ALBERT

Description: A warm anomaly in the upper ocean, colloquially named “the Blob”, appeared in the Gulf of Alaska during the calm winter of 2013-2014, spread across the northern North Pacific (NP) Ocean and shifted eastward and onto the Oregon shelf. At least 14 species of copepods occurred which had never been observed in shelf/slope waters off Oregon, some of which are known to have NP Gyre affinities, indicating that the source waters of the coastal “Blob” were likely of both offshore (from the west) and subtropical/tropical origin. The anomalously warm conditions were reduced during strong upwelling in spring 2015 but returned when upwelling weakened in July 2015 and transitioned to downwelling in fall 2015. The extended period of warm conditions resulted in prolonged effects on the ecosystem off central Oregon, lasting at least through 2016. Impacts to the lower trophic levels were unprecedented and include a novel plankton community composition resulting from increased copepod, diatom and dinoflagellate species richness and increased abundance of dinoflagellates. Additionally, the multi-year warm anomalies were associated with reduced biomass of copepods and euphausiids, high abundance of larvaceans and doliolids (indictors of oligotrophic ocean conditions), and a toxic diatom bloom ( Pseudo-nitzschia ) throughout the California Current in 2015, thereby changing the composition of the food web that is relied upon by many commercially and ecologically important species.

Description: Much of the work investigating sudden changes in streamflow in the U.S. has used only a small subset of all available gage data and has identified only a single change point in each gage's period of record. In this paper, we apply a change point detection and clustering algorithm that uses all U.S. Geological Survey flow gages with near-continuous records, detects multiple change points in annual streamflow, and groups change points into geographic clusters which are not predefined by any political or hydrologic boundaries. We identify 17 spatially distinct change point clusters, 13 of which are related to concurrent changes in precipitation. Several geographic regions display multiple clusters, indicating multiple change points in time. The presence of abrupt changes in streamflow suggests that natural variability in the climate signal may be dominating observed streamflow variations in the last 60 years in many locations in the contiguous U.S.

Description: Aircraft measurements of the ubiquitous marine stratocumulus cloud type, with over 3000 km of in-situ data from the Pacific during the Cloud System Evolution in the Trades (CSET) experiment, show the ability of the Holographic Detector for Clouds (HOLODEC) instrument to smoothly interpolate the small and large droplet data collected with CDP and 2DC instruments. The combined, comprehensive instrument suite reveals a surprisingly large contribution in the pre-drizzle size range of 40-80 μm (transition droplets, or drizzlets), a range typically not measured and assumed to reside in a condensation-to-collision minimum between cloud droplet and drizzle modes. Besides shedding light on the onset of collision coalescence, drizzlets are essential contributors to optical and chemical properties because of a substantial contribution to the total surface area. When adjusted to match spatial resolution of space-borne remote sensing, the missing drizzlets bring in-situ measurements to close agreement with satellite observations.

Description: There remains continued use of non-linear, logistic regression models for predicting water temperature from air temperature. A dominant feature of these non-linear models is an upper bound on river water temperature. This upper bound is often attributed to a large increase in evaporative cooling at high air temperatures, but the exact conditions under which such an increase may occur have not been thoroughly explored. To better understand the appropriateness of the non-linear model for predicting river water temperatures, it is essential to understand the physical basis for the upper bound and when it should and should not be included in the statistical model. This paper applies and validates an energy balance model against eight river systems spread across different climate regions of the U.S. The energy balance model is then used to develop a diagram relating vapor pressure deficit and air temperature to water temperature. With knowledge of future vapor pressure deficit (difference between saturation and actual vapor content in the atmosphere) conditions in a given climate, the diagram can be used to predict the likelihood of an upper bound in the air-water temperature relationship. This investigation offers a fundamental physical explanation of the most appropriate form of statistical models that should be used for predicting future water temperature from air temperature in different geographic regions with different climate conditions. In general, climatic regions that have only a slight increase in vapor pressure deficit with increasing air temperature (typically humid regions) would not be expected to have an upper bound. Conversely, climatic regions in which vapor pressure deficit sharply increases with increasing air temperature (typically arid regions) would be expected to have an upper bound.

Description: We have previously shown that Gs-coupled adenosine receptors (A2a) are primarily involved in adenosine-induced human pulmonary artery endothelial cell (HPAEC) barrier enhancement. However, the downstream events that mediate the strengthening of the endothelial cell (EC) barrier via adenosine signaling are largely unknown. In the current study we tested the overall hypothesis that adenosine-induced Rac1 activation and EC barrier enhancement is mediated by Gs-dependent stimulation of cAMP-dependent Epac1-mediated signaling cascades. Adenoviral transduction of HPAEC with constitutively-active (C/A) Rac1 (V12Rac1) significantly increases transendothelial electrical resistance (TER) reflecting an enhancement of the EC barrier. Conversely, expression of an inactive Rac1 mutant (N17Rac1) decreases TER reflecting a compromised EC barrier. The adenosine-induced increase in TER was accompanied by activation of Rac1, decrease in contractility (MLC dephosphorylation), but not Rho inhibition. Conversely, inhibition of Rac1 activity attenuates adenosine-induced increase in TER. We next examined the role of cAMP-activated Epac1 and its putative downstream targets Rac1, Vav2, Rap1 and Tiam1. Depletion of Epac1 attenuated the adenosine-induced Rac1 activation and the increase in TER. Furthermore, silencing of Rac1 specific guanine nucleotide exchange factors (GEFs), Vav2 and Rap1a expression significantly attenuated adenosine-induced increases in TER and activation of Rac1. Depletion of Rap1b only modestly impacted adenosine-induced increases in TER and Tiam1 depletion had no effect on adenosine-induced Rac1 activation and TER. Together these data strongly suggest that Rac1 activity is required for adenosine-induced EC barrier enhancement and that the activation of Rac1 and ability to strengthen the EC barrier depends, at least in part, on cAMP-dependent Epac1/Vav2/Rap1-mediated signaling. This article is protected by copyright. All rights reserved

Description: We show that distributary channels on river deltas exhibit a mean bifurcation angle that can be understood using theory developed in tributary channel networks. In certain cases, tributary network bifurcation geometries have been demonstrated to be controlled by diffusive groundwater flow feeding incipient bifurcations, producing a characteristic angle of 72 ∘ . We measured 25 unique distributary bifurcations in an experimental delta and 197 bifurcations in 10 natural deltas, yielding a mean angle of 70.4 ∘ ±2.6 ∘ (95% confidence interval) for field-scale deltas and a mean angle of 68.3 ∘ ±8.7 ∘ for the experimental delta, consistent with this theoretical prediction. The bifurcation angle holds for small scales relative to channel width length-scales. Furthermore, the experimental data show that the mean angle is 72 ∘ immediately after bifurcation initiation and remains relatively constant over significant timescales. Although distributary networks do not mirror tributary networks perfectly, the similar control and expression of bifurcation angles suggests that additional morphodynamic insight may be gained from further comparative study.

Description: Hydropower operations optimization subject to environmental constraints is limited by challenges associated with dimensionality and spatial and temporal resolution. The need for high-fidelity hydrodynamic and water quality models within optimization schemes is driven by improved computational capabilities, increased requirements to meet specific points of compliance with greater resolution, and the need to optimize operations of not just single reservoirs but systems of reservoirs. This study describes an important advancement for computing hourly power generation schemes for a hydropower reservoir using high-fidelity models, surrogate modeling techniques, and optimization methods. The predictive power of the high-fidelity hydrodynamic and water quality model CE-QUAL-W2 is successfully emulated by an artificial neural network, then integrated into a genetic algorithm optimization approach to maximize hydropower generation subject to constraints on dam operations and water quality. This methodology is applied to a multipurpose reservoir near Nashville, Tennessee, USA. The model successfully reproduced high-fidelity reservoir information while enabling 6.8 and 6.6 percent increases in hydropower production value relative to actual operations for dissolved oxygen (DO) limits of 5 and 6 mg/L, respectively, while witnessing an expected decrease in power generation at more restrictive DO constraints. Exploration of simultaneous temperature and DO constraints revealed capability to address multiple water quality constraints at specified locations. The reduced computational requirements of the new modeling approach demonstrated an ability to provide decision support for reservoir operations scheduling while maintaining high-fidelity hydrodynamic and water quality information as part of the optimization decision support routines.

Description: Seed-source movement trials using common garden experiments are needed to understand climate, tree (host), and pathogen interactions. Douglas-fir ( Pseudotsuga menziesii var menziesii ) is an important tree species native to western North America influenced by the foliar fungi Phaeocryptopus gaeumannii , a biotroph and causal agent of Swiss needle cast (SNC), and Rhabdocline species, necrotrophs that cause Rhabdocline needle cast. We used the Douglas-fir Seed-Source Movement Trial, a large provenance study of Douglas-fir that consists of populations and test sites chosen to represent the range of climate conditions experienced by Douglas-fir west of the Cascade and northern Sierra Nevada Mountains, USA, to assess disease severity and symptom expression in Douglas-fir in relation to climatic differences between test sites and population sources. Using generalized linear mixed models, probability of disease severity/expression was modeled with respect to the climate variables May through September precipitation (MSP), mean winter temperature (MWT), and continentality. Stark differences in disease expression were observed in trees from different regions, especially in relation to resistance to Rhabdocline spp. and tolerance to P. gaeumannii . There were no major differences across seed-source regions at any particular site in infection levels of P. gaeumannii assessed by fruiting body abundance, yet disease tolerance followed similar geographic patterns as resistance to Rhabdocline spp. Transfers of populations from low to high MSP, and/or cool to warm MWT, increased the probability of moderate to severe Rhabdocline spp. infection and SNC disease symptoms. Our results suggest that local seed sources are adapted to local climate and pathogen pressures and that seed sources from regions with high foliage disease pressure are most resistant/tolerant to those foliage diseases. We also confirm that temperature and precipitation are important epidemiological factors in forest disease and that assisted migration must take into account trophic interactions of trees. Movement of seed sources from dry spring and summer and/or cool winter conditions to mild, mesic environments is likely to lead to increased probability of losses due to these foliage diseases.

Description: Maintenance of the endothelial cell (EC) barrier is critical to vascular homeostasis and a loss of barrier integrity results in increased vascular permeability. While the mechanisms that govern increased EC permeability have been under intense investigation over the past several decades, the processes regulating the preservation/restoration of the EC barrier remain poorly understood. Herein we show that the extracellular purines, adenosine (Ado) and ATPγS can strengthen the barrier function of human lung microvascular EC (HLMVEC). This ability involves protein kinase A (PKA) activation and decreases in myosin light chain 20 (MLC20) phosphorylation secondary to the involvement of MLC phosphatase (MLCP). In contrast to adenosine, ATPγS-induced PKA activation is accompanied by a modest, but significant decrease in cAMP levels supporting the existence of an unconventional cAMP-independent pathway of PKA activation. Furthermore, ATPγS-induced EC barrier strengthening does not involve the Rap guanine nucleotide exchange factor 3 (EPAC1) which is directly activated by cAMP, but is instead dependent upon protein kinase A-anchor protein 2 (AKAP2) expression. We also found that AKAP2 can directly interact with the myosin phosphatase-targeting protein MYPT1 and that depletion of AKAP2 abolished ATPγS-induced increases in transendothelial electrical resistance (TER). Adenosine-induced strengthening of the HLMVEC barrier required the coordinated activation of PKA and EPAC1 in a cAMP-dependent manner. In summary, ATPγS-induced enhancement of the EC barrier is EPAC1-independent and is instead mediated by activation of PKA which is then guided by AKAP2, in a cAMP-independent mechanism, to activate MLCP which dephosphorylates MLC20 resulting in reduced EC contraction and preservation. This article is protected by copyright. All rights reserved

Description: Shells of the marine gastropod Turbo torquatus were sampled from three different locations along the Western Australian coastline, namely Marmion Lagoon (31°S), Rottnest Island (32°S) and Hamelin Bay (34°S). Marmion Lagoon and Rottnest Island have similar sea surface temperature ranges that are ∼1˚C warmer than Hamelin Bay, with all sites influenced by the warm southward flowing Leeuwin Current. The shells were characterized using crystallographic, spectroscopic and geochemical analyses. Shell mineral composition varies between the three sites suggesting the influence of sea surface temperature, oxygen consumption and/or bedrock composition on shell mineralogy and preferential incorporation and/or elemental discrimination of Mg, P and S. Furthermore, T. torquatus was found to exert control over the incorporation of most, if not all, the elements measured here, suggesting strong biological regulation. At all levels of testing the concentrations of Li varied significantly, which indicates that this trace element may not be a suitable environmental proxy. Variation in Sr concentration between sites and between specimens reflects combined environmental and biological controls suggesting that Sr/Ca ratios in T. torquatus cannot be used to estimate sea surface temperature without experimentally accounting for metabolic and growth effects. The mineral composition and microstructure of T. torquatus shells may help identify sea surface temperature variations on geological timescales. These findings support the previously hypothesized involvement of an active selective pathway across the calcifying mantle of T. torquatus for most, if not all, the elements measured here.