ALBERT

Description: This review article aims to provide an overview and insight into the most relevant aspects of wind energy development and current state-of-the-art. The industry is in a very mature stage, so it seems to be the right time to take stock of the relevant areas of wind energy use for power generation. For this review, the authors considered the essential aspects of the development of wind energy technology: research, modeling, and prediction of wind speed as an energy source, the technology development of the plants divided into the mechanical and electrical systems and the plant control, and finally the optimal plant operation including the maintenance strategies. The focus is on the development in Europe, with a partial focus on Germany. The authors are employees of the Fraunhofer Institutes, Institute for Energy Economics and Energy Systems Technology and Institute for Wind Energy Systems, who have contributed to the development of this technology for decades.

Description: Aquatic ecosystems worldwide continue to experience unprecedented warming and ecological change. Warming increases metabolic rates of animals, plants, and microbes, accelerating their use of energy and materials, their population growth, and interaction rates. At a much larger biological scale, warming accelerates ecosystem-level processes, elevating fluxes of carbon and oxygen between biota and the atmosphere. Although these general effects of temperature at finer and broader biological scales are widely observed, they can lead to contradictory predictions for how warming affects the structure and function of ecological communities at the intermediate scale of biological organization. We experimentally tested the hypothesis that the presence of predators and their associated species interactions modify the temperature dependence of net ecosystem oxygen production and respiration. We tracked a series of independent freshwater ecosystems (370 L) over 9 weeks, and we found that at higher temperatures, cascading effects of predators on zooplankton prey and algae were stronger than at lower temperatures. When grazing was weak or absent, standing phytoplankton biomass declined by 85%–95% (〈1-fold) over the temperature gradient (19–30 °C), and by 3-fold when grazers were present and lacked predators. These temperature-dependent species interactions and consequent community biomass shifts occurred without signs of species loss or community collapse, and only modestly affected the temperature dependence of net ecosystem oxygen fluxes. The exponential increases in net ecosystem oxygen production and consumption were relatively insensitive to differences in trophic interactions among ecosystems. Furthermore, monotonic declines in phytoplankton standing stock suggested no threshold effects of warming across systems. We conclude that local changes in community structure, including temperature-dependent trophic cascades, may be compatible with prevailing and predictable effects of temperature on ecosystem functions related to fundamental effects of temperature on metabolism.

Description: Almost all animals and plants are inhabited by diverse communities of microorganisms, the microbiota, thereby forming an integrated entity, the metaorganism. Natural selection should favor hosts that shape the community composition of these microbes to promote a beneficial host-microbe symbiosis. Indeed, animal hosts often pose selective environments, which only a subset of the environmentally available microbes are able to colonize. How these microbes assemble after colonization to form the complex microbiota is less clear. Neutral models are based on the assumption that the alternatives in microbiota community composition are selectively equivalent and thus entirely shaped by random population dynamics and dispersal. Here, we use the neutral model as a null hypothesis to assess microbiata composition in host organisms, which does not rely on invoking any adaptive processes underlying microbial community assembly. We show that the overall microbiota community structure from a wide range of host organisms, in particular including previously understudied invertebrates, is in many cases consistent with neutral expectations. Our approach allows to identify individual microbes that are deviating from the neutral expectation and are therefore interesting candidates for further study. Moreover, using simulated communities, we demonstrate that transient community states may play a role in the deviations from the neutral expectation. Our findings highlight that the consideration of neutral processes and temporal changes in community composition are critical for an in-depth understanding of microbiota-host interactions.

Description: Habitat-forming species sustain biodiversity and ecosystem functioning in harsh environments through the amelioration of physical stress. Nonetheless, their role in shaping patterns of species distribution under future climate scenarios is generally overlooked. Focusing on coastal systems, we assess how habitat-forming species can influence the ability of stress-sensitive species to exhibit plastic responses, adapt to novel environmental conditions, or track suitable climates. Here, we argue that habitat-former populations could be managed as a nature-based solution against climate-driven loss of biodiversity. Drawing from different ecological and biological disciplines, we identify a series of actions to sustain the resilience of marine habitat-forming species to climate change, as well as their effectiveness and reliability in rescuing stress-sensitive species from increasingly adverse environmental conditions.

Description: Eutrophication combined with climate change has caused ephemeral filamentous macroalgae to increase and drifts of seaweed cover large areas of some Baltic Sea sites during summer. In ongoing projects, these mass occurrences of drifting filamentous macroalgae are being harvested to mitigate eutrophication, with preliminary results indicating considerable nutrient reduction potential. In the present study, an energy assessment was made of biogas production from the retrieved biomass for a Baltic Sea pilot case. Use of different indicators revealed a positive energy balance. The energy requirements corresponded to about 30%–40% of the energy content in the end products. The net energy gain was 530–800 MJ primary energy per ton wet weight of algae for small-scale and large-scale scenarios, where 6 000 and 13 000 tonnes dwt were harvested, respectively. However, the exergy efficiency differed from the energy efficiency, emphasising the importance of taking energy quality into consideration when evaluating energy systems. An uncertainty analysis indicated parametric uncertainty of about 25%–40%, which we consider to be acceptable given the generally high sensitivity of the indicators to changes in input data, allocation method, and system design. Overall, our evaluation indicated that biogas production may be a viable handling strategy for retrieved biomass, while harvesting other types of macroalgae than red filamentous species considered here may render a better energy balance due to higher methane yields.

Description: The rich fossil record of horses has made them a classic example of evolutionary processes. However, while the overall picture of equid evolution is well known, the details are surprisingly poorly understood, especially for the later Pliocene and Pleistocene, c. 3 million to 0.01 million years (Ma) ago, and nowhere more so than in the Americas. There is no consensus on the number of equid species or even the number of lineages that existed in these continents. Likewise, the origin of the endemic South American genus Hippidion is unresolved, as is the phylogenetic position of the “stilt-legged” horses of North America. Using ancient DNA sequences, we show that, in contrast to current models based on morphology and a recent genetic study, Hippidion was phylogenetically close to the caballine (true) horses, with origins considerably more recent than the currently accepted date of c. 10 Ma. Furthermore, we show that stilt-legged horses, commonly regarded as Old World migrants related to the hemionid asses of Asia, were in fact an endemic North American lineage. Finally, our data suggest that there were fewer horse species in late Pleistocene North America than have been named on morphological grounds. Both caballine and stilt-legged lineages may each have comprised a single, wide-ranging species.

Description: Bringer of storms and droughts, the El Niño∕Southern Oscillation results from the complex, sometimes chaotic interplay of ocean and atmosphere.

Description: The theory of the interpretation of seismic travel‐time curves for refracted rays in horizontal structures is treated after the manner of Herglotz‐Wiechert, under the customary assumption that the ray paths obey the laws of geometrical optics. Multiple valued travel‐time curves, discontinuous velocity functions, and the discontinuous travel‐time curves associated with a slower speed bed receive special consideration. It appears that interpretations satisfactory from the theoretical point of view may be obtained in these cases, although, experimentally, sufficiently complete data to meet the requirements of theory may often be difficult or impossible to obtain.