Biology subjects

Connors, B.

Publications and source records attributed to Connors, B..

6 recordsLinked to original sources

bioRxiv2026

Climate Impacts on Sockeye Salmon Productivity Vary Across Life Stages and Regions

Many Sockeye salmon (Oncorhynchus nerka) populations have declined over recent decades, and climate change is likely to exacerbate these declines through direct and indirect ecological effects. The response to the associated environmental changes is likely to vary among life stages, populations, and regions. Quantitative estimates of climate change driven impacts that account for this variability could fill a critical gap and provide forward-looking insights into how sockeye are expected to respond to future climate-driven change across their lifecycle. To address this need we developed a hierarchical population dynamics model parameterized with juvenile, adult return and spawner abundance data from 13 sockeye salmon populations from Washington State to northern British Columbia. We used a formal causal inference framework that paired salmon abundance data with a suite of environmental covariates hypothesized to represent ecological conditions across the lifecycle. We used the model to estimate population-specific responses to each environmental driver, then combined parameter estimates with projections from down-scaled climate change models to estimate productivity responses to anticipated environmental change. We found that historical sockeye productivity was strongly associated with environmental covariates, which explained more interannual variability in return abundance than spawner abundance in most populations. However, the life stages and specific environmental covariates with the largest impacts differed among populations and regions, often displaying a latitudinal gradient. Increases in coastal ocean temperatures and mixed layer depth generally had negative effects though they varied among regions. Increased freshwater summer rearing and return migration temperatures had weaker but consistently negative effects. Under future climate conditions, projected changes in these environmental covariates are expected to result in substantial declines in productivity across most populations. Sockeye salmon display varying degrees of sensitivity to climate change across life stages, populations, and regions. Effective future management will require explicitly accounting for these life stage and population-specific responses.

ecology↗

bioRxiv2024

Activity-Dependent Ectopic Spiking in Parvalbumin-Expressing Interneurons of the Neocortex

Canonically, action potentials of most mammalian neurons initiate at the axon initial segment and propagate bidirectionally: orthodromically along the distal axon, and retrogradely into the soma and dendrites. Under some circumstances action potentials may initiate ectopically, at sites distal to the axon initial segment, and propagate antidromically along the axon. These ectopic action potentials (EAPs) have been observed in experimental models of seizures and chronic pain, and more rarely in nonpathological forebrain neurons. Here we report that a large majority of parvalbumin-expressing (PV+) interneurons in upper layers of mouse neocortex, from both orbitofrontal and primary somatosensory areas, fire EAPs after sufficient activation of their somata. Somatostatin-expressing interneurons also fire EAPs, though less robustly. Ectopic firing in PV+ cells occurs in varying temporal patterns and can persist for several seconds. PV+ cells evoke strong synaptic inhibition in pyramidal neurons and interneurons and play critical roles in cortical function. Our results suggest that ectopic spiking of PV+ interneurons is common, and may contribute to both normal and pathological network functions of the neocortex. SIGNIFICANCE STATEMENTA form of neuronal firing that emerges in distal axons and terminals - the ectopic action potential (EAP) - has been detected in a few cell populations of the cerebral cortex. Previous investigations of parvalbumin-positive interneurons in neocortex had suggested only a small percentage of cells can fire EAPs. We found that a large fraction of parvalbumin-positive interneurons in the superficial layers of neocortex, including first-order and higher-order areas, can fire EAPs. These results broaden our understanding of the intrinsic firing characteristics of these critically important inhibitory interneurons.

neuroscience↗

bioRxiv2020

Under-oil autonomously regulated oxygen microenvironments for cell culture

Oxygen levels in vivo are autonomously regulated by a supply-demand balance, which can be altered in disease states. However, the oxygen levels of in vitro cell culture systems, particularly microscale cell culture, are typically dominated by either supply or demand. Further, the oxygen microenvironment in these systems are rarely monitored or reported. Here, we present a method to establish and dynamically monitor autonomously regulated oxygen microenvironments (AROM) using an oil overlay in an open microscale cell culture system. Using this method, the oxygen microenvironment is dynamically regulated via a supply-demand balance of the system. We simulate the kinetics of oxygen diffusion in multiliquid-phase microsystems on COMSOL Multiphysics and experimentally validate the method using a variety of cell types including mammalian, fungal and bacterial cells. Finally, we demonstrate the utility of this method to establish a co-culture between primary intestinal epithelial cells and a highly prevalent human gut species Bacteroides uniformis.

bioengineering↗

bioRxiv2020

Design of synthetic human gut microbiome assembly and function

The assembly of microbial communities and functions emerge from a complex and dynamic web of interactions. A major challenge in microbiome engineering is identifying organism configurations with community-level behaviors that achieve a desired function. The number of possible subcommunities scales exponentially with the number of species in a system, creating a vast experimental design space that is challenging to even sparsely traverse. We develop a model-guided experimental design framework for microbial communities and apply this method to explore the functional landscape of the health-relevant metabolite butyrate using a 25-member synthetic human gut microbiome community. Based on limited experimental measurements, our model accurately forecasts community assembly and butyrate production at every possible level of complexity. Our results elucidate key ecological and molecular mechanisms driving butyrate production including inter-species interactions, pH and hydrogen sulfide. Our model-guided iterative approach provides a flexible framework for understanding and predicting community functions for a broad range of applications.

systems biology↗

bioRxiv2020

Prioritizing conservation actions for Pacific salmon in Canada

O_LICurrent investment in conservation is insufficient to adequately protect and recover all ecosystems and species. The challenge of allocating limited funds is acute for Pacific salmon (Oncorhynchus spp.) in Canada, which lack a strategic approach to ensure that resources are spent on actions that would cost-effectively recover diminished populations. C_LIO_LIWe applied the Priority Threat Management framework to prioritize strategies that are most likely to maximize the number of thriving Pacific salmon populations on the Central Coast of British Columbia, Canada. These included 79 genetically, ecologically and spatially distinct population groups called Conservation Units (CUs) for five salmon species. This region has high salmon biodiversity and spans the territories of four First Nations: the Heiltsuk, Nuxalk, Kitasoo/Xaixais and Wuikinuxv. C_LIO_LIUsing structured expert elicitation of Indigenous and other experts, we quantified the estimated benefits, costs and feasibility of implementing 10 strategies. Under a business-as-usual scenario (i.e., no additional investments in salmon conservation or management), experts predicted that only one in four CUs would have >50% chance of achieving a thriving status within 20 years. Limiting future industrial development, which was predicted to safeguard CUs from future declines, was identified as the most cost-effective strategy. Investment in three strategies: 1) removal of artificial barriers to fish migration, 2) watershed protection, and 3) stream restoration - at 11.3M CAD per year - was predicted to result in nearly half (34 of 79) of the CUs having a >60% chance of meeting the conservation objective. C_LIO_LIIf all conservation strategies were implemented, experts estimated a >50% probability of achieving a thriving status for 78 of 79 CUs, at an annual cost of 17.3M CAD. However, even with the implementation of all strategies, most sockeye salmon CUs were unlikely to achieve higher probability targets of reaching the objective. C_LIO_LIPolicy implications: We illustrate how Priority Threat Management can incorporate the perspectives and expertise of Indigenous peoples and other experts to evaluate and prioritize conservation strategies based on their cost, benefit and feasibility. Timely investment in the strategies outlined in this assessment could help safeguard and recover Pacific salmon in this region of Canada. C_LI

ecology↗

bioRxiv2019

Evaluating the consequences of common assumptions in run reconstructions on Pacific-salmon biological status assessments

Information on biological status is essential for designing, implementing, and evaluating management strategies and recovery plans for threatened or exploited species. However, the data required to quantify status are often limited, and it is important to understand how assessments of status may be biased by assumptions in data analysis. For Pacific salmon, biological status assessments based on spawner abundances and spawner-recruitment (SR) analyses often involve "run reconstructions" that impute missing spawner data, expand observed spawner abundance to account for unmonitored streams, assign catch to individual stocks, and quantify age-at-return. Using a stochastic simulation approach, we quantified how common assumptions in run reconstructions biased assessments of biological status based on spawner abundance. We found that status assessments were robust to most common assumptions in run reconstructions, even in the face of declining monitoring coverage, but that overestimating catch tended to increase rates of status misclassification. Our results lend confidence to biological status assessments based on spawner abundances and SR analyses, even in the face of incomplete data.

ecology↗