The ScholarShip

The ScholarShip is a digital archive for the scholarly output of the ECU community. Its mission is to capture, preserve, and make available the intellectual output of East Carolina University's faculty, staff, and students.

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Now showing 1 - 8 of 8

Recent Submissions

Access status: Metadata only ,
Alpha: A Fortran program for simulating porewater radiolysis
(2022-05-05)
The radiolysis of porewaters by uranium, thorium, and potassium in mineral grains is a recognised source of molecular hydrogen in rock- and sediment-hosted fluids. This radiolytic hydrogen is of geomicrobiological interest as a potential energy source (electron donor) for microbial metabolism, especially in energy-limited settings such as the marine deep biosphere or the subsurface of Mars. Previous efforts to predict the production of radiolytic hydrogen from columns of rock and sediment have tended to rely upon analytic models that cannot account for the attenuation of mineral radiation by grains larger than ~30 microns. To address this, we have developed a Monte Carlo method to simulate the physics of mineral radiation and evaluate the production of H2 as a function of mineral grain size and radioisotope composition. The results confirm that grain size is a major control on radiolytic H2 yield. For example, using the standard geological classification of grain sizes, we find that clay can produce up to an order of magnitude more H2 per unit time than sand. The magnitude of this effect is illustrated using compositional data from real geological units in order to demonstrate the dependence of radiolytic hydrogen flux on natural radionuclide concentration and bulk porosity.
Access status: Metadata only ,
Phenotypic correlates of pelvic spine coloration in the Threespine Stickleback (Gasterosteus aculeatus): Implications for function and evolution
(2022-05-10)
Animal color patches may be static or plastic in expression and concealable or continuously visible, yet these aspects of coloration, and their consequences, have been little studied. We address them here using the threespine stickleback (Gasterosteus aculeatus). Despite a rich history of study of stickleback nuptial color pattern evolution, disagreement persists regarding selection pressures and function. However, little research has addressed the role of pelvic spine coloration, a potentially important, and substantially concealable, color pattern element. We investigated (i) whether male pelvic spine (along with throat and body) coloration is relatively static or plastic across the reproductive cycle, (ii) when pelvic spines are raised versus concealed across behavioral contexts, and (iii) associations between color patches and behavior in males. We found no significant variation in spine color across reproductive stages whereas body color was more plastic and intensely red during courtship and egg/fry care. Conspicuousness of pelvic spine coloration instead varied behaviorally, through increased erection frequency during social interactions and in response to a model predator. Spine erection frequency was positively associated with behaviors that enhance spine color visibility, i.e. flees and leads to nest. These findings suggest that stickleback use pelvic spines to display an intensely red color patch facultatively, either as a complement to similar body coloration or possibly as a substitute. In addition, elevated spine raising in the presence of a model predator, together with the presence of red spine coloration in females, raises the possibility that red spine coloration may also have an anti-predator function.
Access status: Metadata only ,
Figure data and analysis for: The effect of grain size on porewater radiolysis
(2022-06-13)
The radiolysis of porewaters by uranium, thorium, and potassium in mineral grains is a recognised source of molecular hydrogen in rock- and sediment-hosted fluids. This radiolytic hydrogen is of geomicrobiological interest as a potential energy source (electron donor) for microbial metabolism, especially in energy-limited settings such as the marine deep biosphere or the subsurface of Mars. Previous efforts to predict the production of radiolytic hydrogen from columns of rock and sediment have tended to rely upon analytic models that cannot account for the attenuation of mineral radiation by grains larger than ~30 microns. To address this, we have developed a Monte Carlo method to simulate the physics of mineral radiation and evaluate the production of H2 as a function of mineral grain size and radioisotope composition. The results confirm that grain size is a major control on radiolytic H2 yield. For example, using the standard geological classification of grain sizes, we find that clay can produce up to an order of magnitude more H2 per unit time than sand. The magnitude of this effect is illustrated using compositional data from real geological units in order to demonstrate the dependence of radiolytic hydrogen flux on natural radionuclide concentration and bulk porosity.
Access status: Metadata only ,
Data from: Environmental and climate variability drive population size of annual penaeid shrimp in a large lagoonal estuary
(2023-05-04)
Species with short life spans frequently show a close relationship between population abundance and environmental variation making these organisms potential indicator species of climatic variability. White (Penaeus setiferus), brown (P. aztecus), and pink (P. duorarum) penaeid shrimp typically have an annual life history and are of enormous ecological, cultural, and economic value to the southeastern United States and Gulf of Mexico. Within North Carolina, all three species rely on the Pamlico Sound, a large estuarine system that straddles Cape Hatteras, one of the most significant climate and biogeographic breaks in the world, as a nursery area. These characteristics make penaeid species within the Pamlico Sound a critical species-habitat complex for assessing climate impacts on fisheries. However, a comprehensive analysis of the influence of the environmental conditions that influence penaeid shrimp populations has been lacking in North Carolina. In this study, we used more than 30 years of data from two fishery-independent trawl surveys in the Pamlico Sound to examine the spatial distribution and abundance of adult brown, white, and pink shrimp and the environmental drivers associated with adult shrimp abundance and juvenile brown shrimp recruitment using numerical models. Brown shrimp recruitment models demonstrate that years with higher temperature, salinity, offshore windstress, and North Atlantic Oscillation phase predict increased abundance of juveniles. Additionally, models predicting adult brown, white, and pink shrimp abundance illustrate the importance of winter temperatures, windstress, salinity, the North Atlantic Oscillation index, and the abundance of spawning adult populations from the previous year on shrimp abundance. Our findings show a high degree of variability in shrimp abundance is explained by climate and environmental variation and indicate the importance of understanding these relationships in order to predict the impact of climate variability within ecosystems and develop climate-based adaptive management strategies for marine populations.
Access status: Metadata only ,
Detecting regenerating limbs in Hemigrapsus sanguineus based on limb mass
(2023-08-03)
"1. Regeneration of lost appendages is a gradual process in many species, spreading energetic costs of regeneration through time. Energy allocated to regeneration of lost appendages cannot be used for other purposes and therefore commonly elicits energetic trade-offs in biological processes. 2. We used limb loss in the Asian shore crab Hemigrapsus sanguineus to compare the strength of energetic trade-offs resulting from historic limb losses that have been partially regenerated versus current injuries that have not yet been repaired. Consistent with previous studies, we show that limb loss and regeneration results in trade-offs that reduce reproduction, energy storage, and growth. 3. As may be expected, we show that trade-offs in these metrics from historic limb losses far outweigh trade-offs from current limb losses, and correlate directly with the degree of historic limb loss that has been regenerated. 4. As regenerating limbs get closer to their normal size, these historical injuries get harder to detect, despite the continued allocation of additional resources to limb development. Our results demonstrate the importance of a method for identifying historic appendage losses and of quantifying the amount of regeneration that has already occurred, as opposed to assessing only current injury, to accurately assess the strength of energetic trade-offs in animals recovering from non-lethal injury."