Stygobiont Diversity in the San Marcos Artesian Well and Edwards Aquifer Groundwater Ecosystem, Texas, USA

The Edwards Aquifer and related Edwards-Trinity Aquifer of Central Texas, USA, is a global hotspot of stygobiont biodiversity. We summarize 125 years of biological investigation at the San Marcos Artesian Well (SMAW), the best studied and most biodiverse groundwater site (55 stygobiont taxa: 39 described and 16 undescribed) within the Edwards Aquifer Groundwater Ecosystem. Cluster analysis and redundancy analysis (RDA) incorporating temporally derived, distance-based Moran’s Eigenvector Mapping (dbMem) illustrate temporal dynamics in community composition in 85 high-frequency samples from the SMAW. Although hydraulic variability related to precipitation and discharge partially explained changes in community composition at the SMAW, a large amount of temporal autocorrelation between samples remains unexplained. We summarize potential mechanisms by which hydraulic changes can affect community structure in deep, phreatic karst aquifers. We also compile information on 12 other Edwards and Edwards-Trinity Aquifer sites with 10 or more documented stygobionts and used distance-based RDA to assess the relative influences of distance and site type on three measures of β-diversity. Distance between sites was the most important predictor of total dissimilarity and replacement, although site type was also important. Species richness difference was not predicted by either distance or site type.

An unusually sculptured new species of Phreatodrobia Hershler & Longley (Mollusca: Caenogastropoda: Cochliopidae) from central Texas

There are eight described species in Phreatodrobia, minute, phreatic (subterranean aquatic) snails, all stygobitic and endemic to the Edwards-Trinity Aquifer System of Texas. Two species were described from river drift (Pilsbry & Ferriss 1906) and the others more recently by sampling the water flowing from wells or springs (Hershler & Longley 1986b; Hershler & Longley 1987). Recent sampling from spring orifices and the hyporheic zone of streams have extended the known ranges of the phreatic snails of the region and encountered unknown snails (Alvear et al. 2020). Here we describe Phreatodrobia spica n. sp., a rarely encountered species with a large range of about 400 km (Figure 1). We find P. spica in samples with a diverse assemblage of phreatic animals including other species of Phreatodrobia, isopods, amphipods, coleopterans, and mites. Phreatodrobia spica is distinguished from congeners using morphological and molecular evidence and is characterized by an elevated, trochiform shell with unique sculpture that include spikes and pustules. It has an open umbilicus and a complete, reflected lip that is sometimes appressed to the body whorl.

Vulnerability assessment of the Trinity Aquifer in Texas due to sulfonamides antibiotics leaching to groundwater for

<p>Texas has the largest population of cattle farming and the highest production of poultry farming across the United States. In northeastern region, antibiotics have been widely used in Concentrated Animal Feeding Operations (CAFO) as veterinary pharmaceuticals (VP). Not fully metabolized and excreted antibiotics have caused soil pollution and resulted groundwater contamination. Sulfonamides’ high excretion rate from animals, low sorption to soils, and impact on nitrate-reducing bacteria for nitrate reduction capabilities, enhance leaching and secondary pollution from inherent nitrate-N contamination. However, there is a limited understanding of sulfonamides transport from the surface to groundwater. This research assessed the Trinity Aquifer vulnerability by incorporating major hydrogeological factors that affect and control the groundwater contamination using GIS-based DRASTIC along with major chemical factors using HYDRUS solute transport modeling. The study reclassified and refined subareas with different vulnerability potentials by overlaying various spatially referenced digital data layers. Additionally, sulfonamides transport was simulated for different vulnerable scenarios to estimate persistence of the antibiotic and potential concentrations reaching the aquifer, developing predicted methods to prevent, mitigate and remediate groundwater contamination caused by sulfonamides antibiotics.</p><p> </p>

Factors affecting the spatial pattern of nitrate contamination in Texas aquifers

Purpose The elevated level of nitrate in groundwater is a serious problem in Texas aquifers. To control and manage groundwater quality, the characterization of groundwater contamination and identification of the factors affecting the nitrate concentration of groundwater are significant. The purpose of this paper is to determine factors which have significant impacts on the elevated groundwater nitrate concentrations of the Southern High-Plains and the Edwards-Trinity aquifers. Design/methodology/approach The characterization of groundwater nitrate contamination was undertaken by analyzing the hydrochemical data of groundwater within a statistical framework. The multivariate statistical analysis (ordinary least square) and geographically weighted regression (GWR) models were used to study the relationship between groundwater nitrate contamination and land use of the study areas. Findings Results show groundwater nitrate contamination is typically due to an overapplication of N fertilizers to cotton in the Southern High-Plains aquifer and to grassland in the Edwards-Trinity aquifer. Adjusted R2 (0.45) explains variations of nitrate concentration by well-depth, cotton production, shrubland and grassland in the Edwards-Trinity aquifer. The results of an analysis of variations in N concentration with well depth for all 192 wells indicate that nitrate concentrations in water from wells in the Southern High-Plains and Edwards-Trinity aquifers tend to decrease with increasing well-depth. Originality/value In this study, the GWR model was built to identify nitrate concentration within a geographic framework to ensure sustainable use of groundwater, which is important for local management purposes. The analysis should include local spatial variations of elements such as hydrologic characteristics and the land use activities if groundwater nitrate contamination causes adverse effects on human and ecosystem health.

New occurrence records for Eurycea sosorum Chippindale, Price & Hillis, 1993 (Caudata, Plethodontidae) in Travis and Hays counties, Texas, USA

We present 7 new occurrence records for the Barton Springs Salamander (Eurycea sosorum Chippindale, Price & Hillis, 1993) from Hays and Travis counties, Texas, USA, including the first for this species from the Trinity Aquifer. Eurycea sosorum is listed as endangered under the Endangered Species Act of 1973 due to ongoing threats from urbanization and aquifer overdraft throughout its narrow range. Although this species is more widely distributed than when it was first described in 1993, its range is still exceptionally small, restricted to portions of only two watersheds (Onion and Barton creeks) in one of the fastest-growing metropolitan areas in the United States (Austin, Texas). Under any ecologically-relevant criterion that is based on the best available scientific evidence, this species remains in danger of extinction throughout its range.