double until the year 2100. A large number of experiments observed effects of warming or rising CO2 concentrations in the water on phytoplankton’s biomass, growth and chemical composition. The combined effects of both climate change factors are to a large extent still unclear. To address the combined effects of warming and rising pCO2 on natural plankton communities, I conducted three mesocosm experiments. Furthermore, I wanted to find out, if seasonal bloom events with their characteristic differences in phytoplankton species composition and growth conditions vary in their responses to climate change. Overall my studies evidence that warming enhances grazing pressure and can alter trophic relations between phytoplankton and their grazers in the pelagic food web. The results showed that warming effects can be translated to the next higher trophic level by switching a summer plankton community from a bottom-up to a mainly top-down controlled system. Further my results point out that warming has the potential to influence phytoplankton’s chemical composition. Observed changes in the content of essential polyunsaturated fatty acids (PUFAs) suggest a possible impact on the food quality for higher trophic levels. Increasing pCO2 concentrations, instead, seem to affect biomass and chemical composition of natural phytoplankton communities only to a lesser extent.Nach Vorhersagen der IPCC (2014), wird die Oberflächentemperatur der Ozeane voraussichtlich um 3-5°C ansteigen, während gleichzeitig damit gerechnet wird, dass sich die CO2 Konzentration im Wasser bis zum Jahre 2100 verdoppelt haben wird. Zahlreiche Experimente stellten den Einfluss von Erwärmung bzw. vom Anstieg des CO2 Gehalts im Wassers auf die Biomasse, das Wachstum und die chemische Zusammensetzung des Phytoplanktons fest. Die Auswirkungen beider Klimafaktoren zusammen sind jedoch größtenteils noch unbekannt. Um die gemeinsamen Einflüsse von Erwärmung und Anstieg des pCO2 Gehalts auf natürliche Phytoplanktongemeinschaften zu untersuchen, führte ich drei Mesokosmenexperimente durch. Es war des Weiteren mein Ziel herauszufinden, ob saisonale Blütenereignisse, mit ihren charakteristischen Unterschieden in der Artenzusammensetzung und in den Wachstumsbedingungen des Phytoplanktons, in ihren Antworten auf die Klimaveränderung variieren. Insgesamt belegen meine Studien, dass die ansteigende Wassertemperatur zu einem erhöhten Fraßdruck führt und die trophischen Beziehungen zwischen dem Phytoplankton und deren Fraßfeinden im pelagischen Nahrungsnetz verschieben kann. Die Ergebnisse zeigten, dass Auswirkungen von Erwärmung auf die nächst höhere trophische Ebene übertragen werden können. Auf diese Weise veränderte sich die Sommer-Phytoplanktongemeinschaft von einem “bottom-up” zu einem vornehmlichen “top-down” kontrollierten System. Des Weiteren weisen meine Ergebnisse darauf hin, dass Erwärmung potenziell die chemische Zusammensetzung des Phytoplanktons beeinflussen kann. Beobachtete Veränderungen in der Konzentration essenzieller mehrfach ungesättigter Fettsäuren (PUFAs) im Phytoplankton lassen eine mögliche Beeinflussung der Futterqualität für höhere trophische Ebenen vermuten. Steigende pCO2 Werte indessen, scheinen die Biomasse und die chemischen Zusammensetzung natürlicher Phytoplanktongemeinschaften nur in geringerem Maße zu beeinflussen

Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming

Nitrogen fixation is a key source of nitrogen in the Baltic Sea which counteracts nitrogen loss processes in the deep anoxic basins. Laboratory and field studies have indicated that single-strain nitrogen-fixing (diazotrophic) cyanobacteria from the Baltic Sea are sensitive to ocean acidification and warming, two drivers of marked future change in the marine environment. Here, we enclosed a natural plankton community in twelve indoor mesocosms (volume ~1400 L) and manipulated pCO2 to yield six CO2 treatments with two different temperature treatments (16.6°C and 22.4°C, pCO2 range = 360 – 2030 μatm). We followed the filamentous, heterocystous diazotrophic cyanobacteria community (Nostocales, primarily Nodularia spumigena) over four weeks. Our results indicate that heterocystous diazotrophic cyanobacteria may become less competitive in natural plankton communities under ocean acidification. Elevated CO2 had a negative impact on Nodularia sp. biomass, which was exacerbated by warming. Our results imply that Nodularia sp. may contribute less to new nitrogen inputs in the Baltic Sea in future

Warming and Ocean Acidification Effects on Phytoplankton - From Species Shifts to Size Shifts within Species in a Mesocosm Experiment

While the isolated responses of marine phytoplankton to climate warming and to ocean acidification have been studied intensively, studies on the combined effect of both aspects of Global Change are still scarce. Therefore, we performed a mesocosm experiment with a factorial combination of temperature (9 and 15°C) and pCO2 (means: 439 ppm and 1040 ppm) with a natural autumn plankton community from the western Baltic Sea. Temporal trajectories of total biomass and of the biomass of the most important higher taxa followed similar patterns in all treatments. When averaging over the entire time course, phytoplankton biomass decreased with warming and increased with CO2 under warm conditions. The contribution of the two dominant higher phytoplankton taxa (diatoms and cryptophytes) and of the 4 most important species (3 diatoms, 1 cryptophyte) did not respond to the experimental treatments. Taxonomic composition of phytoplankton showed only responses at the level of subdominant and rare species. Phytoplankton cell sizes increased with CO2 addition and decreased with warming. Both effects were stronger for larger species. Warming effects were stronger than CO2 effects and tended to counteract each other. Phytoplankton communities without calcifying species and exposed to short-term variation of CO2 seem to be rather resistant to ocean acidification

Controlling speed in component skills of reading improves the explanation of reading comprehension

Efficiency in reading component skills is crucial for reading comprehension, as efficient subprocesses do not extensively consume limited cognitive resources, making them available for comprehension processes. Cognitive efficiency is typically measured with speeded tests of relatively easy items. Observed responses and response times indicate the latent variables of ability and speed. Interpreting only ability or speed as efficiency may be misleading because there is a within-person dependency between both variables (speed-ability tradeoff [SAT]). Therefore, the present study measures efficiency as ability conditional on speed by controlling speed experimentally with item-level time limits. The proposed timed ability measures of reading component skills are expected to have a clearer interpretation in terms of efficiency and to be better predictors for reading comprehension. To support this claim, this study investigates two component skills, visual word recognition and sentence-level semantic integration (sentence reading), to understand how differences in ability in a timed condition are related to differences in ability and speed in a traditional untimed condition. Moreover, untimed and timed reading component skill measures were used to explain reading comprehension. A German subsample from Programme for International Student Assessment (PISA) 2012 completed the reading component skills tasks with and without item-level time limits and PISA reading tasks. The results showed that timed ability is only moderately related to untimed ability. Furthermore, timed ability measures proved to be stronger predictors of sentence-level and text-level reading comprehension than the corresponding untimed ability and speed measures, although using untimed ability and speed jointly as predictors increased the amount of explained variance. (DIPF/Orig.

Long-term changes in bloom dynamics of Southern and Central Baltic cold-water phytoplankton

In the Baltic Sea, cold-water adapted dinoflagellates and diatoms dominate the phytoplankton spring bloom of the Northern and Eastern Basins of the Baltic Sea. In the Central and Southern parts, where such species are less prominent, they cause occasional biomass peaks. We hypothesized that these dynamics correlate with ice cover, sea surface temperature (SST), and water transport processes, as the large Basins of the Central Baltic Sea are too deep to build-up blooms from their own seed banks. Long-term monitoring data from the past 40 and 20 years in the central and southern Baltic Sea, respectively, were analyzed here for biomass development of five cold-adapted taxa: the diatoms Pauliella taeniata, Thalassiosira baltica, Thalassiosira levanderi and Melosira spp. and the dinoflagellate Peridinella catenata. Results show that diatoms generally reached high biomass peaks in the 1980s and in shorter periods from 1995-1997, 2003- 2006, and 2010-2013 in all areas. We detected good correlations with the length of the ice cover period as well as low minimum and mean winter and spring SSTs. In contrast, biomass dynamics of the dinoflagellate P. catenata are more independent from these factors but have decreased strongly since the beginning of the 21st century. A numerical ocean model analysis confirmed the hypothesis that large blooms in the deep basins are seeded through water transport from adjacent shallow, ice-covered coastal areas such as the Gulf of Finland and the Gulf of Riga. Our results show that under ongoing climate warming, the common cold-water species may disappear from spring blooms in southern and central areas with unknown consequences for the ecosystem

On-Demand-Ridepooling als Beitrag zu Mobilitätswende und Daseinsvorsorge: Erkenntnisse zum Status quo in Deutschland und Entwurf einer Systemtypologie

Der vorliegende Bericht enthält Statistiken zu Bedienzeiten, Angebotsstandards, Bezahloptionen, etc. von 60 im Jahr 2022 erfassten On-Demand-Ridepooling Systemen, sowie Antworten aus einer Befragung von 33 Systembetreibern zu ihren Flottengrößen, Genehmigungsgrundlage und Auflagen, Geschlechtergerechtigkeit, Zielgruppen und vielem mehr. Aufbauend auf der Analyse dieser Daten wird eine Systemtypologie entworfen. Für die neun differenzierten Typen werden jeweils idealtypische Systemcharakteristika skizziert, ihre Nützlichkeit aus ökologischer und sozialer Perspektive beleuchtet und ein Beispielsystem vorgestellt. Für die Sicherung und Steigerung der Daseinsvorsorge im ländlichen Raum stellen demnach insbesondere Systeme, die eine flächendeckende Bedienung ländlicher Gebiete bei geringen Bedienstandards leisten, eine zielführende Option dar (Typ Ländlich 1). Ein Beitrag zur Mobilitätswende im ländlichen Raum ist insbesondere durch eine wabenartige Bedienung von Gebieten rund um Knotenpunkte von Schnellverbindungen des Regionalverkehrs mit Schnellbussen und SPNV möglich (Typ Regional 2). Für den urbanen Raum scheint eine hochqualitative Bedienung mit preislichem Abstand zum ÖPNV die größten Potenziale zu bieten (Typ Urban 2), da diese Charakteristika den Anteil substituierter Fahrten mit dem MIV erhöhen und den Anteil des ersetzten Umweltverbundes senken. Der Bericht zeigt, dass On-Demand-Ridepooling eine wichtige Rolle bei der Transformation der heutigen, privat organisierten und extrem ressourcenintensiven Automobilität in Richtung einer wesentlich nachhaltigeren, geteilten Automobilität leisten kann. Die größte Hürde liegt derzeit in den Systemkosten, die großteils durch das Fahrpersonal entstehen. Skaleneffekte und autonomes Fahren könnten hier Fortschritte bringen. Zudem wären erhebliche Erkenntnisfortschritte zu erfolgversprechenden Systemausgestaltungen für verschiedene Einsatzkontexte möglich, wenn alle verfügbaren Daten gebündelt ausgewertet werden könnten.This report contains statistics on operating times, service standards, payment options, etc. from 60 on-demand ridepooling systems identified in 2022, as well as responses from a survey of 33 system operators on their fleet sizes, gender equality, target groups and much more. based on the analysis of this data, a system typology is designed that differentiates between nine system types. Ideal system characteristics are outlined for each of these, their usefulness is examined from an ecological and social perspective and an exemplary system is presented. Systems that provide nationwide service in rural areas with low service standards are a particularly effective option for securing and increasing basic public mobility provision (type Rural 1). A contribution to the mobility transition in rural areas is possible in particular through a honeycomb-like service of areas around hubs of fast regional transport connections with express buses and regional rail services (type Regional 2). For urban areas, a high-quality service with a price gap to public transport seems to offer the greatest potential (type Urban 2), as these characteristics increase the proportion of substituted journeys by MIT and reduce the proportion of substituted eco-mobility. The report shows that on-demand-ridepooling can play an important role in the transformation of today's privately organized and extremely resource-intensive automobility towards a much more sustainable, shared automobility. The biggest hurdle currently arises from the system costs, which are largely incurred by drivers. Economies of scale and autonomous driving could bring progress here. In addition, significant advances in knowledge on promising system designs for various application contexts would be possible if all available data could be evaluated in a bundled manner