Medieval landscapes and lordship in South Uist

This thesis examines the structures of society and lordship in the Middle Ages in South Uist through historical documentation, oral-tradition, cultural landscapes, monuments and settlement patterns. In this thesis, the medieval period has been defined as that between c. 1000 and c. 1650. The historical evidence is considered along with archaeological evidence to create a holistic understanding of medieval social developments in South Uist. The results have ramifications for interpreting contemporaneous society throughout Scotland and Ireland. The study focuses on rural settlement (farms, townships, field- and transhumance-systems) and high-status monuments (churches, duns and castles). Developments visible in both the historical and archaeological record demonstrate that considerable social, economic and cultural changes took place within the landscape of South Uist throughout the Middle Ages. However, the nature of the evidence polarises the study into two time spheres: the Norse period, c. 1000 - c. 1400, and the Late Medieval period, c. 1550 - c. 1650. Remains belonging to the intervening period have proved difficult to locate. The Norse period landscape was characterised by dispersed farmsteads, possibly siting within an enclosed field-system. It is probable that these farmsteads originated as the homesteads of Viking Age settlers. Between the eleventh century and the end of the 1300s, there was a trend towards social and economic centralisation and the creation of an increasingly formalised social hierarchy: manifestations of this can be seen in the archaeological record and a new system of taxation. Archaeologically this is revealed by increasing divergence in the sizes of farmsteads, the largest of which also exhibit signs of industrial and agricultural control. Increased social differentiation is additionally reflected in artefact assemblages

Non-Skeletal Biomineralization by Eukaryotes: Matters of Moment and Gravity

Skeletal biomineralisation by microbial eukaryotes significantly affects the global biogeochemical cycles of carbon, silicon and calcium. Non-skeletal biomineralisation by eukaryotic cells, with precipitates retained within the cell interior, can duplicate some of the functions of skeletal minerals, e.g., increased cell density, but not the mechanical and antibiophage functions of extracellular biominerals. However, skeletal biomineralisation does not duplicate many of the functions of non-skeletal biominerals. These functions include magnetotaxis (magnetite), gravity sensing (intracellular barite, bassanite, celestite and gypsum), buffering and storage of elements in an osmotically inactive form (calcium as carbonate, oxalate, polyphosphate and sulfate; phosphate as polyphosphate) and acid-base regulation, disposing of excess hydroxyl ions via an osmotically inactive product (calcium carbonate, calcium oxalate). Although polyphosphate has a wide phylogenetic distribution among microbial eukaryotes, other non-skeletal minerals have more restricted distributions, and as yet there seems to be no definitive evidence that the alkaline earth components (Ba and Sr) of barite and celestite are essential for completion of the life cycle in organisms that produce these minerals.Organismic and Evolutionary Biolog

Gloeobacter and the implications of a freshwater origin of Cyanobacteria

The earliest branching cyanobacterium, Gloeobacter, exhibits a number of ancestral traits including the lack of thylakoids. It occurs epilithically in microbial mats, both subaerially and submerged in low-salinity habitats. These habitats and the absence of thylakoids are associated with the occurrence of membrane-associated photosynthetic processes in the plasma membrane, possibly limiting the rate of both assembly and reassembly of the oxygen-evolving complex, as well as the photosynthetic rate and in vitro growth rate. These factors interact with the occurrence of Gloeobacter in mats to constrain productivity in nature. Traits found in living Gloeobacter, with the probable time of origin of oxygenic photosynthesis and diversification of cyanobacteria, can be related to the possible role of oxygenic primary productivity and organic carbon burial on land during the early Earth in low-salinity environments around the time of the global oxidation event

What is the limit for photoautotrophic plankton growth rates?

© 2016 The Author. Knowing the potential maximum photoautotrophic growth rate for planktonic primary producers is fundamental to our understanding of trophic and biogeochemical processes, and of importance in applied phycology. When dayintegrated C-specific growth is considered over natural light:dark cycles, plausible RuBisCO activity (Kcat coupled with cellular RuBisCO content) caps growth to less than a few doubling per day. Prolonged periods of C-specific growth rates above ca. 1.3 d thus appear increasingly implausible. Discrepancies between RuBisCO-capped rates and reported microalgal-specific growth rates, including temperature-growth rate relationships, may be explained by transformational errors in growth rate determinations made by reference to cell counts or most often chlorophyll, or by extrapolations from short-Term measurements. Coupled studies of enzyme activity and day-on-day C-specific growth rates are required to provide definitive evidence of high growth rates. It seems likely, however, that selective pressure to evolve a RuBisCO with a high Kcat (with a likely concomitant increase in Km for CO2) would be low, as other factors such as light limitation (developing during biomass growth due to self-shading), nutrient limitations, CO2 depletion and pH elevation, would all rapidly depress realized specific growth rates

Evolutionary temperature compensation of carbon fixation in marine phytoplankton

The efficiency of carbon sequestration by the biological pump could decline in the coming decades because respiration tends to increase more with temperature than photosynthesis. Despite these differences in the short-term temperature sensitivities of photosynthesis and respiration, it remains unknown whether the long-term impacts of global warming on metabolic rates of phytoplankton can be modulated by evolutionary adaptation. We found that respiration was consistently more temperature dependent than photosynthesis across 18 diverse marine phytoplankton, resulting in universal declines in the rate of carbon fixation with short-term increases in temperature. Long-term experimental evolution under high temperature reversed the short-term stimulation of metabolic rates, resulting in increased rates of carbon fixation. Our findings suggest that thermal adaptation may therefore have an ameliorating impact on the efficiency of phytoplankton as primary mediators of the biological carbon pump

Cell size influences inorganic carbon acquisition in artificially selected phytoplankton

Cell size influences the rate at which phytoplankton assimilate dissolved inorganic carbon (DIC), but it is unclear whether volume-specific carbon uptake should be greater in smaller or larger cells. On the one hand, Fick's Law predicts smaller cells to have a superior diffusive CO2 supply. On the other, larger cells may have greater scope to invest metabolic energy to upregulate active transport per unit area through CO2 -concentrating mechanisms (CCMs). Previous studies have focused on among-species comparisons, which complicates disentangling the role of cell size from other covarying traits. In this study, we investigated the DIC assimilation of the green alga Dunaliella tertiolecta after using artificial selection to evolve a 9.3-fold difference in cell volume. We compared CO2 affinity, external carbonic anhydrase (CAext ), isotopic signatures (δ13 C) and growth among size-selected lineages. Evolving cells to larger sizes led to an upregulation of CCMs that improved the DIC uptake of this species, with higher CO2 affinity, higher CAext and higher δ13 C. Larger cells also achieved faster growth and higher maximum biovolume densities. We showed that evolutionary shifts in cell size can alter the efficiency of DIC uptake systems to influence the fitness of a phytoplankton species