Diversity, salinity adaptation, and role in carbon cycling of microbial communities inhabiting the oxic layer of intertidal hypersaline microbial mats

The main objective of this thesis was to study the diversity, salinity adaptation, and role in carbon cycling of microorganisms inhabiting the oxic layer of intertidal hypersaline microbial mats. For this purpose, mats from the Arabian Gulf coast of Abu Dhabi, United Arab Emirates (UAE), which are subjected to multiple harsh environmental conditions, were investigated. The mats possessed a high microbial diversity and the inhabiting microorganisms showed adaptation mechanisms to strong salinity fluctuations, desiccation, high UV and light intensities, and high temperatures. A new salinity-driven taxis of cyanobacteria in the mat from the upper tidal zone was discovered and termed as Halotaxis. Moreover, this study showed that mats from different tidal positions adjust the structure and function of their bacterial communities in response to the salinity range they experience. Furthermore, cyanobacterial cultures with associated bacteria, obtained from the mats, provided manifold, very complex, and highly specific interactions with a high potential for biotechnological purposes, e.g. for the discovery of new bioactive substances

Stromatolitic Knobs in Storrs Lake, San Salvador, Bahamas: Insights into Organomineralization

Storrs Lake, a hypersaline lake on the east coast of San Salvador Island, Bahamas, contains well-developed microbial mats, some of which have developed calcified structures called microbialites. Many of these microbialites are laminated, and therefore classified as stromatolites. This study focuses on small stromatolitic knobs located in the southern portion of Storrs lake, which are still actively forming, to gain insights into the early stages of stromatolite formation. These knobs appear to be forming as the result of in situ micritic precipitation mediated by both photosynthetic and heterotrophic microbial metabolisms. By comparing these small stromatolitic knobs to larger stromatolitic heads in deeper portions of the same lake, as well as other modern closed-system and open-marine stromatolites, a mechanism for organomineralization and laminae formation can begin to be determined. The mechanism for in situ precipitation is relatively comparible in each of these systems, though the mechanism of laminae formation varies from microbial to more extrinsic controls. This project can be used to inform future studies of fine-grained stromatolites in the fossil record, providing crucial knowledge about the history of Earth’s carbon cycle

Between order and disorder: The supramolecular organization of photosynthetic membrane

Grondelle, R. van [Promotor]Dekker, J.P. [Copromotor]Frese, R.N. [Copromotor

Regulation of Central Carbon and Amino Acid Metabolism in Plants

Due to their lightweight and high specific strength, Mg-based alloys are considered as substitutes to their heavier counterparts in applications in which corrosion is non-relevant and weight saving is of importance. Furthermore, due to the biocompatibility of Mg, some alloys with controlled corrosion rates are used as degradable implant materials in the medical sector. The typical processing route of Mg parts incorporates a casting step and, subsequently, a thermo–mechanical treatment. In order to achieve the desired macroscopic properties and thus fulfill the service requirements, thorough knowledge of the relationship between the microstructure, the processing steps, and the resulting property profile is necessary. This Special Issue covers in situ and ex situ experimental and computational investigations of the behavior under thermo–mechanical load of Mg-based alloys utilizing modern characterization and simulation techniques. The papers cover investigations on the effect of rare earth additions on the mechanical properties of different Mg alloys, including the effect of long-period stacking-ordered (LPSO) structures, and the experimental and computational investigation of the effect of different processing route

HOW DO NOVICE AND EXPERT LEARNERS REPRESENT, UNDERSTAND, AND DISCUSS GEOLOGIC TIME?

This dissertation examined the representations novice and expert learners constructed for the geologic timescale. Learners engaged in a three-part activity. The purpose was to compare novice learners’ representations to those of expert learners. This provided insight into the similarities and differences between their strategies for event ordering, assigning values and scale to the geologic timescale model, as well as their language and practices to complete the model. With a qualitative approach to data analysis informed by an expert-novice theoretical framework grounded in phenomenography, learner responses comprised the data analyzed. These data highlighted learners’ metacognitive thoughts that might not otherwise be shared through lectures or laboratory activities. Learners’ responses were analyzed using a discourse framework that positioned learners as knowers. Novice and expert learners both excelled at ordering and discussing events before the Phanerozoic, but were challenged with events during the Phanerozoic. Novice learners had difficulty assigning values to events and establishing a scale for their models. Expert learners expressed difficulty with determining a scale because of the size of the model, yet eventually used anchor points and unitized the model to establish a scale. Despite challenges constructing their models, novice learners spoke confidently using claims and few hedging phrases indicating their confidence in statements made. Experts used more hedges than novices, however the hedging comments were made about more complex conceptions. Using both phenomenographic and discourse analysis approaches for analysis foregrounded learners’ discussions of how they perceived geologic time and their ways of knowing and doing. This research is intended to enhance the geoscience community’s understanding of the ways novice and expert learners think and discuss conceptions of geologic time, including the events and values of time, and the strategies used to determine accuracy of scale. This knowledge will provide a base from which to support geoscience curriculum development at the university level, specifically to design activities that will not only engage and express learners’ metacognitive scientific practices, but to encourage their construction of scientific identities and membership in the geoscience community

INTERACTIONS OF SEAGRASS BEDS AND THE WATER COLUMN: EFFECTS OF BED SIZE AND HYDRODYNAMICS

NOTE: If you have problems opening the file, save the document to your computer and then try opening it.Beds of seagrass and other submersed angiosperms have been shown to reduce water velocities and water-column dissolved nutrient and seston concentrations. In eutrophic waters, these effects could reduce algal biomass, enhancing light availability to the surface of the leaves and therefore, increasing seagrass growth. Small seagrass beds (1-10m diameter) should have little influence on water flow and water quality, but there is little research on the effect of bed size on these factors. To investigate the effects of seagrass bed size on these interactions, I developed a numerical ecosystem simulation model and used a spatial simulation model. I also conducted mesocosm and field measurements to determine if the expected relationships were evident in reality. I measured water quality, sediment characteristics, epiphyton mass, and hydrodynamic characteristics across beds of the seagrass Ruppia maritima L. in mesohaline Chesapeake Bay. I also measured net community nutrient uptake in mesocosms. Field measurements of water transport and nutrients were used to calibrate a spatial model of water and nutrient flow through Ruppia beds. This model was used to determine the potential effects of water flow velocity and bed size on nutrient gradients. An ecosystem simulation model was constructed and used to investigate the effects of nutrient supply rates and grazer densities on epiphytic algae and macrophyte growth. Simulation model results showed the controlling effect of nutrient loading rate on epiphytic algal and Potamogeton perfoliatus L. biomass. Potamogeton growth rate was highest at low nutrient loading rates, which allowed the angiosperms to reduce nutrients to levels that reduced algal growth. Grazer effects were greatest at intermediate loading rates. Spatial modeling simulations showed the potential influence of bed size and current velocity on water quality changes in shallow water. In the field, ammonium and dissolved inorganic carbon (DIC) decreased, and dissolved oxygen increased with distance into large (> 300 m diameter) beds of one meter tall, moderate density Ruppia. Water quality was little changed in beds smaller than 100 m wide. Epiphyton mass was generally variable, but decreased with distance into beds under low dissolved nutrient conditions in the fall of 2001. Epiphyton dry weight was related to total suspended solids. Large, dense, seagrass beds in shallow water, may have a gradient of trophic conditions from outside to inside, while the surrounding water should dictate conditions in small beds

2005 Florida Bay and Adjacent Marine Systems Science Conference; Hawk’s Cay Resort Duck Key, Florida; December 11-14, 2005: program and abstract book

Conference themes addressed: Applications and Restoration Targets, the Mangrove-Estuarine Transition Zone, Benthic Habitats, Water Quality, Physical Processes, Higher Trophic Levels, and Adjacent Systems

YOUMARES 9 - The Oceans: Our Research, Our Future

This open access book summarizes peer-reviewed articles and the abstracts of oral and poster presentations given during the YOUMARES 9 conference which took place in Oldenburg, Germany, in September 2018. The aims of this book are to summarize state-of-the-art knowledge in marine sciences and to inspire scientists of all career stages in the development of further research. These conferences are organized by and for young marine researchers. Qualified early-career researchers, who moderated topical sessions during the conference, contributed literature reviews on specific topics within their research field

YOUMARES 9 - The Oceans: Our Research, Our Future

This open access book summarizes peer-reviewed articles and the abstracts of oral and poster presentations given during the YOUMARES 9 conference which took place in Oldenburg, Germany, in September 2018. The aims of this book are to summarize state-of-the-art knowledge in marine sciences and to inspire scientists of all career stages in the development of further research. These conferences are organized by and for young marine researchers. Qualified early-career researchers, who moderated topical sessions during the conference, contributed literature reviews on specific topics within their research field

Detritus and microbial ecology in aquaculture

Proceedings of the 1985 Bellagio Conference on Detrital Systems for Aquaculture held in Bellagio, Como, Italy, to analyze and summarize available information on detrital food chains and the means for their manipulation in aquaculture. Contains 16 papers and related discussions.Detritus, Food chains, Microbial ecology, Aquaculture