Regional and global scale modeling of the benthic marine nitrogen cycle

The benthic nitrogen (N) cycle is highly dynamic and diverse due to the strong redox gradients occurring in marine surface sediments and the variety of oxidation states accessible to nitrogen. Since N is a limiting nutrient for biological productivity, fluxes of nitrogenous species across the sediment-water interface may strongly affect the biogeochemistry of nitrogen, carbon and phosphorus in the oceanic water column. In particular, as a major sink for fixed N in the marine environment, benthic denitrification has a profound impact on the availability of bioavailable N in the oceans. Consequently, an understanding of N cycling in marine sediments is of major importance for constraining the global marine nitrogen budget and quantifying benthic-pelagic feedbacks. The thesis addresses benthic N turnover on local and global scales with a special focus on oxygen minimum zones where strong lateral redox gradients lead to unique and highly interesting interactions in N cycling

On the significance of viscoelasticity in a 2D full waveform inversion of shallow seismic surface waves

We perform two tests to investigate to which degree viscoelastic modeling is relevant during a full waveform inversion of shallow seismic surface waves. Firstly, we compare field data with synthetic elastic and viscoelastic data. We show that the optimized source time function acts as a low pass filter in the case of elastic wavefields and can compensate a significant fraction of the residuals between elasticly and viscoelasticly modeled data. However, the viscoelastic data can explain the recorded data better in some aspects like the amplitude decay with offset of the fundamental mode and the near offset traces. Secondly, we run inversion tests for simulated viscoelastic observations (Q=20) using both elastic as well as viscoelastic forward modeling with Q=20, 25, and 10 during the inversion. The results show that it is not possible to infer the steep gradient in the shear wave velocity model in the topmost meter using an elastic inversion. Using a slightly wrong Q factor in the inversion produces very similar results compared to the results obtained by an inversion using the correct Q factor. If we use Q factors that are too far away from the Q factor of the observed data the inversion result becomes worse

Benthic iron and phosphorus fluxes across the Peruvian oxigen minimum zone

Benthic fluxes of dissolved ferrous iron (Fe2+) and phosphate (TPO4) were quantified by in situ benthic chamber incubations and pore-water profiles along a depth transect (11°S, 80–1000 m) across the Peruvian oxygen minimum zone (OMZ). Bottom-water O2 levels were < 2 µmol L-1 down to 500-m water depth, and increased to ~40 µmol L-1 at 1000 m. Fe2+ fluxes were highest on the shallow shelf (maximum 316 mmol m-2 yr-1), moderate (15.4 mmol m-2 yr-1) between 250 m and 600 m, and negligible at deeper stations. In the persistent OMZ core, continuous reduction of Fe oxyhydroxides results in depletion of sedimentary Fe :Al ratios. TPO4 fluxes were high (maximum 292 mmol m-2 yr-1) throughout the shelf and the OMZ core in association with high organic carbon degradation rates. Ratios between organic carbon degradation and TPO4 flux indicate excess release of P over C when compared to Redfield stoichiometry. Most likely, this is caused by preferential P release from organic matter, dissolution of fish debris, and/or P release from microbial mat communities, while Fe oxyhydroxides can only be inferred as a major P source on the shallow shelf. The benthic fluxes presented here are among the highest reported from similar, oxygen-depleted environments and highlight the importance of sediments underlying anoxic water bodies as nutrient sources to the ocean. The shelf is particularly important as the periodic passage of coastal trapped waves and associated bottom-water oxygenation events can be expected to induce a transient biogeochemical environment with highly variable release of Fe2+ and TPO4

Rates and regulation of nitrogen cycling in seasonally hypoxic sediments during winter (Boknis Eck, SW Baltic Sea): Sensitivity to environmental variables

This study investigates the biogeochemical processes that control the benthic fluxes of dissolved nitrogen (N) species in Boknis Eck - a 28 m deep site in the Eckernförde Bay (southwestern Baltic Sea). Bottom water oxygen concentrations (O2-BW) fluctuate greatly over the year at Boknis Eck, being well-oxygenated in winter and experiencing severe bottom water hypoxia and even anoxia in late summer. The present communication addresses the winter situation (February 2010). Fluxes of ammonium (NH4+), nitrate (NO3-) and nitrite (NO2-) were simulated using a benthic model that accounted for transport andbiogeochemical reactions and constrained with ex situ flux measurements and sediment geochemical analysis. The sediments were a net sink for NO3- (-0.35 mmol m-2 d-1 of NO3-), of which 75% was ascribed to dissimilatory reduction of nitrate to ammonium (DNRA) by sulfide oxidizing bacteria, and 25% to NO3- reduction to NO2- by denitrifying microorganisms. NH4+ fluxes were high (1.74 mmol m-2d-1 of NH4+), mainly due to the degradation of organic nitrogen, and directed out of the sediment. NO2-fluxes were negligible. The sediments in Boknis Eck are, therefore, a net source of dissolved inorganic nitrogen(DIN = NO3- + NO2- + NH4+) during winter. This is in large part due to bioirrigation, which accounts for 76% of the benthic efflux of NH4+, thus reducing the capacity for nitrification of NH4+. The combined rate of fixed N loss by denitrification and anammox was estimated at 0.08 mmol m-2 d-1 of N2, which is at the lower end of previously reported values. A systematic sensitivity analysis revealed that denitrification and anammox respond strongly and positively to the concentration of NO3- in the bottomwater (NO3-BW).Higher O2-BW decreases DNRA and denitrification but stimulates both anammox and the contribution ofanammox to total N2 production (%Ramx). A complete mechanistic explanation of these findings is provided. Our analysis indicates that nitrification is the geochemical driving force behind the observed correlation between %Ramx and water depth in the seminal study of Dalsgaard et al. (2005). Despite remaining uncertainties, the results provide a general mechanistic framework for interpreting the existing knowledge of N-turnover processes and fluxes in continental margin sediments, as well as predicting the types of environment where these reactions are expected to occur prominently

Simple transfer functions for calculating benthic fixed nitrogen losses and C:N:P regeneration ratios in global biogeochemical models

Empirical transfer functions are derived for predicting the total benthic nitrate loss(LNO3) and the net loss of dissolved inorganic nitrogen (LDIN) in marine sediments,equivalent to sedimentary denitrification. The functions are dynamic vertically integratedsediment models which require the rain rate of particulate organic carbon to the seafloor(RRPOC) and a proposed new variable(O2-NO3)bw (bottom water O2 concentration minus NO3-concentration) as the only input parameters. Applied globally to maps of RRPOC and(O2-NO3)bw on a 1° x 1° spatial resolution, the models predict a NO3- drawdown of 196 Tg yr-1 (LNO3)of which 153 – 155 Tg yr-1 is denitrified to N2 (LDIN). This is in good agreement with previous estimates using very different methods. Our approach implicitly accounts for fixed N loss via anammox, such that our findings do not support the idea that the relatively recent discovery of anammox in marine sediments might require current estimates of the global benthic marine N budget to be revised. The continental shelf (0 – 200 m) accounts for >50% of global LNO3 and LDIN, with slope (200 – 2000 m) and deep-sea (>2000 m) sediments contributing ca. 30% and 20%, respectively. Denitrification in high-nitrate/low-oxygen regions such as oxygen minimum zones is significant (ca. 15 Tg N yr-1; 10% of global) despite covering only 1% of the seafloor. The data are used to estimate the net fluxes of nitrate (18 Tg N yr-1) and phosphate(27 Tg P yr-1) across the sediment-water interface. The benthic fluxes strongly deviate from Redfield composition, with globally averaged N:P, N:C and C:P values of 8.3, 0.067 and 122, respectively, indicating world-wide fixed N losses (by denitrification) relative to C and P. The transfer functions are designed to be coupled dynamically to general circulation models to better predict the feedback of sediments on pelagic nutrient cycling and dissolved O2 distributions

Extension's Dining with Diabetes: Helping People Prevent and Manage Diabetes in Ohio and throughout the Nation

Diabetes is a common, serious and expensive disease in Ohio, the United States and around the world. The complications of untreated or undertreated diabetes are devastating and include heart, kidney, eye and nerve diseases. Studies have shown that when blood glucose is controlled, complications of diabetes are delayed or possibly prevented. Extension's Dining with Diabetes (DWD) program is designed for people with diabetes, their family members and those at risk; and it consists of education, cooking demonstrations, and taste testing. Participants are engaged on the topics of healthy cooking strategies, meal planning, portion control, label reading, physical activity, and goal setting. The program is delivered as a series of four face-to-face sessions with a three-month reunion led by Extension educators partnering with registered nurses, certified diabetes educators or registered dietatians. In addition to Extension offices, local community centers, faith-based organizations, libraries and hospitals are often used as locations in which to offer the program. State and local health departments, clinics, hospitals, pharmacies and community health coalitions are active in marketing the program. DWD has been implemented in Ohio for more than a decade, and is now a national program with more than 38 states participating. Dining with Diabetes has a successful history of being implemented in Ohio and adapted by other states. The national program and evaluation provides the opportunity to demonstrate national impact and how Ohio's efforts compare with other states in terms of improving diabetes outcomes. The national program evaluation includes assessment of knowledge, attitudes and skill gains related to diabetes management. Medium-term outcomes include reported behavior change in the areas of food selection, food preparation, label reading, and physical activity. Participants who reported at three months follow-up demonstrated the ability to maintain or improve dietary change after completing the program.AUTHOR AFFILIATION: Dan Remley, Field Specialist, Food, Nutrition and Wellness, The Ohio State University Extension, [email protected] (Corresponding Author); Shari Gallup, Educator, Family and Consumer Sciences, The Ohio State University Extension; Margaret Jenkins, Educator, Family and Consumer Sciences, The Ohio State University Extension; Tammy Jones, Educator, Family and Consumer Sciences, The Ohio State University Extension; Jenny Lobb, Educator, Family and Consumer Sciences, The Ohio State University Extension; Susan Zies, Educator, Family and Consumer Sciences, The Ohio State University Extension; Marie Economos, Educator, Family and Consumer Sciences, The Ohio State University Extension; Chris Kendle, Educator, Family and Consumer Sciences, The Ohio State University Extension; Chelsea Peckny, Assistant Professor, College of Pharmacy; Joyce Riley, Educator, Family and Consumer Sciences, The Ohio State University Extension; Amy Meehan, Healthy People Program Specialist; Brian Butler, Evaluation Specialist, The Ohio State University Extension; Ingrid Adams, Associate Professor; Lisa Barlage, Educator, Family and Consumer Sciences, The Ohio State University Extension; Candace Heer, Associate Professor; Amanda Bohlen, Educator, Family and Consumer Sciences, The Ohio State University Extension.Diabetes is a common, serious and expensive disease in Ohio, the United States and around the world. The complications of untreated or undertreated diabetes are devastating and include heart, kidney, eye and nerve diseases. Extension's Dining with Diabetes (DWD) program engages participants on the topics of healthy cooking strategies, meal planning, portion control, label reading, physical activity, and goal setting. The program is delivered as a series of four face-to-face sessions with a three-month reunion led by Extension educators partnering with registered nurses, certified diabetes educators or registered dietitians. DWD has a national curricula and evaluation, providing the opportunity to demonstrate national and state-level impact on knowledge, attitudes and skills related to diabetes management

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

Sediments underlying the Peruvian OMZ - sink or source for reactive N species

Oxygen minimum zones (OMZs) represent key regions for nitrogen (N) turnover in the water column as well as in the sediments. However, the redox dependent source-sink function of sediments for reactive nitrogen (NO3- + NO2- + NH4+) is not well established. To address this issue, we studied benthic nitrogen cycling under different bottom water oxygen concentrations along a transect traversing the Peruvian OMZ at 11°S. In situ fluxes of nitrogen species across the sediment-water interface were measured using benthic landers and the sediment geochemistry was analyzed in recovered multi-core samples. The fieldwork was conducted through (80 - 400 m water depth) and beyond (700 - 1000 m water depth) the extension of the OMZ. The relative importance of different processes in the benthic nitrogen cycle was investigated using a 1D reaction-transport model tuned to the measured data. The reaction network included the release of ammonium during organic matter mineralization, nitrification and heterotrophic denitrification, as well as anammox. Nitrite was explicitly included in the model as an independent variable. Dissimilatory nitrate reduction to ammonium (DNRA) was also considered where mats of large sulfur bacteria were observed during towed camera deployments (~ 80 - 300 m depth). The model was able to simulate the following features of the benthic N cycle determined from the in situ lander deployments: (i) at the upper fringe of the OMZ (~ 80 - 250 m), the sediments acted as a source of reactive nitrogen due to enhanced ammonium release, (ii) at the lower fringe of the OMZ (300 - 400 m), there was a net uptake of reactive nitrogen of up to ~ 1.9 mmol N m-2 d-1 , and (iii) below the OMZ, reactive nitrogen fluxes into the sediments were low (≤ 0.5 mmol N m-2 d-1 ). The model further predicted that denitrification was the major control on N2 production along the entire transect whereas anammox played a minor role (≤ 10%). At the upper fringe of the OMZ, DNRA was driving ammonium release and determined whether the sediments were a net source or sink for reactive nitrogen species. In contrast, at the lower fringe of the OMZ organic carbon mineralization was the dominant process releasing ammonium. The relative importance of DNRA versus organic carbon mineralization for ammonium release varied systematically between these two end-members along the studied transect