Are Southern Resident killer whales on a path to extinction?

Numerous extinctions reveal species tipping points where multiple pressures converge to cause a cascade to demise. This paper examines how multiple pressures impacting Southern Resident Killer Whales (SRKW) could lead to their rapid downward spiral to extinction. The most commonly cited impacts to this population are historically low abundance of chinook salmon prey, vessel disturbance from ships and boats, toxicant loads above established health effects thresholds, and risk of oil spills from increased vessel and rail oil transport. Inbreeding and a heavily skewed male biased sex ratio at birth compound these problems. Lack of prey increases nutritional stress and dependence on fat reserves, while decreasing concentrations of bioactive thyroid hormone (T3). Fat metabolism increases circulating lipophilic toxins, which can further decrease T3 concentrations. Collectively, these impacts appear to increase rates of spontaneous abortion and neonatal loss. They may also lead to immunosuppression with a likely rise in incidence of disease and mortality. Associated population decline inherently increases inbreeding, which can increase male sex ratio bias at birth. Reduced T3 may also affect sex ratio at birth. SRKW seasonal presence in the Salish Sea is declining, attributed to declining prey and increased whale-watch vessels. Breeding events within and between pods are commonly observed during these visits to the inland waters. Their decline in visits may limit opportunities for breeding with a more diverse gene-pool, which could further increase inbreeding and associated potential for male-biased sex ratio bias at birth. Chinook remain at the epicenter of all this, indicating an increase in Chinook salmon abundance to be the single most effective mitigation we can do to recover SRKWs. Salmon are sentinels of ecosystem imbalance spanning from toxic contaminants to habitat destruction. Creative and immediate solutions are essential to expedite the process of recovery and ensure the survival of this iconic species

Performance test of QU-fitting in cosmic magnetism study

QU-fitting is a standard model-fitting method to reconstruct distribution of magnetic fields and polarized intensity along a line of sight (LOS) from an observed polarization spectrum. In this paper, we examine the performance of QU-fitting by simulating observations of two polarized sources located along the same LOS, varying the widths of the sources and the gap between them in Faraday depth space, systematically. Markov Chain Monte Carlo (MCMC) approach is used to obtain the best-fit parameters for a fitting model, and Akaike and Bayesian Information Criteria (AIC and BIC, respectively) are adopted to select the best model from four fitting models. We find that the combination of MCMC and AIC/BIC works fairly well in model selection and estimation of model parameters in the cases where two sources have relatively small widths and a larger gap in Faraday depth space. On the other hand, when two sources have large width in Faraday depth space, MCMC chain tends to be trapped in a local maximum so that AIC/BIC cannot select a correct model. We discuss the causes and the tendency of the failure of QU-fitting and suggest a way to improve it.Comment: 8 pages, 9 figures, submitted to MNRA

The chemical and biological effectiveness of bioretention for preventing sublethal and lethal toxicity in coho embryos exposed episodically to urban stormwater runoff during development

Green stormwater infrastructure (GSI) includes an evolving set of technologies to mitigate the physical and chemical habitat degradation that results from urban runoff entering aquatic ecosystems. Bioretention is a common GSI approach, used, for example in rain gardens, to infiltrate stormwater runoff into soils prior to or instead of discharging into a water body. Initial research has shown that bioretention is biologically effective for preventing most toxicity from urban runoff exposure, but initial trials used fresh bioretention soil media (BSM) with less than 5 repeated treatments. Does bioretention continue to be biologically effective at preventing toxicity over more treatment events? In two concurrent years, coho embryos were fertilized and reared in heath stacks with flow-through well water until hatch. Episodically through development, embryos were exposed to one of several recirculating treatments for 24-48 h; well water, highway runoff, or highway runoff filtered through bioretention. Each filtration event used the same BSM for a total of 25 events across two years of study. Morphometric and molecular measurements of sublethal toxicity were assessed weekly during the final 7 weeks of each year of the study and survival was assessed by the end of each study. Chemical and biological effectiveness of bioretention filtration will be discussed in the context of this study

Assessing the impacts of toxic mixtures over a broad geographic scale: challenges and first steps

Assessing the risks posed by chemical mixtures is a complex process. Ideally, details are available on exposure (e.g. which chemicals and what concentrations) and effects (e.g. mechanisms of action and toxicity data). This can be challenging even for a single location and time such as a lab or field site. Ecological risk assessments often need to cover much larger scales such as an entire watershed or a wide-ranging species. This increase in scale substantially increases the complexity. Thousands of chemicals in use lead to potential environmental mixture exposures, including pesticide runoff and municipal wastewater discharges. At the landscape scale the nature of chemical mixtures will vary across space and time; available monitoring data are inadequate for describing realistic exposure scenarios and effects on aquatic species. Therefore, creative solutions are required to utilize sources of data that are available to identify where and when risk is the greatest. Sources of data are available to develop a less-detailed, but still useful, landscape scale risk assessment for mixtures. These include data on potential use (e.g. pesticide labels) or release (e.g. mapping of NPDES permits) sites, as well as associated land use/cover. For example, the use of crop designations to represent where pesticide use is allowed can be a surrogate of actual use to establish where the greatest potential for exposure occurs. This landscape scale risk assessment for mixtures can establish priority watersheds for monitoring and further study. Similarly, exposure of aquatic species to complex mixtures discharged in wastewater can be related to urban land uses and permit distributions. The goal is to develop a process to prioritize the areas with increased relative risks of exposure to chemical mixtures in aquatic species and identify important data needs necessary for more detailed mixture analyses in the context of a landscape scale risk assessment

Potential for ecological nonlinearities and thresholds to inform Pacific salmon management

AbstractEcology is often governed by nonlinear dynamics. Nonlinear ecological relationships can include thresholds—incremental changes in drivers that provoke disproportionately large ecological responses. Among the species that experience nonlinear and threshold dynamics are Pacific salmon (Oncorhynchus spp.). These culturally, ecologically, and economically significant fishes are in many places declining and management focal points. Often, managers can influence or react to ecological conditions that salmon experience, suggesting that nonlinearities, especially thresholds, may provide opportunities to inform decisions. However, nonlinear dynamics are not always invoked in management decisions involving salmon. Here, we review reported nonlinearities and thresholds in salmon ecology, describe potential applications that scientists and managers could develop to leverage nonlinear dynamics, and offer a path toward decisions that account for ecological nonlinearities and thresholds to improve salmon outcomes. It appears that nonlinear dynamics are not uncommon in salmon ecology and that many management arenas may potentially leverage them to enable more effective or efficient decisions. Indeed, decisions guided by nonlinearities and thresholds may be particularly desirable considering salmon management arenas are often characterized by limited resources and mounting ecological stressors, practical constraints, and conservation challenges. More broadly, many salmon systems are data‐rich and there are an extensive range of ecological contexts in which salmon are sensitive to anthropogenic decisions. Approaches developed to leverage nonlinearities in salmon ecology may serve as examples that may inform analogous approaches in other systems and taxa

Polarity- and Intensity-Independent Modulation of Timing During Delay Eyeblink Conditioning Using Cerebellar Transcranial Direct Current Stimulation

Delay eyeblink conditioning (dEBC) is widely used to assess cerebellar-dependent associative motor learning, including precise timing processes. Transcranial direct current stimulation (tDCS), noninvasive brain stimulation used to indirectly excite and inhibit select brain regions, may be a promising tool for understanding how functional integrity of the cerebellum influences dEBC behavior. The aim of this study was to assess whether tDCS-induced inhibition (cathodal) and excitation (anodal) of the cerebellum differentially impact timing of dEBC. A standard 10-block dEBC paradigm was administered to 102 healthy participants. Participants were randomized to stimulation conditions in a double-blind, between-subjects sham-controlled design. Participants received 20-min active (anodal or cathodal) stimulation at 1.5 mA (n = 20 anodal, n = 22 cathodal) or 2 mA (n = 19 anodal, n = 21 cathodal) or sham stimulation (n = 20) concurrently with dEBC training. Stimulation intensity and polarity effects on percent conditioned responses (CRs) and CR peak and onset latency were examined using repeated-measures analyses of variance. Acquisition of CRs increased over time at a similar rate across sham and all active stimulation groups. CR peak and onset latencies were later, i.e., closer to air puff onset, in all active stimulation groups compared to the sham group. Thus, tDCS facilitated cerebellar-dependent timing of dEBC, irrespective of stimulation intensity and polarity. These findings highlight the feasibility of using tDCS to modify cerebellar-dependent functions and provide further support for cerebellar contributions to human eyeblink conditioning and for exploring therapeutic tDCS interventions for cerebellar dysfunction