Browsing by Subject "Scales"
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Item Habitat use and trophic structure of Atlantic tarpon (Megalops atlanticus) inferred from geochemical proxies in scales(2016-05) Seeley, Matthew Edward; Black, Bryan A.; Walther, Benjamin D.; Fuiman, Lee AAtlantic tarpon, Megalops atlanticus, are highly migratory euryhaline predators that occupy different habitats throughout life. Atlantic tarpon are known to inhabit oligohaline waters, although the frequency and duration of movements across estuarine gradients into these waters are poorly known. This species supports over a two billion dollar industry within the Gulf of Mexico and is currently listed as vulnerable by the International Union for the Conservation of Nature (IUCN). Analysis of trace element and stable isotope compositions of growth increments in fish scales is a non-lethal method for reconstructing migrations across estuaries in vulnerable species. We analyzed Atlantic tarpon scales from the Texas coast to validate this method using inductively coupled plasma mass spectrometry (ICP-MS) for trace elements and isotope ratio mass spectrometry (IR-MS) for stable isotope ratios. Multiple scales and otoliths were taken from the same individual to confirm the consistency of elemental and isotopic uptake within the same individual and between structures. Results show that scale Sr/Ca and δ13C are effective proxies for salinity, while increases in δ15N are consistent with known trophic shifts throughout life history. Patterns of elemental concentrations and isotope values across scales within an individual were consistent with each other. Scale and otolith transects contained the same overarching trend with comparable shifts in elemental concentrations across growth increments in the two structures. Migratory contingents, or groups within distinct populations that exhibit different patterns of habitat use and movement across salinity gradients, were identified. The distribution of contingents indicated that migratory behavior is highly variable, with some, but not all fish transiting estuarine gradients into oligohaline waters. Yet, the majority of individuals sampled exhibited early life residency in oligohaline waters. This work demonstrates the use of low salinity habitats by Atlantic tarpon. Our validation of the methods for analyzing scales will provide novel opportunities to monitor fish migrations across salinity gradients.Item Scales and Scale-like Structures(2011-08-08) Landreneau, Eric BenjaminScales are a visually striking feature that grows on many animals. These small, rigid plates embedded in the skin form an integral part of our description of ?sh and reptiles, some plants, and many extinct animals. Scales exist in many shapes and sizes, and serve as protection, camou?age, and plumage for animals. The variety of scales and the animals they grow from pose an interesting problem in the ?eld of Computer Graphics. This dissertation presents a method for generating scales and scale-like structures on a polygonal mesh through surface replacement. A triangular mesh was covered with scales and one or more proxy-models were used as the scales shape. A user began scale generation by drawing a lateral line on the model to control the distribution and orientation of scales on the surface. Next, a vector ?eld was created over the surface to control an anisotropic Voronoi tessellation, which represents the region occupied by each scale. Then these regions were replaced by cutting the proxy model to match the boundary of the Voronoi region and deform the cut model onto the surface. The ?nal result is a fully connected 2-manifold that is suitable for subsequent post-processing applications, like surface subdivision.Item Study of Multi-Scale Plant-Groundwater Interactions(2014-05-30) Gou, SiGroundwater serves as one of the main and reliable water sources for human-being and groundwater dependent ecosystems (GDEs). GDEs are threatened by insufficient groundwater supply, due to increasing groundwater extraction and climate change. Sustainable groundwater management should address the water needs for both human and ecosystems, which requires a better understanding of the complex interactions between GDEs and groundwater. This dissertation examines plant-groundwater interactions and their implications at a range of scales. At the plant scale (~1 m^(2)), a physically-based model was developed to explore the hydraulic mechanisms of plant groundwater use. New functions of root water uptake and hydraulic redistribution (HR) in the model were driven by the potential gradients along the groundwater-soil-plant-atmosphere continuum, and a new water stress function was based on the linear relationship between stomatal conductance and root hydraulic conductance. These functions were further incorporated into a groundwater-land surface model, ParFlow.CLM, to develop a spatial distributed ecohydrological model at the stand scale (~1000 m^(2)). The modified ParFlow.CLM was used to conduct a 8-year simulation with half hourly time step at a AmeriFlux oak savanna site in California. It performed well when simulating daily, hourly, and spatial changes of water and energy dynamics. It captured the seasonal shift of plant water source from soil water during the wet season to groundwater during the dry season. The model simulated both hydraulic lift and hydraulic descent during oak active and dormant seasons. The model suggested that HR at this site was a mechanism for oaks to compete for water with annual grasses. At the regional scale (~1000 km^(2)), a method was proposed to identify vegetative GDEs using remote sensing data and to generate a detailed GDEs map for the Edwards aquifer region in Texas. This method used Landsat ETM+ and MODIS images to track the changes of NDVI for each vegetation pixel under different precipitation conditions. The NDVI dynamics were used to identify the vegetation with high potential to use groundwater. The method produces a detailed map of potential GDEs, which represents the first step towards sustainable water management associated with these ecosystems.