The depth specific significiance, relative abundance and phylogeography of anaerobic ammonium oxidation (anammox) in marine and estuarine sediments

PhDThe availability of fixed forms of nitrogen is critical to the regulation of primary production. Until recently, denitrification (the sequential reduction of NO3 -, through NO2 - , to di-nitrogen gas) was recognised as the only significant pathway facilitating N removal. The discovery of anaerobic ammonium oxidation (a process whereby NH4 + is anaerobically oxidised with NO2 - to form N2 gas), however, has redefined this concept. Environmental studies clearly indicate that anammox is a globally significant sink for N, yet the factors that govern variations in the potential for anaerobic ammonium oxidation (anammox), the abundance or the natural diversity of these organisms are poorly understood. The purpose of this investigation was to identify the organisms responsible for anammox across a gradient of the Medway estuary, Irish Sea and North Atlantic. DNA amplification was performed using the Planctomycete forward primer ‘S-P-Planc-0046-a- A-18’ in combination with either ‘S-G-Sca-1309-a-A-21’ (targeting members of the genus ‘Scalindua’) or ‘S-*-Amx-0368-a-A-18’reverse. Analysis of 16S rRNA gene fragments indicated that the majority of sequences shared large phylogenetic distances with the ‘candidate’ species ‘Scalindua sorokinni’ (!93% sequence similarity). A number of the sequences extracted from both marine and estuarine sediments, however, cluster into 2 sub-groups that share common origins with the anammox lineage. In addition, the zone of potential anammox activity was characterised using a combination of 15N isotope labelling experiments, pore water oxygen profiles and depth specific rates sediment metabolism (CO2 production). This was performed in combination with fluorescence in situ hybridisation (FISH), to map shifts in the abundance of anammox organisms with depth, thus potentially linking the depth integrated capacity for anammox to deviations in population size. The potential for anammox activity and positive FISH signals confirm the presence of anammox at all sites investigated. The contribution of anammox to total N2 production (ra%) varied, on average, between 4- 35% in estuarine and 13-49% in marine sediments relative to denitrification. This was linked to a small population of anammox organisms constituting <1-3% of total bacteria in the estuarine sediments and <1-5% in marine samples. Whilst the depth specific values of ra correlate with the relative abundance of anammox organisms in continental shelf (r2=0.86, P=0.024) and slope sediments (r2=0.84, P=0.011), no such relationship was observed in the Medway estuary. The overall capacity for therefore appears to be dependant upon the depth integrated potential for anammox and is not inherent to differences in population size.Biological Science Queen Mary universit

Enhancing curriculum through service learning in the social determinants of health course

Service learning bridges classroom learning and community volunteerism and is anchored in the curriculum, classroom discussion, and community. We incorporated service learning projects (SLP) into three Social Determinants of Health courses (2008-2010) to promote: experiential learning; undergraduate scholarship; faculty career development through the scholarship of teaching and learning; and collaborative university-community research to reduce social inequalities in health. We examined whether SLP facilitated student learning of course concepts. We used mixed methods analyzing students’ (n=25) pre-/post-test surveys, research papers, and site supervisors’ (n=17) interviews. Despite positive survey ratings, results showed decreased student agreement about SLP facilitating student learning. Content analysis revealed specific student themes: finding SLP rewarding for future public health careers; aligning student interests with community-based organizations (CBOs)’ goals; and valuing interactive experiences with CBOs’ clients. Students gained beneficial career development skills with CBOs but needed better preparation for their SLP by increased discussion of their and CBOs’ expectations

Denitrification rates in boreo-arctic sponges - data of sponge species from Korsfjord (Norway) and the Schulz Bank (Arctic Ocean)

Sponges are commonly known as general nutrient providers for the marine ecosystem, recycling organic matter into various forms of bio-available nutrients such as ammonium and nitrate. In this study we challenge this view. We show that nutrient removal through microbial denitrification is a common feature in six cold-water sponge species from boreal and Arctic sponge grounds. Denitrification rates were quantified by incubating sponge tissue sections with 15NO3- - amended oxygen saturated seawater, mimicking conditions in pumping sponges, and de-oxygenated seawater, mimicking non-pumping sponges. Rates of anaerobic ammonium oxidation (anammox) using incubations with 15NH4+ could not be detected. Denitrification rates of the different sponge species ranged from 0 to 97 nmol N cm-3 sponge day-1 under oxic conditions, and from 24 to 279 nmol N cm-3 sponge day-1 under anoxic conditions. A positive relationship between the highest potential rates of denitrification (in the absence of oxygen) and the species-specific abundances of nirS and nirK genes encoding nitrite reductase, a key enzyme for denitrification, suggests that the denitrifying community in these sponge species is active and prepared for denitrification. The lack of a lag phase in the linear accumulation of the 15N labelled N2 gas in any of our tissue incubations is another indicator for an active community of denitrifiers in the investigated sponge species. Low rates for coupled nitrification-denitrification indicate that also under oxic conditions, nitrate to fuel denitrification rates was derived rather from the ambient sea-water than from sponge nitrification. The lack of nifH genes encoding nitrogenase, the key enzyme for nitrogen fixation, shows that the nitrogen cycle is not closed in the sponge grounds. The denitrified nitrogen, no matter of its origin, is then no longer available as a nutrient for the marine ecosystem. These results reveal the following scenario for the potential denitrification capacity of sponge grounds based on typical sponge biomass on boreal and Arctic sponge grounds:, Areal denitrification rates of 0.6 mmol N m-2 day-1 assuming non-pumping sponges and still 0.3 mmol N m-2 day-1 assuming pumping sponges may be possible. This is well within the range of denitrification rates of continental shelf sediments. For the most densely populated boreal sponge grounds we calculated potential denitrification rates of up to 1,7 mmol N m-2 day-1, which is higher than typical rates in continental shelf sediments. Increased future impact of sponge grounds by anthropogenic stressors reducing sponge pumping activity and further stimulating sponge anaerobic processes may thus lead to that deep-sea sponge grounds change their role in the marine ecosystem from being mainly nutrient sources to becoming mainly nutrient sinks

Deep-sea sponge grounds as nutrient sinks: Denitrification is common in boreo-Arctic sponges

Sponges are commonly known as general nutrient providers for the marine ecosystem, recycling organic matter into various forms of bioavailable nutrients such as ammonium and nitrate. In this study we challenge this view. We show that nutrient removal through microbial denitrification is a common feature in six cold-water sponge species from boreal and Arctic sponge grounds. Denitrification rates were quantified by incubating sponge tissue sections with 15NO−3-amended oxygen-saturated seawater, mimicking conditions in pumping sponges, and de-oxygenated seawater, mimicking non-pumping sponges. It was not possible to detect any rates of anaerobic ammonium oxidation (anammox) using incubations with 15NH+4. Denitrification rates of the different sponge species ranged from below detection to 97 nmol N cm−3 sponge d−1 under oxic conditions, and from 24 to 279 nmol N cm−3 sponge d−1 under anoxic conditions. A positive relationship between the highest potential rates of denitrification (in the absence of oxygen) and the species-specific abundances of nirS and nirK genes encoding nitrite reductase, a key enzyme for denitrification, suggests that the denitrifying community in these sponge species is active and prepared for denitrification. The lack of a lag phase in the linear accumulation of the 15N-labelled N2 gas in any of our tissue incubations is another indicator for an active community of denitrifiers in the investigated sponge species. Low rates for coupled nitrification–denitrification indicate that also under oxic conditions, the nitrate used to fuel denitrification rates was derived rather from the ambient seawater than from sponge nitrification. The lack of nifH genes encoding nitrogenase, the key enzyme for nitrogen fixation, shows that the nitrogen cycle is not closed in the sponge grounds. The denitrified nitrogen, no matter its origin, is then no longer available as a nutrient for the marine ecosystem. These results suggest a high potential denitrification capacity of deep-sea sponge grounds based on typical sponge biomass on boreal and Arctic sponge grounds, with areal denitrification rates of 0.6 mmol N m−2 d−1 assuming non-pumping sponges and still 0.3 mmol N m−2 d−1 assuming pumping sponges. This is well within the range of denitrification rates of continental shelf sediments. Anthropogenic impact and global change processes affecting the sponge redox state may thus lead to deep-sea sponge grounds changing their role in marine ecosystem from being mainly nutrient sources to becoming mainly nutrient sink

High Prevalence of Metabolic Syndrome Among Adolescents and Young Adults With Bipolar Disorder.

Despite abundant literature demonstrating increased metabolic syndrome (MetS) prevalence and important clinical correlates of MetS among middle-age adults with bipolar disorder, little is known about this topic among adolescents and young adults early in their course of bipolar disorder. We therefore examined this topic in the Course and Outcome of Bipolar Youth (COBY) study. A cross-sectional, retrospective study was conducted of 162 adolescents and young adults (mean ± SD age = 20.8 ± 3.7 years; range, 13.6-28.3 years) with bipolar disorder (I, II, or not otherwise specified, based on DSM-IV) enrolled in COBY between 2000 and 2006. MetS measures (blood pressure, glucose, high-density lipoprotein cholesterol [HDL-C], triglycerides, and waist circumference), defined using the International Diabetes Federation criteria, were obtained at a single timepoint. Mood, comorbidity, and treatment over the 6 months preceding the MetS assessment were evaluated using the Longitudinal Interval Follow-Up Evaluation. The prevalence of MetS in the sample was 19.8% (32/162). Low HDL-C (56.5%) and abdominal obesity (46.9%) were the most common MetS criteria. MetS was nominally associated with lower lifetime global functioning at COBY intake (odds ratio [OR] = 0.97, P = .06). MetS was significantly associated with percentage of weeks in full-threshold pure depression (OR = 1.07, P = .02) and percentage of weeks receiving antidepressant medications (OR = 1.06, P = .001) in the preceding 6 months. MetS was not associated with manic symptoms or medications other than antidepressants. The prevalence of MetS in this sample was at least double compared to the general population. Moreover, MetS is associated with increased burden of depression symptoms in this group. Management of early-onset bipolar disorder should integrate strategies focused on modifying MetS risk factors

The depth-specific significance and relative abundance of anaerobic ammonium-oxidizing bacteria in estuarine sediments (Medway Estuary, UK)

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