Decay of plant detritus in organic-poor marine sediment: Production rates and stoichiometry of dissolved C and N compounds

Initial rates (30–60 days) and C:N stoichiometry of decomposition were examined in an organic-poor sediment (0.5% LOI) amended with fresh and dried yeast (Y) and Ruppia maritima (R) detritus by the use of “open system” core incubations and “closed system” jar incubations. High organic additions (0.5% dw) inhibited anaerobic carbon mineralization (i.e. sulfate reduction) and stimulated DOC production and nitrogen mineralization 3(R) to 15(Y) times (i.e. hydrolysis and fermentation). This indicated that carbon and nitrogen mineralization in the highly amended anaerobic sediments were uncoupled. Low organic additions (0.08% dw), on the other hand, stimulated both carbon and nitrogen mineralization by 1–2(R) and 3(Y) times. The comparison of reaction rates involving CO2, SO42− and NH4+ estimated from (1) modeling of porewater profiles (“open system”), (2) temporal changes in jars (“closed system”) and (3) sediment-water fluxes, documented equal applicability of these techniques in non-bioturbated sediment (except for NH4+ in (3) where nitrification interfered). The modeling approach (1) also suggested that the TCO2 deficiency observed in the uppermost oxidized zone of the sediment can be explained by rapid CO2 fixation by e.g. sulfide oxidizing chemoautotrophs. Although the C:N stoichiometry of inorganic decomposition products based on estimate (1) and (2) generally agreed well, it was found crucial to include dissolved organic pools (i.e. DOC) in estimates from highly amended anaerobic sediments due to the uncoupling of carbon and nitrogen mineralization. The stoichiometry of inorganic mineralization products can only be used to describe particulate organic matter decay in sediments where the concentration of DOC is negligible. C:N ratios obtained in the present study indicated that the major compounds being degraded in unamended (with an indigenous diatom pool) and yeast amended sediment were proteins (C:N = 4–5), whereas in Ruppia amended sediment carbohydrates were more important (C:N = 6–9)

Impact of the soft-shell clam Mya arenaria on sulfate reduction in an intertidal sediment

Sulfate reduction and various parameters related to the sulfur cycle were examined at mm to cm scales around burrows of the soft-shell clam Mya arenaria in an intertidal sediment (Lowes Cove, Maine, USA). Sulfate reduction rates were 1.5 to 2 times higher in the inner 1 to 5 mm region surrounding the burrow than in ambient sediment In contrast, pools of reduced sulfur increased with the distance from the burrow wall to values ≈1.5 times higher in ambient sediment. The highest numbers of sulfate-reducing bacteria (estimated using a most-probable-number technique) and microbial biomass (estimated from phospholipid phosphorous content) relative to ambient sediment were found in the innermost zone around burrows. Results from an artificial burrow experiment showed that artificial burrow irrigation suppressed sulfate reduction in the innermost zone around burrows, while radial profiles of reduced sulfur resembled those from M. arenaria burrows, indicating loss of reduced sulfur from the burrow wall. M. arenaria burrows are thus sites of enhanced microbial activity and a dynamic sulfur cycle, with turnover times of reduced sulfur compounds increasing with distance from the burrow wall. Enhanced sulfate reduction rates near burrows are likely caused by substrate enrichment, perhaps due to organic excretions from M. arenaria. The pattern of reduced sulfur turnover likely results from periodic oxygen inputs during burrow irrigation

Variation in point-of-care testing of HbA1c in diabetes care in general practice

Background: Point-of-care testing (POCT) of HbA1c may result in improved diabetic control, better patient outcomes, and enhanced clinical efficiency with fewer patient visits and subsequent reductions in costs. In 2008, the Danish regulators created a framework agreement regarding a new fee-for-service fee for the remuneration of POCT of HbA1c in general practice. According to secondary research, only the Capital Region of Denmark has allowed GPs to use this new incentive for POCT. The aim of this study is to use patient data to characterize patients with diabetes who have received POCT of HbA1c and analyze the variation in the use of POCT of HbA1c among patients with diabetes in Danish general practice. Methods: We use register data from the Danish Drug Register, the Danish Health Service Register and the National Patient Register from the year 2011 to define a population of 44,981 patients with diabetes (type 1 and type 2 but not patients with gestational diabetes) from the Capital Region. The POCT fee is used to measure the amount of POCT of HbA1c among patients with diabetes. Next, we apply descriptive statistics and multilevel logistic regression to analyze variation in the prevalence of POCT at the patient and clinic level. We include patient characteristics such as gender, age, socioeconomic markers, health care utilization, case mix markers, and municipality classifications. Results: The proportion of patients who received POCT was 14.1% and the proportion of clinics which were “POCT clinics” was 26.9%. There were variations in the use of POCT across clinics and patients. A part of the described variation can be explained by patient characteristics. Male gender, age differences (older age), short education, and other ethnicity imply significantly higher odds for POCT. High patient costs in general practice and other parts of primary care also imply higher odds for POCT. In contrast, high patient costs for drugs and/or morbidity in terms of the Charlson Comorbidity index mean lower odds for POCT. The frequency of patients with diabetes per 1000 patients was larger in POCT clinics than Non-POCT clinics. A total of 22.5% of the unexplained variability was related to GP clinics. Conclusions: This study demonstrates variation in the use of POCT which can be explained by patient characteristics such as demographic, socioeconomic, and case mix markers. However, it appears relevant to reassess the system for POCT. Further studies are warranted in order to assess the impacts of POCT of HbA1c on health care outcomes