Landscape-gradient assessment of thermokarst lake hydrology using water isotope tracers

Thermokarst lakes are widespread in arctic and subarctic regions. In subarctic Québec (Nunavik), they have grown in number and size since the mid-20th century. Recent studies have identified that these lakes are important sources of greenhouse gases. This is mainly due to the supply of catchment-derived dissolved organic carbon that generates anoxic conditions leading to methane production. To assess the potential role of climate-driven changes in hydrological processes to influence greenhouse-gas emissions, we utilized water isotope tracers to characterize the water balance of thermokarst lakes in Nunavik during three consecutive mid- to late summer seasons (2012-2014). Lake distribution stretches from shrub-tundra overlying discontinuous permafrost in the north to spruce-lichen woodland with sporadic permafrost in the south. Calculation of lake-specific input water isotope compositions (I) and lake-specific evaporation-to-inflow (E/I) ratios based on an isotope-mass balance model reveal a narrow hydrological gradient regardless of diversity in regional landscape characteristics. Nearly all lakes sampled were predominantly fed by rainfall and/or permafrost meltwater, which suppressed the effects of evaporative loss. Only a few lakes in one of the southern sampling locations, which overly highly degraded sporadic permafrost terrain, appear to be susceptible to evaporative lake-level drawdown. We attribute this lake hydrological resiliency to the strong maritime climate in coastal regions of Nunavik. Predicted climate-driven increases in precipitation and permafrost degradation will likely contribute to persistence and expansion of thermokarst lakes throughout the region. If coupled with an increase in terrestrial carbon inputs to thermokarst lakes from surface runoff, conditions favorable for mineralization and emission of methane, these water bodies may become even more important sources of greenhouse gases

Transcriptional recapitulation and subversion of embryonic colon development by mouse colon tumor models and human colon cancer

Colon tumors from four independent mouse models and 100 human colorectal cancers all exhibited striking recapitulation of embryonic colon gene expression from embryonic days 13.5-18.5

VO2 kinetics in young people with CF

Accepted manuscript, 12 month embarg

Homologs of genes and anonymous loci on human Chromosome 13 map to mouse Chromosomes 8 and 14

To enhance the comparative map for human Chromosome (Chr) 13, we identified clones for human genes and anonymous loci that cross-hybridized with their mouse homologs and then used linkage crosses for mapping. Of the clones for four genes and twelve anonymous loci tested, cross-hybridization was found for six, COL4A1, COL4A2, D13S26, D13S35, F10, and PCCA. Strong evidence for homology was found for COL4A1, COL4A2, D13S26, D13S35, and F10, but only circumstantial homology evidence was obtained for PCCA. To genetically map these mouse homologs ( Cf10, Col4a1, Col4a2, D14H13S26, D8H13S35 , and Pcca-rs ), we used interspecific and intersubspecific mapping panels. D14H13S26 and Pcca-rs were located on the distal portion of mouse Chr 14 extending by ∼30 cM the conserved linkage between human Chr 13 and mouse Chr 14, assuming that Pcca-rs is the mouse homolog of PCCA. By contrast, Cf10, Col4a1, Col4a2 , and D8H13S35 mapped near the centromere of mouse Chr 8, defining a new conserved linkage. Finally, we identified either a closely linked sequence related to Col4a2 , or a recombination hot-spot between Col4a1 and Col4a2 that has been conserved in humans and mice.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47022/1/335_2004_Article_BF00352413.pd

Using stable isotopes to estimate travel times in a data-sparse arctic catchment: challenges and possible solutions.

We thank the Natural Environment Research Council NERC (HYDRA project NE/K000268/1 and NE/K000284/1) and the European Research Council ERC for funding (VeWa project GA 335910). We also are grateful to Dr Jason Lessels and HYDRA team members for field work and sample collection. We further thank Dr. Jonathan Dick for running the isotope analysis.Peer reviewedPublisher PD