Pollen and grain size records in abyssal sediments of the northwest Pacific Ocean as proxies of Plio-Pleistocene climate change /

A distinctive period of global change occurred during the PUocene between the warm Miocene and subsequent Quaternary cooling. Samples from Ocean Drilling Project Site 11 79 (-5586 mbsl, 41°4'N, 159°57'E), Site 881 (-5765 mbsl, 47°6.133'N, 161°29.490'E) and Site 882 (-3255 mbsl, 50°22'N, 167°36'E) were studied to determine the magnitude and composition ofterrigenous flux to the western mid-latitude North Pacific and its relation to climate change in East Asia since the mid-Pliocene. Dust-sized particles (including pollen), sourced from the arid regions and loess plateaus in East Asia are entrained by prevailing westerly winds and transported to the midlatitude northwest North Pacific Ocean. This is recorded by peaks in the total concentration of pollen and spores, as well as the mean grain size of allochthonous and autochthonous silicate material in abyssal marine sediments. Aridification of the Asian interior due to the phased uplift of the Himalayan-Tibetan Plateau created the modem East Asian Monsoon system dominated by a strengthening of the winter monsoon. The winter monsoon is further enhanced during glacials due to the expansion of desert and steppe environments at the expense ofwoodlands and forests recorded by the composition of palynological assemblages. The late Pliocene-Pleistocene glacials at ODP Sites 1 179, 881, and 882 are characterized by increases in grain size, magnetic susceptibility, pollen and spore concentrations around 3.5-3.3, 2.6-2.4, 1.7-1.6, and 0.9-0.7 Ma (ages based on magnetostratigraphic and biostratigraphic datums). The peaks during these times are relatively rich in pollen taxa derived primarily from steppe and boreal vegetation zones, recording cool, dry climates. The overall size increase of sediment and abundance of terrestrial palynomorphs record enhanced wind strength. The increase in magnitude of pollen and spore concentrations as well as grain size record global cooling and Northern Hemisphere glaciation. The peaks in grain size as well as pollen and spore abundance in marine sediments correlate with the mean grain size of loess in East Asia, consistent with the deflation of unarmoured surfaces during glacials. The transport of limiting nutrients to marine environments enhanced sea surface productivity and increased the rate of sediment accumulation.

Competing demands for a complex system : photosystem II repair, photoprotection and quantum yield

Photosynthesis in general is a key biological process on Earth and Photo system II (PSII) is an important component of this process. PSII is the only enzyme capable of oxidizing water and is largely responsible for the primordial build-up and present maintenance of the oxygen in the atmosphere. This thesis endeavoured to understand the link between structure and function in PSII with special focus on primary photochemistry, repair/photodamage and spectral characteristics. The deletion of the PsbU subunit ofPSII in cyanobacteria caused a decoupling of the Phycobilisomes (PBS) from PSII, likely as a result of increased rates of PSII photodamage with the PBS decoupling acting as a measure to protect PSII from further damage. Isolated fractions of spinach thylakoid membranes were utilized to characterize the heterogeneity present in the various compartments of the thylakoid membrane. It was found that the pooled PSIILHCII pigment populations were connected in the grana stack and there was also a progressive decrease in the reaction rates of primary photochemistry and antennae size of PSII as the sample origin moved from grana to stroma. The results were consistent with PSII complexes becoming damaged in the grana and being sent to the stroma for repair. The dramatic quenching of variable fluorescence and overall fluorescent yield of PSII in desiccated lichens was also studied in order to investigate the mechanism by which the quenching operated. It was determined that the source of the quenching was a novel long wavelength emitting external quencher. Point mutations to amino acids acting as ligands to chromophores of interest in PSII were utilized in cyanobacteria to determine the role of specific chromophores in energy transfer and primary photochemistry. These results indicated that the Hl14 ligated chlorophyll acts as the 'trap' chlorophyll in CP47 at low temperature and that the Q130E mutation imparts considerable changes to PSII electron transfer kinetics, essentially protecting the complex via increased non-radiative charge Photosynthesis in general is a key biological process on Earth and Photo system II (PSII) is an important component of this process. PSII is the only enzyme capable of oxidizing water and is largely responsible for the primordial build-up and present maintenance of the oxygen in the atmosphere. This thesis endeavoured to understand the link between structure and function in PSII with special focus on primary photochemistry, repair/photodamage and spectral characteristics. The deletion of the PsbU subunit ofPSII in cyanobacteria caused a decoupling of the Phycobilisomes (PBS) from PSII, likely as a result of increased rates of PSII photodamage with the PBS decoupling acting as a measure to protect PSII from further damage. Isolated fractions of spinach thylakoid membranes were utilized to characterize the heterogeneity present in the various compartments of the thylakoid membrane. It was found that the pooled PSIILHCII pigment populations were connected in the grana stack and there was also a progressive decrease in the reaction rates of primary photochemistry and antennae size of PSII as the sample origin moved from grana to stroma. The results were consistent with PSII complexes becoming damaged in the grana and being sent to the stroma for repair. The dramatic quenching of variable fluorescence and overall fluorescent yield of PSII in desiccated lichens was also studied in order to investigate the mechanism by which the quenching operated. It was determined that the source of the quenching was a novel long wavelength emitting external quencher. Point mutations to amino acids acting as ligands to chromophores of interest in PSII were utilized in cyanobacteria to determine the role of specific chromophores in energy transfer and primary photochemistry. These results indicated that the Hl14 ligated chlorophyll acts as the 'trap' chlorophyll in CP47 at low temperature and that the Q130E mutation imparts considerable changes to PSII electron transfer kinetics, essentially protecting the complex via increased non-radiative charge.

Bos Indicus-Cross Feedlot Cattle with Excitable Temperaments have Tougher Meat and a Higher Incidence of Borderline Dark Cutters

The article was published in the journal Meat Science, Vol. 46, No.4. The focus is data collected for cattle temperament and the quality of meat produced.