Disentangling artificial and natural benthic weathering in organic rich Baltic Sea sediments

Enhanced mineral dissolution in the benthic environment is currently discussed as a potential technique for ocean alkalinity enhancement (OAE) to reduce atmospheric CO2 levels. This study explores how biogeochemical processes affect the dissolution of alkaline minerals in surface sediments during laboratory incubation experiments. These involved introducing dunite and calcite to organic-rich sediments from the Baltic Sea under controlled conditions in an oxic environment. The sediment cores were incubated with Baltic Sea bottom water. Findings reveal that the addition of calcite increased the benthic alkalinity release from 0.4 μmol cm−2 d−1 (control) to 1.4 μmol cm−2 d−1 (calcite) as well as other weathering products such as calcium. However, these enhanced fluxes returned to lower fluxes after approximately 4 weeks yet still higher than the un-amended controls. Microbial activity appeared to be the primary driver for lowering pore water pH and thus enhanced weathering. In several sediment cores, pH profiles taken at the start of the experiments indicated activity of sulfur oxidizing Beggiatoa spp, which was verified by RNA-profiling of 16S rRNA genes. The pH profiles transitioned to those commonly associated with the activity of cable bacteria as the experiments progressed. The metabolic activity of cable bacteria would explain the significantly lower pH values (~5.6) at sediment depths of 1–3 cm, which would favor substantial calcite dissolution. However, a high abundance of cable bacteria was not reflected in 16S rRNA sequence data. Total alkalinity (TA) fluxes in these cores increased by a factor of ~3, with excess TA/calcium ratios indicating that the enhanced flux originated from calcite dissolution. The dissolution of dunite or the potential formation of secondary minerals could not be identified due to the strong natural flux of silicic acid, likely due to biogenic silica dissolution. Furthermore, no accumulation of potentially harmful metals such as nickel was observed, as highlighted as a potential risk in other studies concerning OAE. Given the complexity of sediment chemistry and changes of the benthic conditions induced by the incubation, it remains challenging to distinguish between natural and enhanced mineral weathering. Further investigation, including the identification of suitable tracers for mineral dissolution, are necessary to assess the feasibility of benthic weathering as a practical approach for OAE and climate change mitigation

Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation

Development and evaluation of rapid and semi-automated devices for the detection of toxic algae

A commercially available PCR ELISA Dig Detection Kit was successfully adapted for the detection of the toxic dinoflagellate Alexandrium minutum by application of ribosomal 18S probes and sandwich hybridization. Furthermore, the assay showed the specificity of 10 additional probe sets for the toxic algal species. The total rRNA isolation protocol was improved and the hybridization procedure for the electrochemical detection of toxic algal species was described in detail and visualized for easy application by inexperienced users. Furthermore, locked nucleic acid probes were tested with known target sequences and the specificity and sensitivity was compared to signal formation of conventional molecular probes. The hybridization signals for both tested solid surface methods could not be enhanced and the conventional DNA probes showed equal or better results. A stand-alone, semi-automated system in combination with multiprobe chips was developed. A multiprobe chip with 16 gold electrodes was designed and adapted for the use in a sandwich hybridisation assay

Entwicklung und Evaluierung von schnellen und halbautomatischen Instrumenten für den Nachweis von giftigen Algen

A commercially available PCR ELISA Dig Detection Kit was successfully adapted for the detection of the toxic dinoflagellate Alexandrium minutum by application of ribosomal 18S probes and sandwich hybridization. Furthermore, the assay showed the specificity of 10 additional probe sets for the toxic algal species. The total rRNA isolation protocol was improved and the hybridization procedure for the electrochemical detection of toxic algal species was described in detail and visualized for easy application by inexperienced users. Furthermore, locked nucleic acid probes were tested with known target sequences and the specificity and sensitivity was compared to signal formation of conventional molecular probes. The hybridization signals for both tested solid surface methods could not be enhanced and the conventional DNA probes showed equal or better results. A stand-alone, semi-automated system in combination with multiprobe chips was developed. A multiprobe chip with 16 gold electrodes was designed and adapted for the use in a sandwich hybridisation assay