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1. Galacto‐Oligosaccharide Supplementation Modulates Pathogen‐Commensal Competition between Streptococcus agalactiae and Streptococcus salivarius

   https://doi.org/10.1002/cbic.202100559  

   Moore, Rebecca E.; Thomas, Harrison C.; Manning, Shannon D.; Gaddy, Jennifer A.; Townsend, Steven D. (November 2021, ChemBioChem)

   Abstract The members of the infant microbiome are governed by feeding method (breastmilk vs. formula). Regardless of the source of nutrition, a competitive growth advantage can be provided to commensals through prebiotics – either human milk oligosaccharides (HMOs) or plant oligosaccharides that are supplemented into formula. To characterize how prebiotics modulate commensal – pathogen interactions, we have designed and studied a minimal microbiome where a pathogen,Streptococcus agalactiaeengages with a commensal,Streptococcus salivarius. We discovered that whileS. agalactiaesuppresses the growth ofS. salivariusvia increased lactic acid production, galacto‐oligosaccharides (GOS) supplementation reverses the effect. This result has major implications in characterizing how single species survive in the gut, what niche they occupy, and how they engage with other community members. 

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2. Light fluctuations are key in modulating plankton trophic dynamics and their impact on primary production

   https://doi.org/10.1002/lol2.10156  

   Morison, Françoise; Franzè, Gayantonia; Harvey, Elizabeth; Menden‐Deuer, Susanne (April 2020, Limnology and Oceanography Letters)

   Abstract Surface‐ocean mixing creates dynamic light environments with predictable effects on phytoplankton growth but unknown consequences for predation. We investigated how variations in average mixed‐layer (ML) irradiance shaped plankton trophic dynamics by incubating a Northwest‐Atlantic plankton community for 4 days at high (H) and low (L) light, followed by exposure to either sustained or reversed light intensities. In deep‐ML (sustained L), phytoplankton biomass declined (μ= −0.2 ± 0.08 d⁻¹) and grazing was absent. In shallow‐ML (sustained H), growth exceeded grazing (μ= 0.46 ± 0.07 d⁻¹;g= 0.32 ± 0.04 d⁻¹). In rapidly changing ML‐conditions simulated by switching light‐availability, growth and grazing responded on different timescales. During rapid ML‐shoaling (L to H),μimmediately increased (0.23 ± 0.01 d⁻¹) with no change in grazing. During rapid ML‐deepening (H to L),μimmediately decreased (0.02 ± 0.09 d⁻¹), whereas grazing remained high (g= 0.38 ± 0.05 d⁻¹). Predictable rate responses of phytoplankton growth (rapid) vs. grazing (delayed) to measurable light variability can provide insights into predator‐prey processes and their effects on spatio‐temporal dynamics of phytoplankton biomass. 

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3. Negative allometry of leaf xylem conduit diameter and double‐wall thickness: implications for implosion safety

   https://doi.org/10.1111/nph.19771  

   Matos, Ilaine Silveira; McDonough, Samantha; Johnson, Breanna Carrillo; Kalantar, Diana; Rohde, James; Sahu, Roshni; Wang, Joyce; Fontao, Adrian; To, Jason; Carlos, Sonoma; et al (June 2024, New Phytologist)

   Summary Xylem conduits have lignified walls to resist crushing pressures. The thicker the double‐wall (T) relative to its diameter (D), the greater the implosion safety. Having safer conduits may incur higher costs and reduced flow, while having less resistant xylem may lead to catastrophic collapse under drought. Although recent studies have shown that conduit implosion commonly occurs in leaves, little is known about how leaf xylem scalesTvsDto trade off safety, flow efficiency, mechanical support, and cost.We measuredTandDin > 7000 conduits of 122 species to investigate howTvsDscaling varies across clades, habitats, growth forms, leaf, and vein sizes.As conduits become wider, their double‐cell walls become proportionally thinner, resulting in a negative allometry betweenTandD. That is, narrower conduits, which are usually subjected to more negative pressures, are proportionally safer than wider ones. Higher implosion safety (i.e. higherT/Dratios) was found in asterids, arid habitats, shrubs, small leaves, and minor veins.Despite the strong allometry, implosion safety does not clearly trade off with other measured leaf functions, suggesting that implosion safety at whole‐leaf level cannot be easily predicted solely by individual conduits' anatomy. 

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4. Vp / Vs Ratio of Incoming Sediments Off Cascadia Subduction Zone From Analysis of Controlled‐Source Multicomponent OBS Records

   https://doi.org/10.1029/2019JB019239  

   Zhu, Jian; Canales, J. Pablo; Han, Shuoshuo; Carbotte, Suzanne M.; Arnulf, Adrien; Nedimović, Mladen R. (June 2020, Journal of Geophysical Research: Solid Earth)

   Abstract P‐to‐S‐converted waves observed in controlled‐source multicomponent ocean bottom seismometer (OBS) records were used to derive theVp/Vsstructure of Cascadia Basin sediments. We usedP‐to‐Swaves converted at the basement to derive an empirical function describing the averageVp/Vsof Cascadia sediments as a function of sediment thickness. We derived one‐dimensional intervalVp/Vsfunctions from semblance velocity analysis ofS‐converted intrasediment and basement reflections, which we used to define an empiricalVp/Vsversus burial depth compaction trend. We find that seaward from the Cascadia deformation front,Vp/Vsstructure offshore northern Oregon and Washington shows little variability along strike, while the structure of incoming sediments offshore central Oregon is more heterogeneous and includes intermediate‐to‐deep sediment layers of anomalously elevatedVp/Vs. These zones with elevatedVp/Vsare likely due to elevated pore fluid pressures, although layers of high sand content intercalated within a more clayey sedimentary sequence, and/or a higher content of coarser‐grained clay minerals relative to finer‐grained smectite could be contributing factors. We find that the proto‐décollement offshore central Oregon develops within the incoming sediments at a low‐permeability boundary that traps fluids in a stratigraphic level where fluid overpressure exceeds 50% of the differential pressure between the hydrostatic pressure and the lithostatic pressure. Incoming sediments with the highest estimated fluid overpressures occur offshore central Oregon where deformation of the accretionary prism is seaward vergent. Conversely, landward vergence offshore northern Oregon and Washington correlates with more moderate pore pressures and laterally homogeneousVp/Vsfunctions of Cascadia Basin sediments. 

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5. Impact of censusing and research on wildlife populations

   https://doi.org/10.1111/csp2.264  

   Kilpatrick, A. Marm; Hoyt, Joseph R.; King, R. Andrew; Kaarakka, Heather M.; Redell, Jennifer A.; White, J. Paul; Langwig, Kate E. (October 2020, Conservation Science and Practice)

   Abstract Population monitoring and research are essential for conserving wildlife, but these activities may directly impact the populations under study. These activities are often restricted to minimize disturbance, and impacts must be weighed against knowledge gained. However, few studies have quantified the effects of research or census‐related visitation frequency on populations, and low visitation rates have been hypothesized to have little effect. Hibernating bats have been hypothesized to be especially sensitive to visitation because they have limited energetic stores to survive winter, and disturbance may partly deplete these stores. We examined the effect of site visitation frequency on population growth rates of three species of hibernating bats, little brown bats (Myotis lucifugus), Indiana bats (Myotis sodalis) and tri‐colored bats (Perimyotis subflavus), both before and after detection of the disease white‐nose syndrome. We found no evidence that more frequent visits decreased population growth rates for any of these species. Estimated coefficients were either the opposite sign as hypothesized (population growth rates increased with visitation frequency) or were very small (difference in population growth rates 0.067% [SE 2.5%]–1.8% [SE 9.8%]) relative to spatial and temporal variation (5.9–32%). In contrast, white‐nose syndrome impacts on population growth rates were easily detected and well‐characterized statistically (effect sizes 4.4–8.0; severe population declines occurred in the second and third years after pathogen detection) indicating that we had sufficient power to detect effects. These results indicate that visitation frequency (forM. sodalis:annual vs. semi‐annual counts; forM. lucifugusandP. subflavus:1–3 three research visits per year) had undetectable impacts on bat population growth rates both with and without the additional stress of an emerging infectious disease. Knowledge gained from censuses and research may outweigh disturbance due to human visitation if it can be used to understand and conserve the species. 

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