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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Incidence and predictors of tuberculosis among children receiving antiretroviral therapy in the Wolaita Zone: A retrospective cohort study

Tuberculosis is the leading cause of morbidity and mortality among children living with the human immunodeficiency virus (HIV), mainly in sub-Saharan Africa, including Ethiopia. Tuberculosis remains a significant health concern for HIV-positive children in Ethiopia. There is a paucity of data on the incidence and predictors of tuberculosis among children living with HIV on antiretroviral therapy in the Wolaita zone. Hence, this study aimed to assess the incidence and predictors of tuberculosis among children living with HIV on antiretroviral therapy in the Wolaita zone between January 2010 to December 2020. A retrospective cohort study was conducted among 389 children receiving antiretroviral therapy in Wolaita zone health facilities between January 2010 to December 2020. The checklist was adapted from the standardized antiretroviral treatment (ART) follow-up form currently used by the institutions’ ART clinics. The Kaplan-Meier survival function and Log-rank were used to estimate the survival for each categorical variable to compare the survival between different exposure groups. Both bivariable and multivariable parametric survival Gompertz models were fitted to identify predictors of tuberculosis among HIV-positive children. The association was summarized using an adjusted hazard ratio (AHR), and statistical significance was declared at 95% CI and p-value < 0.05. The goodness of the model fit was assessed using a Cox-Snell residual plot. The incidence rate of tuberculosis among children living with HIV was 3.5 (95% CI 2.7–4.5) per 100 child years. World Health Organization clinical stage III or IV (AHR = 2.31, 95% CI [1.26, 4.22]), hemoglobin level <10 g/dL (AHR = 2.87, 95% CI [1.51, 5.45]), fair or poor ART adherence (AHR = 4.4, 95% CI[2.18, 9.05]), underweight (AHR = 2.55, 95% CI [1.45, 4.51]), age >10 years (AHR = 3.62; 95% CI [1.29, 10.0]), and cotrimoxazole preventive therapy (AHR = 0.23; 95% CI [0.08, 0.60]) were among the independent predictors of TB occurrence. The incidence of tuberculosis among children on ART was high. HIV-positive children presenting with advanced disease staging (III and IV), anemia, “fair” and “poor” ART adherence, underweight, age above ten years, and not receiving cotrimoxazole preventive therapy were at higher risk of TB. Therefore, counseling on ART adherence, early diagnosis, and prompt treatment of anemia and malnutrition are recommended to avert tuberculosis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Development of Readily Available & Robust High Heat Flux Gardon Gauges

Concentrated solar power (CSP) technologies deliver concentrated solar energy as a heat source to industrial processes, power generation cycles, and chemical cycles. CSP systems require accurate and reliable high flux measurements, and next generation CSP systems will require flux measurement up to 1000 W/cm2. Existing flux measurement devices do not comprehensively meet the flux rating, cycle life, cost, and lead-time needs of stakeholders, necessitating the development of an improved flux sensor. In this study, Sandia National Laboratories (SNL) partnered with Hukseflux Thermal Sensors to develop a low-cost, short lead-time, and robust flux sensor rated to 250 W/cm2. Three prototype circular foil gauge designs were assessed for performance at the National Solar Thermal Test Facility (NSTTF) at SNL. Each gauge design measured flux up to 250 W/cm2 with <5% measurement error. Following baseline error quantification, gauges were exposed to flux above 500 W/cm2 to assess gauge failure mechanisms. Gauges physically survived >500 W/cm2 flux exposure, but measurement error was found to increase after foil coatings reached 400 °C. The results of this study suggest that coating optical properties change at excessive temperatures and that foil coating temperature, rather than heat flux level, dictates the acceptable gauge measurement range.

McLaughlin, Luke (ORCID:0000000303711310)↗
DOE OSTI2023

CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies

Galaxy formation and evolution are regulated by the feedback from galactic winds. Absorption lines provide the most widely available probe of winds. However, since most data only provide information integrated along the line of sight, they do not directly constrain the radial structure of the outflows. In this paper, we present a method to directly measure the gas electron density in outflows (n e ), which in turn yields estimates of outflow cloud properties (e.g., density, volume filling factor, and sizes/masses). We also estimate the distance (r n ) from the starburst at which the observed densities are found. We focus on 22 local star-forming galaxies primarily from the COS Legacy Archive Spectroscopic SurveY (CLASSY). In half of them, we detect absorption lines from fine-structure excited transitions of Si $\tiny{II}$ (i.e., Si $\tiny{II}$ * ). We determine n e from relative column densities of Si $\tiny{II}$ and Si $\tiny{II}$ * , given Si $\tiny{II}$ * originates from collisional excitation by free electrons. We find that the derived n e correlates well with the galaxy's star formation rate per unit area. From photoionization models or assuming the outflow is in pressure equilibrium with the wind fluid, we get r n ~ 1–2r * or ~5r * , respectively, where r * is the starburst radius. Based on comparisons to theoretical models of multiphase outflows, nearly all of the outflows have cloud sizes large enough for the clouds to survive their interaction with the hot wind fluid. Most of these measurements are the first ever for galactic winds detected in absorption lines and, thus, will provide important constraints for future models of galactic winds.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Development of pebble-based extruded carbon rods for extreme plasma heat flux environments

This work presents first experiments toward the development of continuously renewable (extrudable) pebble-based carbon rods for use as plasma-facing components in extreme steady-state plasma flux environments. The primary envisioned application of this work is a first wall that can survive long-term in future magnetic fusion power reactors while also improving recovery of the reactor fuel (tritium and deuterium atoms). Bench tests applying extreme steady-state front-surface heat loads of up to 50 MW/m 2 are presented. Continuous pebble rod front-surface recession and intact pebble recovery are successfully demonstrated, at a rate of order 0.2 cm/s. Numerical simulations of the pebble rod front-surface recession are able to match observations reasonably well, indicating that the recession mechanism can be understood as occurring due to pebble thermal expansion and resulting shock and cracking of the inter-pebble binder. Tests of the pebble rod extrusion demonstrate that friction between the rods and the stainless-steel extrusion channel is tolerably low (<50 N for the expected channel length) over a wide range of temperatures. Front-surface outgassing rates below 1000 Torr L/s/m 2 are achieved, believed to be sufficiently low for use in magnetic fusion reactors. In conclusion, initial parametric scans over pebble rod size and binder fraction to vary front-surface recession rates are presented.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Evolutionary consequences of nascent multicellular life cycles

A key step in the evolutionary transition to multicellularity is the origin of multicellular groups as biological individuals capable of adaptation. Comparative work, supported by theory, suggests clonal development should facilitate this transition, although this hypothesis has never been tested in a single model system. We evolved 20 replicate populations of otherwise isogenic clonally reproducing ‘snowflake’ yeast (Δace2/∆ace2) and aggregative ‘floc’ yeast (GAL1p::FLO1 /GAL1p::FLO1) with daily selection for rapid growth in liquid media, which favors faster cell division, followed by selection for rapid sedimentation, which favors larger multicellular groups. While both genotypes adapted to this regime, growing faster and having higher survival during the group-selection phase, there was a stark difference in evolutionary dynamics. Aggregative floc yeast obtained nearly all their increased fitness from faster growth, not improved group survival; indicating that selection acted primarily at the level of cells. In contrast, clonal snowflake yeast mainly benefited from higher group-dependent fitness, indicating a shift in the level of Darwinian individuality from cells to groups. Through genome sequencing and mathematical modeling, we show that the genetic bottlenecks in a clonal life cycle also drive much higher rates of genetic drift—a result with complex implications for this evolutionary transition. Our results highlight the central role that early multicellular life cycles play in the process of multicellular adaptation.

Life Sciences & Biomedicine - Other Topics↗
DOE OSTI2021

Diol isomer revealed as a source of methyl ketene from propionic acid unimolecular decomposition

Carboxylic acids are important combustion intermediates, especially regarding the combustion of oxygenates such as ethyl esters. The purpose of this study is to discern the unimolecular decomposition pathways of one such carboxylic acid, propionic acid, using microreactor flow experiments with line-tunable photoionization mass spectrometry and infrared spectroscopy, along with high-level electronic structure calculations (CCSD(T)/cc-pV∞Z//M06-2X/cc-pVTZ level of theory) and master equation theory. Here, microreactor experiments were performed at 300–1500 K, pressures decreasing from roughly 300 Torr to vacuum pressure, and around 100 μs residence times. Primary products are methyl ketene, ketene, ethylene, and methyl radical. Theory suggests the two lowest energy bond fissions are active at these conditions and responsible for the production of ketene, methyl radical, and some ethylene. Importantly, theory revealed the significance of the isomerization of propionic acid to propene-1,1-diol, and the subsequent dehydrogenation reaction of the diol as an alternative explanation for the unimolecular formation of methyl ketene. This is predicted to be the dominant thermal decomposition pathway at lower temperatures (up to ~850 K). Line-tunable VUV photons allowed for isomer resolution of the products and showed no evidence of the diol of propionic acid surviving until detection, suggesting propene-1,1-diol decomposes either to methyl ketene and water rapidly, fragments upon ionization to a distonic ion inseparable from methyl ketene through our detection methods, or never stabilizes as propionic acid well-skips directly to methyl ketene. Infrared spectroscopy showed no evidence of the decarboxylation of propionic acid at these conditions. Updated rate constants and branching ratios for propionic acid decomposition are calculated and provided for future modeling studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

eCoral: How Electrolysis Could Restore Seawater Conditions Ideal for Coral Reefs

Coral reefs suffer from climate change, including long-term ocean acidification (OA) and warming and short-term bleaching, tropical storms, and pollution events, all of which are increasing in frequency and severity. It is urgent yet unclear how to intervene to save coral reefs. Reversal of the ocean pH to preindustrial levels could restore coral reefs to their preindustrial growth rates; however, strategies to reverse OA on environmentally relevant scales have not been established. Anecdotally, electrolysis seems to help coral reefs recover from acidification and short-term events, but few uncontrolled studies support such claims. Here, using two independent continuum simulation approaches (COMSOL and CrunchFlow), we show the effect of electrolysis on seawater chemistry relevant to coral reef survival and growth. We conclude that near the negative electrodes, the cathodes, seawater pH, supersaturation, and carbonate concentration all increase significantly. Electrolysis of seawater, therefore, can be used to restore preindustrial ocean conditions locally to save coral reefs, an approach termed eCoral here. We anticipate these simulation results to be the starting point for controlled experiments to test whether seawater electrolysis promotes coral reef growth and restoration, as these simulations predict.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Time as a microbial resource

Microbes need resources for energy and cellular building material. They also need access to clement conditions with liquid water and a cellular damage rate that is lower than repair. When deprived of resources and clement conditions, microbes often enter some form of dormancy (e.g., by ceasing cell division, slowing metabolic rate, or forming an endospore) until they can grow again. For example, at night, phototrophs wait for the sun to return. In winter, soil microbes wait for warmer temperatures. Microbes that cause diseases like tuberculosis can stay dormant for years, waiting for the cessation of antibiotic or immune system bombardment. But what about longer timescales? Unlike multicellular life, microbes survive in an extremely broad range of conditions and can access an amazing variety of resources to maintain cellular functions in the absence of cell division. This means that they have the potential to be dormant for much longer than a few months or years. There is no theoretical reason microbes cannot survive on maintenance energy for hundreds or thousands of years, or longer, with little to no cell proliferation. Here, given this lack of theoretical constraints on the length of microbial dormancy intervals, two questions arise, (i) is there evidence for the existence of organisms experiencing very long dormancies? And (ii) what could be the advantages of such long wait times?

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Stochastic Microgrid Scheduling With Chance‐Constrained Resilience Consideration

Traditionally, it is assumed that microgrids transition seamlessly from grid‐connected operation to islanded mode in the event of sudden main grid outages. In reality, the islanding process, especially unintentional islanding, is rarely seamless. Instead, it is subject to voltage and frequency fluctuations caused by the instantaneous disconnection of the point of common coupling (PCC) switch, variations in loads and renewable generation output and even the protection tripping of distributed energy resources (DERs). To mitigate these fluctuations and facilitate a smooth islanding process, we propose a stochastic microgrid scheduling model that incorporates chance‐constrained resilience measures. Specifically, the resilience measure is defined as the probability of successful islanding (PSI), that is, the probability that a microgrid can mitigate the generation‐demand imbalance caused by the disconnection of the PCC switch, variations in load and renewable generation and DER tripping. This measure is modelled using chance constraints. Unlike existing reliability and resilience indices, which typically neglect the possibility of microgrid/DER failure under extreme events and assume their survival while primarily focussing on reducing impact duration or magnitude, the proposed PSI‐based framework explicitly addresses microgrid and DER survival during the islanding transition. The formulated nonlinear chance constraints are approximated using a multiinterval approach and equivalently represented as a mixed‐integer linear programming (MILP) formulation. Case study results validate the proposed method, showing that the PSI estimation error is reduced to less than 8%, compared to approximately 28% with existing methods. Various sensitivity analyses on the DER tripping rate and PSI settings were performed to validate the robustness of the proposed method. In particular, the necessity of accounting for DER tripping in the PSI calculation was demonstrated.

chance constrained optimization↗
DOE OSTI2023

Spectra and characteristics of somatic mutations induced by ionizing radiation in hematopoietic stem cells

Spectra and frequencies of spontaneous and X-ray-induced somatic mutations were revealed with mouse long-term hematopoietic stem cells (LT-HSCs) by whole-genome sequencing of clonal cell populations propagated in vitro from single isolated LT-HSCs. SNVs and small indels were the most common types of somatic mutations, and increased up to twofold to threefold by whole-body X-irradiation. Base substitution patterns in the SNVs suggested a role of reactive oxygen species in radiation mutagenesis, and signature analysis of single base substitutions (SBS) revealed a dose-dependent increase of SBS40. Most of spontaneous small deletions were shrinkage of tandem repeats, and X-irradiation specifically induced small deletions out of tandem repeats (non-repeat deletions). Presence of microhomology sequences in non-repeat deletions suggested involvement of microhomology mediated end-joining repair mechanisms as well as nonhomologous end-joining in radiation-induced DNA damages. We also identified multisite mutations and structural variants (SV), i.e., large indels, inversions, reciprocal translocations, and complex variants. The radiation-specificity of each mutation type was evaluated from the spontaneous mutation rate and the per-Gy mutation rate estimated by linear regression, and was highest with non-repeat deletions without microhomology, followed by those with microhomology, SV except retroelement insertions, and multisite mutations; these types were thus revealed as mutational signatures of ionizing radiation. Further analysis of somatic mutations in multiple LT-HSCs indicated that large fractions of postirradiation LT-HSCs originated from single LT-HSCs that survived the irradiation and then expanded in vivo to confer marked clonality to the entire hematopoietic system, with varying clonal expansion and dynamics depending on radiation dose and fractionation.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2023

Ionization detail parameters and cluster dose: a mathematical model for selection of nanodosimetric quantities for use in treatment planning in charged particle radiotherapy

Abstract Objective . To propose a mathematical model for applying ionization detail (ID), the detailed spatial distribution of ionization along a particle track, to proton and ion beam radiotherapy treatment planning (RTP). Approach . Our model provides for selection of preferred ID parameters ( I p ) for RTP, that associate closest to biological effects. Cluster dose is proposed to bridge the large gap between nanoscopic I p and macroscopic RTP. Selection of I p is demonstrated using published cell survival measurements for protons through argon, comparing results for nineteen I p : N k , k = 2, 3, …, 10, the number of ionizations in clusters of k or more per particle, and F k , k = 1, 2, …, 10, the number of clusters of k or more per particle. We then describe application of the model to ID-based RTP and propose a path to clinical translation. Main results . The preferred I p were N 4 and F 5 for aerobic cells, N 5 and F 7 for hypoxic cells. Significant differences were found in cell survival for beams having the same LET or the preferred N k . Conversely, there was no significant difference for F 5 for aerobic cells and F 7 for hypoxic cells, regardless of ion beam atomic number or energy. Further, cells irradiated with the same cluster dose for these I p had the same cell survival. Based on these preliminary results and other compelling results in nanodosimetry, it is reasonable to assert that I p exist that are more closely associated with biological effects than current LET-based approaches and microdosimetric RBE-based models used in particle RTP. However, more biological variables such as cell line and cycle phase, as well as ion beam pulse structure and rate still need investigation. Significance . Our model provides a practical means to select preferred I p from radiobiological data, and to convert I p to the macroscopic cluster dose for particle RTP.

Engineering↗
DOE OSTI2022

Hanford Reach Fall Chinook Salmon Productivity Analysis, Brood Years 1975–2016

Updating the Hanford Reach fall Chinook salmon productivity analysis to include seven additional years of data (BY 2010–2016), including three years of record escapements (>150,000 adults), reaffirmed the highly productive nature of this population and the positive effect of flow fluctuation constraints as implemented at Priest Rapids Dam by the VBSA and HRFCPP. The addition of several years of high escapements also revealed that competition among juveniles (and not spawning habitat limitations) is likely the mechanism driving density dependence in the Hanford Reach. The addition of the high escapement brood years also provided evidence for the high recruitment capacity of the population. As such, the WDFW may consider increasing the maximum escapement goal from 42,000 adults to 49,000 adults, which would be more in-line with SMSY as estimated from this update. Given the in-river protections that are in place as part of the HRFCPP, ocean conditions appear to be the primary factor controlling adult production. Therefore, the success of any additional management actions taken in freshwater are likely to be dependent on survival in the ocean. As such, the most effective management actions may be those that limit juvenile competition and density dependent growth effects in the Hanford Reach. Limiting competition would be expected to increase growth, resulting in larger smolts that would be less likely to suffer size-dependent mortality in the marine environment, even during years of poor ocean conditions. Increasing terminal harvest rates when high escapements are anticipated (from downstream dam counts) is one management option that could help to curtail juvenile competition.

Harnish, Ryan A.↗
DOE OSTI2022

Clump survival and migration in VDI galaxies: an analytical model versus simulations and observations

ABSTRACT We address the nature of the giant clumps in high-z galaxies that undergo violent disc instability, distinguishing between long-lived and short-lived clumps. We study the evolution of long-lived clumps during migration through the disc via an analytical model tested by simulations and confront theory with CANDELS-HST observations. The clump ‘bathtub’ model, which considers gas and stellar gain and loss, involves four parameters: the accretion efficiency α, the star formation rate (SFR) efficiency ϵd, and the outflow mass-loading factors for gas and stars, η and ηs. The corresponding time-scales are comparable to the migration time, two-three orbital times. The accretion-rate dependence on clump mass, gas, and stars, allows an analytical solution involving exponential growing and decaying modes. For the fiducial parameter values there is a main evolution phase where the SFR and gas mass are constant and the stellar mass is rising linearly with time. This makes the inverse specific SFR an observable proxy for clump age. When η or ϵd are high, or α is low, the decaying mode induces a decline of SFR and gas mass till the migration ends. Later, the masses and SFR approach an hypothetical exponential growth with a constant specific SFR. The model matches simulations with different, moderate feedbacks, both in isolated and cosmological settings. The observed clumps agree with our predictions, indicating that the massive clumps are long-lived and migrating. A challenge is to model feedback that is non-disruptive in massive clumps but suppresses SFR to match the galactic stellar-to-halo mass ratio.

Dekel, Avishai↗
DOE OSTI2020

Cryptococcus neoformans Secretes Small Molecules That Inhibit IL-1 β Inflammasome-Dependent Secretion

Cryptococcus neoformans is an encapsulated yeast that causes disease mainly in immunosuppressed hosts. It is considered a facultative intracellular pathogen because of its capacity to survive and replicate inside phagocytes, especially macrophages. This ability is heavily dependent on various virulence factors, particularly the glucuronoxylomannan (GXM) component of the polysaccharide capsule. Inflammasome activation in phagocytes is usually protective against fungal infections, including cryptococcosis. Nevertheless, recognition of C. neoformans by inflammasome receptors requires specific changes in morphology or the opsonization of the yeast, impairing proper inflammasome function. In this context, we analyzed the impact of molecules secreted by C. neoformans B3501 strain and its acapsular mutant Δcap67 in inflammasome activation in an in vitro model. Our results showed that conditioned media derived from B3501 was capable of inhibiting inflammasome-dependent events (i.e., IL-1β secretion and LDH release via pyroptosis) more strongly than conditioned media from Δcap67, regardless of GXM presence. We also demonstrated that macrophages treated with conditioned media were less responsive against infection with the virulent strain H99, exhibiting lower rates of phagocytosis, increased fungal burdens, and enhanced vomocytosis. Moreover, we showed that the aromatic metabolite DL-Indole-3-lactic acid (ILA) and DL-p-Hydroxyphenyllactic acid (HPLA) were present in B3501’s conditioned media and that ILA alone or with HPLA is involved in the regulation of inflammasome activation by C. neoformans. These results were confirmed by in vivo experiments, where exposure to conditioned media led to higher fungal burdens in Acanthamoeba castellanii culture as well as in higher fungal loads in the lungs of infected mice. Overall, the results presented show that conditioned media from a wild-type strain can inhibit a vital recognition pathway and subsequent fungicidal functions of macrophages, contributing to fungal survival in vitro and in vivo and suggesting that secretion of aromatic metabolites, such as ILA, during cryptococcal infections fundamentally impacts pathogenesis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Serum amyloid A1: Innocent bystander or active participant in cell migration in triple-negative breast cancer?

Highlights: • SAA1 knockdown reduced cell viability in triple-negative breast cancer cells. • SAA1 knockdown induced a S to G{sub 2}/M cell cycle shift in MDA-MB-231 cells. • SAA1 silencing inhibited cell migration in MDA-MB-231 and HCC70 cells. • SAA1 silencing altered epithelial-to-mesenchymal transition markers in MDA-MB-231 cells. The Serum Amyloid A (SAA) family of proteins is associated with various pathological conditions, including cancer. However, their role in cancer is incompletely understood. Here, we investigated the role of SAA1 in cell cycle regulation, apoptosis, survival signaling, metabolism, and metastasis in models of triple-negative breast cancer (TNBC), using RNAi. Our data show that in untransformed epithelial cells (MCF12A), the knockdown of SAA1 induces the expression of cell cycle regulators (MCM2, p53), the activation of DNA repair (PARP synthesis), and survival signaling (NFκB). In contrast, knockdown of SAA1 in the TNBC cell line (MDA-MB-231) induced the expression p16 and shifted cells in the cell cycle from the S to G{sub 2}/M phase, without the activation of DNA repair. Moreover, in SAA1-deficient MDA-MB-231 and HCC70 cells, metabolism (NADH oxidation) continually increased while cell migration (% wound closure and the rate of wound closure) decreased. However, silencing of SAA1 altered epithelial and mesenchymal markers in MCF12A (E-cadherin, Laminin 1β, Vimentin) and MDA-MB-231 (α-Smooth muscle actin) cells, associated with the metastatic program of epithelial-mesenchymal transition. Nonetheless, our data provide evidence that SAA1 could potentially serve as a therapeutic target in TNBC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Emiliania huxleyi —Bacteria Interactions under Increasing CO 2 Concentrations

The interactions established between marine microbes, namely phytoplankton–bacteria, are key to the balance of organic matter export to depth and recycling in the surface ocean. Still, their role in the response of phytoplankton to rising CO 2 concentrations is poorly understood. Here, we show that the response of the cosmopolitan Emiliania huxleyi (E. huxleyi) to increasing CO 2 is affected by the coexistence with bacteria. Specifically, decreased growth rate of E. huxleyi at enhanced CO 2 concentrations was amplified in the bloom phase (potentially also related to nutrient concentrations) and with the coexistence with Idiomarina abyssalis (I. abyssalis) and Brachybacterium sp. In addition, enhanced CO 2 concentrations also affected E. huxleyi’s cellular content estimates, increasing organic and decreasing inorganic carbon, in the presence of I. abyssalis, but not Brachybacterium sp. At the same time, the bacterial isolates only survived in coexistence with E. huxleyi, but exclusively I. abyssalis at present CO 2 concentrations. Bacterial species or group-specific responses to the projected CO 2 rise, together with the concomitant effect on E. huxleyi, might impact the balance between the microbial loop and the export of organic matter, with consequences for atmospheric carbon dioxide.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Sea Level-Driven Marsh Migration Results in Rapid Net Loss of Carbon

Sea level rise alters coastal carbon cycling by driving the rapid migration of coastal ecosystems, salinization of freshwater systems, and replacement of terrestrial forests with tidal wetlands. Wetland soils accumulate carbon (C) at faster rates than terrestrial soils, implying that sea level rise may lead to enhanced carbon accumulation. Here, we show that carbon stored in tree biomass greatly exceeds carbon stored in adjacent marsh soils so that marsh migration reduces total carbon stocks by ~50% in less than 100 years. Continued marsh soil carbon accumulation may eventually offset forest carbon loss, but we estimate that the time for replacement is similar to estimates of marsh survival (i.e., centuries), which suggests that forest C may never be replaced. These findings reveal a critical C source not included in coastal C budgets driven by migrating ecosystems and rapidly shifting allocations between carbon stored in soils and biomass.

58 GEOSCIENCES↗
DOE OSTI2023

A correlation between seasonally changing photoperiod, whole body lipid, and condition factor in juvenile spring Chinook salmon (Oncorhynchus tshawytscha)

The regulation of lipid stores is a central process for the physiology and ecology of fishes. Seasonal variation in lipid stores has been directly linked to survival of fishes across periods of food deprivation. We assessed whether a seasonally changing photoperiod was correlated to seasonal changes in energetic status to help better understand these important processes. Groups of first feeding Chinook salmon fry were introduced to a seasonal photoperiod cycle, but the point of entrance into the seasonal cycle varied from near the winter solstice (December), to either side of the spring equinox (February & May). Temperature and feeding rate were similar for all treatments. Subsequently, condition factor and whole body lipid content were assessed through a seasonal progression. Throughout most of the experiment, length and weight did not differ between the different photoperiod treatments, however whole body lipid and Fulton’s condition factor did. Furthermore, changes in both whole body lipid and Fulton’s condition factor in all treatment groups followed a similar seasonal pattern that was inversely related to day length (highest K and lipid levels found during days with the least light). These results suggest that regardless of age or size, there is a correlation between seasonal changes in photoperiod and changes in body composition in juvenile Chinook salmonids.

Spangenberg, Dina K. (ORCID:000000018861395X)↗