Interactive Effects of Drought and Fire on Co-Existing Woody and Herbaceous Communities in a Temperate Mesic Grassland

Increased drought and woody encroachment are likely to have substantial and interactive effects on grassland carbon and water cycling in the future. However, we currently lack necessary information to accurately predict grassland responses to drought-by-fire interactions in areas experiencing woody encroachment. A more thorough understanding of these interactive effects on grass-shrub physiology would improve the effectiveness of demographic vegetation models and refine predictions of future changes in grassland ecosystem function. To this end, we constructed passive rainout shelters over mature Cornus drummondii shrubs and co-existing grasses in two fire treatments (1-year and 4-year burn frequency) at the Konza Prairie Biological Station (north-eastern Kansas, USA) that reduced precipitation by 50%. Plant responses to drought and fire were monitored at the leaf-level (gas exchange, predawn and midday water potential, turgor loss point) and the whole-plant level (aboveground biomass). Here, we report results from the 2020 growing season, after three years of treatment. Photosynthetic rates of C. drummondii and Andropogon gerardii, a dominant C4 grass, were lower in drought treatments at the end of the growing season. A. gerardii also exhibited higher photosynthetic rates in the 4-year burn watershed, but C. drummondii rates were not impacted by burn frequency. Predawn and midday leaf water potential for both species, as well as turgor loss point for C. drummondii, were lower in the 4-year burn treatment, indicating increased water stress. This trend was more pronounced in drought shelters for C. drummondii. These results indicate that three years of 50% precipitation reduction has resulted in modest impacts on water stress and gas exchange in both species. Long-term studies of co-existing grasses and shrubs are useful for informing management of woody encroachment during drought and help to identify whether multiple external pressures (drought and fire) are needed to reverse grassland-to-shrubland transitions in temperate mesic grasslands

Survey of dinoflagellate cysts in Barkley Sound, Vancouver Island, Canada

Senior thesis written for Oceanography 445[author abstract] The objective of this study was to examine how groups of dormant, spore-like structures produced by dinoflagellates called ‘cysts’ are distributed in the sediments of an estuary known as Barkley Sound, Vancouver Island, Canada. Samples were collected between 22 January and 3 February 2013 aboard the University of Washington R/V Thomas G. Thompson. Barkley Sound was divided into three areas of interest: Effingham Inlet, Imperial Eagle Channel, and Uchucklesit Inlet. The three regions differed greatly in the number of cysts observed, their diversity, and other characteristics. The number of cysts in Effingham Inlet and Imperial Eagle Channel was greater in less restricted areas and lower in confined areas. The total abundance within Uchucklesit Inlet was greatest in the head and least near the entrance; opposite of the other two regions. Cysts of toxic dinoflagellate genera were found at almost every station in varying concentrations. These differences are related to the unique bathymetry and current patterns of each region.University of Washington School of Oceanograph

Post-Intoxication Inhibition of Botulinum Neurotoxin Serotype A within Neurons by Small-Molecule, Non-Peptidic Inhibitors

Botulinum neurotoxins (BoNTs) comprise seven distinct serotypes that inhibit the release of neurotransmitter across neuromuscular junctions, resulting in potentially fatal flaccid paralysis. BoNT serotype A (BoNT/A), which targets synaptosomal-associated protein of 25kDa (SNAP-25), is particularly long-lived within neurons and requires a longer time for recovery of neuromuscular function. There are currently no treatments available to counteract BoNT/A after it has entered the neuronal cytosol. In this study, we examined the ability of small molecule non-peptidic inhibitors (SMNPIs) to prevent SNAP-25 cleavage post-intoxication of neurons. The progressive cleavage of SNAP-25 observed over 5 h following 1 h BoNT/A intoxication was prevented by addition of SMNPIs. In contrast, anti-BoNT/A neutralizing antibodies that strongly inhibited SNAP-25 cleavage when added during intoxication were completely ineffective when added post-intoxication. Although Bafilomycin A1, which blocks entry of BoNT/A into the cytosol by preventing endosomal acidification, inhibited SNAP-25 cleavage post-intoxication, the degree of inhibition was significantly reduced versus addition both during and after intoxication. Post-intoxication application of SMNPIs, on the other hand, was nearly as effective as application both during and after intoxication. Taken together, the results indicate that competitive SMNPIs of BoNT/A light chain can be effective within neurons post-intoxication

An 1800-year alkenone-based reconstruction of sea surface temperature from the San Lazaro (Soledad) Basin Baja California, Mexico

PCM00-78 box (C) and Kasten (KII-IV) cores were taken in the San Lazaro Basin (SLB) (sometimes referred to as the Soledad Basin) at (25° 10'N, 112° 45'W). The SLB is a suboxic fault-bounded basin 50 km offshore of the Baja California peninsula, with a surface area of ~3000 km2 and a water depth of 540 m. Weak-to-absent bioturbation promotes the preservation of laminated sediments, facilitating high-resolution SST reconstruction. Box core PCM00-78C was stratigraphically tied to Kasten core PCM00-KI via natural Pb decay and reconstructed SST measurements are reported here on a composite depth scale covering all sediment cores. Additional age control is provided by 137Cs and radiocarbon measurements (see manuscript for further details)