PrP genotypes of captive and free-ranging Rocky Mountain elk (\u3ci\u3eCervus elaphus nelsoni\u3c/i\u3e) with chronic wasting disease

The PrP gene encodes the putative causative agent of the transmissible spongiform encephalopathies (TSEs), a heterogeneous group of fatal, neurodegenerative disorders including human Creutzfeldt–Jakob disease, bovine spongiform encephalopathy, ovine scrapie and chronic wasting disease (CWD) of North American deer and elk. Polymorphisms in the PrP gene are associated with variations in relative susceptibility, pathological lesion patterns, incubation times and clinical course of TSEs of humans, mice and sheep. Sequence analysis of the PrP gene from Rocky Mountain elk showed only one amino acid change (Met to Leu at cervid codon 132). Homozygosity for Met at the corresponding polymorphic site (Met to Val) in humans (human codon 129) predisposes exposed individuals to some forms of Creutzfeldt–Jakob disease. In this study, Rocky Mountain elk homozygous for PrP codon 132 Met were over-represented in both free-ranging and farm-raised CWD-affected elk when compared to unaffected control groups

High-frequency NO₃⁻ isotope (<i>δ</i>¹⁵N, <i>δ</i>¹⁸O) patterns in groundwater recharge reveal that short-term changes in land use and precipitation influence nitrate contamination trends

Poultry manure is the primary cause of nitrate (NO3−) exceedances in the transboundary Abbotsford–Sumas aquifer (ASA; Canada–USA) based on synoptic surveys two decades apart, but questions remained about seasonal and spatial aspects of agricultural nitrate fluxes to the aquifer to help better focus remediation efforts. We conducted over 700 monthly δ15N and δ18O of nitrate assays, focusing on shallow groundwater (&lt;&thinsp;5 years old) over a 5-year period to gain new insight on spatio-temporal sources and controls of groundwater nitrate contamination. NO3− concentrations in these wells ranged from 1.3 to 99&thinsp;mg&thinsp;N&thinsp;L−1 (n = 1041) with a mean of 16.2±0.4&thinsp;mg&thinsp;N&thinsp;L−1. The high-frequency 15N and 18O isotope data allowed us to identify three distinctive NO3− source patterns: (i) primarily from synthetic fertilizer, (ii) dynamic changes in nitrate due to changes in land use, and (iii) from a mix of poultry manure and fertilizer. A key finding was that the source(s) of nitrate in recharge could be quickly influenced by short-term near-field management practices and stochastic precipitation events, which ultimately impact long-term nitrate contamination trends. Overall, the isotope data affirmed a subtle decadal-scale shift in agricultural practices from manure increasingly towards fertilizer nitrate sources; nevertheless, poultry-derived N remains a predominant source of nitrate contamination. Because the aquifer does not generally support denitrification, remediation of the Abbotsford–Sumas aquifer is possible only if agricultural N sources are seriously curtailed, a difficult proposition due to longstanding high-value intensive poultry and raspberry and blueberry operations over the aquifer.</p

The quality of exogenous organic matter: short-term effects on soil physical properties and soil organic matter fractions

We examined the short-term effect of five organic amendments and compared them to plots fertilized with inorganic fertilizer and unfertilized plots on aggregate stability and hydraulic conductivity, and on the OC and ON distribution in physically separated SOM fractions. After less than 1 year, the addition of organic amendments significantly increased (P < 0.01) the aggregate stability and hydraulic conductivity. The stability index ranged between 0.97 and 1.76 and the hydraulic conductivity between 1.23 and 2.80 x 10(-3) m/s for the plots receiving organic amendments, compared with 0.34-0.43, and 0.42-0.64 x 10(-3) m/s, respectively, for the unamended plots. There were significant differences between the organic amendments (P < 0.01), although these results were not unequivocal for both soil physical parameters. The total OC and ON content were significantly increased ( P < 0.05) by only two applications of organic fertilizers: between 1.10 and 1.51% OC for the amended plots versus 0.98-1.08% for the unamended and between 0.092 and 0.131% ON versus 0.092-0.098% respectively. The amount of OC and ON in the free particulate organic matter fraction was also significantly increased (P < 0.05), but there were no significant differences (P < 0.05) in the OC and ON content in the POM occluded in micro-aggregates and in the silt + clay-sized organic matter fraction. The results showed that even in less than 1 year pronounced effects on soil physical properties and on the distribution of OC and ON in the SOM fractions occurred