Omnivory by planktivores stabilizes plankton dynamics, but may either promote or reduce algal biomass

Classical models of phytoplankton–zooplankton interaction show that with nutrient enrichment such systems may abruptly shift from limit cycles to stable phytoplankton domination due to zooplankton predation by planktivorous fish. Such models assume that planktivorous fish eat only zooplankton, but there are various species of filter-feeding fish that may also feed on phytoplankton. Here, we extend these classical models to systematically explore the effects of omnivory by planktivorous fish. Our analysis indicates that if fish forage on phytoplankton in addition to zooplankton, the alternative attractors predicted by the classical models disappear for all realistic parameter settings, even if omnivorous fish have a strong preference for zooplankton. Our model also shows that the level of fish biomass above which zooplankton collapse should be higher when fish are omnivorous than when fish are zooplanktivorous. We also used the model to explore the potential effects of the now increasingly common practice of stocking lakes with filter-feeding fish to control cyanobacteria. Because omnivorous filter-feeding fish forage on phytoplankton as well as on the main grazers of phytoplankton, the net effect of such fish on the phytoplankton biomass is not obvious. Our model suggests that there may be a unimodal relationship between the biomass of omnivorous filter-feeding fish and the biomass of phytoplankton. This implies that to manage for reductions in phytoplankton biomass, heavy stocking or strong reduction of such fish is bes

Effects of submerged vegetation on water clarity across climates

A positive feedback between submerged vegetation and water clarity forms the backbone of the alternative state theory in shallow lakes. The water clearing effect of aquatic vegetation may be caused by different physical, chemical, and biological mechanisms and has been studied mainly in temperate lakes. Recent work suggests differences in biotic interactions between (sub)tropical and cooler lakes might result in a less pronounced clearing effect in the (sub)tropics. To assess whether the effect of submerged vegetation changes with climate, we sampled 83 lakes over a gradient ranging from the tundra to the tropics in South America. Judged from a comparison of water clarity inside and outside vegetation beds, the vegetation appeared to have a similar positive effect on the water clarity across all climatic regions studied. However, the local clearing effect of vegetation decreased steeply with the contribution of humic substances to the underwater light attenuation. Looking at turbidity on a whole-lake scale, results were more difficult to interpret. Although lakes with abundant vegetation (>30%) were generally clear, sparsely vegetated lakes differed widely in clarity. Overall, the effect of vegetation on water clarity in our lakes appears to be smaller than that found in various Northern hemisphere studies. This might be explained by differences in fish communities and their relation to vegetation. For instance, unlike in Northern hemisphere studies, we find no clear relation between vegetation coverage and fish abundance or their diet preference. High densities of omnivorous fish and coinciding low grazing pressures on phytoplankton in the (sub)tropics may, furthermore, weaken the effect of vegetation on water clarity

Comparative genomics of Enterococcus faecalis from healthy Norwegian infants

<p>Abstract</p> <p>Background</p> <p><it>Enterococcus faecalis</it>, traditionally considered a harmless commensal of the intestinal tract, is now ranked among the leading causes of nosocomial infections. In an attempt to gain insight into the genetic make-up of commensal <it>E. faecalis</it>, we have studied genomic variation in a collection of community-derived <it>E. faecalis </it>isolated from the feces of Norwegian infants.</p> <p>Results</p> <p>The <it>E. faecalis </it>isolates were first sequence typed by multilocus sequence typing (MLST) and characterized with respect to antibiotic resistance and properties associated with virulence. A subset of the isolates was compared to the vancomycin resistant strain <it>E. faecalis </it>V583 (V583) by whole genome microarray comparison (comparative genomic hybridization (CGH)). Several of the putative enterococcal virulence factors were found to be highly prevalent among the commensal baby isolates. The genomic variation as observed by CGH was less between isolates displaying the same MLST sequence type than between isolates belonging to different evolutionary lineages.</p> <p>Conclusion</p> <p>The variations in gene content observed among the investigated commensal <it>E. faecalis </it>is comparable to the genetic variation previously reported among strains of various origins thought to be representative of the major <it>E. faecalis </it>lineages. Previous MLST analysis of <it>E. faecalis </it>have identified so-called high-risk enterococcal clonal complexes (HiRECC), defined as genetically distinct subpopulations, epidemiologically associated with enterococcal infections. The observed correlation between CGH and MLST presented here, may offer a method for the identification of lineage-specific genes, and may therefore add clues on how to distinguish pathogenic from commensal <it>E. faecalis</it>. In this work, information on the core genome of <it>E. faecalis </it>is also substantially extended.</p

Domestic ventilation rates, indoor humidity and dust mite allergens : are our homes causing the asthma pandemic?

This paper is concerned with historical changes in domestic ventilation rates, relative humidity and the associated risk of house dust mite colonization. A controlled trial evaluated allergen and water vapour control measures on the level of house dust mite (HDM) Der p1 allergen and indoor humidity, concurrently with changes in lung function in 54 subjects who completed the protocol. Mechanical heat recovery ventilation units significantly reduced moisture content in the active group, while HDM allergen reservoirs in carpets and beds were reduced by circa 96%. Self reported health status confirmed a significant clinical improvement in the active group. The study can form the basis for assessing minimum winter ventilation rates that can suppress RH below the critical ambient equilibrium humidity of 60% and thus inhibit dust mite colonization and activity in temperate and maritime in' uenced climatic regions

Language differences in qualitative research: is meaning lost in translation?

This article discusses challenges of language differences in qualitative research, when participants and the main researcher have the same non-English native language and the non-English data lead to an English publication. Challenges of translation are discussed from the perspective that interpretation of meaning is the core of qualitative research. As translation is also an interpretive act, meaning may get lost in the translation process. Recommendations are suggested, aiming to contribute to the best possible representation and understanding of the interpreted experiences of the participants and thereby to the validity of qualitative research

An assessment on potential long-term health effects caused by antibiotic resistance marker genes in genetically modified organisms based on antibiotic usage and resistance patterns in Norway.

Source at https://vkm.no/Usage of antibiotics selects for resistant bacteria, resulting in reduced treatment options, and increased morbidity and mortality from microbial infections. Development of resistance in susceptible bacteria can occur through spontaneous mutation or horizontal gene transfer (HGT). Our current understanding of resistance development in bacterial pathogens is more descriptive than predictive in nature. That is, whereas the acquisition or development of new resistance determinants in bacteria can be retrospectively described relatively easily at the molecular, species and geographical distribution levels, the initial horizontal transfer events, the resistance gene donor, and the environmental location and conditions that produced the first generation of the resistant bacteria remain largely unknown. Without this latter knowledge and without a clear understanding of directional selection and genetic drift in natural bacterial populations, it is impossible to predict accurately further resistance development occurring through HGT. Some of the antibiotic resistance marker (ARM) genes used in the production of genetically modified organisms (GMO) encode resistance to antibiotics in clinical and veterinary use. Thus, concerns have been raised that the large-scale release of such genes in commercialized GMOs may increase the rate of, and broaden the locations where, bacteria horizontally acquire resistance genes

The Clumping Transition in Niche Competition: a Robust Critical Phenomenon

We show analytically and numerically that the appearance of lumps and gaps in the distribution of n competing species along a niche axis is a robust phenomenon whenever the finiteness of the niche space is taken into account. In this case depending if the niche width of the species $\sigma$ is above or below a threshold $\sigma_c$, which for large n coincides with 2/n, there are two different regimes. For $\sigma > sigma_c$ the lumpy pattern emerges directly from the dominant eigenvector of the competition matrix because its corresponding eigenvalue becomes negative. For $\sigma </- sigma_c$ the lumpy pattern disappears. Furthermore, this clumping transition exhibits critical slowing down as $\sigma$ is approached from above. We also find that the number of lumps of species vs. $\sigma$ displays a stair-step structure. The positions of these steps are distributed according to a power-law. It is thus straightforward to predict the number of groups that can be packed along a niche axis and it coincides with field measurements for a wide range of the model parameters.Comment: 16 pages, 7 figures; http://iopscience.iop.org/1742-5468/2010/05/P0500

Radiotherapy for patients with ledderhose disease:long-term effects, side effects and patient-rated outcome

BACKGROUND: The purpose of this study was to investigate the long-term effects of radiotherapy for patients with Ledderhose disease. METHODS: Questionnaires were sent to all patients with Ledderhose disease who had been treated with radiotherapy at our centre between 2008 and 2017 and who consented to participate. Radiotherapy was performed with orthovolt or electrons in two separate courses of five daily fractions of 3 Gy. The questionnaires addressed items such as pain from Ledderhose disease (Brief Pain Inventory), quality of life (EURO-QOL-5D-5L), long-term side effects, and patients' levels of satisfaction with the effect of treatment. Descriptive statistics and non-parametric tests were used to analyse the results. RESULTS: A total of 102 feet were irradiated in 67 patients (28 men, 39 women). Radiotherapy resulted in significant pain reduction: the mean pain score prior to radiotherapy, collected retrospectively, was 5.7 and 1.7 at time of assessment (p-value<0.001). The following pain response scores were reported: progressive pain (0%), no change (22%; 22 feet), partial pain response (37%; 38 feet) and complete pain response (absence of pain) (41%; 42 feet). Seventy-eight percent of patients were satisfied with the treatment effect and 57% did not consider radiotherapy burdensome. The scores for societal perspective (0.856) and patients' perspective on quality of life (82.3) were each comparable to the reference values from the Dutch population in the same age category (0.857 and 80.6, respectively). The most commonly reported residual long-term side effect was dryness of the skin (n=10; 15%). CONCLUSION: Radiotherapy for Ledderhose disease results in long-term pain reduction in the majority of patients and has limited side effects. The treatment is well tolerated, patients feel satisfied, and quality of life is comparable to the reference population