Spatial and Statistical Analysis of the Causes of Saltmarsh Loss Along the Texas Coast

In the state of Texas, cities and counties located along the coastline have all experienced an increase in population due to its navigable waterways and natural resources. Policy makers are faced with a difficult task to plan for the growth of urban development while using natural resources in a sustainable fashion. Despite efforts to protect valuable natural areas such as marshes, wetland loss continues to occur. In a study conducted in 2015 by Armitage et al., it was recently discovered that saltmarsh areas on the Texas coastline decreased by 77.8 km^2 from 1990-2010 within the Coastal Zone Management (CZM) boundary. When a formerly extensive area of salt marshes has been reduced by conversion to agricultural land, urban development or for industrial use and port facilities it can become quite a significant problem (Boorman,1999). Saltmarshes are given great value due to their ability to absorb impacts from storms, provide wildlife habitat, and provide social and economic benefits. It then becomes critical that analysis be conducted to identify the major causes of wetland loss along the Texas coastline. This thesis aims to understand the major drivers of saltmarsh change throughout the 20-year time frame. Using the change in saltmarsh area for 1990-2010 as the dependent variable and watersheds as the unit of analysis, a regression model was estimated to evaluate drivers of saltmarsh change. Results indicate that if more saltmarsh area was present prior to 2010, then the change would decrease significantly. Additionally, Section 404 permits granted by the U.S. Army Corps of Engineers that permitted the alteration of wetlands indicated that as more permits were distributed, the change that occurred from 1990-2010 increased significantly. Change in population proved quite the opposite. As population change occurred, it decreased the amount of area change in saltmarshes. Similarly, sea level rise also demonstrated to decrease the amount of change exhibited by saltmarsh area. Discussion of the results for all four statistically significant variables reveal that more studies will need to be conducted to further understand their effects on saltmarshes

Estimation of Groundwater Recharge in Texas Related to Aquifer Vulnerability to Contamination

This study aimed to estimate groundwater recharge rates for major porous media aquifers in Texas, essential for assessing aquifer vulnerability to contamination. Recharge rates were estimated through one-dimensional unsaturated flow modeling and limited field studies in the Southern High Plains and Seymour aquifers. Field studies involved measuring soil physics and environmental tracers in soil samples from boreholes in various land use settings. Numerical modeling of unsaturated flow utilized long-term climatic data, soils data, and vegetation data. Simulated recharge rates varied from 54 mm/yr in west Texas to 720 mm/yr in east Texas, positively correlated with precipitation. High recharge rates in east Texas suggest climate is not the limiting factor, with soil texture and vegetation playing crucial roles in reducing recharge. Layered soil profiles led to locally variable recharge estimates, but areally weighted averages were less variable and positively correlated with precipitation. Vegetation significantly reduced recharge rates in all cases, with simulations including vegetation and layered soil profiles resulting in recharge rates ranging from 0.2 to 114 mm/yr. The 30-year average recharge rates across simulated stations in the state were positively correlated with precipitation, suggesting long-term precipitation as a predictor of recharge. This comprehensive approach provides valuable insights into groundwater recharge dynamics, crucial for assessing aquifer vulnerability to contamination.Bureau of Economic Geolog

Ground Water Surface Water Interactions in Texas

Groundwater-surface water interactions need to be evaluated to optimize water management in Texas. This study provides an overview of the impacts of groundwater-surface water (gw-sw) interactions on water quality and water quantity using available data. A literature review was conducted to assess the status of knowledge of gw-sw interactions. A total of 300 references were compiled. References were subdivided into those related to water quantity issues, water quality including point and nonpoint sources of contamination, and methods such as seepage and temperature approaches and modeling analyses. Additional topics covered by the reference list include impacts of climate variability and land use/land cover changes on gw-sw interactions and ecological issues. A compilation of data and information sources for assessing gw-sw interactions in Texas is also provided. This section includes web links to online report catalogs and databases and a listing of offline reports and catalogs provided by state and federal agencies.Bureau of Economic Geolog

Different rates of spontaneous mutation of chloroplastic and nuclear viroids as determined by high-fidelity ultra-deep sequencing

[EN] Mutation rates vary by orders of magnitude across biological systems, being higher for simpler genomes. The simplest known genomes correspond to viroids, subviral plant replicons constituted by circular non-coding RNAs of few hundred bases. Previous work has revealed an extremely high mutation rate for chrysanthemum chlorotic mottle viroid, a chloroplastreplicating viroid. However, whether this is a general feature of viroids remains unclear. Here, we have used high-fidelity ultra-deep sequencing to determine the mutation rate in a common host (eggplant) of two viroids, each representative of one family: the chloroplastic eggplant latent viroid (ELVd, Avsunviroidae) and the nuclear potato spindle tuber viroid (PSTVd, Pospiviroidae). This revealed higher mutation frequencies in ELVd than in PSTVd, as well as marked differences in the types of mutations produced. Rates of spontaneous mutation, quantified in vivo using the lethal mutation method, ranged from 1/1000 to 1/800 for ELVd and from 1/7000 to 1/3800 for PSTVd depending on sequencing run. These results suggest that extremely high mutability is a common feature of chloroplastic viroids, whereas the mutation rates of PSTVd and potentially other nuclear viroids appear significantly lower and closer to those of some RNA viruses.This work was supported by the European Research Council (erc.europa.eu; ERC-2011-StG-281191-VIRMUT to RS), the Spanish Ministerio de Economia y Competitividad (www.mineco.gob.es; BFU2013-41329 grant to RS, BFU2014-56812-P grant to RF, and a predoctoral fellowship to ALC), and the Spanish Junta de Comunidades de Castilla-La Mancha (www.castillalamancha.es;postdoctoral fellowship to CB). 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The double [3+2] photocycloaddition reaction

One of a synthetic organic chemists‟ greatest challenges is to create step-efficient routes toward compounds with high molecular complexity. Therefore, reactions such as the meta photocycloaddition of an olefin to a benzene derivative, which provide more than one bond in a single step are of significant importance. It this remarkable reaction three new σ bonds, three new rings and up to six new stereocenters are formed simultaneously. Additional complexity can be added by tethering the two reacting partners together and this form of the reaction has found many uses in natural product synthesis. In this work a remarkable double [3+2] photocycloaddition reaction is reported that results in the formation of a complex cis, cis, cis, trans-[5, 5, 5, 5] fenestrane derivative from a simple flat aromatic acetal with two branching alkenes. During this dramatic transformation four carboncarbon bonds, five new rings and seven new stereocenters are created in a single one-pot process using only UV light. The reaction occurs in a sequential manner from the linear meta photocycloadduct, via a secondary [3+2] addition of the alkene across the cyclopropane of the adduct. In addition, an angular meta photocycloadduct also produced in the initial addition step, undergoes an alternative fragmentation-translocation photoreaction to afford a silphinene-like angular tricyclic compound. In this work the investigation of this newly discovered process is discussed via the synthesis and subsequent irradiation of a series of photosubstrates containing different functional groups in the arene-alkene tether. In addition, attempts toward the synthesis of alternative structures using the same double [3+2] photocycloaddition are reported

A Method for the Simultaneous Estimation of Selection Intensities in Overlapping Genes

Inferring the intensity of positive selection in protein-coding genes is important since it is used to shed light on the process of adaptation. Recently, it has been reported that overlapping genes, which are ubiquitous in all domains of life, seem to exhibit inordinate degrees of positive selection. Here, we present a new method for the simultaneous estimation of selection intensities in overlapping genes. We show that the appearance of positive selection is caused by assuming that selection operates independently on each gene in an overlapping pair, thereby ignoring the unique evolutionary constraints on overlapping coding regions. Our method uses an exact evolutionary model, thereby voiding the need for approximation or intensive computation. We test the method by simulating the evolution of overlapping genes of different types as well as under diverse evolutionary scenarios. Our results indicate that the independent estimation approach leads to the false appearance of positive selection even though the gene is in reality subject to negative selection. Finally, we use our method to estimate selection in two influenza A genes for which positive selection was previously inferred. We find no evidence for positive selection in both cases