The intention of the project is to create an environment where the viewer can explore and form a personal narrative in the process of organic interaction with the work. At first glance, the scale of the installation will attract the viewer to the exhibition, however, upon close investigation he will discover there is deterioration, decay, and mutation. The ideas of time, beauty, decay, mortality, and interdependence will be discussed in this paper. The visitors are invited to interact with the work. I hope through spontaneous interaction the arrangements from the viewer will result in evolution of the work. The balance and tension between patterns and evolution, between creativity and predictability will evolve naturally. I hope the viewer can build a meaningful experience based on his or her cultural, intellectual, and social background through interacting with the installation.

The intention of the project is to create an environment where the viewer can explore and form a personal narrative in the process of organic interaction with the work. At first glance, the scale of the installation will attract the viewer to the exhibition, however, upon close investigation he will discover there is deterioration, decay, and mutation. The ideas of time, beauty, decay, mortality, and interdependence will be discussed in this paper. The visitors are invited to interact with the work. I hope through spontaneous interaction the arrangements from the viewer will result in evolution of the work. The balance and tension between patterns and evolution, between creativity and predictability will evolve naturally. I hope the viewer can build a meaningful experience based on his or her cultural, intellectual, and social background through interacting with the installation.

Nanoparticle (NP) implementation in industry has increased during the last years. However, the consequences of NP release to the environment have not been fully understood yet and long-term effects are hardly predictable. Information regarding a possible NP uptake by organisms is urgently needed. Here, we investigate the uptake of presynthesized AuNPs of different diameters by living diatoms. To better understand the influence of NPs on diatoms, cells were monitored in vivo using Surface Enhanced Raman Spectroscopy (SERS). By 3D Raman imaging, AuNPs with diameters ≥50 nm could clearly be localized inside the cells, whereas smaller AuNPs were never detected in the cell interior. This indicates a size-dependent uptake mechanism that comes along with different toxicities. As diatoms present an essential source of the marine food chain, this observation is relevant not only for diatoms themselves but also for higher organisms.

Diatoms have a successful history of use in assessments of wetland biological condition. In North America and across Europe, diatom assemblages are used for routine wetland condition assessments to meet the statutory requirements of the European Water Framework Directive and the National Aquatic Resource Survey by the US Environmental Protection Agency. In South Africa, the use of diatom assemblages as indicators of wetland condition may be a promising alternative to the traditional biotic assemblages employed, such as macroinvertebrates or macrophytes, which have proven to be ineffective. We present a preliminary investigation on the feasibility of diatoms in wetland biological assessments in South Africa by evaluating the use of diatoms as indicators of biological condition for depressional wetlands in the Mpumalanga Highveld region of South Africa. Depressional wetlands typically found in this region are either temporary (seasonally inundated) or permanent depressions. Temporary depressional wetlands are expected to be affected by natural environmental disturbances (e.g., seasonal fluctuations in water-level which may cause changes in water chemistry) as compared to relatively stable permanent ones. Establishing whether diatoms are suitable indicators of natural environmental disturbances in temporary depressional wetlands in this region is necessary for further investigations of anthropogenic disturbances. We sampled epiphytic diatoms from three least human-disturbed temporary depressional wetlands during various stages of inundation and showed that the species composition of epiphytic diatom communities were strong indicators of temporally changing environmental conditions. Using the same diatom and physical and chemical data, we also demonstrated that simplifying the taxonomy by using the functional composition (ecological guilds, life-forms) of the epiphytic diatom communities, can assess temporally changing environmental conditions as effectively as the species composition. Moreover, these functional groups provide valuable ecological information that is not available from the species data. Acid mine drainage (AMD) is the predominant stressor in permanent depressional wetlands of the Mpumalanga Highveld region, where coal mines utilise these wetlands for storage of AMD, which has severe impacts on the structure and function of the ecosystem. In order to develop an approach for impact assessment and management of depressional wetlands in the region, we developed an epiphytic diatom multimetric index (MMI) for AMD impacted permanent depressional wetlands. This is also the first diatom index to quantify AMD impacts in wetland habitats. Data collected from 34 sites that represented a range of conditions along an AMD gradient within the Mpumalanga Highveld was used to select responsive diatom metrics which we combined into a multimetric index. We developed separate MMIs for classes of depressional wetland types in order to account for natural variation among diatom assemblages, and compared their performance with an MMI that did not account for natural variation. To account for natural variation, we classified reference sites based on diatom typologies and hypothesised that by using this approach, we would improve MMI performance. Overall, all MMIs performed considerably well, although grouping sites by diatom typology to account for natural variation improved MMI performance, especially the precision, responsiveness and sensitivity to disturbance. We conclude that diatoms have strong potential for use in wetland ecological assessments in South Africa. The experimental and statistical approaches used in this study should expand our knowledge of diatom ecology and further advance the research and development of diatom bioassessment. / Thesis (PhD)--University of Pretoria, 2017. / Paraclinical Sciences / PhD / Unrestricted

Several species of the diatom genus Thalassiosira Cleve, were observed in freshwater phytoplankton samples collected from a fifty-two kilometer reach of the San Joaquin River in the vicinity of Stockton, California, USA. The study was conducted between the South Airport Way bridge near Vernalis and the Stockton Deep Water Ship Channel during fall and summer of both 2005 and 2006. The entire reach is freshwater habitat with the lower twenty-eight km strongly influenced by tidal flow reversals driven by the San Francisco Estuary. Ninety four whole water samples were collected from surface waters during the months of July, August, September and October in 2005 and the months of July and August in 2006. Six species of Thalassiosira were identified using scanning electron and light microscopy: T. weissjlogii (Grunow), T. gessneri Hustedt, T. lacustris (Grunow), T. visurgis (Grunow), T. decipiens (Grunow), and T. incerta (Makarova). Of the species observed, only T. weissjlogii has been previously reported in the freshwater portion of the San Joaquin River. The other five species have been previously reported from sites in the San Joaquin- San Francisco Estuary characterized as brackish, suggesting they are distributed in waters of various salinities ranging from freshwater to brackish within the river and estuary.

The occurrence of phytoplankton taxa, with special focus on harmful algal bloom (HAB) taxa, was monitored for one year off the central coast of California to examine both their co-occurrence and physical and chemical variables influencing their temporal patterns. Bi-weekly samples were taken from October 6, 2008 to October 5, 2009 in San Luis Obispo Bay, CA. Canonical correspondence analysis (CCA) of weekly samples indicated that 46.1% of the variability in species abundance was explained by the variables in the model, higher than previous reports. Cluster analysis divided phytoplankton communities into HAB and non-HAB groups of species, while shared distribution analysis identified specific co-occurring species of HABs. The HAB dinoflagellate group consisted exclusively of HAB taxa, including Cochlodinium polykrikoides Margalef, Dinophysis acuminata Claparède & Lachmann, and Alexandrium spp., and was correlated with a homogeneous water column and high nitrate concentration during the fall and winter seasons. The domoic acid producing diatoms Pseudo-nitzschia seriata (Cleve) H. Peragallo complex and Pseudo-nitzschia delicatissima (Cleve) Heiden complex grouped with several other non-HAB diatoms, and were correlated with warm, thermally stratified waters of the summer season. These results contradict the classic diatom / dinoflagellate succession theory and suggest that event-scale processes influencing water column stability within seasons may influence the distribution of HAB species in near shore upwelling dominated regions.

The recent, rapid decline in Arctic summer sea ice extent has prompted questions as to the rates and magnitude of previous sea ice decline and the affect of this physical change on icerelated ecosystems. However, satellite data of sea ice only extends back to 1978, and mapped observations of sea ice prior to the 1970s are sparse at best. Inventories of boreal ecosystems are likewise hampered by a paucity of investigations spanning more than the past few decades. Paleoclimate records of sea ice and related primary productivity are thus integral to understanding how sea ice responds to a changing climate. Here I examine modern sedimentation, decadal-scale climate change in the recent past, and centennial- to millennial-scale changes of the past 400 ka using both qualitative and quantitative diatom data in concert with sedimentology and organic geochemistry. Diatom taxonomy and corresponding ecological affinities are compiled in this study and updated for the Bering Sea region and then used as recorders of past climate changes. In recent decades, the Pacific Decadal Oscillation and the strength of the Aleutian Low are reflected by subtle changes in sediment diatom assemblages at the Bering Sea shelf-slope break. Farther back in time, the super-interglacial, marine isotope stage (MIS) 11 (428-390ka), began in Beringia with extreme productivity due to flooding of the Bering Land Bridge. A moisture-driven advance of Beringian glaciers occurred while eustatic sea level was high, and insolation and seasonality both decreased at the global peak of MIS 11. Atlantic/Pacific teleconnections during MIS 11 include a reversal in Bering Strait throughflow at 410 ka and a relationship between North Atlantic Deep Water Formation and Bering Sea productivity. Finally, concentrations of the biomarker-based sea ice proxy, IP25, are compared to sea ice concentration across the Bering and Chukchi seas. Changes in the concentration of IP25 in the sediments may be driven by the length of time that the epontic diatom bloom lasts. When combined with a sediment-based proxy for sea surface temperatures, IP25 can be used to reconstruct spring ice concentration.

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No description available.

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