We measured seasonal variations in the vertical distribution of methane concentration, methane oxidation rates, and lipid biomarkers in the northern basin of Lake Lugano. Methane consumption below the oxic-anoxic interface co-occurred with concentration maxima of 13 C-depleted C 16 fatty acid biomarkers (with d 13 C values as low as 270%) in the anoxic water column, as well as characteristic d 13 C CH 4 profiles. We argue that the conspicuous methane concentration gradients are primarily driven by (micro-)aerobic methane oxidation (MOx) below the chemocline. We measured a strong MOx potential throughout the anoxic water column, while MOx rates at in situ O 2 concentration . 10 nmol L 21 were undetectable. Similarly, we found MOx-related biomarkers and gene sequences encoding the particulate methane monooxygenase in the anoxic, but not the oxic, water. The mechanism of (episodic) oxygen supply sustaining the MOx community in anoxic waters is still uncertain. Our results indicate that a bacterial methanotrophic community is responsible for the methane consumption in Lake Lugano, without detectable contribution from archaeal methanotrophs. Bacterial populations that accumulated both at the suboxic-anoxic interface and in the deeper anoxic hypolimnion, where maximum potential MOx rates were observed throughout the year (1.5-2.5 mmol L 21 d 21 ) were mainly related to Methylobacter sp. Close relatives are found in lacustrine environments throughout the world, and their potential to thrive under micro-and anoxic conditions in Lake Lugano may imply that micro-aerobic methane oxidation is important in methane cycling and competition for methane and oxygen in stratified lakes worldwide.

Pediatric dermatology is a new topic and no epidemiologic data exist from Switzerland. Therefore we performed a survey of the pediatric population referred to the hospital of Aarau, Switzerland, between 1998 and 2001. All inpatients and outpatients less than 16 years old with a dermatologic diagnosis were included prospectively in our study. Demographic data (age, mean age, sex distribution), referral method, pattern and frequency of the different diagnoses in various age groups, diagnostic pattern, and therapy were analyzed. A total of 1105 children were included, with a slightly higher proportion of girls (53.8% versus 46.2%). The average age was 6.8 years and infants and school children represented 60% of the study population. Half of the patients (51%) were external referrals, almost one-third (29%) presented spontaneously, and the remaining 20% were sent from other hospital departments. With a frequency of 25.9%, atopic dermatitis was the most frequent diagnosis, followed by pigmented nevi (9.1%) and warts (5.0%). Local therapy was prescribed in 66% of patients and systemic therapy in 18.6%. Other treatments such as curettage, surgery, cryotherapy, ultraviolet therapy, and electrotherapy were rarely performed (2%). We found that atopic dermatitis was the most frequent skin disorder seen in all age groups. As this was a dermatologic subspecialty clinic, higher frequencies of chronic and uncommon dermatoses such as genetic and autoimmune diseases were seen, whereas frequent diagnoses such as diaper rash and miliaria were rarely seen and the frequencies of other common skin disorders such as scabies, pediculosis, impetigo contagiosa, warts, and molluscum contagiosum were expected to be higher compared with the figures in the literature. In our study these dermatoses are underreported, as most patients are treated by general practitioners and pediatricians. Our survey documents the most common skin diseases in childhood primarily seen by pediatricians. We emphasize that dermatologic education of medical students, primary care physicians, and pediatricians should focus on allergic skin diseases, skin infections, pigmentary disorders, and vascular lesions.

In addition to organotrophic denitrification, alternative pathways, such as anaerobic ammonium oxidation (anammox) or sulfide-dependent denitrification may be important modes for the removal of fixed nitrogen (N) from lakes. We used Lake Lugano as a model system with which to assess possible controls on the concurrence of multiple suboxic N 2 production pathways in a lacustrine water column. In the northern basin of Lake Lugano, concentration gradients of dissolved inorganic N toward the hypolimnetic redox transition zone (RTZ) indicate ammonium oxidation and nitrate reduction occurring in close vicinity. Ammonium reaches undetectable levels 15 m below the depth of oxygen disappearance, indicating its anaerobic consumption. The presence of anammox bacteria was confirmed by 16S ribosomal ribonucleic acid gene sequencing. Quantitative polymerase chain reaction revealed a maximum in anammox bacterial abundance at the same water depth where ammonium becomes exhausted. 15 N-labeling experiments indicate that anammox activity within the Lake Lugano RTZ can contribute up to , 30% of total N 2 production. Incubation experiments with various potential electron donorsglucose, acetate, Mn(II), Fe(II), and H 2 S-revealed that N 2 formation was sulfide-dependent and that organotrophic denitrification is only of minor importance for the elimination of fixed N from the Lake Lugano north basin. Maximum potential rates of anammox and chemolithotrophic denitrification were comparatively low but consistent with nutrient fluxes calculated from concentration gradients. This study provides evidence for the coexistence of anammox bacteria and sulfide-dependent denitrifiers in the stratified water column of a lacustrine environment.

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We evaluated the seasonal variation of denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) rates in the sediments and the integrative N (and O) isotopic signatures of dissolved inorganic nitrogen (DIN) compounds in the overlying water column of the monomictic Lake Lugano south basin. Denitrification was the dominant NO { 3 reduction pathway, whereas the contribution of anammox and DNRA to total benthic NO { 3 reduction was , 6% and , 12%, respectively. Sedimentary denitrification rates were highest (up to 57.2 6 16.8 mmol N m 22 h 21 ) during fully oxic bottom water conditions. With the formation of seasonal bottom water anoxia, NO { 3 reduction was partitioned between water column and sedimentary processes. Total benthic NO { 3 reduction rates determined in 15 N-label experiments and sediment-water interface N 2 fluxes as calculated from water column N 2 : Ar gradients revealed that sedimentary denitrification still accounted for , 40% of total N 2 production during bottom water anoxia. The partitioning between water column and sedimentary denitrification was further evaluated by the natural abundance stable N isotope composition of dissolved NO from approximately 7% to 20% and from 2% to 14%, respectively. Using a closed-system (Rayleigh) model, the N and O isotope effects associated with community NO { 3 consumption were 15 e < 13.7% and 18 e < 11.3%, respectively. With the assumptions of a relatively low net N isotope effect associated with sedimentary denitrification (i.e., 15 e sed 5 1.5-3%) vs. a fully expressed biological N isotope fractionation during water column denitrification (i.e., 15 e water 5 20-25%), our results confirm that 36-51% of NO { 3 reduction occurred within the sediment. The general agreement between the indirect (isotopic) approach and the flux and rate measurements suggests that water column nitrate isotope measurements can be used to distinguish between benthic and pelagic denitrification quantitatively.