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We combine sea level records and repeat lidar surveys at 8 sites in the United Kingdom and the United States to explore controls on marsh accretion. We compare marsh elevations relative to sea level as well as lidar-derived marsh accretion rates to simple 0-dimensional settling simulations in order to explore constraints on suspended sediment concentration and particle size.We find that the marsh platforms examined occupy a narrow range of elevations in the upper tidal frame, situated between Mean High Tide $MHT$ and the Observed Highest High Tide $OHHT$. Under sinusoidal tidal forcing, common in marsh accretion models, marshes at these elevations are never inundated, highlighting the inadequacy of sinusoidal forcing in numerical models of salt marshes.Forcing the model with year-long tidal records, deposition rates follow hyperbolic contour lines when expressed as a function of sediment concentration and median grain size.We also observe that when using a median sediment grain size $D_{50} = 50 \ \mu m$ and sediment concentrations derived from satellite data, modeled deposition rates are much lower than when using field data.We find that the deposition of coarse, concentrated sediment is necessary for platforms in the upper tidal frame to withstand sea level rise, suggesting a strong dependance on infrequent high-deposition events.This is particularly true for marshes that are very high in the tidal frame, making accretion increasingly storm-driven as marsh platforms gain elevation.Finally, we reflect on the capacity of marshes to regenerate after erosion events within a context of changing sediment supply conditions.

Background: Several bacterial taxa that are consistently enriched in the gut microbiome of CRC cases are also found in the oral cavity. They exhibit phenotypic traits such as adherence to host epithelial cells, mucus degradation, and biofilm formation, which promote bacterial survival in the colon and may play a role in both oral disease and colorectal carcinogenesis by stimulating an inflammatory response. We evaluated the effect of a 6-week aspirin intervention on the relative abundance of oral bacterial taxa in a randomized placebo-controlled trial. Methods: Fifty healthy subjects, 50-75 years old, were randomized to receive either aspirin (N=30) or placebo (N=20) for 6 weeks. Oral samples were collected at baseline and after treatment (6 weeks) and amplicon sequencing of the V4 region of the 16S rRNA gene was done using Illumina MiSeq technology. The data were analyzed using the standard DADA2 workflow. We used linear regression analysis, PERMANOVA, and negative binomial regressions (DESeq2 package) to assess the association between intervention assignment (aspirin vs. placebo) and α-diversity, β-diversity, and fold change in specific taxa, after adjustment for age, gender, and BMI at baseline and postintervention. Intervention assignment was hypothesized to influence the following bacterial taxa a priori: Fusobacterium, Porphyromonas, Prevotella, Gemella, Neisseria, Streptococcus, Haemophilus, Campylobacter, Veillonella, Actinomyces based on previous studies. We estimated the association between aspirin use and the changes in the relative abundance of the specified taxa from pre- to post-treatment (baseline to week 6) using a mixed-effect regression model (lme4 package) with a binomial distribution in which the log of odds ratio (β estimate) for the interaction term compared aspirin to placebo intervention for post- versus pretreatment. Results: Aspirin treatment was not associated with α- or β- diversity at baseline or postintervention. However, the change in relative abundance of 8 out of the 10 prespecified taxa over time differed between the aspirin and placebo groups. In the aspirin group, there were greater increases in the relative abundances of Neisseria, Streptococcus, Actinomyces, and greater decreases in the relative abundance of Prevotella, Veillonella, Fusobacterium, and Porphyromonas. Conclusions: These preliminary findings suggest that aspirin may change the relative abundance of oral taxa associated with oral dysbiosis or CRC. Further studies are needed to understand the impact that the duration and dosage of the aspirin intervention may have on the oral microbiome. Citation Format: Guillaume C. Chinedu, Christopher M. Staley, Ryan T. Demmer, Shaukat Aasma, Tim R. Church, Anna E. Prizment. Effects of aspirin intervention on health and disease-associated oral bacterial taxa [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr A04.

Salt marshes filter pollutants, protect coastlines against storm surges, and sequester carbon, yet are under threat from sea level rise and anthropogenic modification. The sustained existence of the salt marsh ecosystem depends on the topographic evolution of marsh platforms. Quantifying marsh platform topography is vital for improving the management of these valuable landscapes. The determination of platform boundaries currently relies on supervised classification methods requiring near-infrared data to detect vegetation, or demands labour-intensive field surveys and digitisation. We propose a novel, unsupervised method to reproducibly isolate salt marsh scarps and platforms from a digital elevation model (DEM), referred to as Topographic Identification of Platforms (TIP). Field observations and numerical models show that salt marshes mature into subhorizontal platforms delineated by subvertical scarps. Based on this premise, we identify scarps as lines of local maxima on a slope raster, then fill landmasses from the scarps upward, thus isolating mature marsh platforms. We test the TIP method using lidar-derived DEMs from six salt marshes in England with varying tidal ranges and geometries, for which topographic platforms were manually isolated from tidal flats. Agreement between manual and unsupervised classification exceeds 94% for DEM resolutions of 1 m, with all but one site maintaining an accuracy superior to 90% for resolutions up to 3 m. For resolutions of 1 m, platforms detected with the TIP method are comparable in surface area to digitised platforms and have similar elevation distributions. We also find that our method allows for the accurate detection of local block failures as small as 3 times the DEM resolution. Detailed inspection reveals that although tidal creeks were digitised as part of the marsh platform, unsupervised classification categorises them as part of the tidal flat, causing an increase in false negatives and overall platform perimeter. This suggests our method may benefit from combination with existing creek detection algorithms. Fallen blocks and high tidal flat portions, associated with potential pioneer zones, can also lead to differences between our method and supervised mapping. Although pioneer zones prove difficult to classify using a topographic method, we suggest that these transition areas should be considered when analysing erosion and accretion processes, particularly in the case of incipient marsh platforms. Ultimately, we have shown that unsupervised classification of marsh platforms from high-resolution topography is possible and sufficient to monitor and analyse topographic evolution., Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe, 936

This article gives a brief outline of the life of Sergio Salbany (1941–2005) and of his mathematical career, coupled with his social outreach and political activity in South Africa until 1980, in Zimbabwe 1981–1992, in Botswana 1993–1997, and finally again in South Africa 1997–2005. We include a list of his mathematical publications. Salbany was best known for his research in the area of asymmetric topology, comprising topics such as bitopological spaces, quasi-uniform spaces, ordered spaces and quasi-pseudometric spaces. His publications in this area were essentially the first that explicitly described the functors that served to clarify the structure and aims of the then novel theory.