Mercury concentrations in south Texas game fishes

Mercury (Hg) is one of the most ubiquitous and controversial metals in the world primarily due to the toxicity of the organic form of the metal, methylmercury (MeHg). MeHg is a neurotoxin at high levels, known to manifest its effects on humans primarily through consumption of certain fish and marine mammals, which tend to bioaccumulate MeHg in their tissues over time. Increased fish consumption and, thus, mercury intake in residents of coastal areas necessitates a better awareness of MeHg content in game fish species, thus the subject of this study. Three hundred thirty-nine tissue samples were taken from 19 south Texas marine species collected primarily at three fishing tournaments in 2004, tested for total Hg concentrations and analyzed with regression analyses and ANOVA. Results of individual species regression analyses all indicate exponential correlations for the comparisons of fish length (curved fork length for pelagic species and total length for the remainder) vs. total Hg. Sampled species were divided into four groups for further analysis: demersal vs. pelagic and inshore vs. offshore. Inshore and demersal fish species were found to exhibit mean concentrations of total Hg of 0.22 and 0.19 ppm. Both offshore and pelagic fish species had higher mean total Hg concentrations of 0.80 ppm. Two species were found to equal or exceed the U.S. Food and Drug Administration\u27s action level of 1.0 ppm for fish. Those were blackfin tuna (Thunnus atlanticus) and king mackerel (Scomberomorus cavalla). Tissue samples were analyzed from blue crab (Callinectes sapidus) taken from the Arroyo Colorado, yielding a low unadjusted mean total Hg concentration of 0.15±0.08 ppm for a mean carapace length 14. 5 cm. Consumption limit comparisons are presented for 11 south Texas game fish species using EPA recommendations based on a reference dose (RID) of 0.0001 mg/kg of body weight/day (U.S. EPA, 1999). Similar comparisons are offered for different size ranges of nine of those species with significant length to total Hg relationships

Evaluating the Impacts of Dam Construction and Longshore Transport upon Modern Sedimentation within the Rio Grande Delta (Texas, U.S.A.)

The modern Rio Grande delta system has experienced a century of dam construction, water removal for irrigation and municipal use, and land use modifications that have dramatically reduced its sediment load. This study examines whether damming has sufficiently limited delivery of upstream sediment to permit locally eroded sources and/or littoral transport along the coast to influence the provenance signal of the Rio Grande delta. Changes in sediment provenance within the Rio Grande’s delta can be detected and quantified by measurement of detrital zircon Uranium–lead dating age distributions. Previous provenance studies indicate that modern Rio Grande river sand upstream of Falcon Dam is enriched in zircon derived from Oligocene volcanic fields within the southern Rocky Mountains and the Sierra Madre Occidental. Results from this study indicate that the abundance of Oligocene zircon is depleted in the modern Rio Grande delta relative to river sand sampled upstream of Falcon Dam. Mixing calculations performed with age distributions representative of Eocene– Miocene fluvial sedimentary deposits that crop out downstream of the dam indicate that erosional reworking of these materials has significantly altered sedimentary provenance within the delta. The importance of north-directed longshore transport along the Mexican (Tamaulipas-Veracruz) Gulf Coast was also evaluated. The absence of distinctive zircon from the Trans Mexican volcanic belt and the basement of southern Mexico within the barrier islands of the Rio Grande delta support previous conclusions that sediment transport along the Tamaulipas-Veracruz shelf is highly compartmentalized and restricted in lateral movement due to seasonal variation in littoral current polarity, topographic barriers along the shelf, and other phenomena. Nevertheless, the results of this study demonstrate that construction of dams across rivers such as the Rio Grande is capable of sufficiently limiting upstream sediment transport to permit otherwise unimportant local sources to dominate sand provenance within their delta systems

Finding and sharing: new approaches to registries of databases and services for the biomedical sciences

The recent explosion of biological data and the concomitant proliferation of distributed databases make it challenging for biologists and bioinformaticians to discover the best data resources for their needs, and the most efficient way to access and use them. Despite a rapid acceleration in uptake of syntactic and semantic standards for interoperability, it is still difficult for users to find which databases support the standards and interfaces that they need. To solve these problems, several groups are developing registries of databases that capture key metadata describing the biological scope, utility, accessibility, ease-of-use and existence of web services allowing interoperability between resources. Here, we describe some of these initiatives including a novel formalism, the Database Description Framework, for describing database operations and functionality and encouraging good database practise. We expect such approaches will result in improved discovery, uptake and utilization of data resources. Database URL: http://www.casimir.org.uk/casimir_dd

Carbon disulfide. Just toxic or also bioregulatory and/or therapeutic?

The overview presented here has the goal of examining whether carbon disulfide (CS2) may play a role as an endogenously generated bioregulator and/or has therapeutic value. The neuro- and reproductive system toxicity of CS2 has been documented from its long-term use in the viscose rayon industry. CS2 is also used in the production of dithiocarbamates (DTCs), which are potent fungicides and pesticides, thus raising concern that CS2 may be an environmental toxin. However, DTCs also have recognized medicinal use in the treatment of heavy metal poisonings as well as having potency for reducing inflammation. Three known small molecule bioregulators (SMBs) nitric oxide, carbon monoxide, and hydrogen sulfide were initially viewed as environmental toxins. Yet each is now recognized as having intricate, though not fully elucidated, biological functions at concentration regimes far lower than the toxic doses. The literature also implies that the mammalian chemical biology of CS2 has broader implications from inflammatory states to the gut microbiome. On these bases, we suggest that the very nature of CS2 poisoning may be related to interrupting or overwhelming relevant regulatory or signaling process(es), much like other SMBs

Suspended Sediment Dynamics of Texas Estuaries

A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR of PHILOSOPHY in COASTAL AND MARINE SYSTEM SCIENCE from Texas A&M University-Corpus Christi in Corpus Christi, Texas.Suspended sediments are an integral part of estuarine systems in that they impact water quality and form habitats; their flux is driven by the interplay between freshwater inflow, tidal currents, wind-wave resuspension, commercial fishing, and dredging operations. The objective of this dissertation is to investigate the relative importance of the aforementioned drivers of suspended sediment in the three largest Texas estuaries (Galveston, Matagorda, and Corpus Christi Bays) using a variety of analysis methods. Analyses of suspended sediment drivers using a Texas State water quality database of in situ samples (Chapter II), development of an algorithm to transform satellite imagery into suspended sediment concentrations (Chapter III), and analysis of a 12-year time series of satellite-derived suspended sediment concentrations (Chapter IV) were used to accomplish the dissertation objectives. The relative importance of freshwater inflow, tidal currents, and wind-wave resuspension was determined by statistical analyses of in situ point measurements of total suspended solids (TSS) and environmental forcings for the period of 2000-2010. The findings from these analyses show that wind-wave resuspension is the most dominant forcing of TSS in Corpus Christi, Matagorda, and Galveston Bays. The analyses further indicated that freshwater inflow in Galveston Bay and astronomical tides in Matagorda Bay also influence the variability of TSS. An algorithm to transform satellite reflectance data into TSS was created Analyses determined the best model was an exponential fit of a red-green band ratio. The algorithm was then used to create synoptic time series of TSS for the period of 2002-2014 for the estuaries. Analysis of the satellite-derived time series shows how freshwater inflow, tidal currents, wind-wave resuspension, commercial fishing, and dredging operations influence the long-term variability of TSS in Galveston, Matagorda, and Corpus Christi Bays. Median and interquartile range composites of suspended sediments were generated for seasonal wind and inflow regimes in each estuary. TSS patterns show that the Galveston Bay system is dominated by riverine inflow with some influence from frontal passages. Surprisingly, the influence of oyster harvesting causing locally high TSS values in Galveston Bay is the most salient pattern within the estuary. Matagorda Bay’s patterns indicate that the system is mostly controlled by wind-wave resuspension with patterns changing between northern frontal passages and southeasterlies dominated seasons. Corpus Christi Bay is similarly influenced by wind-wave resuspension with different patterns during the predominant northerlies and prevalent southeasterlies seasons. The impact of dredging is also apparent in long-term patterns of Corpus Christi Bay as concentrations of suspended sediments over dredge spoil disposal sites are higher and more variable than surrounding areas, which is most likely due to less consolidated sediments and shallower depths requiring less wave energy for sediment resuspension. For Corpus Christi and Matagorda Bays, this research (Chapters II & IV) showed that wind-wave resuspension is the dominant forcing of TSS. Satellite data allowed the identification of patterns characteristic of different wind regimes. Additionally the point data analysis (Chapter II) showed that tidal forcing has an influence on TSS in Matagorda Bay. Both analyses (Chapters II & IV) show that wind forcing is less influential in Galveston Bay as compared to the other estuaries, and that freshwater inflow are important in Galveston Bay. A major highlight of this research is the advantage provided by long synoptic time series of satellite-derived TSS that elucidated the major drivers of suspended sediments in estuaries as well as their seasonal variability. With usage of satellite data, this research identified oyster harvesting to be a significant source of suspended sediment in Galveston Bay.Physical and Environmental SciencesCollege of Science and Engineerin

Estuarine Suspended Sediment Dynamics: Observations Derived from over a Decade of Satellite Data

Suspended sediment dynamics of Corpus Christi Bay, Texas, USA, a shallow-water wind-driven estuary, were investigated by combining field and satellite measurements of total suspended solids (TSS). An algorithm was developed to transform 500-m Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua satellite reflectance data into estimated TSS values. The algorithm was developed using a reflectance ratio regression of MODIS Band 1 (red) and Band 3 (green) with TSS measurements (n = 54) collected by the Texas Commission on Environmental Quality for Corpus Christi Bay and other Texas estuaries. The algorithm was validated by independently collected TSS measurements during the period of 2011–2014 with an uncertainty estimate of 13%. The algorithm was applied to the period of 2002–2014 to create a synoptic time series of TSS for Corpus Christi Bay. Potential drivers of long-term variability in suspended sediment were investigated. Median and IQR composites of suspended sediments were generated for seasonal wind regimes. From this analysis it was determined that long-term, spatial patterns of suspended sediment in the estuary are related to wind-wave resuspension during the predominant northerly and prevalent southeasterly seasonal wind regimes. The impact of dredging is also apparent in long-term patterns of Corpus Christi Bay as concentrations of suspended sediments over dredge spoil disposal sites are higher and more variable than surrounding areas, which is most likely due to their less consolidated sediments and shallower depths requiring less wave energy for sediment resuspension. This study highlights the advantage of how long-synoptic time series of TSS can be used to elucidate the major drivers of suspended sediments in estuaries

A Restoration Suitability Index Model for the Eastern Oyster (Crassostrea virginica) in the Mission-Aransas Estuary, TX, USA

Oyster reefs are one of the most threatened marine habitats on earth, with habitat loss resulting from water quality degradation, coastal development, destructive fishing practices, overfishing, and storm impacts. For successful and sustainable oyster reef restoration efforts, it is necessary to choose sites that support long-term growth and survival of oysters. Selection of suitable sites is critically important as it can greatly influence mortality factors and may largely determine the ultimate success of the restoration project. The application of Geographic Information Systems (GIS) provides an effective methodology for identifying suitable sites for oyster reef restoration and removes much of the uncertainty involved in the sometimes trial and error selection process. This approach also provides an objective and quantitative tool for planning future oyster reef restoration efforts. The aim of this study was to develop a restoration suitability index model and reef quality index model to characterize locations based on their potential for successful reef restoration within the Mission-Aransas Estuary, Texas, USA. The restoration suitability index model focuses on salinity, temperature, turbidity, dissolved oxygen, and depth, while the reef quality index model focuses on abundance of live oysters, dead shell, and spat. Size-specific Perkinsus marinus infection levels were mapped to illustrate general disease trends. This application was effective in identifying suitable sites for oyster reef restoration, is flexible in its use, and provides a mechanism for considering alternative approaches. The end product is a practical decision-support tool that can be used by coastal resource managers to improve oyster restoration efforts. As oyster reef restoration activities continue at small and large-scales, site selection criteria are critical for assisting stakeholders and managers and for maximizing long-term sustainability of oyster resources

Spatially interpolated environmental measurements in the Mission-Aransas Estuary, TX, USA.

<p>Mean (left column) and standard deviation (SD, right column) for salinity (sal; A and B), temperature (temp; C and D), and turbidity (turb; E and F). Frequency of dissolved oxygen <4 mg/l (G); and depth (H).</p