Global biogeography of SAR11 marine bacteria

The ubiquitous SAR11 bacterial clade is the most abundant type of organism in the worldĝ€™s oceans, but the reasons for its success are not fully elucidated. We analysed 128 surface marine metagenomes, including 37 new Antarctic metagenomes. The large size of the data set enabled internal transcribed spacer (ITS) regions to be obtained from the Southern polar region, enabling the first global characterization of the distribution of SAR11, from waters spanning temperatures ĝ̂'2 to 30°C. Our data show a stable co-occurrence of phylotypes within both ĝ€̃ tropicalĝ€™ (>20°C) and ĝ€̃ polarĝ€™ (<10°C) biomes, highlighting ecological niche differentiation between major SAR11 subgroups. All phylotypes display transitions in abundance that are strongly correlated with temperature and latitude. By assembling SAR11 genomes from Antarctic metagenome data, we identified specific genes, biases in gene functions and signatures of positive selection in the genomes of the polar SAR11ĝ€"genomic signatures of adaptive radiation. Our data demonstrate the importance of adaptive radiation in the organismĝ€™s ability to proliferate throughout the worldĝ€™s oceans, and describe genomic traits characteristic of different phylotypes in specific marine biomes. © 2012 EMBO and Macmillan Publishers Limited All rights reserved

The effect of coastal diabatic heating gradients on the dynamics of cold fronts

Despite cold fronts being the predominate meteorological feature in the mid-lattitudes, little work has been done to determine how they are affected by boundary layer turbulence, the diurnal cycle or differential diabatic heating. The interaction of fronts with coastlines is especially important in the Southern Hemisphere as observations show frontogenesis is strongest on the western sides of the Southern Hemisphere continents. In Australia, cold fronts form in the southern ocean and are swept onshore in the southern half of the continent. This interaction with the sea-breeze can affect the timing and strength of cold fronts as they cross the coastline. In the work presented a confluent deformation model is used to examine how cold fronts are affected by sharp heating gradients associated with coastlines. The confluent deformation model is formulated in sigma co-ordinates on an f-plane and moist processes are neglected for simplicty. The boundary layer turbulence is parametrised with the Mellor-Yamada 2.25 scheme. The work examines the strength and timing of cold fronts in three cases: frontogenesis above a homogenous land surface; frontogenesis above a homogenous ocean surface; and the dynamics of a cold front as it crosses a coastline and interacts with the sea-breeze.Pages: 1857-185

Projected changes in the tropical Pacific Ocean of importance to tuna fisheries

International audienceFuture physical and chemical changes to the ocean are likely to significantly affect the distribution and productivity of many marine species. Tuna are of particular importance in the tropical Pacific, as they contribute significantly to the livelihoods, food and economic security of island states. Changes in water properties and circulation will impact on tuna larval dispersal, preferred habitat distributions and the trophic systems that support tuna populations throughout the region. Using recent observations and ocean projections from the CMIP3 and preliminary results from CMIP5 climate models, we document the projected changes to ocean temperature, salinity, stratification and circulation most relevant to distributions of tuna. Under a business-as-usual emission scenario, projections indicate a surface intensified warming in the upper 400 m and a large expansion of the western Pacific Warm Pool, with most surface waters of the central and western equatorial Pacific reaching temperatures warmer than 29°C by 2100. These changes are likely to alter the preferred habitat of tuna, based on present-day thermal tolerances, and in turn the distribution of spawning and foraging grounds. Large-scale shoaling of the mixed layer and increases in stratification are expected to impact nutrient provision to the biologically active layer, with flow-on trophic effects on the micronekton. Several oceanic currents are projected to change, including an increased upper equatorial undercurrent, which could modify the supply of bioavailable iron to the eastern Pacific

How's your little maltese cat.

Gift of Dr. Mary Jane Esplen.Piano vocal [instrumentation]C major [key]Moderato [tempo]Popular song [form/genre]Cat; photo:Marshall Montgomery [illustration]Publisher's advertisement on front inside cover & back cover [note

Anodic Ta2O5 for CMOS compatible low voltage electrowetting-on-dielectric device fabrication

This paper reports a CMOS compatible fabrication procedure that enables electrowetting-on-dielectric (EWOD) technology to be post-processed on foundry CMOS technology. With driving voltages less than 15 V it is believed to be the lowest reported driving voltage for any material system compatible with post-processing on completed integrated circuits wafers. The process architecture uses anodically grown tantalum pentoxide as a pinhole free high dielectric constant insulator with an overlying 16 nm layer of Teflon-AF®, which provides the hydrophobic surface for droplets manipulation. This stack provides a very robust dielectric, which maintains a sufficiently high capacitance per unit area for effective operation at a reduced voltage (15 V) which is more compatible with standard CMOS technology. The paper demonstrates that the sputtered tantalum layer used for the electrodes and the formation of the insulating dielectric can readily be integrated with both aluminium and copper interconnect used in foundry CMOS