Exploring anaerobic CO2 production response to elevated nitrate levels in Gulf of Mexico coastal wetlands: Phenomena and relationships.

Recent studies have shown the effect of nitrate (NO3-) on carbon gas emissions from wetland soils that contradict thermodynamic predictions. In this study, CO2 production in three Mississippi River deltaic plain wetland soils (forest swamp, freshwater and saline marshes) with the presence of different NO3- levels (0.2, 2.0, and 3.2 mM) was evaluated in an anaerobic microcosm. Molecular composition of dissolved organic matter (DOM) of these soils was investigated using pyrolysis-GC/MS, and soil microbial community was characterized based on phosphorus lipid fatty acid (PLFA) method to elucidate the underlying mechanisms. Addition of NO3- promoted CO2 production in swamp forest soil, but inhibited CO2 emission from marsh soils. Pyrolysis-GC/MS analysis showed that swamp soil contained more polysaccharides, whereas both marsh soils had high abundance of phenolic compounds. Total PLFAs of forest swamp soil were 34% and 66% higher than freshwater and saline marsh soils, respectively. The PLFA profiles indicated different microbial distribution along a salinity gradient with the forest swamp having a higher proportion of fungi and NO3- reducers but lower sulfate (SO42-) reducers than marsh soils. Overall, the study indicated that the inherent differences in soil DOM and microbial community led to the contrasting response in soil CO2 respiration between forest swamp and marsh ecosystems to NO3- loading. These differences should be considered in determining the fate of nitrate entering Louisiana coastal wetlands from river diversions and other sources and their management.

Fresh and weathered crude oil effects on potential denitrification rates of coastal marsh soil.

On April 20, 2010, the Deepwater Horizon oil platform experienced an explosion which triggered the largest marine oil spill in US history, resulting in the release of ∼795 million L of crude oil into the Gulf of Mexico. Once oil reached the surface, changes in overall chemical composition occurred due to volatilization of the smaller carbon chain compounds as the oil was transported onshore by winds and currents. In this study, the toxic effects of both fresh and weathered crude oil on denitrification rates of coastal marsh soil were determined using soil samples collected from an unimpacted coastal marsh site proximal to areas that were oiled in Barataria Bay, LA. The 1:10 ratio of crude oil:field moist soil fully coated the soil surface mimicking a heavy oiling scenario. Potential denitrification rates at the 1:10 ratio, for weathered crude oil, were 46 ± 18.4% of the control immediately after exposure and 62 ± 8.0% of the control following a two week incubation period, suggesting some adaptation of the denitrifying microbial consortium over time. Denitrification rates of soil exposed to fresh crude oil were 51.5 ± 5.3% of the control after immediate exposure and significantly lower at 10.9 ± 1.1% after a 2 week exposure period. Results suggest that fresh crude oil has the potential to more severely impact the important marsh soil process of denitrification following longer term exposure. Future studies should focus on longer-term denitrification as well as changes in the microbial consortia in response to oil exposure.

Health plan retention and pharmacy costs of newly diagnosed patients with chronic kidney disease in a managed care population.

BACKGROUND: Chronic kidney disease is prevalent in the United States, and diabetes and hypertension cause up to two thirds of all new cases. Many health plans believe that these patients do not retain their health plans for a long duration, therefore plans do not focus on prevention for this disease. OBJECTIVE: To determine health plan retention rates and direct healthcare costs of adults with newly diagnosed chronic kidney disease with diabetes or hypertension. METHODS: A total of 31,917 patients with chronic kidney disease were included in this study between January 1995 and December 2006, using a managed care database. Patients were divided into 3 subgroups for cost comparison-patients with chronic kidney disease only (n = 8836), those with chronic kidney disease with diabetes (n = 11,252), and patients with chronic kidney disease with hypertension (n = 20,836). Follow-up of patients from index period of initial kidney disease diagnosis was 5 years. Average enrollment duration was 38 months; 60% of all patients remained enrolled at 3 years postdiagnosis. RESULTS: On average, patients with chronic kidney disease and diabetes and those with chronic kidney disease and hypertension remained enrolled slightly longer than chronic kidney disease-only patients (39 months, 40 months, and 36 months, respectively). The largest number of claims was for inpatient medical, followed by pharmacy and laboratory. Mean annual direct healthcare costs were higher for patients with chronic kidney disease and diabetes ($20,165) and those with chronic kidney disease and hypertension ($17,612) compared with patients with chronic kidney disease only ($9390). CONCLUSION: The study findings indicate that most patients who are newly diagnosed with chronic kidney disease retain their health plan affiliation for a considerable period, including those with diabetes or hypertension. Increased direct healthcare costs were associated with the presence of comorbidities in patients with chronic kidney disease.